N-2NSPML (BW) RIRs 1-22 - Redacted
182 passages
NON-CONFIDENTIAL 1 Response IR-03: 2 3 a-b) 4 The availability of the Maritime Link for the period 2018 to 2025 is provided in the table 5 below. This includes the Bipole availability (i.e. annual percentage of time when both poles 6 were...
AI summary The text discusses the availability of the Maritime Link transmission line between 2018 and 2025, including metrics such as Bipole and Monopole availability, and Energy Availability. It also describes how NSPML calculates availability using CIGRE guidelines and introduces the concept of Forced Energy Unavailability (FEU).
NSPML Responses to Bates White Information Requests 1 c-d) 2 The Maritime Link's transfer capability and actual flow delivered at the Woodbine (NS) 3 converter station is provided in Attachment 1 for each hour of the compliance period. 4 5...
AI summary NSPML provides data on the Maritime Link's transfer capability and actual energy flow at the Woodbine converter station, including projected availability performance and underlying assumptions about energy availability and outages.
CONFIDENTIAL (ATTACHMENTS ONLY) 1 Request IR-04 2 3 Please refer to Exhibit N-1, page 5 lines 31-32, page 11 lines 24 to page 12 line 2, and Board 4 Matter M05419. 5 6 a) Please provide the actual annual availability (%) of the LIL for 202...
AI summary The document contains a series of information requests related to the availability and performance of the Labrador Intermediate Line (LIL) and Muskrat Falls Generating Station, including annual availability, forced outage rates, transfer capability, and flow data. It also requests the CIGRE Report and assumptions used in a regulatory proceeding (M05419).
CONFIDENTIAL (ATTACHMENTS ONLY) - 1 c) Please see Confidential Attachment 1. - d) Please see Confidential Attachment 1. - e) The LIL availability assumed would have been in line with the published studies included in this IR submitted to t...
AI summary The text references confidential attachments and discusses data availability related to the Muskrat Falls project, noting that raw aggregate plant output data is not unit-specific and a histogram illustrates high availability. It also mentions data limitations preventing calculations.
SYSTEM RELIABILITY INTERRELATIONSHIPS To understand the concept of system reliability and overall impact the addition of a 900 MW HVdc transmission link between Labrador and Newfoundland will have on the Island Interconnected Transmission...
AI summary The text explains the need to understand interrelationships between system planning, transmission line design, and system operations to assess how a 900 MW HVdc transmission link between Labrador and Newfoundland will impact the Island Interconnected Transmission System's reliability.
System Planning Components Least cost reliable planning of the Island Interconnected Transmission System is comprised of two main components: generation planning and transmission planning.
AI summary The planning of the Island Interconnected Transmission System involves two key components: generation planning and transmission planning, focusing on least-cost reliable system design.
Generation Planning Generation planning for the Island Interconnected System ensures that there is sufficient generation, both capacity (MW) and energy (MWh) to supply the load as provided in load forecasts for future years. NLH uses an in...
AI summary Generation planning for Nova Scotia's Island Interconnected System ensures sufficient capacity (MW) and energy (MWh) to meet load forecasts using the Strategist® program. Key criteria include a LOLH target of ≤2.8 hours/year and firm energy capability. Deficiencies trigger additions of energy sources or low-cost combustion turbines, with iterations for least-cost expansion. LOLH excludes grid outage rates.
CSA Standard C22.3 No. 1‐06 Overhead Systems CSA Standard C22.3 No. 1‐06 Overhead systems provides the transmission line designer with a choice between deterministic and reliability‐based design methods. CSA C22.3 No. 1‐06 covers the deter...
AI summary CSA Standard C22.3 No. 1‐06 outlines deterministic and reliability-based design methods for overhead systems, specifying four weather load conditions (severe, heavy, medium loading A/B) classified using local experience and weather records. Annex C provides minimum load maps, adjustable based on local data.
Reference to Annex C indicates that: - The area surrounding the Churchill River is considered to have a loading condition of medium loading B; - The area traversed by the proposed HVdc line from Muskrat Falls to the Strait of Belle Isle is...
AI summary The text outlines loading conditions for different regions in Newfoundland and Labrador, specifying ice thickness requirements from Table 30. Medium loading B (12.5 mm), heavy loading (12.5 mm), and severe loading (19 mm) are assigned to specific geographic areas, including the Churchill River, HVdc transmission route, and the Bonavista/Avalon Peninsulas.
System Operations With all equipment available and in service the Island Interconnected System operates at its most reliable level as the generation planning exercise ensures there is sufficient generation to meet the load even for loss of...
AI summary The Island Interconnected System maintains reliability through generation and transmission planning, ensuring sufficient capacity to handle single equipment losses. Forced outages and maintenance require System Operations to reconfigure the grid, scheduling maintenance to preserve backup capacity during unplanned outages.
IMPACT OF THE LABRADOR – ISLAND HVdc LINK ON ISLAND SYSTEM RELIABILITY The Labrador – Island HVdc Link has the following nominal ratings: - ±320 kV operating voltage (bipole); - 2 x 450 MW, 1406 A per pole; - 900 MW at Muskrat Falls; - 92....
AI summary The Labrador-Island HVdc Link's 900 MW capacity and 92.1 MW losses impact Island System Reliability, modeled as a generator with a forced outage rate. Additional 50 MW combustion turbines are required to maintain LOLH below 2.8 hours/year. Generation planning ensures firm energy supply until 2036, with future sources like Portland Creek and wind needed thereafter.
Pole Outages CIGRE 2010 paper B4_209_2010 "A survey of the Reliability of HVdc Systems Throughout the World During 2007 – 2008" provides the latest available outage statistics for HVdc transmission systems worldwide. It must be noted that...
AI summary The text discusses reliability concerns for HVdc transmission systems, referencing CIGRE 2010 outage statistics. It highlights potential pole outages in the Labrador–Island HVdc Link, their impact on system frequency, and measures like temporary ratings (2 p.u. for 10 minutes) to prevent under-frequency load shedding. The proposed system's operational parameters and mitigation strategies are detailed.
Pole Outages – Maritime Link In Service Of the 807.9 MW delivered to Soldiers Pond, 162.2 MW is assigned to supply the Emera block, leaving 645.7 MW as the peak deliveries to the Island Interconnected System. For loss of a pole the Emera b...
AI summary The document analyzes the impact of pole outages on the Maritime Link HVdc system, noting a 27.5 MW shortfall during monopolar operation. However, spinning reserves and 150 MW of combustion turbine capacity (including new units) ensure no under-frequency load shedding, maintaining system reliability for the Island Interconnected System.
Pole Outages – No Maritime Link Should the Maritime Link component of Phase I of the Lower Churchill Project not proceed, operation of the Labrador – Island Link would be somewhat modified. Under the Maritime Link scenario, System Operatio...
AI summary The document discusses the operational implications of not proceeding with the Maritime Link component of the Lower Churchill Project, emphasizing the need for increased spinning reserve capacity on the Labrador–Island Link to maintain system reliability. It highlights the role of NERC standards in ensuring no load loss from single pole outages and NLH's alignment with these criteria through curtailment strategies.
Bipole Outages The CIGRE statistics for bipole outages of two terminal HVdc systems with one converter per pole are summarized in Table 1. The data indicates an average bipole outage rate varying from zero per year to a high of 0.42 outage...
AI summary CIGRE statistics show bipole outages for HVdc systems range from 0 to 0.42 per year, with durations of 1.03–2.27 hours. Outages trigger curtailments and load-tripping via SPS to prevent blackouts. Restoration under 3 hours is deemed acceptable due to backup generation and import coordination via the Maritime Link.
Table 1 Summary of Frequency and Duration of Forced Bipole Outages 2 Terminal Systems – 1 Converter per Pole Average 1988 – 2008 System Years Frequency Duration – hours Skagerrak 1 & 2 20 0.13 1.03 Square Butte 18 0.42 2.27 CU 20 0.28 1.66...
AI summary The document presents data on forced outages for HVdc transmission lines from 1988 to 2008, highlighting the concerns related to the Labrador – Island HVdc Link due to its length and environmental conditions. The CIGRE statistics do not provide long-term averages, and no system is a direct comparison to the Labrador – Island Link. Table 2 provides 2007–2008 data, but causes of outages are not reported.
Table 3 summarizes the generation supply available on the Island Interconnected System following the loss of the Labrador – Island Link. Table 3 Island Interconnected System Generation Supply for Loss of Labrador – Island Link Maritime Own...
AI summary Table 3 outlines the generation supply available on the Island Interconnected System following the loss of the Labrador – Island Link, listing various generators and their capacities.
Table 4 Isolated Island Interconnected System Generation Generation Capacity East of Bay d'Espoir TL202 and TL206 Outage Owner Type Capacity – MW NLH hydroelectric 8.0 Thermal1 465.5 stand by diesel 0.0 turbine2 combustion 50.0 Newfoundlan...
AI summary Table 4 presents the generation capacity of the isolated island interconnected system, including details on various generators and their capacities in megawatts. NLH and Newfoundland Power are listed as major contributors with hydroelectric and thermal generation capacities.
the 1:25 year design for TL202 and TL206, the probability of unsupplied energy in 2017 for the Isolated Island Scenario is 0.0987 \ 0.04 = 0.00394 or 0.39%. The resultant availability equals 99.6%9 . Table 5 summarizes the exposure levels...
AI summary The analysis compares energy availability and exposure levels under Isolated Island and Interconnected Scenarios, noting reduced exposure in the Isolated Scenario due to capacity additions (e.g., retiring 50 MW Hardwoods CT and building a 170 MW CCCT). The Interconnected Scenario shows rising exposure until 2037 due to delayed capacity additions, though availability remains higher than current Isolated Scenario levels.
rates of all other generating units to derive the LOLH expectation target. Based upon the Strategist ® analysis, the LOLH target is not exceeded until 2036 requiring additional capacity in 2036‐2037. To eliminate the hours of exposure to z...
AI summary The document discusses the LOLH expectation target and the need for additional capacity by 2036-2037. It evaluates the cost and impact of installing combustion turbines to mitigate exposure to unsupplied load during a permanent bipole outage, suggesting incremental additions over time as a more cost-effective approach.
stion turbine plant in stand by on day one. Similarly, the incremental additions provide for a more attractive cumulative present worth cost alternative over the single 800 MW up front stand by plant. By comparison, Table 7 provides the im...
AI summary The text compares the cost-effectiveness of incremental combustion turbine additions versus a single 800 MW standby plant, noting that incremental additions offer a more attractive present worth cost. It also highlights the impact of including the Maritime Link on reducing the number of combustion turbines needed to achieve the same level of exposure to permanent loss of the bipole.
Table 6 Level of Exposure and Unsupplied Energy No Maritime Link 50 MW Combustion Turbines Added Year Load Forecast Island Level of Exposure Availability Unsupplied Energy Standby Load Exceeds % Worst 2 wk Window Generation Generation MW G...
AI summary The table presents data on the level of exposure and unsupplied energy for a 50 MW combustion turbine added without a maritime link, across different years from 2017 to 2037. It includes metrics such as load forecast, generation availability, and unsupplied energy in MWh, highlighting increasing exposure and energy shortages over time.
- 1: 1 x 50 MW CT added - 2: 2 x 50 MW CT added - 3: 3 x 50 MW CT added - 4: 4 x 50 MW CT added - 5: 5 x 50 MW CT added - 6: Hardwoods 50 MW CT retired in 2022 7: 6 x 50 MW CT added 8: 7 x 50 MW CT added 9: Stephenville 50 MW CT retired in...
AI summary The text outlines the addition and retirement of multiple combustion turbine (CT) units, including the retirement of the Hardwoods 50 MW CT in 2022 and the Stephenville 50 MW CT in 2024, alongside the addition of new CTs and a new combined cycle combustion turbine (CCCT) at Portland Creek.
Table 7 Level of Exposure and Unsupplied Energy With Maritime Link 50 MW Combustion Turbines Added Year Load Forecast Island Level of Exposure Availability Unsupplied Energy Standby % Load Exceeds Worst 2 wk Window Generation Generation MW...
AI summary Table 7 analyzes the level of exposure and unsupplied energy with the addition of 50 MW combustion turbines from the Maritime Link. It includes data on load forecasts, generation availability, and unsupplied energy for various years from 2017 to 2037.
n observed icing events in one of the most heavily loaded sections of the HVdc route. For the refined icing event analysis the following periods are extracted for the annual load shape for evaluation: - Based upon the load shape presented...
AI summary The document discusses icing events on the HVdc route, analyzing exposure hours during specific periods (February, April, and December) and their impact on energy availability. The analysis shows that the Maritime Link significantly reduces exposure hours and increases availability when only icing load conditions are considered.
Table 8 Level of Exposure and Unsupplied Energy Known Avalon Peninsula Icing Events No Maritime Link 50 MW Combustion Turbines Added Year Load Forecast Island Standby Generation Level of Exposure Load Exceeds Generation Availability % Unsu...
AI summary The table presents data on the level of exposure and unsupplied energy for the Avalon Peninsula under different icing events scenarios with the addition of 50 MW combustion turbines. It includes metrics such as load forecast, standby generation, availability percentage, and unsupplied energy across multiple years from 2017 to 2037.
- 1: 1 x 50 MW CT added - 2: 2 x 50 MW CT added - 3: 3 x 50 MW CT added - 4: Hardwoods 50 MW CT retired in 2022 - 5: 4 x 50 MW CT added - 6: 5 x 50 MW CT added - 7: Stephenville 50 MW Ct retired in 2024 - 7: 6 x 50 MW CT added - 8: 7 x 50...
AI summary The document lists additions and retirements of 50 MW combustion turbine (CT) units over time, including specific units retired in 2022 and 2024, and ongoing additions from 1 to 9 units.
- 11: Portland Creek at 23 MW and new CCCT at 170 MW Added Table 9 Level of Exposure and Unsupplied Energy Known Avalon Peninsula Icing Events With Maritime Link 50 MW Combustion Turbines Added Year Load Forecast Island Standby Level of Ex...
AI summary The text discusses the addition of a 23 MW Portland Creek and a 170 MW Combined Cycle Combustion Turbine (CCCT) in the context of energy generation and exposure levels. It includes a table showing load forecasts, standby generation, level of exposure, availability, and unsupplied energy for various years, highlighting changes in generation capacity and reliability over time.
city and energy from alternate sources while the overhead HVdc line is being repaired. The question ultimately becomes "to what standard does one build the overhead HVdc line so that it doesn't fail"?
AI summary The text highlights the need to maintain city and energy supply using alternate sources during HVdc line repairs, raising the critical question of the construction standards required to ensure the HVdc line's reliability and prevent failures.
SUMMARY To date the generation planning process incorporates the forced outage rate and associated impacts of the HVdc transmission line between Labrador and the Island portion of the Province along with appropriate capacity and energy sou...
AI summary The generation planning process incorporates forced outage rates and capacity additions for the Labrador–Island HVdc transmission line, ensuring compliance with NERC reliability standards. Low-probability outage events may result in minimal unserved energy (under 0.4% annually), mitigated through load rotation rather than additional combustion turbines to minimize customer costs.
LO WER CHURCHILL PROJECT Document Title: Reliability & Availability Assessment of the H HVdc Island Link Total Number of Pages Incl. Front Sheet 32+6
AI summary The document discusses the reliability and availability assessment of the HVdc Island Link project, focusing on technical aspects related to high voltage direct current transmission lines and their impact on system reliability.
Date: 10-Apr-2012 Prepared by: Peter Anderson 2.1 2.2 2.3 2.4 HVdc Converter Stations HVdc Line HVdc Submarine Cable Electrode Line 7 8
AI summary The document provides a table with sections prepared by Peter Anderson, outlining HVdc components such as converter stations, lines, submarine cables, and electrode lines, with corresponding page numbers.
1.1 Overview of the System This Report presents the results of the reliability and availability analysis carried out to determine the expected performance of the ±350 kV, 900 MW HVdc interconnection between Muskrat Falls and Soldiers Pond...
AI summary This section provides an overview of the reliability and availability analysis for the ±350 kV, 900 MW HVdc interconnection between Muskrat Falls and Soldiers Pond (Island Link). The assessment focuses on the performance of the Island Link and excludes other components such as generation and interconnections outside the link.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Revision Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 2 Figure 1-1: Project Area Map
AI summary The document presents a reliability and availability assessment of the HVDC Island Link project, including a project area map. It includes document numbers, revision details, and a date.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Revision Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 3 1.2 Objectives of the Studies
AI summary The document outlines the objectives of studies related to the reliability and availability assessment of the HVDC Island Link. It references specific document numbers and a revision date, indicating a technical evaluation process.
The objectives of this Reliability and Availability (R&A) Assessment are: - To develop R&A performance indices for the converter stations - To develop R&A performance indices for the HVdc transmission line from Muskrat Falls to Soldiers Po...
AI summary This Reliability and Availability (R&A) Assessment aims to develop and evaluate performance indices for various components of the HVdc transmission system, including converter stations, transmission lines, and submarine cables, as well as assess potential improvements through design enhancements.
This section examines the reliability indicators available for the individual elements within the Island Link: HVdc converter stations, HVdc overhead line, HVdc transition compounds, HVdc submarine cables and electrode lines. An explanatio...
AI summary This section evaluates the reliability indicators for various components of the Island Link, including HVdc converter stations, overhead lines, submarine cables, and electrode lines, with reliability calculations detailed in Appendix A.
2.1 HVdc Converter Stations A major input to this assessment was the information compiled by CIGRE on the performance of HVdc converter stations covering 158 terminal-years over the period 1988-2008[2] and the information contained in the...
AI summary This section discusses the assessment of HVdc converter stations, referencing data from CIGRE and PTI reports. Key performance indicators such as Forced Outage Rate and Forced Unavailability are identified for evaluation.
2.3 HVdc Submarine Cable There is even less information related to the reliability of submarine cables than for overhead dc lines. Cable installations of all types are generally considered to be very reliable since they are installed in a...
AI summary The reliability of HVdc submarine cables is discussed, noting that while they are generally reliable due to being in a protected environment, repairs can be lengthy due to the need for specialized equipment. A spare cable is being installed for the Straits of Belle Isle crossing, with each cable rated to carry rated power and have overload capability.
will still be possible to operate the link at rated power with the unbalance current being handled by the station ground or, at worst, running at reduced power in monopolar mode using metallic return. The electrode line at the Muskrat Fall...
AI summary The document discusses the operational considerations of a power link, including handling unbalance current and potential reliability improvements of an electrode line when mounted on the main DC line rather than on a separate wood-pole line.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 11 associated with the electrode line. Thus the common-mode failure...
AI summary The document discusses the reliability and availability assessment of the HVDC Island Link, focusing on the common-mode failure of electrode line circuits within the bipole system. The impact of such failures is noted to be relatively small.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 12 3 COMPOSITE SYSTEM
AI summary The document presents a reliability and availability assessment of the HVDC Island Link, focusing on the composite system analysis. It includes technical details and evaluations related to the system's performance and reliability.
Table 3-1: Reliability Performance of One Pole of the HVdc Line Element Failure Rate (f/yr) Repair Time (hrs) Downtime (hrs/yr) L1-388 km 0.741 1.78 1.32 C-Submarine cable 0.0022 4,163 9.24 L2-680 km 1.3 1.78 2.31 Total 2.042 6.3 12.87 REL...
AI summary Table 3-1 presents the reliability performance of one pole of the HVdc line, including failure rates, repair times, and downtime for various elements such as L1-388 km, C-Submarine cable, and L2-680 km. The data highlights the reliability and availability assessment of the HVDC Island Link.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 14 The reliability indices for the coincident, independent failure...
AI summary The document discusses the reliability indices for the coincident, independent failure of two poles in parallel within the HVDC Island Link project. It references specific document numbers and dates, indicating a technical assessment of reliability and availability.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 16 maintenance, the link will be operated in mono-polar mode at a p...
AI summary The document discusses the reliability and availability assessment of the HVDC Island Link, noting that during maintenance, the link will be operated in mono-polar mode at a power level up to 150% of rated power per pole on a continuous basis.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Revision Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 18 4 CONCLUSIONS & RECOMMENDATIONS
AI summary This section presents conclusions and recommendations from the reliability and availability assessment of the HVDC Island Link. It discusses the performance and reliability of the system, including key metrics such as reliability and availability, and provides recommendations for improvements.
4.1 Conclusions The provision of a spare transformer of each type and a spare smoothing reactor at each converter station will significantly improve the availability of the converters. This has become common practice in recent HVdc schemes...
AI summary The provision of spare transformers and smoothing reactors at converter stations is expected to enhance the reliability of the Island Link HVdc system. Predicted forced unavailability is approximately 0.1% overall and less than 2.5% for full power capability.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 A-1 Individual Components
AI summary The document presents a reliability and availability assessment of the HVDC Island Link, focusing on individual components. It includes document numbers, dates, and page references, indicating a technical evaluation of the system's reliability.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Revision Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 B APPENDIX B
AI summary The document presents an appendix titled 'Reliability & Availability Assessment of the HVDC Island Link,' which is part of a technical evaluation related to the High Voltage Direct Current (HVDC) transmission system. The appendix includes document numbers, revision details, and a date.
RELIABILITY & AVAILABILITY ASSESSMENT OF THE HVDC ISLAND LINK Revision Nalcor Doc. No.: ILK-SN-CD-8000-EL-SY-0004-01 B1 Date Page SLI Doc.: No. 505573-480A-47ER-0017 00 10-Apr-2012 B-1 CIGRE Historical Data 1988-2008 per Terminal
AI summary The document presents a reliability and availability assessment of the HVDC Island Link, referencing CIGRE historical data from 1988 to 2008 per terminal. It includes document numbers, revision details, and a date, indicating it is part of a technical evaluation process.
2 Terminal Systems - 1 Converter per Pole 2 007 2008 Average 1988-2008 Name Po ole Bipole Pole Bipole Years Pole ole Bipole fp dp fb db fp dp fb db fp dp fb db Skagerrak 1 & 2 1.25 3.1 0 0 2 3.8 0.5 1 20 1.54 17.1 0.13 1.03 Square Butte 1...
AI summary The text presents a table comparing various HVDC systems, including metrics such as forced outage rates (FOR) and forced unavailability (FU) for different systems like Skagerrak 1 & 2, Square Butte, and others. It also includes average values and downtime statistics, highlighting the performance and reliability of these systems.
Labrador-Island Link
AI summary The Labrador-Island Link (LIL) is a proposed High Voltage Direct Current (HVDC) transmission project connecting Newfoundland and Labrador to the Island of Newfoundland, aiming to enhance grid reliability and facilitate renewable energy integration. The initiative involves Nova Scotia Power Marketing Limited (NSPML) and Newfoundland and Labrador Hydro (NLH), with regulatory considerations under the Utility and Review Board (UARB).
1.2 Operations During the fourth quarter of 2025, there were two trip events on the LIL as described in the Rolling 12 for the twelve months ended December 31, 2025. The first event occurred on October 7, 2025, when Pole 1 tripped while in...
AI summary Two trip events occurred on the Labrador-Island Link (LIL) in Q4 2025. The first involved Pole 1 tripping due to a voltage differential, causing an underfrequency load shedding event. The second event saw Pole 1 blocking and tripping, transferring load to Pole 2 with no customer impact. Both incidents were resolved through repairs and relay replacement.
Soldiers Pond Synchronous Condensers Outside of planned outages, the Soldiers Pond Synchronous Condensers ("SCs") have been in continuous operation at all times since the last LIL update, with the exception of one event on SC2 and one even...
AI summary The Soldiers Pond Synchronous Condensers experienced two incidents in 2025: SC2 failed to start due to a loss of excitation fault, and SC3 shut down during maintenance due to LLD trip levels. Both were resolved without customer impact. Hydro's operational data is reported in the Rolling 12 report.
Muskrat Falls Generation As reported in its most recent Rolling 12 report, the Muskrat Falls total plant DAFOR7 performance through the end of the fourth quarter of 2025 was 1.35%, which was significantly better than the Electricity Canada...
AI summary The Muskrat Falls Generation plant achieved a DAFOR of 1.35% in Q4 2025, outperforming Electricity Canada's average of 5.27% for similar units. This highlights superior reliability compared to industry benchmarks.
U.S. Hydropower Market Report
AI summary The U.S. Hydropower Market Report provides an overview of the hydropower sector, including industry trends, technological advancements, and regulatory considerations. It examines market dynamics, capacity utilization, and the role of hydropower in renewable energy integration.
Hydropower in the United States is used extensively for power system flexibility and resilience. - » In many parts of the country, hydropower provides more frequency regulation and reserves than its share of installed capacity. - » In near...
AI summary Hydropower in the U.S. provides significant power system flexibility and resilience, contributing disproportionately to frequency regulation, hourly ramping flexibility, and black start resources despite representing less than 6.7% of total electricity generation capacity.
U.S. hydropower capacity continues to grow through upgrades to existing plants and other types of innovative new projects. - » Hydropower capacity has increased by a net of 431 MW since 2017, with total net growth of 1,688 MW from 2010 to...
AI summary U.S. hydropower capacity grew by 431 MW since 2017, with 1,688 MW total growth from 2010-2019, driven by upgrades to existing plants, new conduit/canal projects, and non-powered dams (NPDs). As of 2019, 1,490 MW from 217 projects were in development, with 93% focused on NPDs and facility expansions.
o NPDs and conduits. » Capacity added from new projects or upgrades to the existing fleet from 2010 to 2019 (2,225 MW) outweighed capacity reductions due to plant retirements or downrates (538 MW).10 5 A plant is defined as a facility cont...
AI summary From 2010–2019, U.S. hydropower capacity grew due to new projects and upgrades (2,225 MW added), exceeding losses from retirements (538 MW). In 2017–2019, 583 MW of new capacity was added, while 215 MW was lost through downrates. Wind surpassed hydropower as the largest U.S. renewable energy source in 2019 (300 TWh vs. 274 TWh).
FERC RELICENSING ACTIVITY SET TO MORE THAN DOUBLE IN THE COMING DECADE — In the past decade, FERC issued 80 relicenses that extended the authorization to operate an additional 30 to 50 years to projects accounting for 17% (6.9 GW) of FERC-...
AI summary FERC relicensing activity is set to more than double in the coming decade, with 281 licenses expiring between 2020-2029, affecting 12% of hydropower and 50% of PSH capacity. The Northeast region hosts the majority of expiring licenses, including small hydropower plants and one PSH facility. Economic factors drive license surrenders, with median project capacity at 0.5 MW.
RELICENSES AFFECT THE OPERATIONAL FLEXIBILITY OF THE U.S. HYDROPOWER FLEET A relicense extends the authorization to operate a hydropower project, subject to compliance with a set of terms and conditions agreed among the licensee and projec...
AI summary Relicensing hydropower projects can alter operational flexibility, with some requiring run-of-river operations (e.g., Claytor, Waterbury, Scotland) or turbine upgrades. While some relicenses restrict flexibility (e.g., ramping rate limits), others enhance it (e.g., Yards Creek PSH). Construction requirements often focus on environmental measures or recreational facilities.
U.S. PSH PROJECTS WITH FERC LICENSES At the end of 2019, three PSH facilities had issued licenses: Eagle Mountain in California, Gordon Butte in Montana, and Swan Lake in Oregon. FERC licensed Swan Lake in April 2019 with a capacity of 393...
AI summary The text details three U.S. PSH projects with FERC licenses (Eagle Mountain, Gordon Butte, Swan Lake), their capacities, construction timelines, and challenges like right-of-way negotiations. It also notes FERC's 2019 preliminary permits and the growing PSH development pipeline, with smaller projects increasingly using closed-loop and abandoned mine sites.
Chapter 3 — U.S. Hydropower in the Global Context GLOBAL HYDROPOWER CAPACITY REACHED 1,150 GW AT THE END OF 2019 — Eighty-four countries have more than 1 GW of installed hydropower capacity and the top six fleets (China, Brazil, European U...
AI summary Global hydropower capacity reached 1,150 GW by 2019, with the U.S. accounting for 7%. China leads, followed by other regions. PSH capacity is 158 GW, with the U.S. at 14%. The development pipeline includes 4,545 projects, mostly in Asia, Africa, and South America.
AT THE END OF 2019, THE GLOBAL DEVELOPMENT PIPELINE INCLUDED 284 PSH PROJECTS WITH A TOTAL CAPACITY OF 226 GW. Figure ES-9 summarizes the regional distribution of the global PSH pipeline. Thirteen countries were constructing 50 PSH project...
AI summary Global PSH pipeline had 284 projects (226 GW) in 2019, with China leading at 102 GW. North America invested $11.6B in R&U for hydropower/PSH, the oldest fleet globally. 90% of global capital expenditures target new plant development, with Asian regions dominating hydropower/PSH investments.
Chapter 4 — U.S. Hydropower Price Trends U.S. FEDERAL POWER MARKETING ADMINISTRATIONS (PMAS) INCREASE PARTICIPATION IN OTHER ORGANIZED ELECTRICITY MARKETS — To better adapt to the ongoing changes in market structure, generation mix, and th...
AI summary U.S. Federal Power Marketing Administrations (PMAs) are increasing participation in competitive wholesale electricity markets like SPP and CAISO. Federal hydropower prices remain competitive with regional wholesale prices, though peaking power prices from SWPA and SEPA exceed regional rates. The median 2018 hydropower PPA price was $48.47/MWh, higher than the overall median of $47.61/MWh. Utilities and corporations, including Microsoft, are key off-takers in hydropower PPAs.
Chapter 5 — U.S. Hydropower Cost and Performance Metrics AFTER TWO YEARS OF HIGH DOMESTIC HYDROPOWER PRODUCTION (~300 TWH) IN 2017–2018, PRODUCTION RETURNED TO A LEVEL CLOSE TO THE 2003–2018 AVERAGE IN 2019 (274 TWH). Canadian imports cont...
AI summary U.S. hydropower production dropped to 274 TWh in 2019 after a peak of ~300 TWh in 2017–2018, with Canadian imports expected to rise due to U.S. renewable standards and new transmission capacity. Small hydropower plants (10–100 MW) had the highest O&M costs ($122/kW in 2018), which grew faster than inflation between 2016–2018. Figure ES-11 highlights O&M cost trends by plant size and age.
IN MULTIPLE ISOs. THE SHARES OF FREQUENCY REGULATION AND RESERVES PROVIDED BY HYDROPOWER ARE MUCH HIGHER THAN HYDROPOWER'S SHARE OF INSTALLED CAPACITY - For instance, in the Pennsylvania- Jersey-Maryland (PJM) Interconnection, hydropower s...
AI summary Hydropower contributes disproportionately to frequency regulation and reserves in ISOs like PJM compared to its installed capacity share. Data from 2014-2019 shows hydropower's reserve contribution declined, while EIA reporting requirements (effective 2018) enabled more detailed analysis. Hydropower provides 40% of U.S. black start resources despite representing <10% of generation capacity.
Chapter 6 — Trends in U.S. Hydropower Supply Chain THE U.S. HYDRAULIC TURBINE MARKET REMAINS DIVERSE AND ROBUST — Almost 12 GW of hydropower and PSH turbine capacity has been installed in the United States since 2010. Seventy-nine percent...
AI summary The U.S. hydropower turbine market has seen 12 GW of installations since 2010, with 79% focused on rehabilitating existing facilities. Five major manufacturers (American Hydro, Andritz, GE, Voith, Toshiba) dominate large turbine production, while Kaplan turbines dominate new low-head projects. The 2015–2019 trade balance was nearly neutral, with Canada and Mexico as top export destinations.
1.1 New Project Development and Capacity Changes (2010–2019) Hydropower capacity in the United States (excluding PSH) increased by 1,688 MW from 2010 to 2019. The net increase was primarily from capacity additions to the existing fleet, bu...
AI summary U.S. hydropower capacity (excluding PSH) increased by 1,688 MW (2010–2019), driven by 562 MW from 119 new plants and upgrades. PSH capacity rose from 20.5 GW to 21.9 GW, with upgrades at six plants, including Northfield Mountain (228 MW increase). Net gains occurred in all regions.
CALLIGAN CREEK The Calligan Creek hydropower plant started operation in 2018 in King County (Washington). The developer of this NSD, PUD No.1 of Snohomish County, submitted a license application in August 2013, and the Federal Energy Regul...
AI summary The Calligan Creek hydropower plant, a 6-MW run-of-river facility in Washington, began operation in 2018. Developed by PUD No.1 of Snohomish County, it received its FERC license in 2015 after construction started in 2014. The project includes a Pelton turbine, weir, fish ladder, and grid interconnection.
1.2 Ownership Changes (2010–2019) FERC has approved 287 license and exemption transfers since 2010 which resulted in ownership changes for more than 300 hydropower plants and three PSH plants. After a period (2012-2017) in which 30 or more...
AI summary FERC approved 287 license transfers (2010–2019), affecting 356 hydropower/PSH plants (6.3 GW total capacity). 95% of transfers occurred between private entities, with notable cases including FirstLight Hydro's affiliate transfers and Eversource Energy's divestiture. Most recent transfers (2018–2019) involved smaller plants, reflecting reduced activity post-2017.
1.3 Investment in Refurbishments and Upgrades (2010–2019) Since 2010, at least $7.8 billion have been invested in R&U to the U.S. hydropower and PSH fleets. In 2017–2019, R&U investments have included dozens of projects in the federal flee...
AI summary From 2010–2019, $7.8 billion was invested in R&U for U.S. hydropower and PSH fleets, with 49 projects ongoing by 2019. Investments were uneven across regions, with Midwest plants receiving disproportionate attention due to the Ludington PSH upgrade. Federal fleets accounted for 47% of hydropower R&U investment, while private owners spent more per kilowatt. The Robert Moses Niagara plant's $1.1 billion R&U initiative highlights ongoing large-scale efforts.
1.4 Relicensing Trends (2010–2019) In the past decade, FERC issued 80 relicenses that extended the authorization to operate an additional 30 to 50 years to projects accounting for 17% (6.9 GW) of FERC-licensed hydropower capacity and 37% (...
AI summary From 2010–2019, FERC issued 80 hydropower and PSH relicenses, extending operations by 30–50 years. Relicensing requires multi-year stakeholder consultation, environmental studies, and compliance with updated regulations, often necessitating significant investments. Project owners may transfer or surrender licenses if relicensing becomes unfeasible financially.
new impoundment dam. For the rest, proposed project facilities included weirs—structures whose main purpose is diverting flow to a canal or penstock ending at the powerhouse rather than storing water. NPDs in the Northeast had the largest...
AI summary The U.S. hydropower development pipeline saw increased NPD projects in the Northeast (26 to 35 from 2018–2019). By 2019, 83 MW of new projects were under construction, with four NPDs and one NSD project accounting for 95% of capacity. Existing plants planned 366 MW of additions, with federal projects leading in expansion. Over half of 129 authorized projects had stalled for three+ years.
than open-loop projects (Saulsbury, 2020). Closed-loop projects can request to use (along with qualifying NPDs) the expedited two-year licensing process introduced by FERC in 2019 as required by AWIA. Proposed new PSH projects have a very...
AI summary The text outlines the U.S. PSH development pipeline, highlighting projects ranging from 5 MW to 4,000 MW, including large proposals like the 4,000 MW Ulysses project. It notes FERC's 2019 issuance of 14 preliminary permits, mentions closed-loop projects using abandoned mine sites, and references AWIA's expedited two-year licensing process for closed-loop projects with NPDs.
dropower Assets dataset, EIA; Other resource types and other countries/regions: IRENA Renewable Capacity Statistics. Note: European Union includes EU27 countries. Labels refer to hydropower capacity. In 2019, hydropower was the largest ren...
AI summary In 2019, hydropower was the largest renewable energy source globally and in major countries like China, Russia, Brazil, and Canada. Wind surpassed hydropower in the U.S. and EU. China led with 326 GW installed capacity, while Brazil's Belo Monte project made it the second-largest hydropower fleet. Mature regions like the U.S. and EU saw slower growth, averaging less than 1% annual capacity increases from 2010–2019.
3.2.2 Global Hydropower and PSH Investment Global hydropower and PSH investment (planned and under construction) amounted to $1.1 trillion at the end of 2019. PSH projects account for 24% of the total. More than 90% of global expenditures...
AI summary Global hydropower and PSH investment reached $1.1 trillion by 2019, with PSH accounting for 24%. Asia dominates expenditures (73% hydropower, 69% PSH), while the U.S. and Canada contribute 4% of global hydropower and at least 20% of PSH investments. Figure 18 (IIR) details regional capital expenditure distribution.
hydropower project owners in countries with different project authorization models (i.e. licenses versus concessions). Authorization duration and renewal processes vary substantially across countries. 24 As an exception, projects under the...
AI summary The text compares global hydropower permitting models, highlighting differences between license-based systems (e.g., U.S. FERC) and concession-based systems (e.g., India, China). It notes U.S. FERC fees tied to capacity and generation, state-level additional charges, and concession models involving royalties based on generation, capacity, or revenue. Reclamation projects require a Lease of Power Privilege instead of FERC licenses.
4. U.S. Hydropower and PSH Price Trends This chapter provides an analysis of trends in hydropower energy prices—both for the federal and nonfederal segments of the fleet—and hydropower asset sale prices. It also presents data on revenue co...
AI summary This chapter analyzes U.S. hydropower and pumped storage hydropower (PSH) price trends, covering federal and nonfederal segments. It examines energy prices, asset sale prices, and revenue composition data from PSH plants, focusing on energy and ancillary services.
4.1 Trends in Hydropower Energy Prices The price of hydropower varies significantly by region, energy market structure, and ownership type among other factors. Federal hydropower is sold by PMAs at cost-based rates; nonfederal hydropower,...
AI summary Hydropower energy prices vary by region, market structure, and ownership type. Federal hydropower is sold at cost-based rates by PMAs, while non-federal hydropower uses PPAs, bilateral contracts, or ISO/RTO markets. Revenue differences arise from ancillary services, capacity components, and environmental attributes, necessitating segmented analysis of U.S. hydropower fleet trends.
4.1.1 Federal Hydropower Prices On average, federal hydropower prices remain competitive with regional wholesale prices. Hydrologic conditions are the key variable that affects the average prices paid by federal hydropower customers. The p...
AI summary Federal hydropower prices remain competitive with regional wholesale prices, influenced by hydrologic conditions. PMAs (BPA, WAPA, SWPA, SEPA) market federal hydropower, with varying allocation methods. SWPA and SEPA offer limited peaking power, while BPA meets full load requirements for customers.
CORPORATE (AND OTHER NON-UTILITY) PPAS FOR U.S. HYDROPOWER International Renewable Energy Agency (2018) estimates that more than half of the 465 TWh of renewable electricity used by corporations worldwide comes from hydropower which is lar...
AI summary The text discusses the limited role of hydropower in current U.S. corporate PPA trends, contrasting historical industrial reliance on hydropower with recent solar/wind dominance. Examples include Microsoft's 50 MW hydropower agreement with Chelan County and Apple's 2014 acquisition of a 3 MW hydro project for a data center.
ervices (frequency regulation, voltage control, spinning or supplemental reserve, black start) ranged between 0.1% (J.S. Eastwood, 2014) and 26% (Helms, 2017) across the plants and periods considered. The mix of ancillary services provided...
AI summary Ancillary service revenue (frequency regulation, voltage control, spinning reserve, black start) varies between 0.1% and 26% across plants. Helms derives most revenue from spinning reserve, Seneca from frequency regulation/voltage control, and ISO-NE plants provide a diversified but low-revenue mix of services.
5. U.S. Hydropower and PSH Cost and Performance Metrics This chapter reports a wide array of metrics regarding hydropower cost and performance. It provides updates on databases of U.S. hydropower construction and O&M costs. Then, it turns...
AI summary The chapter details U.S. hydropower and PSH metrics, including construction and O&M costs, generation trends, capacity factors, availability factors by region and season, and grid reliability contributions through ramping and ancillary services.
5.1.1 Hydropower Approximately $3 billion have been invested in new hydropower plant construction since 2005. Average capital costs were in the $4,000/kW-$5,000/kW range for the various project types, but there was large variability around...
AI summary The text details $3 billion in U.S. hydropower investments since 2005, with capital costs ranging from $2,500/kW to $7,500/kW. Factors like project type, capacity, and hydraulic head influence costs. Low-head projects (avg. $5,059/kW) are more expensive than medium/large-head projects. Small facilities dominate new developments, explaining higher per-kW costs compared to global averages.
r compressed air energy storage (CAES), but there are only two CAES projects installed worldwide (built in 1978 and 1991) versus more than 150 PSH projects. Therefore, PSH is a more mature technology. Schmidt et al. (2019) proposed the lev...
AI summary The text compares PSH to CAES, noting PSH's greater maturity and historical deployment. It references studies showing PSH's cost competitiveness declining by 2025 due to lithium-ion battery advancements, though it remains viable in specific applications. Hybrid systems combining PSH and batteries are proposed to enhance grid services.
counts. They include labor, materials, and overhead associated with operation, supervision, engineering and maintenance of the electric plant and associated structures, and rents from leased property. The capacity-weighted average O&M cost...
AI summary The text details O&M cost variations by hydropower plant size, noting higher costs for smaller plants and economies of scale in larger ones. It highlights the U.S. Department of Energy's efforts to reduce costs through standardization and modularization, and compares EIA's O&M cost assumptions for hydropower with those for wind, solar, and gas plants.
Average O&M costs for the federal fleet are similar to those of the nonfederal fleet FERC Form 1 is required for investor-owned utilities and some public utilities. The two agencies that own more than 90% of federal hydropower (U.S. Army C...
AI summary The text compares O&M costs of federal (U.S. Army Corps of Engineers, Bureau of Reclamation) and nonfederal fleets, noting similarities. Federal agencies' O&M budgets include congressional appropriations and PMA financing. Average costs were $471M (USACE) and $469M (Reclamation) from FY2018–2020, with median plant sizes influencing expenses.
5.3.1 Hydropower Generation and Canadian Imports After two years of high domestic hydropower production (~300 TWh) in 2017–2018, production returned to a level close to the 2003–2018 average in 2019 (274 TWh). Canadian imports contributed...
AI summary Domestic hydropower production in the U.S. decreased from ~300 TWh (2017–2018) to 274 TWh in 2019, returning to the 2003–2018 average. Canadian imports contributed 35–45 TWh of hydroelectricity and are projected to rise in the 2020s due to renewable standards, new Canadian capacity, and U.S.-Canada transmission projects. Regional U.S. hydropower generation showed stability in the Northwest and Northeast but high variability in the Southwest.
EFFECTS OF EXTREME HYDROLOGICAL CONDITIONS ON HYDROPOWER Given drought's unpredictability and its dependence not only on atmospheric variables but also on soil moisture and land surface conditions, the relationship between drought and clim...
AI summary The text examines how extreme hydrological conditions, such as droughts and floods, impact hydropower generation. It highlights the complexity of drought-climate change relationships, the need for downscaled climate models, and projected shifts in hydropower output due to changing precipitation and temperature patterns. Mitigation strategies like operational adjustments and infrastructure investments are discussed.
5.3.2 Pumped Storage Hydropower In 2017, gross PSH generation reached 22,867 GWh, the highest value since 2011. Both 2011 and 2017 were wet years. In 2018-2019, gross PSH generation was ~21,000 GWh. Regional distribution of PSH output has...
AI summary The text provides historical data on U.S. Pumped Storage Hydropower (PSH) generation from 2003–2019, noting peak output in 2003 (27,019 GWh) and a decline to 20,740 GWh in 2019. Regional distribution remains stable, with the Southeast accounting for ~50% of national generation. PSH output is driven more by market signals than hydrology, though hydrologic conditions still influence reservoir filling.
ercentages experiencing drought conditions in the Pacific Northwest and California HUC-2 regions-which contain 55% of installed hydropower capacity in the United States-were 3% in 2006 and 0% in 2011. Figure 40 also shows that every year h...
AI summary The text discusses variations in hydropower capacity factors across U.S. regions, influenced by drought conditions, operational modes, ownership types, and market structures. Northern regions (Northwest, Midwest, Northeast) have higher average capacity factors (43-45%) compared to southern regions (Southwest, Southeast at 27-32%), with resource quality and market dynamics contributing to the disparity.
slightly from year to year. On average, 16% of U.S. hydropower units ≤10 MW, 67% of U.S. hydropower units >10-100 MW, and 76% of U.S. hydropower units >100 MW reported data to NERC GADS in 2005-2018. In 2016-2018, the average number of ava...
AI summary The text analyzes U.S. hydropower unit availability factors from 2005-2018, noting stable large-unit availability, declining medium-unit availability, and variable small-unit availability. It highlights trends in outage types, planned outage increases for large units, and forced outage growth for small units, correlating with hydrologic conditions and data from NERC GADS.
FURTHER ANALYSIS OF HYDROPOWER OPERATIONAL STATUS AND AVAILABILITY TRENDS IS NEEDED The NERC GADS data presented in this section provide a useful high-level breakdown of the operational status of hydropower and PSH units. With a timespan o...
AI summary The text highlights gaps in understanding hydropower and PSH operational trends, including regional differences in planned outages, revenue during Reserve Shutdown, voltage support usage, and market design impacts. It emphasizes the need for further analysis and references the DOE's HydroWIRES initiative to address these questions through case studies and valuation models.
5.6 Hydropower Operation Flexibility Power system flexibility is the ability to effectively cope with variations in the supply or demand of electricity (International Energy Agency, 2019). Mismatches between supply and demand take place at...
AI summary Hydropower flexibility is critical for balancing electricity supply and demand, especially with variable renewables. Flexibility varies by facility design and operational constraints, while increased use for grid services may accelerate equipment degradation. Metrics like ramping, ancillary services, and unit starts are used to assess U.S. hydropower's contribution to grid reliability.
5.6.1 Ramping (hourly frequency) The average and range of one-hour ramps of electricity production performed by the hydropower fleet (including PSH) vary widely across BAs. In 34 out of 36 BAs analyzed, hourly ramps were larger (and their...
AI summary Hydropower (including PSH) exhibits larger and more variable one-hour production ramps compared to natural gas in 34 of 36 BAs analyzed, potentially impacting grid reliability and management strategies.
Variable renewable penetration does not help explain cross-sectional variability in average one-hour ramps across the BAs. Variable renewable energy (solar and wind) penetration is another BA attribute that is useful to investigate in rela...
AI summary The analysis finds no strong correlation between variable renewable energy penetration and cross-sectional variability in average one-hour hydropower ramps across balancing authorities (BAs). Only one of 11 BAs with high hydropower ramping has significant solar/wind penetration. Sub-hourly ramp data, critical for flexibility products, remains uncomputable with available hourly data.
5.6.2 Unit Starts The median number of starts is consistent with one or more cycles per day only for the PSH fleet. In contrast, small units typically start 8 to 12 times per year. The median number of starts for large and medium hydropowe...
AI summary The text analyzes hydropower and PSH unit start frequencies, noting PSH units operate as peaking units with high start rates, while smaller units function as baseload. Trends show decreasing starts for large units and increased starts for medium units between 2013-2016. Data is sourced from NERC GADS, highlighting coverage percentages and operational patterns.
5.6.3 Contribution to Provision of Ancillary Services With increasing variable renewable energy penetration, maintaining the reliability and resilience of the grid, which is underpinned by various ancillary services and dispatchable genera...
AI summary Hydropower's flexibility and ancillary service capabilities are critical for grid reliability with high renewable penetration. While hydropower offers rapid startup, black start, and voltage control, constraints like multi-purpose dams and water availability limit its operational flexibility. PJM and EIA data highlight its technical advantages but note challenges in prioritizing electricity generation.
In ISO-NE, at least two thirds of hydropower capacity receive uplift revenue and provide reserves and voltage control. Market data from ISOs/RTOs help document hydropower's versatility in the provision of grid services. Figure 53 shows how...
AI summary In ISO-NE, two-thirds of hydropower capacity receives uplift revenue for grid services like reserves and voltage control. Market data shows hydropower's role in spinning reserves, regulation, and black start capabilities, with trends linked to solar/wind penetration and NERC standard revisions. Figure 53 (FERC Electric Quarterly Report) illustrates service provision from 2008-2017.
In PJM and CAISO, the shares of frequency regulation and some reserve products provided by hydropower are much higher than the share of installed capacity. In its annual State of the Market Report, PJM provides technology-specific informat...
AI summary The text highlights that in PJM and CAISO, hydropower contributes disproportionately to frequency regulation and reserve products compared to its installed capacity share. In PJM, hydropower's role in reserves has declined recently, though it remains significant for regulation.
6.1 Hydropower and PSH Turbine Installations Almost 12 GW of hydropower turbine capacity has been installed in the United States since 2010. Seventy-nine percent of the 291 turbine installations went toward R&U of existing hydropower facil...
AI summary The text details U.S. hydropower and PSH turbine installations since 2010, highlighting 12 GW of capacity with 79% focused on refurbishments and upgrades (R&U). Five major companies produced large turbines, while Consumers Energy led 41% of replaced capacity through Ludington PSH upgrades costing $800 million, extending the facility's life by 40 years.
6.2 Hydropower and PSH Turbine Imports/Exports For 2015–2019, the U.S. hydraulic turbine trade balance was very close to zero ($279 million imports and $263 million exports). In the past five years, the top three countries from which the U...
AI summary The U.S. hydropower turbine trade balance between 2015–2019 was nearly balanced, with China, Canada, and Brazil as top importers and Canada/Mexico as primary exporters. The Harmonized Tariff Schedule enables detailed tracking of turbine trade, though some small hydropower equipment lacks specific classification.
Glossary Capacity addition – This category, as shown in Figure 2 and Figure ES-2, includes additions of new turbinegenerator units to existing hydropower projects as well as upgrades to existing turbine-generator units that result in an in...
AI summary This glossary defines key terms related to hydropower projects, including capacity addition, conduit, plant downrate, new stream-reach development, non-powered dams, plant refurbishment, retirement, unit upgrades, and expansions, providing clarity on terminology used in regulatory contexts.
PSH Energy Storage Capacity For each PSH plant, energy storage capacity is computed as the product of its generation capacity (MW) and its storage duration (i.e., the number of hours it takes to empty the maximum volume of water in its upp...
AI summary Energy storage capacity for Pumped Storage Hydropower (PSH) plants is calculated by multiplying generation capacity (MW) by storage duration (hours). Data sources include ORNL's Existing Hydropower Assets dataset, the Department of Energy's Global Energy Storage Database, and MWH (2009). For some plants, storage duration was estimated using reservoir volume metrics or assumed conservatively at 4 hours.
NERC Generating Availability Data System The sample size for the NERC GADS dataset is not constant over time. Until 2011, hydropower plant owners were reporting to NERC on a voluntary basis. Reporting became mandatory for units greater tha...
AI summary The NERC GADS dataset's sample size has evolved over time, with mandatory reporting starting in 2012 for units >50 MW and 2013 for units >20 MW. The analysis highlights challenges in data anonymity, segmentation of hydropower vs. PSH units, and the impact of changing sample composition on interpreting availability trends.
Table A1. Selected Electricity Balancing Authorities BA Acronym BA Name NERC Region BPAT Bonneville Power Administration Trasmission WECC CISO California Independent System Operator WECC PJM PJM Interconnection, LLC RFC TVA Tennessee Valle...
AI summary Table A1 lists selected electricity balancing authorities with their acronyms, full names, and NERC regions. This information provides a reference for understanding the structure and geographic distribution of power systems in North America.
11 1.2 Ultimate Limit States - 12 The ULS is outside the CSA standard. This scenario was considered as the governing component of the - 13 LIL is the OPGW, and considering a return period and failure rate on the governing component only do...
AI summary The analysis examines the Ultimate Limit State (ULS) for the Labrador-Island Link (LIL), considering structural failure scenarios beyond CSA standards. By increasing strength factors to maximum limits, the ULS scenario indicates a 1:160-year return period with a 0.48% annual failure rate, highlighting risks to power delivery reliability.
2.2 EFLA's Rime Ice Modelling - 23 To further its understanding of rime ice impacts on the LIL, Hydro subsequently contracted EFLA to - 24 complete weather forecasting modelling of the LIL's Alpine regions, which would be necessary to - 25...
AI summary Hydro contracted EFLA to model rime ice impacts on the Labrador-Island Link (LIL) using historical and forecasting data. The 2020 findings confirmed the original line routing avoided high-exposure areas, resulting in significantly lower rime ice loading (up to six times less) and improved reliability in remote Alpine zones.
3.2 Ultimate Limit State Analysis - The return period and failure rates under an ULS was also considered to provide a more complete picture of the considerations necessary with respect to the LIL reliability. The ULS analysis was undertake...
AI summary The ULS analysis of the LIL infrastructure assesses extreme loading scenarios, identifying a 1:160-year return period and 0.48% annual failure rate. Design differences from typical utility practices are noted, with Hydro asserting that mechanical failures are unlikely to cause extended outages due to buffer capacity. Operational protocols and ice removal techniques are highlighted as mitigation strategies.
4.2 Unbalanced Loading - 13 CSA 60826 suggests that unequal ice accumulations or shedding in adjacent spans will induce critical - 14 out-of-balance longitudinal loads on the supports. This loading can occur either during ice accretion or...
AI summary The text discusses unbalanced ice loading on the Labrador-Island Link (LIL) infrastructure, referencing CSA 60826 standards and Haldar & Associates' recommendations. It highlights discrepancies between CSA guidelines, Hydro's past practices, and the LIL's design, which includes anti-cascading towers. Haldar & Associates argues for deterministic load treatment and further studies due to Labrador's colder climate, increasing ice residence time and risk.
4.3 Wind Speed-Up Factors - 12 CSA provides limited direction on the use of wind speed-up factors associated with local elevated terrain - 13 for line design. According to the Haldar & Associates Assessment, it is expected this will have a...
AI summary The text discusses the impact of wind speed-up factors on line design, noting that CSA standards provide limited guidance on elevated terrain. Haldar & Associates' assessment found potential 30% higher wind loads at Hawke Hill, though existing structures meet criteria. Original designs used site-specific data and reserve capacity, but some areas lack Hydro's operating experience.
4.4 Combined Wind & Ice - 5 CSA provides direction on load case combinations for wind on ice accumulation. Within these scenarios, - 6 the standard provides a low and high range of factors associated with occurrence. Typically, the decisio...
AI summary The text discusses the application of CSA standards for combined wind and ice loading scenarios, emphasizing the need for site-specific analysis in areas with limited operational experience like Labrador. Haldar & Associates recommends using lower load factors where experience exists but advocates for detailed modeling to validate high-range factors in regions with limited data, to avoid over-conservative designs.
1 Based on CSA 60826 (DLS analysis), the as-built design of the LIL reflects a return period of 1:72 years 2 with an associated annual failure rate of 1.10%. Exceeding DLS limits is not expected to result in an 3 extended outage due to maj...
AI summary The analysis of the Labrador-Island Link (LIL) under CSA 60826 highlights reliability risks under Ultimate Load Scenario (ULS) conditions, with a 0.48% annual failure rate and a 1:160-year return period. Hydro advocates for design adjustments based on Haldar & Associates' findings, which identify higher risks of extended outages under ULS scenarios compared to Design Load Scenario (DLS) analysis.
Executive Summary This report presents the impact of two types of icing on the structural reliability of the Labrador-Island Link (LIL) HVdc transmission line. The two types of icing are (a) glaze icing due to freezing precipitation and (b...
AI summary This report evaluates the structural reliability of the Labrador-Island Link (LIL) HVdc transmission line under glaze and rime icing conditions. It assesses failure rates, validates LIL design against CSA 60826-2010, and compares failure rates normalized by line length with operational data. The study informs reliability planning by quantifying outage risks from extreme weather.
1.0 Introduction Newfoundland and Labrador Hydro (NLH) manages approximately 5300 km of transmission line operating at 69 kV, 138 kV, 230 kV, 315 kV, and 735 kV voltage levels. The transmission network system consists of wood pole structur...
AI summary Newfoundland and Labrador Hydro (NLH) operates a vast transmission network with multiple voltage levels, facing operational challenges due to harsh weather conditions like freezing rain, snow, and strong winds, which impact overhead line maintenance in the region.
The Maritime link includes: - The transport power to the west coast of Newfoundland - A submarine cable system to the Maritimes The current study is based on a recent EFLA report entitled "Structural Capacity of as-built Design of the LIL...
AI summary The study evaluates the structural capacity of the Labrador Island Transmission Link (LIL) using an EFLA report and Nalcor documents, with data from NLH engineers. The Maritime link is excluded. High-level data review was conducted without validating design assumptions.
1.3 Historical Information on LIL Review – Critical Data Following the 2011 submission of a Public Utility Board (PUB) document entitled "Generation Expansion Alternatives for the Island Interconnected Electrical System" for the Muskrat Fa...
AI summary The document reviews the historical evaluation of the Labrador Island Transmission Link (LIL) design, noting initial 2011 concerns by the Public Utility Board (PUB) and Manitoba Hydro International (MHI) about inadequate reliability standards. Nalcor's 2018 response claimed compliance with CSA 60826-10 for selected zones, but vulnerabilities in critical LIL sections remain, as highlighted by subsequent reports.
1.6 Scope of this Study This study evaluated the overall line reliability of LIL with respect to the likelihood of failure based on a range of climatological loading scenarios. This report includes the inputs and data from the following re...
AI summary This study evaluates the line reliability of the Labrador Island Transmission Link (LIL) under climatological loading scenarios, incorporating structural capacity assessments, rime icing recalibration, and benchmarking against utility operational data. Findings will inform failure likelihood, repair rates, and outage duration calculations.
1.9 Layout of the Report Section 1 provides a brief historical background of this project and the objective and the primary focus of this study. This section also presents a high-level chronological overview on the Nalcor's submissions to...
AI summary The report outlines a structured analysis of the Labrador Island Transmission Link (LIL) design, focusing on reliability, system planning, and CSA standard compliance. It emphasizes the impact of line length on reliability for a long HVdc radial line, critiques CSA 60826-2010, and benchmarks against NLH's operational experience. Key themes include reliability-based design, transmission planning, and system reliability considerations.
2.1 Power System Hierarchy A typical power delivery system consists of three basic components: generating power plants, transmission lines and facilities, and distribution lines and facilities and the distribution of customer types. Figure...
AI summary The power delivery system comprises generating plants, transmission lines, and distribution lines. Figure 2.1 illustrates the hierarchical structure of the electrical grid and customer distributions, referencing a 2007 Florida Public Service Commission report.
3.2 Introduction – CSA 60826-06/10 Under reliability class of loads, CSA 60826-10 stipulates that extreme ice, extreme wind, two types of combined wind and ice loads, and unbalanced ice load cases be considered in line design. CSA also rec...
AI summary CSA 60826-06/10 outlines reliability design standards for power lines, emphasizing extreme weather load cases, return period values for HV lines, and climatological parameters. It distinguishes between damage limit state (DLS) for reliability analysis and security load failure criteria, noting that DLS violations do not always equate to structural failure. The standard lacks national maps for rime icing, a significant hazard for the LIL line.
651 3.3 Understanding Failure Modes and Determining Reliability of a Transmission 652 Tower The failure of a single member in a tower system does not necessarily result in the failure of the complete system (i.e., the collapse of the tower...
AI summary The failure of a single member in a transmission tower does not necessarily cause the entire tower to collapse due to the high degree of redundancy in the structure. Load redistribution among remaining elements can prevent collapse, even if some members exceed DLS criteria.
3.4 Limit States of Transmission Lines –Examples
AI summary The section provides examples of limit states for transmission lines, focusing on technical criteria and safety margins relevant to power system reliability and infrastructure design standards.
3.4.1 Damage Limit State (DLS) Three 735kv lines run parallel from the Churchill Falls generating station to the Hydro Quebec Montagnasis substation and serve to transport power to the Hydro Quebec system. These lines have experienced seve...
AI summary The text details two incidents (1995 and 1997) where severe icing on 735kV lines from Churchill Falls to Hydro Quebec caused flashovers and outages due to Damage Limit State (DLS) violations. Icing led to ground wire sagging, phase-ground short circuits, and line outages. The 1995 event involved a failed U-bolt, while the 1997 incident required cutting the ground wire to restore power.
Manitoba Hvdro + 500kV HVdc Lines Manitoba Hydro HVDC transmission system consists of three Bipole lines called Bipole I(BP1), Bipole II (BP2), and Bipole III (BP3) respectively. Bipoles I and II were built in the 70's and 80's (?) while B...
AI summary Manitoba Hydro's HVDC transmission system, including Bipole I, II, and III, faces reliability risks from severe weather events. A 1996 microburst caused simultaneous failures of Bipoles I and II, leading to a 2020 MW outage and four-day power restoration. The incident prompted significant R&D investments to mitigate High Intensity Wind (HIW) impacts on transmission infrastructure.
3.6 Review of CSA 60826 (2010) In the CSA standard, the line is considered a system that consists of many major components (subsystems), such as supports, foundations, conductors, insulators, and hardware. Each component can be further bro...
AI summary The CSA 60826 (2010) standard outlines transmission line design, emphasizing system reliability through component strength exceeding weather-related loads, with figures illustrating system hierarchy and connectivity.
. A 1/T - 1/2T approach could lead to the overestimation or the underestimation of the POF value. In addition, the choice of the distribution function can also make this POF estimation quite variable. Gumbel Type 1 distribution of wind spe...
AI summary The text discusses challenges in estimating probability of failure (POF) in structural design, highlighting issues with the 1/T - 1/2T approach, distribution function selection, and validation. It critiques the Gumbel Type 1 distribution's application to wind and ice loads, advocates for log-normal distributions, and identifies gaps in standard design methods for complex structures like towers.
4.0 Loading and Strength of LIL Line Overhead lines are normally designed for two types of loads, (1) reliability (normal) loads and (2) security loads. During the operation of the asset, normal loads—sometimes called probabilistic climato...
AI summary The text discusses the design of overhead transmission lines for reliability and security loads, emphasizing challenges in meteorological data collection, reliance on Environment Canada weather maps, and the impact of under/overestimating wind and ice loads on line reliability and capital costs.
4.3 Wind Loads The design wind speed and pressure used in the reliability analysis are based on CSA 60826-10 for 50, 150, and 500-year return period values and is presented in Figure 4.8. $\begin{array}{c} 1047 \\ 1048 \end{array}$ Figure...
AI summary The section outlines wind load design parameters for reliability analysis, referencing CSA 60826-10 standards for 50, 150, and 500-year return periods. It includes figures detailing wind pressure ratios and rime ice data from numerical weather models, citing EFLA reports from 2020 and 2021.
4.5 Unbalanced Ice Loads Apart from direct climatological loads (transverse and vertical), the line is also exposed to loads arising from differential ice loads. These loads arise from non-uniform ice formation or ice shedding, when ice dr...
AI summary The text discusses unbalanced ice loads on transmission lines, emphasizing the dynamic nature of ice shedding and its impact on structural integrity. It critiques deterministic methods for oversimplifying the phenomenon, advocates for stochastic analysis, and references CSA 60826-10 and CEATI studies. NLH's long-term use of deterministic approaches is noted, alongside the need for probabilistic modeling to address uncertainties.
4.5.1 Brief Review of Design Philosophy for Unbalanced Ice Loads including NLH's Design Brief In Newfoundland and Labrador Hydro (NLH), unbalanced ice loads have always played a significant role because of the harsh environment and towers...
AI summary NLH's design philosophy for unbalanced ice loads emphasizes conservative load considerations, including full and partial ice thickness scenarios, and evolved from historical practices (SAE towers) to modern standards (e.g., NLH A1-2200-T-546). Load combinations for all phase configurations are analyzed to ensure structural safety.
4.6.1 Characteristic Capacity The characteristic capacity $(R_c)$ of a component is determined based on an exclusion limit of e%, and for a normal distribution $$R_c = \overline{R} (1 - k_\alpha V_R) \tag{4.2}$$ where $\overline{R}$ define...
AI summary The characteristic capacity (R_c) is calculated using a formula involving mean strength, a factor for exclusion limits, and coefficient of variation, with 90% confidence that strength exceeds R_c, as illustrated in Figure 4.10.
5.1 LIL Modelled as a Series System The LIL is modelled as a series system and the system acts as a "weak link" because the system fails and may lose its functionality if one of the line element fails. The series system model is described...
AI summary The Labrador Island Transmission Link (LIL) is modeled as a series system where failure of any component leads to system failure. Reliability is analyzed using N-1/N-2 criteria, with equations for upper and lower bounds of failure probability based on Cornell (1967). Mechanical failures can cause prolonged outages despite electrical redundancy.
5.1.1 Correlation Issue – Among Key Elements Figure 4.7 presents the element layout diagram used to determine the correlation value of a typical segment. Ten key elements are considered for two sub-systems. The selection of ten elements is...
AI summary The text discusses a correlation study among key system elements under extreme ice load conditions, highlighting a correlation value generally above 0.90. It outlines reliability analysis methods, including mathematical bounds for failure probabilities across multiple load cases and subsystems, referencing diagrams and equations for calculation.
rs may not survive should they encounter the specific load combination of OPGW and Pole conductor shedding simultaneously. It is to be noted that industry's current best practices are to take at least one OPGW and one phase conductor in lo...
AI summary The analysis evaluates the Labrador Island Transmission Link (LIL) reliability under NLH design criteria, highlighting concerns about load combinations of OPGW and conductor shedding. It notes NLH's robust design practices for UBI and recommends checking critical towers using NLH load combinations in future LIL reliability studies.
1612 Table 6.1 Various Assumptions Made in Determining the LIL POF/Reliability (Component 1613 to System) Level Scenario Description Remarks 1 1 (No regional grouping, full correlation along the entire Can be compared directly to line leng...
AI summary Table 6.1 outlines various assumptions made in determining the Long International Line (LIL) probability of failure (POF)/reliability, including different scenarios related to regional grouping, correlation, and exposure levels. The table references CSA 60826-10 and discusses the comparison of POF with CSA 60826 Table A2 in equivalent terms due to differences in assumptions.
7.0 Sensitivity Study This section presents the sensitivity of some key parameters regarding the load effects and strength on LIL POF and reliability. In section 1, the author listed several issues that were raised through RFI process. Upo...
AI summary This sensitivity study evaluates key parameters affecting load effects and reliability of the Labrador Island Transmission Link (LIL) power outage frequency (POF). Case studies assess terrain roughness, wind speed, ice loads, and uncertainties in rime ice predictions. Collaboration with NLH is noted, with item 3 excluded due to WRF model alignment with CSA standards.
7.1 Terrain Roughness To address the effects of terrain roughness (Type B vs. Type C) and topographical issue with respect to "wind speed up effect", the profile of the line on the top of the Hawke Hill is selected. This site is 25km of we...
AI summary The analysis examines terrain roughness (Type B vs. C) and topographic effects on wind load at Hawke Hill, focusing on tower S5-494. CSA 60826-10 defines wind speed calculations, with Nalcor using terrain type C (factor 0.85) for LIL design. The study highlights increased failure probability under Type B terrain but deems it acceptable. The site's open exposure justifies Type B classification despite prior line failures.
7.2 Uncertainty on the topographical effect on LIL design Lines are normally designed for two primary classes of loads (1) reliability class and (2) security class. Under reliability class of loads, structures and major line components are...
AI summary The text discusses the impact of topographical effects on the design of Long International Line (LIL) transmission systems, highlighting how wind speed-up effects in hills, valleys, and mountains can significantly increase wind and combined wind-ice loads on support structures. Current design standards like CSA 60826-10 do not account for these topographic effects, which can lead to increased risk of failure. The study by Bitsuamlak et al. (2015) recommends assessing these effects for specific terrain configurations.
7.4.1 Review Literature and show the effects on Thickness (Reduction in Transverse Load) Clause 6.3.4.1 of CSA states that an ice load adjustment can be made if the cable diameter is different than the diameter of rod that was used in the...
AI summary The text discusses adjusting ice load calculations for cables with diameters different from the standard 25mm rod used in CSA maps. A Kd factor of 1.33 is applied, and studies show larger cables have less ice accretion. Environment Canada simulations confirm a 30% reduction in icing for a 56.9mm conductor compared to CSA predictions, impacting design ice thickness for LIL lines.
7.5 Underestimation of OPGW Icing Clause 6.3.4.1 suggests considering equivalent conductor load in the design of OPGW in the same span. Research by McComber et al and others (2001) have shown that the OPGW cable has lower torsional rigidit...
AI summary Research by McComber et al (2001) indicates that OPGW cables, with lower torsional rigidity than pole conductors, accrete more ice initially but may catch up over time. Designing OPGW to the same ice thickness as conductors is currently considered best practice, though further field validation is needed. Alternative mitigation strategies, such as increasing torsional rigidity at critical points, are suggested as cost-effective solutions.
7.6 Rime Icing on LRM – (EFLA & KVT Study, Full Effects of Topography and Terrain Characteristics) Several studies have been presented as part of this LIL project to assess rime ice loads on the LIL. As reported in Section 4, the recent st...
AI summary The section discusses studies on rime ice loads for the Labrador Island Transmission Link (LIL) using the WRF model, noting the use of USGS landuse data but omission of topographic effects like escarpments. The author recommends a separate study for glaze icing.
8.3.1 East Coast Failures (Avalon Peninsula, Haldar 1988, 1996, 2006) The line failures on the Avalon Peninsula occurred in 1970, 1984, 1988, and 1994 (Haldar, 1995). Figure 8.3 depicts the observed glaze ice sample on conductor during the...
AI summary The Avalon Peninsula experienced multiple transmission line failures between 1970 and 1994 due to ice overload, leading to conductor/hardware failures and cascading outages. Design weaknesses and underestimated ice loads (up to 50mm radial glaze ice) were identified, prompting a revision of design standards to 63mm ice thickness. Failures included bridge collapses, tower failures, and significant repair costs, highlighting systemic infrastructure vulnerabilities.
8.5.1 Line from a Canadian Utility To compare the reliability of LIL with other utility lines, the author decided to benchmark the structural reliability of an important line in Canada. This is a line from a 700 MW generating station in No...
AI summary The reliability of a 700 MW Canadian transmission line (connected to a 230kV grid) was benchmarked against the Labrador Island Link (LIL). Analysis using CSA 60826-10 showed low annual failure probability with high safety margins, attributed to security-load-driven design rather than reliability-based factors. Four load scenarios (ice, wind, combined, unbalanced ice) were evaluated.
03/year/100km based on the assumption that 10% of these EHVAC faults are permanent. Although the repair time could vary between couple hours to week, an average time of 24h is suggested in this paper. A further review of the Linden et al p...
AI summary The text discusses estimating DC line failure rates using EHVAC data from a CIGRE paper, noting the lack of similar data for EHVDC lines and challenges in direct comparison due to limited data. Estimates range from 0.003 to 0.025 per year per 100 km for EHVAC lines, but comparable data for EHVDC remains scarce.
hese violations under DLS can create safety hazard and other serviceability problems, and if not controlled or mitigated may lead to LIL outages because of the failure of the support and wire systems. Results presented in Table 6.2 only re...
AI summary The text highlights structural inadequacies in the Labrador Island Transmission Link (LIL) under unbalanced ice (UBI) loads, violating design criteria and posing risks of outages. It recommends presenting a report to the Public Utilities Board (PUB) with follow-up work, including evaluating failure rates under Ultimate Limit State (ULS) criteria, to ensure system reliability.
9.2.1 Probability of Failure (POF) -DLS Based on our study we find the POF of LIL can range from little over 1% for Scenario # 1 to 5% for Scenario # 4D (Table 6.2). Each scenario considers a set of assumptions and these are presented in T...
AI summary The study evaluates the Probability of Failure (POF) for the Labrador Island Transmission Link (LIL) under four scenarios, ranging from 1% to 5%. Key factors include icing types, weather zones, and correlation assumptions. The LIL's reliability is emphasized as distinct due to its length, power transfer capability, and exposure to two icing types. The cable system is identified as weaker than structural supports, contradicting industry practices. Reducing unavailability requires improved monitoring and maintenance.
9.2.2 Probability of Failure (POF) -ULS at a High Level A high level Ultimate Limit State (ULS) analysis for cable systems provides a relative comparison of the risk levels between DLS and ULS and shows that POF under ULS is almost forty-t...
AI summary A high-level ULS analysis shows POF under ULS is 43% of DLS risk, translating to a 160-year return period. The LIL design is vulnerable to ice shedding, failing CSA and Hydro standards, with weaknesses in load combinations for unbalanced ice loads, particularly in Labrador's harsh environments.
9.3 Recommendations Based on this study, the decision to make appropriate generation expansion study should not be done strictly based on DLS criteria satisfying CSA 60826-10 rather by doing a full ULS analysis of the structure-cable syste...
AI summary The study recommends moving beyond DLS criteria (CSA 60826-10) for generation expansion studies, emphasizing the need for a comprehensive ULS analysis of the structure-cable system and its impact on LIL failure rates. Current ULS assessments lacked consideration of system coupling effects, necessitating future studies to refine LIL POF calculations.
c Icing of Structures (IWAIS), Choongqing, China, May,8p. • Haldar, Asim 2009 Assessment of Optimum Design Return Period of a ± 450kv HVDC Line, Nalcor Report ##, WTO# 1081, Prepared for LCP project • Haldar, Asim, Veitch, Maria, Andrews,...
AI summary The text lists technical studies and reports on transmission line reliability, HVDC systems, and ice monitoring, including works by Asim Haldar and others. References include CIGRE SCB2 and Nalcor reports related to the Lower Churchill Project.
Short Biography of Dr. Asim Haldar, P.Eng. Asim Haldar received his Master's in Structural Engineering and Ph. D in Ocean Engineering from Memorial University of Newfoundland in 1977 and 1985 respectively, with a specialization in behavior...
AI summary Dr. Asim Haldar, a retired Nalcor Energy engineer, has 41 years of experience in utility engineering, specializing in HV line design, ice load monitoring, and offshore structures. He developed the RIGD ice sensor, led major transmission projects, and contributed to international committees like CIGRE and CEATI. His work includes R&D, publications, and conferences on EHV line design and asset management.
Quarterly Report on Asset Performance in Support of Resource Adequacy For the Twelve Months Ended December 31, 2025 February 5, 2026 A report to the Board of Commissioners of Public Utilities
AI summary A quarterly report on asset performance for resource adequacy, submitted to the Board of Commissioners of Public Utilities, covering the twelve months ended December 31, 2025. The report provides data on asset reliability and availability to support regulatory assessments of resource adequacy.
Quarterly Report on Asset Performance in Support of Resource Adequacy for the Twelve Months Ended December 31, 2025 - 3.03%. The DAFOR value was based on historical data reflective of Hydro's maintenance program over - the long term. - For...
AI summary The report analyzes forced outage rates (FOR) for hydroelectric facilities, noting that Muskrat Falls uses historical data for near-term rates, while long-term planning assumes regulated maintenance standards. Holyrood TGS's reliability concerns under standby operations necessitate DAUFOP over DAFOR, with a 20% FOR recommendation and 34% sensitivity. Operations remain base-loaded due to LIL's early-stage performance.
4.2 Paradise River Facility - 10 The Paradise River unit DAFOR of 2.84% for the current period is above the near-term planning analysis - 11 value of 2.50% but is below the resource planning analysis value of 3.03% for an individual hydrau...
AI summary The Paradise River Facility's DAFOR of 2.84% exceeds near-term planning analysis values (2.50%) but remains below resource planning analysis thresholds (3.03%). The elevated rate resulted from four forced outages, with no additional outages since the last filing.
6.2 Holyrood TGS Unit 3 - Considering individual thermal unit performance, the DAFOR of 32.75% for Unit 3 at the Holyrood TGS is - above the near-term and resource planning analysis value of 20.00% for a unit at the Holyrood TGS and "2024...
AI summary Holyrood TGS Unit 3 has a DAFOR of 32.75%, exceeding the 20% planning target due to extended outages from March 2025 to December 2025, including forced maintenance and an external crane failure. Return to service is scheduled for mid-February 2026.
7.2 Holyrood Combustion Turbine - 9 The Holyrood CT DAUFOP was 25.13% for the current period, which is above the near-term and resource - 10 planning analysis value of 4.90%. This decline in performance is the result of forced outages, as...
AI summary The Holyrood Combustion Turbine's performance is below expected standards, with a DAUFOP of 25.13%, significantly higher than the planning value of 4.90%. This is attributed to forced outages, including an unexpected extension of maintenance from October 27 to November 12, 2025.
Appendix A Soldiers Pond Synchronous Condensers
AI summary Appendix A references 'Soldiers Pond Synchronous Condensers,' likely detailing technical specifications or project information related to this facility. The inclusion of an image suggests visual context for the condensers' design or operational parameters.
Table A-1: Quarterly Rolling 12-Month Operating Hours for Soldiers Pond Synchronous Condensers ("SC") Unit Operating Hours1 % Availability2 SC1 8,091.02 92.36 SC2 8,284.37 94.57 SC3 7,813.33 89.19 1 Further information on the operation of...
AI summary Table A-1 provides quarterly rolling 12-month operating hours and availability percentages for the Soldiers Pond Synchronous Condensers (SC1, SC2, SC3). SC2 had the highest operating hours and availability at 8,284.37 hours and 94.57%.
Quarterly Report on Asset Performance in Support of Resource Adequacy for the Twelve Months Ended December 31, 2025, Appendix B
AI summary This document is a quarterly report on asset performance supporting resource adequacy for the twelve months ending December 31, 2025, presented as Appendix B. It likely details generator availability, outage rates, and reliability metrics critical to Nova Scotia's electricity system.
Quarterly Report on Asset Performance in Support of Resource Adequacy for the Twelve Months Ended December 31, 2025, Appendix B - power control issues on the LIL. The OEM identified the root cause of the issue to be a manufacturing - defec...
AI summary The text discusses power control issues on the Labrador-Island Link (LIL) due to a manufacturing defect in fiber optic cables affecting six DCCTs at the Muskrat Falls HVdc Converter Station, which have been replaced. GE has proposed a revised plan involving a new DCCT provider and contractual spares, with Hydro collaborating to mitigate the issue.
LIL Strengthening Overview January 2026
AI summary The document provides an overview of efforts to strengthen the Labrador-Island Link (LIL) in January 2026, focusing on enhancing transmission infrastructure and reliability for the power grid. The context highlights technical and regulatory considerations for interregional energy connectivity.
2.0 Background - Line L3501/2 is the 350 kV High Voltage direct current ("HVdc") overland transmission line portion of the - LIL, traversing approximately 1,100 km through three major meteorological loading zones, referred to as - average,...
AI summary The document describes the 350 kV HVdc transmission line (L3501/2) as part of the Labrador-Island Link (LIL), detailing its route, structure, and design considerations, including meteorological loading zones and tower types.
Optimizing Clamp Designs - Three alternative suspension clamps were installed on the electrode conductor at 10 structures in 2024, - and will be inspected annually for performance. These alternative clamp designs are intended to reduce - s...
AI summary The document outlines the installation of alternative suspension clamps on electrode conductors and OPGW assemblies to reduce stress from oscillations and ice loading. An ice study informed updated design loads, leading to tower reinforcement plans. Redesigned clamps and modified tower structures aim to improve system reliability and mitigate overloading risks.
5.0 LIL Strengthening Capital Project (2026–2028)
AI summary Section 5.0 outlines the LIL Strengthening Capital Project (2026–2028), aimed at enhancing the Labrador-Island Link's reliability, capacity, and resilience. The project involves infrastructure upgrades to ensure grid stability and support growing energy demands in the region.
5.2 Recommended Alternative - The recommended alternative is the Reinforcement and Re-design of OPGW Peaks and EL Crossarms - with Re-design of the EL Assembly for most sections, with two exceptions. The combination of these - alternatives...
AI summary The recommended alternative involves reinforcing and redesigning OPGW peaks and EL crossarms, with exceptions in sections of southern Labrador due to higher icing and absence of electrode conductor. Installing new sections is deemed more cost-effective than reinforcing existing ones. Exceptions include removing EL conductor from towers in specific areas and redesigning only OPGW peaks where electrode conductor is absent.
5.3 Scope of Work - The project scope includes procurement and installation work on a total of 309 Type A1 towers, as - follows: - Replacement of OPGW peaks, EL crossarms, and EL assemblies for 186 towers: - o 18 A1 towers from structure 1...
AI summary The project involves replacing OPGW components and reinforcing towers across specific line sections, prioritizing areas with past failures. Material procurement includes reinforcement for ice load risks, with repairs deemed non-urgent due to no outage risk. Selection criteria prioritize sections with multiple past events.
LIL Engineering Study – Mid-Span Structure Addition Report Newfoundland and Labrador Hydro Report No. ILK-TT-CD-6200-TL-H15-0003-01 TT Document Number 705-2579500100-REP-G0002-00 May 23, 2025
AI summary The document is a technical report titled 'LIL Engineering Study – Mid-Span Structure Addition Report' submitted by Newfoundland and Labrador Hydro. It provides engineering details related to the Labrador-Island Link (LIL) project, focusing on infrastructure modifications.
3.4.1 Wind and Weight Span Overstresses are observed in the peak, electrode cross-arms, and the cage above the pole compression chord connection, therefore the OPGW and electrode loads are most relevant. The OPGW and electrode wind & weigh...
AI summary The analysis identifies overstressing in OPGW and electrode components due to wind and weight spans. Existing and modified span lengths are compared, showing significant reductions when mid-span structures are added. The OPGW wind/weight spans are presented as representative of electrode spans, with visual comparisons in Figure 5.
3.7 REINFORCED MODEL OVERSTRESSES
AI summary Section 3.7 discusses the issue of a reinforced model being overstressed, potentially impacting system reliability or capacity. The context includes technical and regulatory terms related to energy systems, but no specific claims or arguments are detailed in the provided text.
Appendix C LIL Engineering Study – A1 Electrode Suspension Assembly
AI summary Appendix C contains an engineering study titled 'LIL Electrode Suspension Assembly,' referencing images related to technical components. No substantive text is provided beyond the heading and image placeholders.
3.7 OPTION 2 PERMISSIBLE INCREASE The tower type A1 reinforcement scope showed significant overusages in most of the electrode cross-arm members that are not easily addressed with reinforcement. For this reason, it is more economical to de...
AI summary Option 2 for tower reinforcement prioritizes cross-arm replacement over reinforcement due to overusage in electrode cross-arm members. The permissible increase is 325 mm, governed by maximum wind swing cases, with potential for an additional 50 mm if the climbing bolt is removed, as confirmed by NL Hydro.
5.0 OPTION 1 DESIGN The design solution for option 1 to meet the permissible insulator length increase of 295 mm is to add a socket ball extension SLACAN catalogue no. 63149 between the bottom insulator and the socket tongue, see Figure 8....
AI summary Option 1 design addresses a 295 mm insulator length increase by adding a socket ball extension (SLACAN 63149) between the bottom insulator and socket tongue, ensuring compliance with 350 kV HVdc technical specifications. This requires replacing the arcing horn to maintain spark gap geometry, with design details in Appendix C.
8.0 CONCLUSIONS The two proposed options meet the required minimum electrical clearances and improve the performance issues seen on the electrode. The primary means of improvement is to increase the insulator length available to balance lo...
AI summary Two options improve electrical clearances and insulator performance on the electrode by increasing insulator length and avoiding conductor contact. Option 1 requires minimal construction, while Option 2 adds insulator capacity. The LIL Engineering Study (A1 Electrode Suspension Assembly) is referenced, with Newfoundland and Labrador Hydro as the entity involved.
APPENDIX B: NEW HARDWARE CUTSHEETS LIL Engineering Study – A1 Electrode Suspension Assembly Newfoundland and Labrador Hydro
AI summary Appendix B includes new hardware cut sheets and references a LIL Engineering Study on an electrode suspension assembly by Newfoundland and Labrador Hydro. The document contains technical figures and engineering details related to power infrastructure.
LIL Engineering Study – Calculations for OPGW Peak Reinforcement Newfoundland and Labrador Hydro Report No. ILK-TT-CD-6200-TL-H15-0002-01 TT Document Number: 705-2579500100-REP-G0003-00 July 21, 2025
AI summary This document is a report from Newfoundland and Labrador Hydro titled 'LIL Engineering Study – Calculations for OPGW Peak Reinforcement,' dated July 21, 2025. It outlines engineering calculations related to reinforcing the Optical Ground Wire (OPGW) for the Labrador-Island Link (LIL).
LIL Engineering Study - Calculations for OPGW Reinforcement Newfoundland and Labrador Hydro Figure 2: OPGW Peak Model for Towers A4 and B1 - a) Isometric View - b) Plan View
AI summary The LIL Engineering Study details calculations for OPGW (Optical Ground Wire) reinforcement, including visual representations of the OPGW Peak Model for Towers A4 and B1. The study is conducted by Newfoundland and Labrador Hydro.
Analysis of Removing the Electrode Conductor from L3501/2 May-2025
AI summary The document outlines an analysis regarding the removal of the electrode conductor from L3501/2, likely within the context of a regulatory proceeding related to power generation or grid infrastructure in Nova Scotia.
er types (A1, A2, A3, A4, B1, B2, C1, C2, D1, D2, and E1) were designed to meet the loading requirements, which consist of a specified wind load, ice load, and combination of both applied to the line. There have been a number of failures t...
AI summary Transmission line failures in central Labrador (2021, 2022) caused damage to electrode crossarms and conductors due to unbalanced ice loads exceeding design specifications (50 mm radial glaze ice). Events involved ice thicknesses of 54-72 mm, with damage attributed to ice shedding on A1-type towers.
percentage of structure failures range between 40% to 82% as the unbalanced increases. - on EL1, EL2, P1, and P2 there are no structure failures. Under unbalanced ice load (UBL) with 70 mm of ice: - structures with the electrode: - the per...
AI summary The text analyzes structure failure rates under unbalanced ice loads (UBL) with and without electrodes. Structures with electrodes exhibit significantly higher failure rates (up to 100%) compared to those without (lower rates, especially on EL1, EL2, P1, P2). Removing electrodes in certain sections reduces failures, highlighting reliability benefits.
1.1 900 MW Test and Software All software functionality required for operation up to 900 MW was proven and accepted as satisfactory during pole overload tests in winter 2023 prior to April 2023 commissioning; however, as committed, 1 "Newf...
AI summary The document outlines the status of 900 MW pole overload tests for the Labrador-Island Link (LIL), including completed winter 2023 testing, planned fall 2024 tests, and prerequisites like system conditions and risk mitigation. It also addresses software upgrades, grounding studies, and equipment replacement timelines.
NON-CONFIDENTIAL 1 Request IR-22: 2 3 Please refer to Exhibit N-1, Attachment 1, page 35 lines 10-12. Did the Witness quantify the 4 "value" of the Muskrat Falls assets to "customers?" If so, please provide that analysis and 5 supporting w...
AI summary The request (IR-22) inquires whether the witness quantified the value of Muskrat Falls assets to customers. The response clarifies no quantitative analysis was conducted, but qualitative benefits such as fuel price stability and reduced fossil fuel exposure were highlighted as key customer advantages.
N-4NSPML (IG) RIRs 1-26 - Redacted
70 passages
PARTIALLY CONFIDENTIAL - Capacity of the NS Block has been at a level that allows NS Power (and now the IESO-NS) to treat the NS Block in the same manner as its other generation assets for short-, mid- and long-term planning. Yes, there ha...
AI summary NSPML argues that the NS Block's capacity is integrated with Nova Scotia's generation assets, resulting in minimal outage impacts and benefits exceeding costs. It notes that planned outages by NLH during non-winter periods have not caused system outages and that the holdback is tied to the Lower Churchill Project's performance.
third party in connection with the March–April 2024 29 icing event, including any findings comparing actual weather conditions to design criteria and 30 any recommendations for design upgrades. 1 2 3 A. a) Line L3501/2 is the 350 kV HVdc o...
AI summary The third party inquired about the March–April 2024 icing event's impact on the 350 kV HVdc transmission line L3501/2, including design criteria comparisons and upgrade recommendations. The line spans 1,100 km through three meteorological zones, with 19 loading zones and 11 tower types. Damage occurred to specific towers during the incident.
ds and utility experience. Structure numbers that sustained damage 10 during the April 2024 incident are str. 1218–1228 and 1232, located on the south coast of Labrador in an average loading zone.1 11 12 The main root cause of the damage t...
AI summary Structural damage to power line L3501/2 occurred due to ice loads exceeding design specifications (100–125 mm radial ice) and potential galloping-induced cyclic loading. The incident, located on Labrador's south coast, prompted a 2024–2025 capital project to implement mitigation measures, with CSA 22.3 No. 60826 referenced for load standards.
Appendix A: Summary of all Failure Investigation Recommendations Appendix B: LIL Engineering Study – Mid-Span Structure Addition Report Appendix C: LIL Engineering Study – A1 Electrode Suspension Assembly Appendix D: LIL Engineering Study...
AI summary The document includes appendices summarizing failure investigation recommendations and engineering studies related to the Lower Island Link (LIL), including mid-span structure additions, electrode suspension assemblies, OPGW peak reinforcement calculations, wood pole and mid-span cost estimates, and analysis of removing an electrode conductor.
1.0 Introduction - The Labrador-Island Link ("LIL") is an important transmission line for the provincial energy grid due to its - power carrying capacity that is used to deliver a large portion of the winter peak energy and demand to - the...
AI summary The Labrador-Island Link (LIL) transmission line has experienced ten failures over five years due to icing-related overloading. Investigations identified root causes and led to a 2026–2028 capital project to strengthen the line through infrastructure upgrades, including ice monitoring, tower modifications, and electrode conductor reconfiguration to enhance reliability and reduce failure risks.
5.1.4 Reinforcement and Re-design of OPGW Peaks and EL Crossarms - This alternative would include replacing the existing electrode crossarms and OPGW peak with new - reinforced sections and adding reinforcing members to the existing cage....
AI summary This section discusses reinforcing OPGW peaks and EL crossarms with new reinforced sections and additional members to address ice load issues from past events. The reinforcement can be installed during monopole outages at a relatively low cost per structure, though it does not resolve electrode conductor failures. Estimated costs are $36,000 per structure for both components and $29,000 for only the crossarm.
LIL Engineering Study – Mid-Span Structure Addition Report Newfoundland and Labrador Hydro Report No. ILK-TT-CD-6200-TL-H15-0003-01 TT Document Number 705-2579500100-REP-G0002-00 May 23, 2025
AI summary This document is a report on the LIL Engineering Study focusing on the addition of a mid-span structure. It is authored by Newfoundland and Labrador Hydro and dated May 23, 2025. The report likely addresses infrastructure planning and grid modernization related to the Labrador-Island Link (LIL) project.
3.4.1 Wind and Weight Span Overstresses are observed in the peak, electrode cross-arms, and the cage above the pole compression chord connection, therefore the OPGW and electrode loads are most relevant. The OPGW and electrode wind & weigh...
AI summary The text analyzes structural stresses in OPGW and electrode systems, noting overstresses in peak areas and compression chords. It compares wind and weight spans under existing and modified mid-span structure configurations, showing significant reductions in span lengths when structures are added, as illustrated in Table 8 and Figure 5.
2.0 WORK COMPLETED TO DATE Extensive study of the performance issues has previously been completed by NL Hydro and the root cause of most of the issues is that the line has experienced weather loading events that exceeded the initial desig...
AI summary The line L3501/2 experienced performance issues due to weather loading events exceeding initial design assumptions, primarily caused by electrode suspension longitudinal loading during icing events. Reports from 2021 and 2024 detail the damage and root causes, including unbalanced ice accumulation and shedding.
3.0 PERMISSIBLE LENGTH INCREASE The length that the electrode suspension insulator string can be increased is dependent on the required electrical clearances, minimum separations to pole conductors, and existing tower geometry. The main in...
AI summary The permissible length increase for electrode suspension insulator strings depends on electrical clearances, conductor separations, and tower geometry. Key inputs include drawings ILK-JY-SD-6200-TL-D99-0012-01-A3 and ILK-SN-CD-6200-TL-DD-0112-01-C4. Inspections of NL Hydro's PLS-CADD models focus on damaged tower ranges (e.g., 244-340, 342-388) to assess as-built conditions for 239 A1 towers.
3.3 TRANSVERSE SWING UNDER MAXIMUM WIND SWING The transverse swing angle on the tower type A1 electrical clearance drawing ILK-JY-SD-6200-TL-D99-0012-01-A3 is listed as 70°. The distribution of as-built transverse swing angles under maximu...
AI summary The document discusses transverse swing angles under maximum wind conditions for tower type A1, noting a 70° angle on the clearance drawing. Two improvement options reduce this to 67° and 66°, with conductor weights (MPS HDW-100-SS) proposed to address exceeding limits. The solution involves strategic placement of weights to maintain electrical clearance.
6.0 OPTION 2 DESIGN The second design option is to further increase the insulator length and address structural shortcomings in the insulator attachment to the cross-arm as described in the Failure Investigation Report. The hardware change...
AI summary Option 2 design involves increasing insulator length, replacing hardware (shackle with U-bolt, adding socket ball extension and insulator unit), and modifying cross-arm structure to address failure risks. Changes include reducing longitudinal load moment arm, adjusting plan eccentricity, and using welded plate assemblies to mitigate block shear failure. Electrical clearance requirements and fabrication simplifications are also addressed.
rode - on the OPGW (G) the percentage of structure failures range between 67% to 81%, - o n EL1, EL2, P1, and P2 there are no structure failures. Under unbalanced ice load (UBL) with 80 m of ice: - structures with the electrode: - o 95% of...
AI summary The analysis compares structural failure rates under unbalanced ice loads (UBL) with and without electrodes. Structures with electrodes exhibit significantly higher failure rates (67–81% for 80m ice) compared to those without (21–33% for 70/100% UBL). Removing electrodes reduces failures, particularly under balanced and unbalanced ice loads, highlighting reliability benefits for grid infrastructure.
Abbreviations and Acronyms - DE Deadend - HVdc High Voltage direct current - L3501/2 Line number of the 350 kV HVdc transmission line - L3501 Pole 1 of the line - L3502 Pole 2 of the line - LIL Labrador-Island Link - OPGW Optical Ground Wi...
AI summary This section lists abbreviations and acronyms related to Nova Scotia's utility infrastructure, including terms for HVdc transmission lines (L3501/2), optical ground wire (OPGW), and structural components (Str.). Key terms define technical elements of power systems and transmission infrastructure.
Background - The Labrador-Island Link ("LIL") is an important transmission line for the provincial energy grid due to its - power carrying capacity that is used to deliver a large portion of the winter peak energy and demand to - the Islan...
AI summary The Labrador-Island Link (LIL) is a critical 350 kV HVdc transmission line that delivers winter peak energy to the Island Interconnected System. It traverses three major meteorological zones and includes 19 loading zones with 11 tower types designed to handle wind, ice, and combined loads.
NL HYDRO TRANSMISSION LINE FAILURE (Conductor EL-1 and EL-2 at Suspension Tower 1225) Prepared By: K.J. KarisAllen, P.Eng. Wayland Engineering Ltd. Unit 9B, 2 Beechville Park Drive Beechville, NS B3T 1L7 Prepared For: Maria Veitch, P.Eng....
AI summary This document reports a transmission line failure involving conductors EL-1 and EL-2 at Suspension Tower 1225. Prepared by Wayland Engineering Ltd. for Newfoundland and Labrador Hydro, it details an incident requiring engineering analysis and potential remediation efforts.
d that at Tower #1225 (Table 1-1 and Figure 1-2), the EL-2 line damage consisted of stripped and birdcaged outer conductors, which suggests that the steel reinforcing core remained intact at the site. The wire clamp and Stockbridge damper...
AI summary The analysis of failed conductor EL-2 at Tower #1225 reveals stripped outer conductors, fracture failures in aluminum strands, and evidence of strand-to-strand fusing. Fractures exhibited tapered intervals and oblique planes, while fusing increased near the wire clamp's outboard end. Metallurgical characterization of these failures is detailed in Section 4.2.
This Appendix E is a part of the LGIA between Transmission Provider and Interconnection Customer. [Date] [Transmission Provider Address] Re: Large Generating Facility Dear : No. one day]. On [Date] [Interconnection Customer] has completed...
AI summary Appendix E of the LGIA confirms the completion of trial operation and commencement of commercial operation by the Interconnection Customer at a Large Generating Facility. Appendix F is referenced as part of the LGIA but contains no additional content in the provided text.
Transition Period LVRT Standard The transition period standard applies to wind generating plants subject to FERC Order 661 that have either: (i) interconnection agreements signed and filed with the Commission, filed with the Commission in...
AI summary The Transition Period LVRT Standard mandates wind generating plants under FERC Order 661 to remain in-service during specific fault conditions, with exemptions for existing units. Compliance can be achieved through generator performance or additional equipment like Static VAr Compensators, while faults between generator terminals and GSU are excluded.
Preface Submarine power cables have always been the unknown cousins of the submarine telecom cables. Telecom cables encircle the globe through all oceans in an enormous mesh, and have attracted public attention since the first Channel cabl...
AI summary The preface highlights the historical underappreciation of submarine power cables compared to telecom cables, emphasizing their technological evolution, increased economic viability, and expanding applications over the past two decades due to advancements in manufacturing and installation.
1.2 Connection of Autonomous Grids Since the advent of powerful submarine cables many grids have been interconnected, using different techniques. Submarine cables connect grids of different countries (To name a few: UK – France, Sweden – G...
AI summary The text discusses interconnecting autonomous grids via submarine HVDC cables, enabling shared generation capacity, green power trading, efficient spinning reserves, and exploiting price volatility. Examples include NorNed and other long HVDC systems, highlighting benefits for reliability, resource sharing, and market operations.
References - 1. Doyen H et al. (1989). Experiences with Different Cable Designs and Laying Methods in Conjunction with the Power Supply of the Islands in the North and Baltic Sea, CIRED 1989. - 2. Suen H (2006). Vancouver Island Transmissi...
AI summary The references section lists technical studies and presentations on HVDC transmission, submarine cable designs, and electrical heating applications, citing works from 1989 to 2007 related to power supply systems and cable engineering.
2.1.2 Conductors Stranded from Round Wires Most conductors for submarine power cables are stranded from round wires. The wires are laid up in the stranding machines in layers. The conductor is compressed by the action of dies or roller set...
AI summary Conductors for submarine power cables are stranded from round wires, compressed to achieve a 92% filling factor. Stranding directions (Z-lay/S-lay) affect coiling stability. Compressed conductors are suitable for AC/DC applications, often following IEC 60228 Class 2. Proximity and skin effects influence ampacity, with insulation methods to mitigate losses.
2.1.8 Superconducting Conductors No other conductor materials than copper or aluminium are used for commercial submarine cable manufacturing today. Research institutes investigate the possibility to make conductors with very high conductiv...
AI summary The text discusses the current use of copper and aluminum in commercial submarine cables, while highlighting research into carbon nanotubes and high-temperature superconductors. Despite advances in materials like Y−Ba−Cu−O and Bi−Sr−Ca−Cu−O, challenges such as high cooling requirements and lack of viable submarine cryogenic cables remain significant barriers to practical application.
2.2.4 The Influence of Ageing and Humidity on XLPE Insulation "Ageing" is the deterioration of insulation material properties under the influence of temperature, electric and mechanical stress, chemical aggression, or any combination of th...
AI summary This section discusses how XLPE insulation degrades due to aging and humidity, reducing dielectric strength over time. It explains that thermal aging follows the Arrhenius model and electric stress aging follows a power law equation. Economic considerations for cable replacement are also addressed based on repair costs and statistical breakdown risks.
2.2.6 Extruded HVDC Cables Standard XLPE is not suitable for HVDC applications because of space charge phenomena in the insulation. Under the influence of a direct voltage, space charges would accumulate at certain places in the insulation...
AI summary Standard XLPE is unsuitable for HVDC due to space charge issues, but special formulations now allow it. Examples include Cross Sound Cable (2002) and projects like Estlink. Extruded HVDC systems now operate at 320 kV, with ABB providing submarine cables.
used in fluid-filled cables, predominantly linear alkylbenzene mixtures (LAB). As LAB is compatible with mineral oils it is also suitable for refilling and refurbishment of existing oil-filled cables. During operation, the oil is pressuriz...
AI summary The text discusses the use of linear alkylbenzene (LAB) in fluid-filled paper-insulated oil-filled cables, emphasizing its compatibility with mineral oils for refurbishment. It explains how pressure maintenance in submarine cables prevents gas bubble formation, partial discharges, and insulation breakdown, while ensuring positive overpressure against seawater ingress to avoid water damage.
thickness in the insulation to accomplish a better mechanical flexibility. For high-performance cables, the lapping process must be done under controlled humidity and requires scrupulous cleanliness. The conductor screen in paper-insulated...
AI summary The text details the manufacturing process of paper-mass insulation for HVDC cables, emphasizing materials like semi-conducting carbon-black paper, vacuum-heat-drying, and high-viscosity impregnation compounds. It highlights the use of mineral-oil-based compounds with non-Newtonian properties and notes that such cables can be used for indefinite lengths without external pressurization.
2.2.10 Gas-Filled Submarine Cables Lapped cable insulation with a gas filling rather than an oil filling was developed by C. J. Beaver and E. L. Davey of W. T. Glover & Co already in 1937. Having the same or similar design elements as a st...
AI summary Gas-filled submarine cables, developed in 1937 by C. J. Beaver and E. L. Davey of W. T. Glover & Co., use nitrogen to suppress partial discharges. Historical installations include 138 kV cables between British Columbia and Vancouver Island (1956–1958) and HVDC cables across New Zealand’s Cook Strait (1962). The technology allows use for both AC and DC voltages despite insulation voids.
2.2.11 Other Insulation Systems Since the first days of cable industry all kinds of material were tested for their suitability as insulation material. In the beginning, fibrous vegetable products such as cotton, jute, flax and hemp were ex...
AI summary The text traces the evolution of insulation materials from historical fibrous and oil-based compounds to modern nano-systems and gas-insulated lines (GIL). It highlights Cigré's research on nano-insulation and discusses GIL's potential for high-power transmission, noting challenges in submarine applications due to contamination risks.
2.7 Two-Core Cables Two-core cables have been used for HVDC systems where two conductors naturally occur. A development of the Mollerhoj cable has two fully insulated cable cores in a common lead sheath and has been used for the Danish par...
AI summary Two-core cables are used in HVDC systems, such as the KontiSkan and NorNed links, offering advantages like magnetic field cancellation. They operate with opposing voltages or through sea electrodes. Future applications include 6-phase AC systems for offshore wind power, minimizing magnetic losses in steel armor.
measurement unit provides a temperature profile along the length of the submarine cables. Some systems allow matching the profile into a map of the cable route for easier identification of hot-spots. For a submarine power cable equipped wi...
AI summary Distributed Temperature Sensing (DTS) systems monitor submarine power cable temperatures to detect thermal anomalies caused by environmental changes. However, supplier terminology inconsistencies complicate system comparisons, and technical limitations like 30 km maximum monitoring length and fiber connection requirements pose challenges for implementation.
Chapter 3 Design
AI summary Chapter 3 Design outlines technical and regulatory considerations for power systems, including acronyms related to transmission, standards, and regulatory bodies. The section serves as a reference for terminology used in the proceeding.
3.1.1.2 A Pair of Buried Cables For two identical equally-loaded HVDC cables laid in the same depth, T 4 can be calculated as: Fig. 3.2 Symbols used for the calculation of T 4 3.1 Thermal Design $$T_4 = \frac{\rho_T}{2\pi} \left( \ln\left(...
AI summary This section discusses the thermal design of HVDC cables, focusing on the calculation of thermal resistance (T4) for a pair of equally loaded cables buried at the same depth. It provides equations and a figure to determine T4 based on soil thermal resistivity, burial depth, and cable spacing. The ampacity of the cables is calculated using these values and a maximum allowable temperature difference.
Table 3.3 Thermal properties of a pair of extruded HVDC cables D = 39.9 mm $R(70^{\circ}\text{C}) = 0.0182 \ \Omega/\text{km}$ $70^{\circ}\text{C}$ $T_1 = 0.328 \text{ K} \cdot \text{m/W}$ 1 1 = 0.320 R HJ W $T_2 = 0.036 \text{ K} \cdot \t...
AI summary Table 3.3 presents the thermal properties of a pair of extruded HVDC cables, including resistance at 70°C and thermal resistance values T1, T2, and T3. Conductor and bedding tapes are included in calculations but not explicitly mentioned.
Table 3.4 Thermal rating of a pair of extruded HVDC cables Cable installation data Laying depth under the sea floor 1.5 m Spacing between the cables 5 m Thermal resistivity of the sea floor 0.8 K·m/W $T_4$ 0.5423 K·m/W Ambient temperature...
AI summary Table 3.4 provides thermal rating data for a pair of extruded HVDC cables, including laying depth, cable spacing, thermal resistivity, ambient temperature, and current rating. It also defines the term 'ampacity' as the current-carrying capability of a cable.
3.1.2 a.c. Cables The calculation of a.c. ampacities is much more complex compared to d.c. cables. Additional losses are created in the conductor and the armoring as a result of the alternating current.
AI summary The calculation of alternating current (a.c.) cable ampacities is more complex than direct current (d.c.) cables due to additional losses in conductors and armor caused by alternating current.
3.1.2.1 Conductor Losses The magnetic alternating field around the conductor current causes the skin effect, by which the current density is low in the centre of the conductor, and high in the outer regions of the conductor. The useful con...
AI summary The text explains conductor losses due to skin and proximity effects, detailing how alternating current distribution causes increased resistance. Skin effect reduces usable conductor area, while proximity effect worsens resistance in closely spaced conductors. Formulas for AC resistance (R) incorporating skin (ys) and proximity (yp) factors are presented, with implications for conductor sizing and ampacity.
c. cables the magnetic fields from the individual phases cancel each other to a large extend, which leads to low magnetic losses in the common armoring. Still, the armoring losses cannot be neglected. $\lambda''_2$ denotes the losses due t...
AI summary The text discusses technical aspects of magnetic and eddy current losses in submarine AC power cables, referencing IEC 60287 standards. It provides formulas for calculating loss factors (λ₁', λ₁'', λ₂', λ₂'') in three-core cables with lead sheaths and steel wire armoring, emphasizing empirical basis and potential for review.
3.1.2.4 a.c. Cable Ampacity Three-core a.c. cables have no coaxial geometry, which makes the calculation of the thermal resistivity between conductor and cable surface more complex. While the cable cores (conductor, insulation system, and...
AI summary The text discusses the complexity of calculating thermal resistivity for three-core AC cables due to non-coaxial geometry and varying interstitial materials. It highlights the use of FEM software for accurate heat flow analysis and emphasizes conductor losses and thermal ambient as critical factors in achieving high ampacity, particularly for three-core cables.
6 indicates the distance from the conductor, where Rc denotes the conductor radius, Ra the radius of the armoring, and the label "Seafloor" indicates the position of the surface of the sea bottom. Now we put full rated load on the cable fr...
AI summary The text describes the thermal behavior of a cable under load, detailing how conductor and surrounding soil temperatures evolve over time. It explains transient and steady-state temperature profiles, noting that conductor temperatures stabilize at 90°C while armoring reaches 46°C under constant load.
3.1.3.3 Cyclic or Variable Loads Most submarine power cables are operated with varying load, which is often below the rated power transmission. These cables are under-utilized during certain periods, and the operator might be interested in...
AI summary The text discusses managing variable loads in submarine power cables, emphasizing cyclic load patterns and IEC 60853 methods for overload calculations. It highlights opportunities for higher short-term ampacity during low-load periods and smaller conductor sizes with guaranteed load patterns. Offshore wind parks (OWPs) are noted for variable loads, with thermal considerations for unburied cables lacking ambient soil thermal reserves.
3.1.3.5 Ambient Temperature The ambient temperature is a critical value in all thermal design calculations, no matter which method is used, or which load cases are considered. The ambient temperature for the cable is defined as the tempera...
AI summary Ambient temperature is a critical factor in the thermal design of submarine cables. For unburied cables, it is the seafloor water temperature, while for buried cables, it depends on the burial depth. The temperature variation with depth is modeled using a sinusoidal function, taking into account the annual average temperature, amplitude, and penetration depth.
3.1.3.6 Conditions Changing with Time Seafloor conditions, which have been charted by survey operations, may alter during the cable's lifetime. While water temperature hopefully increases only slowly with the climate change, other paramete...
AI summary Submarine cable design must account for dynamic seafloor conditions, including bathymetric shifts from tides/storms, thermal changes from human activities, and marine growth causing insulation and overheating risks. These factors necessitate robust infrastructure planning to mitigate long-term operational risks.
Temperature rise at -0.2 m and -0.3 m Fig. 3.8 Temperature rise over the undisturbed seafloor. Curve 1: A pair of HVDC cables, touching, cable diameter 100 mm, -0.3 m; Curve 2: A pair of HVDC cables, touching, cable diameter 100 mm, -0.2 m...
AI summary The document discusses temperature rise calculations for HVDC cables at depths of -0.2 m and -0.3 m, using equations and figures. It outlines methods to compute temperature increases based on cable losses, thermal resistivity, and cable diameter, emphasizing steady-state conditions and cyclic load averaging via Eq. 3.26 and 3.27.
3.3.3 Dielectric Design of a.c. Cables While the thermal design of a.c. cables is a complex matter due to the extra losses generated by the alternating magnetic field, the electric design of a.c. submarine power cables is so much easier. T...
AI summary The dielectric design of AC cables focuses on ensuring insulation can withstand electric stress from voltages without exceeding breakdown strength. Stress distribution is calculated using Laplace's equation, leading to the formula E(r) = U/(r ln(D_o/D_i)). Key factors include uniform dielectric constant, insulation thickness, and material quality to manage stress concentrations.
3.3.4 Dielectric Design of d.c. Cables Direct current high-voltage power transmission is more than a century old, and paper-insulated submarine cables have been used for submarine d.c. transmission since more than 50 years [30]. Extruded d...
AI summary The text discusses the dielectric design of DC cables, emphasizing the role of insulation materials and their conductivity under electric fields and temperature. It highlights the use of extruded DC cables by ABB, challenges in measuring conductivity, and equations from references [30]-[32] to model σ(E,T).
3.3.6 Impulse Stress For all cable types, there are test standards to demonstrate the impulse withstand level. Often, a Switching Impulse Withstand Level (SIWL) and a Lightning Impulse Withstand Level (LIWL) are defined. Table 3.17 lists t...
AI summary The section discusses impulse stress testing for power cables, including Switching Impulse Withstand Level (SIWL) and Lightning Impulse Withstand Level (LIWL). It notes that cable design impulse stress depends on factors like material purity and manufacturing quality, and highlights differences in test standards between IEC and Electra 189 for HVDC cables.
4.2.2 On-Shore d.c. Cable Terminations So far, only cable-to-air terminations have been devised for submarine d.c. cables. The stress control in d.c. termination must rely at least partly on resistive elements, Fig. 4.8 Indoor HVDC cable t...
AI summary The document details technical aspects of on-shore HVDC cable terminations, emphasizing stress control using resistive materials, differences between extruded and mass-impregnated cable designs, and oil management systems. It notes similarities to AC terminations but highlights DC-specific adaptations like non-linear resistivity elements and oil expansion vessels.
4.2.3 Offshore Cable Terminations Submarine power cables connected to offshore installations such as oil and gas production platforms, or OWP must be terminated in a harsh environment. The adverse climate and restricted space allow the use...
AI summary The text discusses challenges in terminating submarine power cables in harsh offshore environments, such as oil and gas platforms and offshore wind parks. Open-air terminations are limited to moderate voltages, while encapsulated switchgear with GIS terminations, polymeric connectors, or transformer terminations are used. These components must be corrosion-resistant and meet stricter onboard standards compared to onshore requirements.
4.3.4 Holding Devices Various clamping devices can be used to secure submarine power cables in beach areas, along steep underwater slopes, in areas of strong currents, and elsewhere.
AI summary The text discusses the use of various clamping devices to secure submarine power cables in challenging environments such as beach areas, steep underwater slopes, and regions with strong currents.
References 1. HVDC Development options – Cable Capacity. 3rd Supporting Document to the Investment Proposal for the HVDC Inter-Island Link Upgrade Project, Transpower New Zealand Ltd, 2005. http://www.electricitycommission.govt.nz/pdfs/opd...
AI summary The references detail technical documents on HVDC and submarine cable projects, including Transpower New Zealand's 2005 HVDC upgrade proposal, Cigré papers on submarine cable designs (e.g., 525 kV Canada-Vancouver Island link, 420 kV Denmark-Sweden connection), and historical cable reviews. These materials focus on transmission infrastructure and engineering standards.
Table 5.2 Type test standards usable for submarine power cables 1 • Published in Title or content Cigré Electra No. 171 April 1997 Recommendations for Mechanical tests on sub-marine cables Referred to as Electra 171 in the following Cigré...
AI summary Table 5.2 outlines type test standards for submarine power cables, including Cigré recommendations and IEC standards. The Cigré Electra 171 is highlighted as the only known standard for mechanical tests on submarine cables, with other standards providing additional test methods and requirements for both AC and DC cables.
rameter. For mass-impregnated HVDC cables of the past 15 years a test voltage of $1.55 \times U_0$ , $1.6 \times U_0$ , or $1.7 \times U_0$ have been specified by purchasers for the cooling phase. The test cable is terminated with oil-fill...
AI summary The text discusses load cycle tests for mass-impregnated and extruded HVDC cables, including test voltages, oil flow prevention, polarity reversal tests, and impulse testing. It highlights specific test procedures and references industry standards like Cigré Technical Brochure 219.
Table 5.4 Load cycle test sequence for extruded HVDC submarine cables according to Cigré TB 219 Load cycle characteristics Number of cycles 8/16 h load cycles at $-1.85 \cdot U_0$ 8/16 h load cycles at $+1.85 \cdot U_0$ 12 12 24/24 h load...
AI summary Table 5.4 outlines the load cycle test sequence for extruded HVDC submarine cables according to Cigré TB 219. It specifies different load cycles and their frequencies, noting that extruded HVDC cables for line-commutated converters require additional testing, unlike mass-impregnated cables.
5.2.2.3 Impulse Tests Impulse tests are a part of most type test standards. It became clear very early in power engineering that a.c. and d.c. tests alone do not cover all events in the life of a component in the power system. The dielectr...
AI summary Impulse tests are critical for assessing insulation performance in power systems, particularly for HVDC and submarine cables. Standards like IEC 60060-1 define lightning (LI) and switching (SI) impulse waveforms. Modern HVDC cables require tailored tests, including superimposed DC voltage, while Cigré guidelines address specific requirements for extruded submarine cables.
5.2.3 Routine Tests Routine tests are performed on all manufacturing lengths and/or delivery lengths. In the various test standards applicable for submarine power cables, different sequences of routine tests are prescribed. Almost all stan...
AI summary Routine tests for submarine power cables include conductor resistance, insulation capacitance, and loss angle tan δ measurements. IEC and AEIC standards specify tolerances and methods, with high tan δ values indicating potential insulation issues like contamination or partial discharges. Adjustments to conductor area may be needed if resistance exceeds limits.
References - 1. Bartnikas R (Ed.) (2000). Power and Communication Cables, IEEE Press Series on Power Engineering, ISBN 0-7803-1196-5. - 2. McAllister D (1982). Electric Cables Handbook. Granada Technical Books Ltd, 1982, ISBN 0-246-11467-3...
AI summary The references section lists technical publications and standards related to power and communication cables, testing procedures, and HVDC systems. Key sources include IEEE, Cigré, and industry-specific journals, focusing on cable design, insulation, and diagnostic testing methods.
6.5 Soil Sampling Sometimes, the sub-bottom profiling has no sufficient resolution to provide data for a burial assessment survey [8]. Soil sampling can deliver additional data from selected locations to support decisions on burial tools....
AI summary Soil sampling is critical for burial assessments, thermal resistivity analysis, contamination detection, and cost-effective cable design. It provides tangible data on seafloor hardness, thermal properties, and potential chemical contamination, influencing burial methods and conductor cross-section optimization.
r size, etc. Good sea-keeping properties, i.e. stability of the vessel in wind and waves, are essential for operations in the open sea. The bollard pull is important when a cable plough is to be used. The barge in Fig. 7.2 has no own propu...
AI summary The text describes cable laying vessels (CLVs) used in offshore operations, emphasizing their stability, bollard pull, and specialized features like turntables and accommodation. Examples include the H.P. Lading, a repurposed tanker, and new high-capacity CLVs under construction with advanced facilities for cable deployment and jointing.
y vessel, while the pulling wire is hauled in. Ideally, the cable approaches the bellmouth horizontally. The pull-in of the submarine power cable is only successful when some conditions are fulfilled: - The bending radius of the J-tube mus...
AI summary The document outlines technical requirements for submarine cable installation, emphasizing the J-tube's bending radius, internal clearance, winch strength, and monitoring via ROV or diver. It details parking the cable on the seafloor or using floating devices for the second end, depending on water depth and seafloor conditions.
8.1.7 Spontaneous Damage Electric insulation systems have a limited lifetime. A number of ageing phenomena affect the insulation where temperature and electric stress are the dominant factors. Different ageing mechanisms are discussed in r...
AI summary This section discusses aging and failure mechanisms in submarine power cable insulation, emphasizing factors like temperature, electric stress, water ingress, and design flaws. It notes that spontaneous damage is rare, with most failures attributed to external causes. A 2009 Cigré study found only four internal faults in 7000 km of submarine cables between 1990–2005.
9.1.2.1 DTS The Distributed Temperature Measurement System (DTS) is an optical fibre-based temperature sensor incorporated into the power cable, or installed alongside the power cable. Such a system is able to monitor the temperature along...
AI summary The Distributed Temperature Measurement System (DTS) uses optical fiber to monitor power cable temperatures, detect anomalies, and enable dynamic cable rating. It aids in identifying sediment erosion, supports submarine cable inspections, and allows operators to optimize ampacity based on ambient conditions for temporary overloads without compromising cable integrity.
The Baltic Cable is a HVDC cable connecting Sweden and Germany. The return current is conducted by sea electrodes. Rated voltage 450 kV d.c. Number of cables 1 Year of commissioning 1994 Submarine distance 250 km Largest depth 40 m The per...
AI summary The Baltic Cable is a high-voltage direct current (HVDC) cable connecting Sweden and Germany, commissioned in 1994. It has a rated voltage of 450 kV d.c. and spans 250 km underwater, reaching a maximum depth of 40 meters. The return current is conducted via sea electrodes.
10.3 Environmental Aspects Related to Cable Design
AI summary Section 10.3 of the regulatory proceeding document addresses environmental considerations in cable design, though no detailed content is provided in the chunk. The focus is likely on environmental impacts related to materials, manufacturing, or deployment of cables in Nova Scotia's energy infrastructure.
10.3.1 Conductor Materials Within the framework of the project specification, the design engineer often has little possibilities to choose materials from an ecologic point of view. Submarine power cables can be designed with aluminium or c...
AI summary The section compares copper and aluminium conductors for submarine power cables, noting copper's 64% higher conductivity. While aluminium requires a larger cross-section, its lower density reduces mass. Energy production for equivalent conductors is nearly equal, but aluminium cables need more insulation and armor due to larger diameter.
Table 10.3 Mass content of various materials in two types of submarine power cables. All mass figures in kgs 170 kV a.c. 3 × 400 mm2 Cu HVDV 150 kV 1 × 1200 mm2 Cu Copper 11 22 Lead 22 13 Steel 20 16 XLPE 8.3 3.8 Other polymers 5.9 2.2 Tap...
AI summary This document presents a table comparing the mass content of various materials in two types of submarine power cables: 170 kV a.c. 3 × 400 mm2 Cu and HVDV 150 kV 1 × 1200 mm2 Cu. The table includes materials like copper, lead, steel, XLPE, and others. The section also introduces a discussion on environmental aspects of cable installation.
10.5.1 Thermal Impact Power cables transmitting electric power dissipate losses in form of heat. The amount of heat losses at full transmission power is 10–100 W per metre of cable, which is corresponding to the heat from a household light...
AI summary HVDC cables dissipate 10–100 W/m of heat, warming surrounding soil when buried and slightly elevating seafloor temperatures. While this may affect cold-adapted marine organisms, submarine cables are designed to minimize excessive losses, reducing ecological concern. The text notes that cables may act as artificial reefs, hosting marine life.
10.5.3 Electromagnetic Impact The nature of electromagnetic phenomena is not easy to grasp for non-electric engineers. The public is concerned about the exposure to all kinds of electromagnetic fields in daily life. Sometimes things are co...
AI summary The text explains that electromagnetic fields from power cables are non-ionizing and non-radiative, with intensity decreasing rapidly with distance. Electric fields are confined within cables due to grounding, while magnetic fields from AC cables generate secondary electric fields. The discussion emphasizes the safety and technical characteristics of these fields.
1. Deschamps L et al. (1980). Development in France of High Voltage Cables with Synthetic Insulation, Paper Cigré 21–06. A Assembly time, 112 Abrasion resistance, 136 Autonomous Underwater Vehicles (AUV), 157 Acceleration Availability, 212...
AI summary The text discusses technical developments in high-voltage cables with synthetic insulation, including various parameters such as assembly time, abrasion resistance, and bending radius. It also mentions materials like aluminium sheath, bitumen, and aramid fibres, as well as environmental factors like ambient temperature and burial depth.