Topic:"System Reliability" in M12744

Why do this project? The 92H-331 feeder at Tidewater substation is overloaded during periods of high load. The construction of the new three phase feeder section along Peggys Cove Road from 92H substation will allow for the offload of 92H-...

AI summary The 92H-331 feeder at Tidewater substation is overloaded, necessitating the construction of a new three-phase feeder along Peggys Cove Road to offload 92H-331, improve reliability, and reduce strain on the distribution system. A planning study (M-AREA-2025-002) outlines immediate and long-term solutions, including a new substation, to address capacity and reliability challenges in the area.

Why do this project now? Feeder 92H-331 has a winter peak load beyond the 325 Amp, NS Power Capital Expenditure Justification Criteria (CEJC) and has experienced cold load pickup issues, as observed during the February 4, 2024 extreme cold...

AI summary Feeder 92H-331 exceeds NS Power's 325 Amp design criterion, faces cold load pickup issues, and has a 4% annual load growth rate. Adjacent feeders are also over capacity, limiting operational flexibility. A new feeder is proposed to reduce loading, improve voltage, and enhance reliability. The project is deemed in-service after infrastructure upgrades by July 2026, with a Final Cost Date in June 2027.

Why do this project this way? The proposed construction of a new three-phase feeder along Peggy's Cove Road provides the most effective nearterm solution in conjunction with CI C0071888 upgrading 92H-T61 with a larger 25 MVA transformer to...

AI summary The proposed construction of a new three-phase feeder along Peggy's Cove Road is presented as the most effective near-term solution to address loading and voltage constraints on feeder 92H-331, aligning with a staged infrastructure plan. Immediate feeder offloading is required before broader system upgrades, including future substation development and voltage conversion in the Hubley area. No viable alternative routes exist for the feeder.

Document No: XXX-XX-XXXX-XXXX Estimate Classification Class 4 Class 3 Class 2 Started or Preliminary Class 5 0% to 2% 1% to 15% 10% to 40% 30% to 75% 65% to 100% Maturity Level of Project Definition Deliverables Defined or Complete General...

AI summary The text presents a structured table outlining various project classification, maturity levels, and deliverables related to a project. It includes details on project location, requirements, technology selection, planning, studies, and technical deliverables, with varying levels of definition and completeness across different categories.

EXECUTIVE SUMMARY This study evaluates capacity constraints affecting the 92H-Tidewater and 137H-Hammonds Plains substations and identifies capital investments required to maintain compliance with NS Power planning criteria and accommodate...

AI summary This study identifies capacity constraints at 92H-Tidewater and 137H-Hammonds Plains substations, recommending capital investments to meet NS Power planning criteria and accommodate load growth through 2035. Key projects include transformer replacements, new feeders, and the Stillwater Lake substation. These upgrades aim to restore compliance, improve reliability, and address forecasted overloads.

TABLE OF CONTENTS EXECUTIVE SUMMARY TABLE OF CONTENTS i LIST OF APPENDICES ii LIST OF TABLES AND FIGURES ii 1.0 SCOPE 1 2.0 Existing System 2 2.1 Transmission 2 2.2 Distribution Ξ 2.2.1 92H-Tidewater ε 2.2.2 137H-Hammonds Plains Distributi...

AI summary The document outlines the existing electrical system in Nova Scotia, focusing on transmission and distribution infrastructure, load history, reliability concerns, and potential capacity alternatives. It details issues such as transformer overloads, voltage problems, and aging equipment in specific areas like Tidewater and Hammonds Plains, and presents various solutions to address these challenges.

1.0 SCOPE This study was initiated to address transformer and feeder overloads at the 92H-Tidewater and 137H-Hammonds Plains substations. Both substations have experienced sustained loading above planning criteria during recent winter peak...

AI summary This study addresses transformer and feeder overloads at 92H-Tidewater and 137H-Hammonds Plains substations due to sustained winter peak loading and forecasted residential growth. It evaluates alternatives to meet planning criteria (133% transformer loading, 325 A feeders) and contingency capacity (e.g., mobile transformers, load transfer) over a 15-year period, recommending capital investments to resolve overloads and ensure reliability.

4.0 RELIABILITY NSPI tracks the reliability of each distribution feeder in NS, including the number of Customer Interruptions (CI) and Customer Hours of Interruption (CHI). These are utilized to determine the CKAIFI and CKAIDI parameters,...

AI summary NSPI tracks the reliability of distribution feeders in Nova Scotia using metrics like CKAIFI and CKAIDI, which measure the average frequency and duration of customer interruptions. These metrics are calculated based on customer interruptions and total number of customers over a year.

- CKAIDI = Sum of (Outage) Customer Hours of Interruptions / Total number of customers All Events Include d Per rformanc e Standa rds Source Year CKAIFI CKAIDI Year CKAIFI CKAIDI 92H-331 2020 3.92 5.46 92H-331 2020 3.37 2.27 2021 3.06 2.51...

AI summary The document presents data on CKAIFI and CKAIDI metrics for various feeders from 2020 to 2024, showing fluctuations in outage frequency and duration. These metrics are used to evaluate the performance of the power distribution system.

5.0 OVERLOADS AND OTHER CONCERNS This section will highlight key findings from the analysis of the existing system and load forecasts for the Tidewater and Hammonds Plains areas. These findings are addressed in Section 6.

AI summary Section 5.0 outlines key findings from system and load forecasts analysis for Tidewater and Hammonds Plains, with further discussion in Section 6. The focus is on overloads and related concerns arising from infrastructure and demand planning.

5.1.1 92H Transformer Overload The transformer 92H‑T61 would have recorded a peak load of 20.5 MVA in 2025 without embedded hydro generation, exceeding 164% of its 12.5 MVA top nameplate rating. Historical loading on this transformer has i...

AI summary Transformer 92H-T61 is overloaded, exceeding 164% of its 12.5 MVA rating without hydro generation. Winter peaks surpass planning criteria, and mobile transformers installed in 2026 are not viable long-term solutions. Hydro generation was used in 2025 but is unreliable due to drought, necessitating permanent corrective action.

5.1.2 92H Feeder Overloads Feeder 92H‑331 reached a 2025 winter peak of 432 A, with an annual growth rate of 4.3% from 2022– 2025. This significantly exceeds the 325 A planning criterion and presents an immediate reliability and capacity c...

AI summary Three feeders (92H-331, 92H-332, 92H-334) are exceeding planning criteria due to increasing loads. Feeder 92H-331 requires immediate action, 92H-332 needs long-term modifications by 2029, and 92H-334 requires continued monitoring due to uncertain growth. All pose reliability and capacity concerns.

5.1.3 Voltage Issues Based on the CYME modelling for the 2025 winter peak, low voltage issues are present on the 92H-331 and 92H-332 feeders. Alternatives to address these overloaded feeders will also ensure the voltage is maintained at 11...

AI summary Low voltage issues on feeders 92H-331 and 92H-332 during the 2025 winter peak require solutions to maintain 114 V, ensuring customer service entrances meet NSPI's 110 V nominal limit. Alternatives to address overloaded feeders are necessary.

5.2 Hammonds Plains Area Concerns The overloads identified in this section are based on measured winter peak conditions, with future violations forecasted using the observed annual growth rates from 2022–2025. Several major developments in...

AI summary The Hammonds Plains area faces potential grid overloads due to new developments adding 5.7 MW (Bedford West) and 15 MW (Sandy Lake) of residential/mixed-use load, plus a 6.9 MVA commercial expansion. These projects may accelerate capacity violations beyond historical growth trends, introducing uncertainty in loading patterns.

5.2.1 137H Transformer Overload The transformer 137H-T61 reached a winter peak load of 50.6 MVA in 2025, equal to 121% of its 42 MVA top rating. Historical loading on this transformer has increased by 4.1% annually and it is forecasted to...

AI summary Transformer 137H-T61 exceeded its winter load rating in 2025, with annual loading increases projected to surpass design limits by 2026. The 137H substation's contingency capacity is insufficient, risking system reliability. Immediate corrective actions are required to address overload and capacity issues.

5.2.3 Voltage Issues Based on the CYME modelling for 2025 winter peak there is a low voltage issue past the Pockwock intersection on the 137H-412 feeder. Alternatives to address these overloaded feeders will also ensure the voltage is main...

AI summary The text identifies a voltage issue on the 137H-412 feeder past the Pockwock intersection during the 2025 winter peak, as modeled by CYME. Alternatives are needed to address overloaded feeders and maintain voltage at 114 V to meet NSPI's 110 V nominal requirement at customer service entrances.

6.1.1 92H-T61 Replacement Winter peak load supplied by transformer 92H-T61 significantly exceeds the transformer rating when hydro is unavailable. Replacement with a new 15/20/25 MVA transformer is required. Monitoring limitations, rapid l...

AI summary Transformer 92H-T61 is overloaded during winter when hydro is unavailable, requiring replacement with a larger unit. Temporary solutions like modified hydro dispatch and mobile transformers are insufficient. Alternatives such as load transfers or adding a second transformer are infeasible due to infrastructure constraints and high costs. Replacement remains the only viable long-term solution.

6.2 Hammonds Plains Capacity Winter peak loading at 137H-Hammonds Plains has increased to the point where both normal loading limits and contingency capacity shortfall present near-term risk. The existing station exceeds its available cont...

AI summary Winter peak loading at Hammonds Plains has exceeded contingency capacity limits, with feeders surpassing design criteria. Alternatives are needed to restore compliance with planning standards and accommodate future growth in Hammonds Plains and Bedford.

6.3 Tidewater Capacity The immediate concerns for Tidewater are addressed by the immediate actions recommended in Section 6.1. However, in 2029 the feeder 92H-332 is expected to exceed the 325 A planning criterion and the total station loa...

AI summary The Tidewater area faces capacity and voltage challenges by 2027-2033, including overloaded feeders (92H-332, 103H-432, 92H-334) and low voltage in Five Island Lake. Solutions include converting 12kV distribution in Hubley, expanding 92H Tidewater capacity, and infrastructure upgrades like line extensions. Deteriorated 92H substation structures also require attention.

7.4.2 Hammonds Plains Alternative B: Second Transformer at Hammonds Plains Adding a second transformer at 137H provides additional substation capacity and improves operational redundancy at the existing station. The 137H site was originall...

AI summary Alternative B proposes adding a second transformer at Hammonds Plains to enhance substation capacity and redundancy. While it resolves feeder capacity issues, it introduces reliability risks from long feeders, construction challenges due to heavy development along Hammonds Plains Road, and defers a Stillwater Lake substation until 2032, increasing overall costs. These factors make Alternative B less favorable than Alternative A.

2037: - Install a second transformer at 137H-Hammonds Plains. Implementation of these projects will restore compliance with planning criteria, provide sufficient contingency capacity, and accommodate forecast load growth in the Tidewater a...

AI summary The document outlines the installation of a second transformer at 137H-Hammonds Plains to restore compliance with planning criteria, ensure contingency capacity, and accommodate load growth in Tidewater and Hammonds Plains. Continued monitoring of development in Bedford West, Sandy Lake, and Hubley/Timberlea is recommended to adjust project timelines and identify long-term needs.

NON-CONFIDENTIAL 1 Request IR-1: 1 distinct planning recommendation, and the need for the feeder project remains unchanged 2 regardless of whether or when the transformer replacement proceeds. 1 Request IR-2: 2 3 Please describe the expect...

AI summary The document discusses the need for a feeder project to improve system reliability and resiliency by offloading feeder 92H-331, which currently exceeds load limits and has no available load transfer options. The project is expected to reduce the risk rating of the feeder and improve restoration times during outages.

NON-CONFIDENTIAL The typical planning limit for distribution feeders is 325 A, unless a lower limit applies due to feeder-specific thermal or protection-coordination constraints. This planning limit is intended to keep standard equipment w...

AI summary The text discusses distribution feeder planning limits (325A), SCADA upgrades planned for 2026, and overload issues on feeder 92H-331. NS Power addresses customer complaints about power quality through feeder balancing and regulator repairs, citing a specific Board file (M12730). Overloads occur during winter peak loads, prompting infrastructure improvements.

NON-CONFIDENTIAL 1 Request IR-11: 24 generation is not always available to support winter peak loading or contingency supply at 25 92H. The study states that hydro capacity is not included in 92H contingency capacity 26 calculations becaus...

AI summary The text discusses infrastructure upgrades at the 92H substation due to material deterioration and the need for permanent solutions to support winter peak loading. It also mentions the exclusion of hydro capacity from contingency calculations during winter peak seasons.

M12744 - CI C0080102 - Nova Scotia Power Inc. - 92H-331 Double Circuit Peggy's Cove Rd - $4,303,210 On March 13, 2026, Nova Scotia Power Inc. (NS Power) filed a request with the Nova Scotia Energy Board (Board) for approval of a 2026 Subse...

AI summary Nova Scotia Power Inc. (NSP) seeks approval for the 92H-331 Double Circuit Peggy's Cove Rd project, with a $4.3M cost increase due to extending a feeder from 5.5 km to 8.5 km. The project aims to resolve overload issues on the existing 12 kV feeder, which exceeds its design capacity during winter peaks, and minimize service interruptions by constructing under live conditions.

System Security Item 3: Partial confidentiality was applied to the Distribution Planning Study (Attachment 1) for this capital work order. The enclosed distribution diagrams are confidential due to system security concerns. Protection of t...

AI summary Partial confidentiality was applied to the Distribution Planning Study (Attachment 1) due to system security concerns. The enclosed distribution diagrams are protected to preserve power system reliability and mitigate risks from external threats.

Request IR-2: - Please describe the expected improvement in system reliability and resiliency by completing this - project.

AI summary Request IR-2 seeks information on expected improvements in system reliability and resiliency resulting from a project. The focus is on quantifying reliability and resiliency outcomes, though specific details about the project or metrics are not provided in the excerpt.

Request IR-3: - Please describe the load pickup issues experienced by Feeder 92H-331 during the February 4, - 2025, extreme cold event.

AI summary Request IR-3 seeks information about load pickup issues on Feeder 92H-331 during an extreme cold event on February 4, 2025, focusing on technical performance during weather-related stress on the power grid.

Request IR-10: - In Attachment 1 (M-AREA-2025-002), Section 3.1, NS Power noted that limited SCADA/PI data - is available, and data prior to 2022 could not be validated. In addition, Table 7 and Figure 4 - indicate that the winter peak loa...

AI summary Request IR-10 seeks clarification from NS Power on delayed infrastructure proposals, overload management on feeder 92H-331, technical procedures for distribution system overloads, and customer complaints related to power quality. The winter peak load on the feeder has exceeded design limits since 2022, with proposed annual growth of 4.3%.

Request IR-13: - In Attachment 1, Section 5.1.1, NS Power noted the following: - ... recent operating experience has shown that hydro availability cannot be relied upon during winter peak seasons. For these reasons, the hydro capacity are...

AI summary NS Power notes that hydro availability cannot be relied upon during winter peak seasons, leading to exclusion of hydro capacity from 92H contingency calculations. The request seeks clarification on NS Power's strategy for utilizing hydro generation and its impact on system planning for feeder and facility upgrades.

capacity during winter peak load; therefore, load transfer through step-down transformers is not possible. As such, existing feeder 92H-331 has limited load transfer capability with adjacent feeders. NS Power stated that extending feeder 9...

AI summary NSP seeks approval to extend feeder 92H-335 to reduce winter peak load on 92H-331 from 320A to 179A, citing a Planning Study showing load growth will remain within design limits for 10 years. The Board requested clarifications on transformer overload issues at Tidewater substation, which NSP plans to resolve via a $1M transformer upgrade using an existing spare unit.