N-1Storm Report
34 passages
METHODOLOGY - The report assigns the temperature and wind data based on the highest observed speeds that occurred during the event. - Full accounting of hourly weather data is provided as an appendix for the eight representative stations u...
AI summary The methodology outlines how temperature and wind data are analyzed using eight representative stations to assess storm impacts. It defines 'Unique Customer Impacts' and 'Total Customer Impacts' for outage tracking, emphasizing province-wide analysis over site-specific data. NS Power's weather consultant guided station selection to ensure consistency and historical benchmarking.
SECTION 4: PROVINCIAL HIGHLIGHTS Zone Date/ Time Weather Station Direction (Degrees) Wind (km/h) Max Wind Gusts (km/h) Temp (°C) Cause Sub-Cause Description Customers Impacted Duration (Hours) Valley 12/19/2025 23:03 Greenwood l 210 28 96...
AI summary This section presents a table detailing weather-related power outages in Nova Scotia on December 19-20, 2025. Each entry includes the zone, time, weather conditions, cause of the outage, number of customers impacted, and duration of the outage. The primary causes were high winds, heavy rain, and falling trees, leading to recloser operations and broken leads on transmission lines.
SECTION 4: ZONE SUMMARY IMPACT SUMMARY – VALLEY This region was impacted by high winds and heavy rain during the weather event. The largest cause of outages was due to tree contacts, as winds peaked at 96 km/h in the region.
AI summary The Valley region experienced significant outages due to high winds (peaking at 96 km/h) and heavy rain, with tree contacts identified as the primary cause of disruptions during the weather event.
Outage Summary: Customers Impacted: 43,852 Customer hours of interruption: 289,711 Full Restoration\ : 66.8 Hours
AI summary An outage affected 43,852 customers, resulting in 289,711 customer hours of interruption. Full restoration was achieved after 66.8 hours, indicating the duration of service disruption and recovery efforts.
Adverse Weather Cause of Outage (CHI) \ elapsed time from first outage event to restoration of last event
AI summary The document section titled 'Adverse Weather Cause of Outage (CHI)' includes visual data (Figures 14 and 15) and a footnote referencing elapsed time between outage events and restoration. The content focuses on analyzing weather-related outage causes and recovery timelines.
Duration Zone Date/ Time Weather Station Direction (Degrees) Wind (km/h) Temp (°C) Cause Sub-Cause Description Customer s Impacted Duration (Hours) , /alley 12/20/2025 8:56 Greenwood 250 56 96 2 Tree Contacts Falling Trees High winds cause...
AI summary The document details two power outage incidents in December 2025 caused by high winds and falling trees, impacting 1 and 3,404 customers respectively. Outages lasted 49.3 and 10.53 hours, with causes including tree contact and adverse weather conditions at Greenwood weather station.
SECTION 4: ZONE SUMMARY IMPACT SUMMARY – SOUTH SHORE Cause of Outages (CHI) This region was impacted by high winds and heavy rain during the weather event. The largest cause of outages was due to tree contacts, as winds peaked at 83 km/h i...
AI summary The South Shore region experienced outages due to high winds (83 km/h) and heavy rain, with tree contacts being the primary cause of power disruptions during the weather event.
Customers Restored within X hours of Storm Onset South Shore % Within 6 Hrs 3.66% Within 12 Hrs 17.17% Within 24 Hrs 70.01% Within 48 Hrs 96.35% This table represents the percentage of customers restored within 6, 12, 24, or 48 hours of th...
AI summary The table shows the percentage of customers in the South Shore region restored within various timeframes after a storm, with 96.35% restored within 48 hours. The average restoration time for the region was 23.1 hours.
Adverse Weather Cause of Outage (CHI) \ elapsed time from first outage event to restoration of last event
AI summary The text discusses adverse weather as a cause of outages, referencing figures and images that illustrate the impact of weather-related events on power systems. It includes a note on elapsed time from the first outage event to the restoration of the last event.
SECTION 4: ZONE IMPACT SUMMARY – NORTHERN Cause of Outages (CHI) This region was impacted by high winds and heavy rain during the weather event. The largest cause of outages was due to a transmission line outage which caused outages for 13...
AI summary The Northern region experienced outages due to high winds and heavy rain, with a transmission line outage being the primary cause, affecting 13,000 customers for 5–8 hours during the weather event.
Outage Summary: Customers Impacted: 20,595 Customer hours of interruption: 126,874 Full Restoration\ : 64.03 Hours
AI summary An outage impacted 20,595 customers, resulting in 126,874 customer hours of interruption. Full restoration was achieved after 64.03 hours, reflecting the duration of service disruption and recovery efforts.
SECTION 4: ZONE IMPACT SUMMARY – NORTHERN TOP TWO EVENTS BY DURATION & CUSTOMER IMPACT
AI summary Section 4 analyzes the Northern zone's top two outage events by duration and customer impact, focusing on CHI (Cause of Outages) as a key factor. The summary highlights the duration and scope of these events, though specific details are not provided in the heading.
SECTION 4: ZONE IMPACT SUMMARY – NORTHEAST This region was impacted by high winds and heavy rain 1% Cause of Outages (CHI) during the weather event. The largest cause of outages was due to tree contacts, as winds peaked at 104 km/h in the...
AI summary The Northeast region experienced outages caused by high winds (104 km/h) and heavy rain, with 1% of outages attributed to the Cause of Outages (CHI). Tree contacts were the primary cause of disruptions during the weather event.
Outage Summary: Customers Impacted: 55,377 Customer hours of interruption: 525,566 Full Restoration\ : 72.92 Hours
AI summary An outage affected 55,377 customers, resulting in 525,566 customer hours of interruption. Full restoration was achieved after 72.92 hours, highlighting the scale and duration of the service disruption.
Duration Zone Date/ Time Direction (Degrees) Wind (km/h) Max Wind Gusts (km/h) Temp (°C) Cause Sub-Cause Description Customers Impacted Duration (Hours) Northeast 17/19/7075 Carib ou Pt. 170 46 57 11 Tree Contacts Falling Trees High winds...
AI summary The table details outage events in the Northeast zone caused by high winds and falling trees, impacting 49 and 1 customers respectively, with durations of 69.84 and 64.66 hours. Another event on 12/19/2025 affected 8,140 customers due to transmission line damage from severe weather, lasting 8.59 hours.
Outage Summary: Customers Impacted: 92,007 Customer hours of interruption: 559,818 Full Restoration\ : 69.97 Hours
AI summary The outage impacted 92,007 customers, resulting in 559,818 customer-hours of interruption. Full restoration was achieved after 69.97 hours, providing a quantified overview of the event's scope and resolution timeline.
SECTION 4: ZONE IMPACT SUMMARY – METRO TOP TWO EVENTS BY DURATION & CUSTOMER IMPACT
AI summary This section presents a summary of the top two events in the Metro zone, ranked by duration and customer impact. It focuses on outage data and analysis, highlighting key factors affecting service reliability and customer experience. The discussion includes metrics related to outage causes, duration, and the number of affected customers.
Outage Summary: Customers Impacted: 9,865 Customer hours of interruption: 69,045 Full Restoration\ : 56.69 Hours
AI summary An outage impacted 9,865 customers, resulting in 69,045 customer-hours of interruption. Full restoration took 56.69 hours. The summary quantifies the outage's scope and duration.
SECTION 4: ZONE IMPACT SUMMARY – CAPE BRETON WEST TOP TWO EVENTS BY DURATION & CUSTOMER IMPACT
AI summary Section 4 presents a zone impact summary for Cape Breton West, highlighting the top two events by duration and customer impact. The analysis focuses on outage causes (CHI) and their effects on service reliability and customer experience.
SECTION 4: ZONE IMPACT SUMMARY – CAPE BRETON EAST This region was impacted by high winds and heavy rain during the weather event. Winds were above warning levels reaching 91 km/h during the event. Trees contacting power lines was the large...
AI summary The Cape Breton East region experienced severe weather with winds exceeding 91 km/h, leading to power outages primarily caused by trees contacting power lines. This was the largest contributing factor to outages in the area during the event.
SECTION 4: ZONE IMPACT SUMMARY – CAPE BRETON EAST TOP TWO EVENTS BY DURATION & CUSTOMER IMPACT
AI summary Section 4 presents a zone impact summary for Cape Breton East, highlighting the top two events by duration and customer impact. The section focuses on outage analysis and grid reliability implications but does not provide detailed data or specific event descriptions in the provided text.
Duration Zone Date/ Time Direction (Degrees) Wind (km/h) Max Wind Gusts (km/h) Temp (°C) Cause Sub-Cause Description Customers Impacted Duration (Hours) Cape Breton East 12/19/2025 21:27 Sydney 190 48 70 11 Adverse Weather Wind High winds...
AI summary The table details four outage events in Cape Breton East, caused by high winds, heavy rain, and falling trees. Each entry includes dates, wind conditions, temperature, cause (adverse weather/tree contacts), number of impacted customers, and outage durations ranging from 6 to 61 hours.
Event December 19- 20 2025 January 4-5 2018 Customers Interrupted 268,354 412,793 Customer Hours of Interruption 2,112,088 2,094,094 Customers Restored in 48hrs 98.93 99.88 Field Resources Available >600 >440 Peak Winds 115 km/h 150 km/h
AI summary The table compares outage data from two events: December 19-20, 2025, and January 4-5, 2018. It shows the number of customers interrupted, customer hours of interruption, restoration rates, field resources available, and peak wind speeds during each event.
SECTION 6: LESSONS LEARNED - Prediction model Actual high wind durations exceed forecasts provided to NSP, resulting in more outages than anticipated. - Transmission crews were staged near possible transmission events to allow for quick re...
AI summary The section highlights inaccuracies in wind duration forecasts leading to more outages than expected. NS Power used ground patrols due to helicopter limitations and utilized overnight damage assessment crews to prioritize restoration efforts, which proved effective.
CEA DEFINITIONS CI = Customer Interruptions Total number of customers without power CHI = Customer Hours of Interruption Combination of customers and duration SAIFI = Average Outage Frequency Customer interruptions / # of customers SAIDI =...
AI summary Defines acronyms related to power outage metrics, including Customer Interruptions (CI), Customer Hours of Interruption (CHI), and indices like SAIFI, SAIDI, and CAIDI, which measure outage frequency, duration, and impact.
Unknown/other Interruptions with no apparent cause or reason identified that could have contributed to the outage
AI summary The text references interruptions with no identifiable cause or contributing factor to the outage, highlighting gaps in understanding or documentation of the event.
Scheduled outage Interruptions due to the planned disconnection for construction or maintenance purposes
AI summary The document discusses scheduled outages caused by planned disconnections for construction or maintenance, impacting customer hours of interruption and service reliability.
Loss of supply Interruptions due to problem in the bulk electricity system (transmission)
AI summary The document addresses interruptions in the bulk electricity system (transmission) resulting in loss of supply, impacting customer interruptions and outage metrics.
Tree contacts Interruptions caused by trees or tree limbs contacting energized circuits
AI summary The document discusses power outages caused by trees or tree limbs making contact with energized electrical circuits, highlighting a specific cause of service interruptions in the regulatory context.
Lightning Interruptions due to lightning strike on energized circuits
AI summary The document discusses power interruptions caused by lightning strikes on energized circuits, highlighting their impact on service reliability.
Defective equipment Interruptions resulting from equipment failures
AI summary The document addresses interruptions caused by defective equipment, focusing on metrics like Customer Interruptions (CI), Customer Hours of Interruption (CHI), and reliability indicators SAIFI, SAIDI, and CAIDI. These metrics quantify outage frequency, duration, and impact on customers.
Adverse weather Interruptions resulting from weather conditions (e.g. Rain, ice storms, snow, winds, extreme ambient temperatures, freezing fog, or frost)
AI summary The document discusses power interruptions caused by adverse weather conditions such as rain, ice storms, snow, and extreme temperatures. These events impact customer hours of interruption (CHI) and outage metrics like SAIDI and CAIDI, highlighting the relationship between weather and grid reliability.
Adverse environment Interruptions due to equipment being subjected to abnormal environmental conditions (e.g. Salt spray, contamination, humidity, corrosion, vibration, fire, or flooding)
AI summary The text discusses interruptions caused by equipment exposure to abnormal environmental conditions such as salt spray, contamination, humidity, corrosion, vibration, fire, or flooding, highlighting factors that may affect system reliability and service continuity.
Foreign interference Interruptions due to external contacts beyond the control of the utility (e.g. Birds, animals, vehicles, dig -ins, or other foreign objects)
AI summary The document discusses interruptions caused by external factors beyond utility control, such as animals, vehicles, and foreign objects. These events impact service reliability and are illustrated in an accompanying image showing related data.
N-2NSPI (NSEB) RIRs 1-14
18 passages
Unknown/other Interruptions with no apparent cause or reason identified that could have contributed to the outage
AI summary The text references interruptions with no identifiable cause, highlighting outages that lack clear contributing factors. This suggests challenges in diagnosing or preventing such events, potentially impacting system reliability and customer service metrics.
Loss of supply Interruptions due to problem in the bulk electricity system (transmission)
AI summary The document discusses interruptions in the bulk electricity system (transmission) leading to loss of supply. Key metrics include customer interruptions (CI), customer hours of interruption (CHI), and outage duration indicators (SAIDI, CAIDI). The focus is on system reliability and outage frequency/duration.
Tree contacts Interruptions caused by trees or tree limbs contacting energized circuits
AI summary The document addresses power interruptions caused by trees or tree limbs contacting energized circuits, leading to customer interruptions (CI) and associated metrics like SAIFI, SAIDI, and CAIDI. It highlights the impact of vegetation management on grid reliability and outage frequency/duration.
Lightning Interruptions due to lightning strike on energized circuits
AI summary The document addresses interruptions caused by lightning strikes on energized circuits, referencing metrics such as Customer Interruptions (CI), Customer Hours of Interruption (CHI), SAIFI, SAIDI, and CAIDI to quantify outage frequency and duration. The focus is on system reliability and outage management related to lightning events.
Defective equipment Interruptions resulting from equipment failures
AI summary The section discusses interruptions caused by equipment failures, focusing on their impact on service reliability and customer experience. No specific data or mitigation strategies are detailed in the provided text.
Adverse environment Interruptions due to equipment being subjected to abnormal environmental conditions (e.g. Salt spray, contamination, humidity, corrosion, vibration, fire, or flooding)
AI summary The document discusses interruptions caused by equipment exposure to adverse environmental conditions such as salt spray, contamination, humidity, corrosion, vibration, fire, and flooding, impacting service reliability and operational performance.
Human element Interruptions due to errors of utility staff in construction, maintenance, or operations
AI summary The document highlights that service interruptions can occur due to human errors by utility staff in construction, maintenance, or operational activities, emphasizing the importance of addressing human factors in reliability and safety.
Foreign interference Interruptions due to external contacts beyond the control of the utility (e.g. Birds, animals, vehicles, dig -ins, or other foreign objects)
AI summary The text discusses interruptions in utility services caused by external factors such as birds, animals, vehicles, dig-ins, and other foreign objects, which are beyond the control of the utility.
Storm Outage Analysis Report December 19-20 NSEB IR-3 Attachment 1 Page 5 of 5 Classification 5 (a) The observed or inferred cause or contributing factor for each outage (e.g., wind, 6 lightning, ice, flooding); and 7 8 (b) A summary of cu...
AI summary The report identifies wind as the only inferred cause of outages during the windstorm event on December 19-20. The total Customer Hours of Interruption (CHI) attributed to wind outages was 569,313.
1 Request IR-5: 2 - 3 Please provide a comprehensive list of all outages classified as resulting from equipment - 4 failure or mechanical failure. For each outage, include: 5 6 (a) The type of equipment involved; 7 8 (b) The age of the equ...
AI summary The request asks for a comprehensive list of outages caused by equipment failure, including details on equipment type, age, prior defects, and findings from post-event reviews. The response refers to Attachment 1 and provides information on outages during the Dec 19-20 20 storm event, including CHI and event counts.
NON-CONFIDENTIAL 1 (d) NS Power does not re‑evaluate all equipment failures associated with weather‑related 2025-12-20 81S-306 94.9 1.6 1 1.581333333 Defective Equipment Mechanical Failure Event Day Jumper 2025-12-19 101H-423 119.9 2.0 14...
AI summary The document provides details on equipment failures, including dates, matter numbers, and associated metrics such as customer interruptions and outage durations. NS Power is noted for not re-evaluating all equipment failures linked to weather-related events.
(a) The number of unique customers affected and the duration of the outage; (b) Whether system redundancy existed and how it functioned during the event; and (c) Whether this failure mode had been previously identified in planning studies...
AI summary Thirteen outage events occurred during a December 19-20 storm due to a broken transmission line lead in a substation caused by high winds, affecting 19,379 customers with outages lasting 4.5 to 8.5 hours. The outage was due to a single initiating event on the transmission system, and three of the four affected substations had radial transmission lines, preventing customer restorations until the source was restored.
14 Provincial % Within 6 Hours 51.75 Within 12 Hours 75.74 Within 24 Hours 96.85 Within 48 Hours 99.75 15
AI summary The table presents the percentage of provincial service interruptions resolved within specific timeframes, indicating that 51.75% of interruptions were resolved within 6 hours, 75.74% within 12 hours, 96.85% within 24 hours, and 99.75% within 48 hours.
17 Region Unknown / Scheduled Loss of Tree Failed Adverse Adverse Foreign events may also include outages not originating on a customer's service line, but would still only impact a single customer. Event Type Sum of CI Sum of CH Average o...
AI summary The text discusses outage events categorized by type, including service line outages, and provides statistics such as the number of customer interruptions (CI), customer hours of interruption (CHI), and average outage duration. It clarifies that some outages may not originate on a customer's service line but still impact a single customer.
1 (b) The table below shows the minimum temperature recorded during the weather event. Weather Zone Minimum Temperature During Weather Event (°C) Valley -11 South Shore -7 Northern -12 Northeast -10 Metro -10 Eastern Shore -7 CB West -8 CB...
AI summary The text provides two tables showing the minimum temperatures recorded during a weather event and the average duration of power outages after temperatures fell below freezing in various weather zones across Nova Scotia.
NSEB, large weather events are inherently unique, and differences in timing, damage NON-CONFIDENTIAL 22 b) The average hourly storm rates of the above-mentioned resources vary greatly. They range 23 from $46 for traffic control personnel t...
AI summary The document discusses NS Power's damage prediction model, which uses weather forecasts and historical data to estimate the impact of adverse weather events on the power system. The model helps predict outage levels and customer interruptions, aiding in emergency response planning.
Date Filed: April 17, 2026 NSPI (NSEB) IR-12 Page 2 of 2 1 Request IR-13: 2 3 In M12592, the Board recently approved NS Power's capital expenditure application for 4 ECC Dynamic Line Rating (DRL) Implementation on transmission lines L-6415...
AI summary The document refers to the Board's approval of NS Power's capital expenditure for the DLR Implementation on several transmission lines. It discusses the potential benefits of the DLR project in mitigating system impacts during extreme weather events, such as the November 2018 ice storm, and asks whether the approved lines caused customer impacts during the December 19-20, 2025 storm.
For each zone, explain and quantify the expected differences in the number of customers impacted and the duration of outages. Response IR-13: (a) No. (b) N/A (c) In this event, no customer impacts were ultimately the result of outages to t...
AI summary NS Power explains that the deployment of DLR technology on transmission lines will allow for real-time monitoring and pre-emptive corrective actions, reducing the likelihood of outages caused by adverse weather conditions such as heavy wet snow and freezing rain. This is expected to minimize customer impacts and outage durations in future events.
101380NSEB (NSPI) IR-1 to IR-14
11 passages
NOVA SCOTIA ENERGY BOARD IN THE MATTER OF: THE PUBLIC UTILITIES ACT - and - IN THE MATTER OF: AN APPLICATION by NOVA SCOTIA POWER INCORPORATED for the Storm Outage Analysis Report – December 19-20, 2025 INFORMATION REQUESTS To: Nova Scotia...
AI summary Nova Scotia Power Inc. has applied for a Storm Outage Analysis Report following a December 2025 storm. The Nova Scotia Energy Board is requesting detailed information from the company, with responses due by April 17, 2026. The process is governed by the Public Utilities Act.
Request IR-2: - Please provide NS Power's storm event cause assignment methodology, including definitions, - decision rules, hierarchy of cause coding, and the proportion of events whose causes were - confirmed by field inspection versus i...
AI summary Request IR-2 seeks Nova Scotia Power's methodology for assigning causes to storm events, including definitions, decision rules, hierarchy of cause coding, and the proportion of events with confirmed versus inferred causes.
Request IR-3: - For all outages attributed to tree contact, please provide a detailed breakdown, including: - a) The number and percentage of incidents involving trees located within the maintained right-of-way; - b) The number and percent...
AI summary Request IR-3 seeks detailed data on tree-related outages, including categorization by right-of-way status, tree ownership, line type, urban/rural location, and prior vegetation management records. The request emphasizes quantifying impacts and identifying root causes for storm-related service disruptions.
Request IR-4: - For all outages attributed to adverse weather, please provide: - a) The observed or inferred cause or contributing factor for each outage (e.g., wind, lightning, ice, flooding); and Document: 328746 Date Filed: 03/26/26 Pag...
AI summary Request IR-4 seeks data on outages caused by adverse weather, including specific causes (e.g., wind, ice) and summaries of customer interruptions categorized by weather mechanisms. The request focuses on transparency in outage reporting and categorization.
Request IR-5: - Please provide a comprehensive list of all outages classified as resulting from equipment failure or mechanical failure. For each outage, include: - a) The type of equipment involved; - b) The age of the equipment at the ti...
AI summary Request IR-5 seeks a detailed list of outages caused by equipment or mechanical failures, requiring specifics on equipment type, age, prior defects, and post-event reviews to determine if failures were driven by weather, age, or maintenance factors.
Request IR-6: - Please provide a detailed explanation for each loss of supply or transmission outage referenced in the report. For each event, include: - a) The number of unique customers affected and the duration of the outage; - b) Wheth...
AI summary Request IR-6 seeks detailed explanations for each supply/transmission outage, requiring data on affected customers, system redundancy during events, and prior identification of failure modes in planning studies or maintenance assessments.
Request IR-7: - Please provide restoration performance in the following additional forms: - a) Restoration within 6,12,24 and 48 hours measured from each outage start, not storm onset; and - b) The number of outages by region and by cause...
AI summary Request IR-7 seeks detailed restoration performance metrics, including outage resolution times (6, 12, 24, 48 hours post-outage start) and outage categorization by region and cause. The focus is on granular data rather than storm-related timelines.
Request IR-8: - Please provide Customer Hours of Interruption (CHI), Customer Interruptions (CI), and average outage duration, categorized by the following event types: - a) Transmission-supplied events; - b) Substation events; - c) Feeder...
AI summary Request IR-8 seeks data on outage metrics (CHI, CI, average duration) categorized by event types (transmission, substation, etc.), aiming to assess system reliability and service quality in Nova Scotia's electricity distribution.
Request IR-9: - Section 5 refers to the storm bringing, "… upwards of 40 mm of heavy rain that tapered off before - temperatures fell below freezing". Provide the following for each zone where customers were - restored after temperatures f...
AI summary Request IR-9 seeks data on customer restoration after a storm caused freezing temperatures, including the number of customers restored, temperature deviations below freezing, and restoration duration per zone. The focus is on service reliability during extreme weather events.
Request IR-10: - The report refers to a January 4-5, 2018 storm. Compared to the December 19-20, 2025 storm, - the January 2018 storm included snow, ice pellets and freezing rain; interrupted 144,439 more - customers; had 17,994 fewer cust...
AI summary The text compares the January 2018 storm (with snow, ice, and higher winds) to the December 2025 storm, noting the 2018 event interrupted more customers but used fewer resources and restored service faster. It questions why this discrepancy occurred despite the 2018 storm being more severe.
Request IR-13: - In M12592, the Board recently approved NS Power's capital expenditure application for ECC - Dynamic Line Rating (DRL) Implementation on transmission lines L-6415a, L-6415b, L-7003, L- - 7004, L-7005, L-8001, and L-8004. In...
AI summary Request IR-13 seeks details on customer impacts from the December 2025 storm related to specific transmission lines approved for DLR implementation. It asks NSP to identify affected lines, provide meteorological data, and explain how DLR could have mitigated outages compared to the actual storm response.