Topic:"Unplanned Outage" in M12728

Outage Restoration Profile: Metric Result Unique Customers Impacted 198,998 Customer Interruptions 268,354 Total Customer Hours 2,112,088 Event Start Time Dec 19 15:25 Event End Time Dec 20 19:33 Main Regions Impacted Entire Province

AI summary The outage restoration profile details a widespread power outage impacting 198,998 unique customers across the entire province, resulting in 268,354 customer interruptions and 2,112,088 total customer hours. The event occurred from December 19 at 15:25 to December 20 at 19:33.

\ \ 93.62% of customers were restored prior to the stormy weather ceasing. Average restoration time for the storm was under 19.5hrs.

AI summary The document indicates that 93.62% of customers were restored before the stormy weather ended, with an average restoration time of under 19.5 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.

Customers Restored within X hours of Storm Onset Northeast % Within 6 Hrs 1.86% Within 12 Hrs 40.82% Within 24 Hrs 82.42% Within 48 Hrs 97.71% This table represents the percentage of customers restored within 6, 12, 24, or 48 hours of the...

AI summary The table shows the percentage of customers in the Northeast region restored within specific timeframes after a storm, with 97.71% restored within 48 hours. The average restoration time for the region was 25.2 hours.

Duration Zone Date/ Time Direction (Degrees) Max Wind Gusts (km/h) Temp (°C) Cause Sub-Cause Description Customer s Impacted Duration (Hours) Cape Breton West 12/19/2025 21:18 Gr. Étang 160 57 93 13 Tree Contacts Falling Trees High winds c...

AI summary The document details two outage events in Cape Breton West, Nova Scotia, caused by high winds and falling trees, impacting a total of 1,574 customers over a combined duration of 81.54 hours. Both incidents involved tree contacts with primary lines, leading to fuse or recloser operations.

SECTION 5: COMPARISON TO SIMILAR OUTAGE EVENTS - The 2018 storm brought stronger peak winds than the 2025 event, but both produced significant tree and line damage across the province. - Both storms began with above freezing temperatures,...

AI summary This section compares the 2018 and 2025 storms, noting differences in weather conditions and their impacts on infrastructure. The 2018 storm had stronger winds and included freezing precipitation, while the 2025 storm brought heavy rain and occurred under conditions that slowed repair efforts.

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.

Storm Outage Analysis Report December 19-20 NSEB IR-3 Attachment 1 Page 5 of 5 Classification 15S-303 suburban #N/A 1.02 16N-301 rural 2025 2.53 16N-302 rural 2025 2.83 16V-314 rural 2025 2.59 16V-315 rural 2025 2.22 16W-301 rural 2025 1.9...

AI summary The document presents a storm outage analysis report detailing classifications, trim years, and average vegetation condition for various areas in Nova Scotia. It includes data on rural, urban, and suburban classifications, along with metrics such as average outage frequency and duration.

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 2 outages unless new evidence warrants further review. Further investigation may be 3 undertaken where anomalies are identified dur...

AI summary NS Power does not re-evaluate all equipment failures related to weather-related outages unless new evidence warrants further review. The document indicates that only a small proportion of outages (less than 1%) were attributed to device failure or defective equipment during the event in question.

(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.

NON-CONFIDENTIAL 1 Request IR-7: 2 3 Please provide restoration performance in the following additional forms: 4 5 (a) Restoration within 6,12,24 and 48 hours measured from each outage start, not storm 6 onset; and 7 8 (b) The number of ou...

AI summary The response to Request IR-7 provides restoration performance metrics, including the number of customers restored within specific timeframes (6, 12, 24, and 48 hours) following outages, and categorizes outages by region and cause.