Prior To Major Event
1. Did the distributor have any prior warning that the Major Event would occur?
Yes.
Please Provide Additional Comments:
Weather forecasts on Monday, April 28th, 2025, indicated that there was a risk of scattered strong thunderstorms along with strong wind gusts of over 60 km/h forecasted for the Ottawa area for the afternoon of Tuesday, April 29th, 2025.
2. If the distributor did have prior warning, did the distributor arrange to have extra employees on duty or on standby prior to the Major Event beginning? Brief description of arrangements, or explain why extra employees were not arranged.
Yes.
Please provide a brief description of the arrangements, or explain why extra employees were not arranged:
Additional control room operators and four extra emergency response field staff were brought in for the night shift on April 29th. The on-call team consisted of 6 powerline maintainers, 2 power cable technicians, and 2 substation electricians. Staff were placed on rest time for the day of Tuesday, April 29th. They were then directed to report to their work centres at 3:00 pm in order to stand by for the coming storm.
3. If the distributor did have prior warning, did the distributor issue any media announcements to the public warning of possible outages resulting from the pending Major event?
Hydro Ottawa issued social media posts on its main outage communications platforms (X, Facebook and Bluesky), sharing Environment Canada's warning, emphasizing preparedness, reminding customers of outage reporting methods, and reiterating that crews were ready to respond and encouraged registration to our outage alerts.
In addition, Hydro Ottawa posted a banner on its outage map and revised that after the storm hit to include restoration update messaging.
4. Did the distributor train its staff on the response plans for a Major Event?
Yes.
During The Major Event
1. Please identify the main contributing Cause of the Major Event as per the table in section 2.1.4.2.5 of the Electricity Reporting and Record Keeping Requirements.
- Lightning
- Adverse Weather - Wind
- Adverse Weather - Snow
- Adverse Weather - Freezing Rain/Ice Storm
- Adverse Environment - Fire
- Adverse Environment - Flooding
- Others
Please provide a brief description of the event (i.e. what happened). If selected "other", please explain:
A severe thunderstorm on April 29, 2025, resulted in widespread Hydro Ottawa outages affecting 40,337 customers. These outages were attributed to tree contacts, equipment damage, and two loss of supply events. Apart from the loss of supply events, four major outages occurred, with the largest—caused by a downed conductor—impacting 10,038 customers. Additionally, tree contact caused three feeder outages affecting 13,698 customers and two loss of supply outages affected 8,941 customers.
2. Was the IEEE Standard 1366 used to identify the scope of the Major Event?
Yes, used IEEE Standard 1366
3. When did the Major Event begin (date and time)?
Date: 4/29/2025
Time: 4:20 PM
4. Did the distributor issue any information about this Major Event, such as estimated times of restoration, to the public during the Major Event?
Yes, estimated time of restorations (ETRs) were provided as per Hydro Ottawa protocol.
If yes, please provide a brief description of the information. If no, please explain:
Estimated time of restoration was shared with the public on the outage map and via outage alerts (emails or text messages, depending on customer notification preference).
Social media updates also included images of restoration work, updates on progress, and sent people to the outage map for the most updated information.
5. How many customers were interrupted during the Major Event?
40,337 customers were interrupted during the Major Event.
What percentage of the distributor's total customer base did the interrupted customers represent?
The event interrupted 11% of Hydro Ottawa's total customer base
6. How many hours did it take to restore 90% of the customers who were interrupted?
98% of the impacted customers were restored by 2:40 AM on April 30th, which was 10 hours and 20 minutes after the event began.
Please provide any additional comments relevant to question #6:
N/A
7. Were there any outages associated with Loss of Supply during the Major Event? If yes, please report on the duration and frequency of Loss of Supply outages.
Yes.
If yes, please report on the duration and frequency of the loss of supply outages:
During the Major Event, two Loss of Supply outages began at 6:32 PM, affecting the Uplands MS and Merivale MS stations. These outages interrupted 8,941 customers, which resulted in 7,071 customer hours. Both restored within an hour.
8. In responding to the Major Event, did the distributor utilize assistance through a third party mutual assistance agreement with other utilities?
No.
If yes, please provide the name of the utilities that provided the assistance:
N/A
9. Did the distributor run out of any needed equipment or materials during the Major Event?
No.
If so, please describe the shortages:
N/A
After the Major Event
1. What steps, if any, are being taken to be prepared for or mitigate such Major Events in the future (i.e., staff training, process improvements, system upgrades)?
- No further action is required at this time.
- Additional staff training
- Process improvements
- System upgrades
- Others
Additional Comments:
In an attempt to reduce the impact of Tree Contact Impact during Forecasted Outage Events of this type, Hydro Ottawa will ensure additional forestry resources are on standby.