Prior To Major Event
1. Did the distributor have any prior warning that the Major Event would occur?
No.
Please Provide Additional Comments: This event was triggered by a broken conductor on the Hydro One owned transmission circuit and subsequently, Hydro Ottawa equipment failure. There was no prior warning that this event would occur.
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.
No.
Please provide a brief description of the arrangements, or explain why extra employees were not arranged: N/A - No prior warning
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?
N/A - No prior warning
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.
- Loss of Supply
- Lightning
- Adverse Weather - Wind
- Adverse Weather - Snow
- Adverse Weather - Freezing Rain/Ice Storm
- Adverse Environment - Fire
- Adverse Environment - Flooding
- Others
1.1. Please provide a brief description of the event (i.e. what happened?).
On March 27, 2025, starting at 02:31 am, a downed conductor led to two Hydro One circuit trips (C7BM and S7M). Power was gradually restored throughout the morning. During restoration, at 07:36 am, a blue phase insulator on the Hydro Ottawa Centrepointe T1 transformer failed. Centrepointe T1 was isolated, allowing C7BM to be restored. All customers were back online at 9:26 am.
2. Was the IEEE Standard 1366 used to identify the scope of the Major Event? If not, why not?
Yes. Hydro Ottawa used the IEEE Standard 1366.
3. When did the Major Event begin (date and time)?
March 27, 2025, at 2:31 AM
4. Did the distributor issue any information about this Major Event, such as estimated times of restoration, to the public during the Major Event? If yes, please provide a brief description of the information. If no, please explain.
Yes. Estimated time of restorations (ETRs) were provided as per Hydro Ottawa protocol.
5. How many customers were interrupted during the Major Event?
A total of 63,978 customers were interrupted during the Major Event.
What percentage of the distributor's total customer base did the interrupted customers represent?
The Major Event interrupted 17% of Hydro Ottawa's total customer base.
6. How many hours did it take to restore 90% of the customers who were interrupted?
90% of customers' power was restored in 4 hours and 48 minutes.
Please provide any additional comments relevant to question #6:
This represented 46,355 of the 51,601 customers restored by 07:19 am EDT, both through efforts by Hydro One and Hydro Ottawa to resupply stranded customers.
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:
The main contributing factor to the MED was the Hydro One loss of supply outage (S7M / C7BM trip). The outage impacted 51,601 customers for 2 hours and 22 minutes, which were restored on March 27th at 4:53 am.
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:
Post Event Debrief and Switching Order Review with System Office Staff Completed Hydro Ottawa's Stations Inspection Program Continuation to support the potential early identification of equipment at risk of failure.