July 28, 2023

Prior To Major Event

1. Did the distributor have any prior warning that the Major Event would occur?

Yes. Thunderstorms were forecasted; however, the severity of the storm exceeded what was expected.

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. In the challenging scenario of a labour disruption, Hydro Ottawa took specific measures to ensure staff readiness and on-call staff and contractors were on stand-by.

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?


4. Did the distributor train its staff on the response plans for a Major Event?


During the Major Event

1. Please identify the main contributing Cause of the Major Event as per the table in section 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 July 28, 2023, there was a hailstorm event that caused some significant outages:

i) A circuit breaker tripped at the Lincoln Heights TD substation due to fallen trees on overhead primary conductor infrastructure. 2,261 customers were affected.

ii) A circuit breaker tripped at the Lincoln Heights TD substation as extreme winds knocked down a tree branch onto an overhead primary conductor segment. 1763 customers were interrupted.

iii) Downed primary conductor segments at multiple locations on a circuit tied to the Woodroffe TW substation. 1535 customers were impacted.

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)?

July 28, 2023 at 1:22 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? If yes, please provide a brief description of the information. If no, please explain.

Yes. Estimated Time of Restauration (ETRs) were provided on social media (Twitter/X) and through the Outage Map.

5. How many customers were interrupted during the Major Event? What percentage of the distributor’s total customer base did the
interrupted customers represent?

37,821 customers were interrupted during the Major Event, representing 10.41% of Hydro Ottawa’s total customer base.

6. How many hours did it take to restore 90% of the customers who were interrupted?

92.3% of the interrupted customers (34,906) were restored by 4:15 AM on July 29, 2023.

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. There were two Loss of Supply (LOS) outages the day of the hailstorm event:

i) On the Hawthorne TS substation that impacted 19,100 customers for a duration of 4 minutes.

ii) On the Orleans TS substation that impacted 4,373 customers for a duration of 9 minutes.

8. In responding to the Major Event, did the distributor utilize assistance through a third party mutual assistance agreement with other utilities? If yes, please provide the name of the utilities who provided the assistance?


9. Did the distributor run out of any needed equipment or materials during the Major Event? If so, please describe the shortages.


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:

Review of emergency response processes during the labour disruption.

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