Issue 80 - August 2025
Distribution Reliability
Electricity Canada’s Distribution Reliability Committee recently released their annual report breaking down the data of power interruptions in 2024. The report identifies the duration time of the average interruption, to the frequency of them happening and much more! Current Affairs sat down with Dan Gent, Director of Transmission and Reliability to learn how this affects customers.
Hi Dan, thanks for joining us! What does the reliability data in this report get used for?
When I think about it, it’s like it's a benchmarking report. Any utility can take a look at the report and identify how they're comparing in against all the participants in the Distribution Reliability Committee at Electricity Canada. Through this report you can identify the biggest contributors of an outage per company.
If you can identify what is causing the most outages (trees, weather, animals etc.), you can identify where you want to put your resources. The report provides proof of increasing trends, and it gives utilities justification to increase their investments in capital planning for their rate filing.
Describe the national indicators and what they mean?
There are many national indicators, but I will touch on the most popular ones, SAIDI and SAIFI. These are global industry standards so if you go to France, Brazil, Germany – they all measure system performance in this way. They’re also used by governments and regulators to determine how well the electricity system is preforming.
SAIDI stands for System Average Interruption Duration Index, which is the amount of time in minutes the average customer has been without power.
SAIFI stands for the System Average Interruption Frequency, so it measures the amount of times customers have been without power.
To get the whole picture we can calculate the Customer Average Interruption Duration Index which is CAIDI. This looks at on a national level, how many hours the average customer has been out individually.
What are some fun facts that have come out from this year’s report?
For the past several years, trees have been in the number one contributor for power interruptions. They are the biggest contributor in terms of outage duration at 33% in 2024.
If a tree falls on a line, it is an issue around safety because you have to shut off the power line and make sure the area is safe so the utility can remove it. You’re also taking into consideration debris from the tree, things the tree has hit on the way down and assess any trees that might have fallen or be on the verge of falling. And it’s not just big storms that cause this, branches can also fall on blue sky days. It’s a bit longer of a process to put that line back up and reconnect the power.
Also in 2024, 15% of outages were related to equipment failure. What's happening on a regular basis now is that high winds or ice storms are coming through more frequently, and that causes wear and tear on the infrastructure and equipment. I mean, how often can a distribution line or a pole withstand 120-kilometre winds until it breaks? How often can the power lines hold 2 tonnes of ice before it snaps? You could maybe survive the first time, but after three times, maybe not so much.
The data shows that we need to think about the age of some of the equipment and the wear and tear it is getting on a yearly basis.
If the reliability of the grid calculated as 99.9286%, how can some people be out of power for weeks and some minutes?
Well, the reliability index is a calculation based on the entire population. So you total up the amount of hours of outages and the amount of hours that people are connected to the grid.
You’re connected to the grid 8760 hours a year, but you might experience an outage for a month. Then you’re calculating the 720 hours in the month divided by 8760 which is actually less than 10%. When you flip it around, your availability or connected reliability to the grid is actually about 92%.
It’s the ENTIRE population and EVERY outage whether it’s a minute or a week out of 8760 hours. It’s a big impact to the individual customer obviously, but from the availability of the system perspective, it’s so small.
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