Causes of outages

Breakdown of service interruptions in Québec (without considering number of customers affected). (2006-2007 data).

35 % Foreign objects

The largest proportion of service interruptions are caused by contact with or damage from foreign objects, such as vegetation, animals, birds or vehicles, or by vandalism.

24 % Scheduled outages

The power is sometimes cut off deliberately so that crews can safely carry out system maintenance, modifications or reinforcement work.

21 % Equipment or apparatus

Equipment failure or a mechanical or electrical defect on the distribution system.

13 % Weather events

Power failures caused by weather events (lightning, ice, wet snow, high winds, etc.) generally attract a lot of attention, since they affect many customers at once over large geographical areas.

4 % Loss of supply

Loss of supply from a transformer substation, the transmission system or a generating facility can affect many customers at once.

2 % Environmental factors

Environmental factors such as pollution, high humidity, or rust on equipment can lead to power failures.

1 % Human error

A relatively small percentage are caused by operating errors, testing of defective equipment, accidental contact, etc.