Breakdown of service interruptions in Québec (without considering number of customers affected). (2006-2007 data).
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.
The power is sometimes cut off deliberately so that crews can safely carry out system maintenance, modifications or reinforcement work.
Equipment failure or a mechanical or electrical defect on the distribution system.
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.
Loss of supply from a transformer substation, the transmission system or a generating facility can affect many customers at once.
Environmental factors such as pollution, high humidity, or rust on equipment can lead to power failures.
A relatively small percentage are caused by operating errors, testing of defective equipment, accidental contact, etc.
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