Reasons for Power Outages

There are two major categories of power outages, “Momentary” or “Sustained”, depending on the duration. In addition to these two types of outages, there are also planned power interruptions that are required for certain types of maintenance and repairs on the system. In these cases, Alectra Utilities notifies affected customers prior to the interruption. 

Momentary Outage is defined as a brief power interruption lasting one minute or less, but typically is only one or two seconds. While momentary outages are inconvenient, the automatic equipment on the Alectra Utilities distribution system helps to prevent longer duration outages. 

Sustained Outage is defined as a power interruption that lasts longer than one minute and may require Alectra Utilities staff to be dispatched to fix the problem. The time required to restore the power is dependent on many factors, but is often restored within hours. 

Outages may last a few seconds or a few hours, depending on the cause.  

Outage Causes

The most common causes of power outages are adverse weather (storms, tree contact and snow), animal contact, equipment failure and planned power interruptions. These and other common causes are defined further below; 

  • Adverse Weather 
    Strong storms (high winds, snow and ice) can cause trees, branches or other objects to fall on power lines resulting in outages. Lightning storms can damage distribution equipment, also resulting in power outages. 
  • Animal Contacts 
    Animals such as birds, squirrels and raccoons from time to time come into contact with a piece of energized electrical equipment, resulting in a power outage. 
  • Dig Ins 
    Occasionally, underground cables get damaged by individuals who accidentally dig into them. This can lead to a power outage. It is the law to call before you dig. Cable failures are difficult and timely to repair. 
  • Equipment Failures 
    Alectra Utilities inspects and maintains its equipment on a regular basis, however sometimes equipment can reach its end of life prior to us replacing it. This can result in an outage depending on the nature of the equipment. 
  • Planned Outages 
    Alectra Utilities notifies the customer in advance of any power interruptions due to planned maintenance or plant upgrade activity. Our Customer Care department works with affected customers to plan the outage around their schedules in order to minimize disruption. 
  • Vehicle Accidents 
    Vehicle collisions with utility poles or equipment can cause outages. 

Ontario Electricity Emergency Plan

The Province of Ontario and the Independent Electricity System Operator (IESO) have an Ontario Electricity Emergency Plan that is used in the event of a large-scale electricity emergency in Ontario. The IESO, in consultation with the Ministry of Energy, can declare an electricity emergency. 

A sustained power outage has the potential to adversely impact public safety, the environment, security and the economy. The general public can prepare for power outages before they happen. 

The IESO has a three-level media advisory process to alert the public to any power disruptions. Others in the electricity industry can also be expected to issue media advisories to address local or specific issues. 

1. Power Advisory 

This is issued when electricity is in tight supply. All electricity consumers and industries are asked to voluntarily reduce their electricity consumption. 

2. Power Warning 

This is issued when there is an elevated level of concern about the reliability of the electricity supply and the IESO is implementing emergency control actions. All electricity consumers, including industries, are asked to immediately reduce their electricity consumption. Any further unforeseen increase in electricity demand, or reduction in supply, may result in the need to implement load shedding. Load shedding means that electricity supply to consumers will be disrupted on a rotating basis across the province for approximately 30 minutes to an hour, depending on the extent of the electricity shortfall. Under these circumstances, advance notice may not be possible. 

3. Power Emergency 

This is issued as a last resort when the IESO must implement load shedding. 

Community Response

As with any emergency, communities have emergency response plans and organizations in place to deal with an extended power outage. They work closely with their local electricity distributor (e.g. Alectra Utilities) and Emergency Management Ontario to monitor the situation, and ensure that public safety is protected during a power outage. 

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