Power Outages Explained: Why They Occur

Power Outages Explained: Why They Occur

The electric grid in the San Diego region has been recognized as one of the most reliable in the Western United States for 14 consecutive years. At SDG&E, we understand that there is no convenient time to be without power and work hard to prevent outages. Unfortunately, they do occur infrequently for various reasons, sometimes without advance notice to our customers.

This article will explain the different types of outages, their causes and how the notification process works.

Unplanned Outages

Outages that occur unexpectedly are referred to as "unplanned outages." These occur for various reasons, such as traffic accidents, damage to power lines caused by falling tree branches, storms, high winds and even metallic balloons caught in overhead wires. Unplanned outages typically last longer than planned outages, because personnel and equipment need to be mobilized without advance notice to respond to an emergency.

When these types of outages happen, and whenever it is safe to do so, we work to isolate the damaged area and reroute power so service can be partially restored to some customers while repairs are underway. Also, we will post information on the cause and the estimated time power will be restored on our outage map (sdge.com/outages). Customers may also want to sign up for alerts through sdge.com/MyAccount.

Planned Outages

Planned power outages can be necessary when our company needs to perform maintenance and system improvements to your neighborhood's power system (or perhaps to connect new developments). System upgrades include replacing outdated or worn-out equipment and building out the system to support future growth. To safely complete the work, it's necessary to turn off power in some areas.

With planned outages, crews and materials are organized to complete the work as quickly and as safely possible. Planned outages to replace equipment before it breaks can help avoid extended, sudden outages.

We will provide advance notice regarding planned outages to customers. These notifications come in the form of mailed letters and/or automated phone calls. To receive all notifications, please make sure to update your personal contact information through sdge.com/MyAccount.

CAISO Rotating Outages

The California Independent System Operator (CAISO) is responsible for operating the state's larger electric grid. In certain circumstances, particularly when high energy demand puts a strain on the electric grid, or there is a shortage of energy supply, the CAISO may call for voluntary conservation by issuing "Flex Alerts." When conservation efforts aren't enough, the CAISO may order rotating outages as a last resort to maintain grid stability. This occurred in August of this year, the first in California in nearly two decades when an extended heatwave drove up electricity demand to very high levels and supplies were insufficient to meet the demand.

Our company must follow the direction of the CAISO, who makes every effort to provide an advanced warning so utilities follow suit. Depending on how quickly circumstances change, it may be difficult to provide significant notice of a rotating outage in the preceding day or hours before they occur. If CAISO officials inform utilities of a potential need for rotating outages, we will reach out to customers through local media, social media and phone calls, as well as post information on sdge.com, to alert them of the situation. However, grid conditions are dynamic and can change within minutes – either necessitating or eliminating the need for rotating outages.

We must submit what is called a load curtailment (rotating outages) plan to the California Public Utilities Commission (CPUC) annually, which outlines in what order outages will occur if needed. Power will be turned off to groups of customers according to their rotating outage block number. Our customers can always see whether they may be affected by checking their circuit number and curtailment block number on their paper bill, via our SDG&E app and sdge.com/MyAccount. Affected customers can then compare their circuit and block numbers with the list posted at sdgenews.com, during times when rolling outages are expected.

Public Safety Power Shutoff (PSPS)

When dangerous fire weather conditions are forecasted, we may need to turn off power to help prevent wildfires. Public Safety Power Shutoffs (PSPS), which are approved by state regulators to protect public safety, are used as a last resort. In addition to notifying local media and posting information on its website and social channels, we will communicate directly with customers through our Emergency Notification System by phone, text, or email in advance of an event. Communications will occur 24-48 hours prior, and again before shutting off power and throughout the event until power is restored.

Turning off customers' power is not something we take lightly, but PSPS events are necessary to ensure the public's safety.

Our new Public Safety Power Shutoff mobile app: Alerts by SDG&E is a great tool to help customers stay on top of information about potential and active PSPS events, including estimated restoration times.

We recognize that power outages are inconvenient and can create challenges, and appreciate customers' patience and understanding. Our customers can always refer to the outage map for the latest information.