City of Vernon California

Information on Outages

What Causes Power Outages?

There are many different causes for power outages throughout the country and the world. Wind, rain, extreme heat, ice, and snow are some of the most common causes of widespread power outages.  Trees can also be a common cause of power outages due to high wind conditions, or when trimming by an untrained trimmer, tree limbs can come into contact with power lines, ultimatley causing power interruptions.  Mylar balloons coming into contact with power lines can cause the circuit to short and create an outage.  Vehicle collisions with utility poles are also common cause for power outages.  Seismic activity of any size can damage electrical facilities and power lines.  Animals such as birds, rats, squirrels, ect. may cause power lines to short circuit.  When lightning strikes electrical equipment, transmission towers, wires, and poles, outages may occur.  Underground cabling may be disturbed by digging activity.  During heat waves and other unusually high power demand conditions, overburdened electric cables, transformers, and other electrical equipment can fail.

What Is A Rolling Blackout?

A rolling blackout, also referred to as load shedding, is an intentionally-engineered electrical power outage where electricity delivery is stopped for non-overlapping periods of time throughout geographical regions. Rolling blackouts are a last-resort measure used by an electric utility company in order to avoid a total blackout of the power system. They are usually in response to a situation where the demand for electricity exceeds the power supply capability of the network. Rolling blackouts may be localized to a specific part of the electricity network or may be more widespread and affect entire countries and continents. Rolling blackouts generally result from two causes: insufficient generation capacity or inadequate transmission infrastructure to deliver sufficient power to the area where it is needed. In a Stage 1 emergency only a general call for voluntary conservation is issued, while a Stage 2 emergency results in power being temporarily cut off to certain large users, primarily industrial concerns, who have agreed to this arrangement in exchange for lower rates. When a Stage 3 power emergency is declared, electricity to one of the grids is shut off for a fixed period of time, which can range from 60 minutes to 2½ hours. If after this period of time the Stage 3 emergency still exists, power is restored to this grid but then the next grid in the sequence is blacked out, and so on, until the situation is stabilized — the blackout thus "rolls" from one grid to the next.

Unscheduled Outages

Unscheduled outages are typically one of two types: a) forced outages and b) circuit outages. Forced outages are where an immediate problem is identified that must repaired as soon as possible to prevent further damage or mitigate a potentially longer outage.  In this case, the impacted customer may or may not be notified due to time constraints.  In the case of a circuit outage, typically an entire circuit is out, and all affected customers cannot be notified in advance. An emergency unplanned outage is a result of the loss of a section of the power network due to a fault. There are several major categories of faults which may occur without prior indication. Some common types are equipment failure, cable faults, damage by third parties or severe climatic conditions adversely affecting the networks (such as a lightning strike). In these situations, there is no possibility of giving consumers early warning of an impending outage.

Restoring Service

Priorities during an unplanned outage are to ensure safety to the public and utility personnel, to limit damage to equipment and to efficiently restore service to substations and primary lines. During an outage, the Light & Power department will send utility personnel into the field to locate and monitor safety hazards such as downed wires and poles. Crews then make sure electricity has been turned off to them to ensure the public is safe from any possible hazards. In addition, practicing good common sense can keep you and safe from potential electric shock. Please avoid all areas where wires have fallen or where trees and or vehicles have come into contact with lines or a power pole. Remember, any wire that has fallen on the ground should be considered very dangerous and reported to the City of Vernon immediately. Under severe circumstances, it may take some time to find the cause of an outage. Please be patient as field crews are working diligently to restore power as quickly and safely as possible to customers.