Keeping the lights on when nature works against you
“Our line workers take pride in keeping the lights on,” says Phillip Mullins, Southwest Tennessee Electric’s new vice president of operations and engineering. “But despite the best of efforts,” Mullins continues, “outages do sometimes occur.” Damage caused by wind, lightning, or severe storms usually occurs at several points in the transmission and distribution system. “This is especially true of ice.”
Ice accumulations can cause tremendous damage to an electric distribution system. Diameters of ice-coated distribution lines may reach several inches, adding 10 to 20 pounds-per-foot of weight to wires and supporting structures. Though lines are designed to support heavy ice loading, the combined effects of wind and falling trees and branches will typically result in damaged equipment and power outages. “Damage from storms is usually isolated to a few areas,” says Mullins, “but ice storms can affect hundreds of square miles and make recovery painfully slow.”
As the weather turns colder and the winter storm season begins, STEMC crews prepare and plan to deal with severe winter weather. In the event of widespread outages, STEMC crews follow an outage management plan that is designed to restore service to the largest number of members in the shortest amount of time.
“Outages appear on a map in our dispatch center,” says Mullins. “When a crew is dispatched to the outage, a truck appears on the map. Outage management is all about being efficient when you have more outages than crews to send.”
According to the plan, crews first determine if STEMC substations are energized. In the situation depicted below, the substation is energized, so crews then begin checking main distribution lines. They quickly find Problem 1. By fixing Problem 1, service will be restored to the 10 members in Neighborhood A as well as Member D. Crews see Problem 3, but realize their time will be used more efficiently by fixing Problem 2. This restores service to the 8 members in Neighborhood B. They continue moving along main distribution lines restoring power to large groups of members.
Once problems impacting multiple members have been repaired, the crews then return to Problem 3 and restore service to Member C. Finally Member E will have service restored once Problem 4 is repaired.
All of these activities, which are often much larger in scale than the example depicted here, is carefully orchestrated by STEMC’s dispatch center. Here, dispatchers answer calls, monitor the system, assist with remote operation of substations, and oversee the restoration of service.
STEMC line workers are trained and equipped to deal with the catastrophic effects of winter weather. Despite the cold, crews will work as quick and as safe as possible to restore service to every member.
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