As the electric grid develops to incorporate renewable generation, more robust transmission and smart meters, utilities are beginning to work on the final segment of delivery by automating their distribution networks. Despite incremental improvements, most of today’s power systems that run out from substations to customers use circa 1940’s technology, and approximately 80 percent of outages that occur in distribution are caused by storms, falling trees or mechanical failures. More than 90 percent of U.S. distribution lines have little or no automatic backup, so one failure event can cause outages miles away. Finding faults also is problematic, as this mostly relies on customer calls to identify the general fault location and boots on the ground to find it.
The solution is a smart distribution system that responds to an outage by automatically reconfiguring circuits to reroute power to as many customers as possible and reporting the fault location to expedite repairs. Industry experts estimate that approximately 50 percent of U.S. substations have been automated, but less than 10 percent have distribution systems. While equipment manufacturers around the world are in a hot competitive race to digitize distribution, S&C Electric Co., a global provider of equipment and services for electric power systems, has been developing its pulseclosing technology, which utilities are adopting.
Here’s how it works: After a conventional recloser or relayed circuit breaker opens to interrupt a fault, it typically recloses into the fault several times to determine if the fault is still present.
Pulseclosing, however, tests whether the fault is still present without creating high-current surges that cause feeder stress. The pulsecloser shuts at a precise point on the voltage waveform and re-opens its contacts very rapidly to send a very short low-current pulse down the line; it then analyzes the pulse to determine the next course of action. If the pulse indicates a persistent fault, the pulsecloser will keep the contacts open, waits a user-configurable interval, and pulses again. This process repeats several times until the pulsecloser determines that the line is no longer faulted. It then closes to restore service. If the fault persists for the duration of the test sequence, the pulsecloser will lock out to isolate the faulted section. Pulseclosing is used in S&C’s IntelliRupter overhead switching equipment, a component of the IntelliTeam automated control system.
Pulseclosing does less damage to power system equipment, keeps more lights on and more precisely identifies the location of the fault, making repairs easier for line personnel.