Improving Reliability Through Greater Feeder Segmentation
Some utilities have begun looking to increase feeder segmentation with advanced communications-based coordination, which would enable them to go beyond the limitations of conventional coordination techniques for traditional reclosers or circuit breakers.
Today, feeder restoration commonly uses a loop scheme, where two sources with a number of sectionalizing devices, typically reclosers, are on a feeder and a tie point is between the two circuits. Through a loop scheme, the faulted section of the feeder can be isolated, and the unfaulted section can tie back to the second source. However, because the reclosers must coordinate using Time-Current Characteristic curve techniques, such restoration schemes are limited to typically about five segmentation devices—two normally closed devices for each source and the open point.
Use of this technique provides reliability improvement beyond just having straight feeders with no alternate sources, but the segmentation is limited by the number of devices you can coordinate.
Using advanced fault-interrupting devices capable of coordinating with each other through communication-based segmentation can expand segmentation even further. This technology uses prioritized messaging and low-latency wireless or fiber-optic communications to send messages between devices, adapting to adjust coordination at the onset of a fault.
When using communications capable of providing a low-latency/high-bandwidth response, utilities theoretically can have an unlimited number of devices set with the same coordination characteristics. Once the devices see a fault, they communicate among themselves to properly coordinate the right device to respond to the fault, thus maintaining power in unaffected areas.
This strategy and communications technique will benefit anyone who has built out their infrastructure to the limitations that prevent them from further segmenting their feeders. It’s something they can evolve to after the basic infrastructure setup.
As we move forward, customers will see a greater need to put more robust communications out on their feeders. As they build up their communication infrastructure, this technology will allow them to leverage that infrastructure to expand their feeder segmentation even further to improve their grid reliability efforts.
I’d like to hear you thoughts on this in the Comments section below. In an upcoming blog item, I’ll discuss ways to reduce the stress fault current places on utility equipment.
September 21, 2016