Case Study #1
City Recloser Settings
Overview:
“Every time we want to close a switch to energize a subdivision we have to go to the substation and block the ground trip on the recloser.” This became the line crew’s standard practice to avoid a trip and reclose operation on the circuit. Active Power Engineering helped this city power department discover the problem with the substation’s recloser settings, and develop, install, and test new recloser settings. Since implementing these changes crews have been able to energize subdivisions without blocking the ground trip and without have the nuisance recloser operation.
Case Study #2
Substation Breaker Mis-operations
Overview:
“Why was there a trip and reclose on Feeders 511 and 513, when the fault was on Feeder 514?” This question kicked-off Active Power Engineering’s analysis of the breaker operations at one city’s substation. On August 26, 2020, after a C-phase to ground fault (a failed single-phase transformer) on Feeder 514, the breaker on Feeder 514 operated. The breakers on Feeders 511 and 513 also operated. The event recordings from the SEL 351 relays on the three breakers were downloaded and analyzed to determined what happened, why it happened, and what could be done to prevent unnecessary operations.
