Mitigating Carrier Holes in Power Line Carrier

Carrier holes is loss of a power line carrier signal when it should be present during a fault resulting in a miss-operation. A study was performed to determine the dominant cause of unexplained carrier holes which has pointed to the extended firing time of spark gaps located in line tuners and CCVTs (Coupling Capacitor Voltage Transformers). Then lab tests and field tests were performed to simulate carrier holes caused by transients in typical pilot protection systems. Finally, the same tests were run with improved spark gaps and compared with significant improvements noted. Results are presented, and recommendations made to mitigate carrier holes.