An Automatic Trip-and-Carrier Test for Phase-Comparison Carrier-Current Relays

This paper describes a system which, every 4 hours, automatically makes a trip-and-carrier test on phase comparison carrier current relays. It is intended to duplicate, as nearly as is practical, the trip-and-block test recommended by the relay manufacturer. The equipment is designed for installation on transmission lines between unattended stations. During the trip portions of the test the relay is blocked for approximately 1/2 second. However, if a fault should occur during this time, the protective relay will be restored to normal service in 10 cycles.