The project involved engineering prior to installation to determine the relay settings, a wiring schematic, assistance with panel layout, removal of equipment with replacement as well as testing and field commissioning. A total of 4 circuit breakers at 2 different substations were completed, replacing 20 existing relays.

Below, right, is a bench test of one of the relays after programming to verify correct functionality. The latching relay in the lower left hand corner was connected to simulate the operation of an oil circuit breaker open close operation with 52a contact transition during reclosing. Both relays were tested in this fashion to speed installation. Once the relays were installed, current injection tests were performed to verify ct continuity as well as functional testing of the control scheme.

Relays to be removed were 8 directional over current relays and 2 reclosing re-lays. The replacement units were SEL 351A functionally the same. The directionality of the ground relay was dependent on a broken corner delta con-figuration. This was not necessary with the new 351A. That wiring was removed.

The test set up above shows two computers, one controlling the test set and the other connected to the relay. This allows the engineer to verify the injected signal into the relay to insure the proper magnitude, phase angle and phase relationship.

The completed relay installation with OCBs back in service.