Relay testers test protective relays to answer one of three questions:

1. “Did the relay manufacturer send us a functioning relay?” is answered via an Acceptance Test
2. “Will the relay operate correctly in this application as programmed?”  is answered with a Commissioning Test
3. “Is the relay still functioning correctly?” is answered with a Maintenance Test

We covered the first two questions in previous lessons. The videos in this lesson will show you a variety of maintenance testing techniques to determine if a relay is still functioning correctly.