The MVAP 22 is essentially a fuse failure relay with changeover output contacts enabling it’s use for either voltage selection or fuse failure protection. A typical application as a voltage selection relay is the automatic connection of metering equipment to an alternative supply if the normal or preferred supply fails. As a fuse failure relay, it will monitor the output of a voltage transformer and give an alarm or disconnect protection circuits for VT fuse failure.

The relay monitors the three phase voltage supply and operates if the supply is interrupted or becomes unbalanced due to failure of the voltage transformers primary or secondary fuses.

The MVAP 22 relay can be applied to provide an equivalent function to the voltage balance relay by using one MVAP 22 per voltage transformer and connecting the output contacts of the two MVAP 22 relays. The relay combination can be used to block relays or other devices that will operate incorrectly when a voltage transformer primary and/or secondary fuse(s) blow or to give an alarm for the faulty voltage transformer.