Self-supervision

The relay’s built-in self-supervision system continuously

monitors the state of the relay hardware and the operation of

the relay software. Any fault or malfunction detected is used for

alerting the operator.

A permanent relay fault blocks the protection functions to

prevent incorrect operation.

The relay can store the records of the latest 128 fault events.

The records can be used to analyze the power system events.

Each record includes, for example, current, voltage and angle

values and a time stamp. The fault recording can be triggered

by the start or the trip signal of a protection block, or by both.

The available measurement modes include DFT, RMS and

peak-to-peak. Fault records store relay measurement values

when any protection function starts. In addition, the maximum

demand current with time stamp is separately recorded. The

records are stored in the nonvolatile memory.