The IRF contact functions as an output contact for the self-supervision system of the protection relay. Under normal operating conditions, the protection relay is energized and the contact is closed (X100:3-5). When a fault is detected by the self-supervision system or the auxiliary voltage is disconnected, the contact X100:3-5 drops off and the contact X100:3-4 closes.
| Terminal | Description |
|---|---|
| X100:3 | IRF, common |
| X100:4 | Closed; IRF, or Uaux disconnected |
| X100:5 | Closed; no IRF, and Uaux connected |