Technical data

1MRS751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

If the fault is considered too dangerous to maintain normal protection, an inoperative

IRF state is entered and no output relay operations are allowed. On the other hand

if, for example, one output relay is found faulty and the others healthy, normal

operations targeted to a healthy relay are allowed.

Even a total breakdown of the relay, for example, on loss of power supply, will be

detected as the IRF relay operates in a fail-safe mode, causing a signal when the

relay drops off. The serial communication will also indicate loss of contact to the

module. When the relay is in the IRF state, it tries to recover by restarting every five

minutes.

As long as the fault remains, the relay continues to perform internal tests. Should the

fault prove to be of temporary nature, normal operation is recovered after restart and

an event “IRF reset” (E30) is sent over the serial communication.

5.1.11.1. Fault indication

The self-supervision signal output operates on the closed circuit principle. Under

normal conditions the output relay is energized and the contact gap 3-5 is closed.

Should the auxiliary power supply fail or an internal fault be detected, the contact

gap 3-5 is opened.

A051908

Fig. 5.1.11.1.-1 Self-supervision output (IRF)

When a fault has been detected, the green READY LED indicator starts blinking, a

fault indication text is displayed on the HMI and an event “IRF activated” (E31) is

generated over serial communication.

IRF

Normal condition

Fault condition