Principle of Operation

The three-phase overcurrent unit continuously measures the phase currents of the protected object. 

On detection of a fault the relay starts, trips the circuit breaker, records fault data etc. in accordance with the application.

REF601 has overcurrent protection with low set, high set and very high set module.

The product support both DMT and IDMT times in low set (I>) while high set (I>>) and Very high set (I>>>) supports to DMT timings. 

As the fault current exceeds the set value, trip time counting is started and start LED on front panel of relay glows ON. 

If fault current falls down below the drop off value of set current for 40 ms before trip time gets complete, start LED

will be turned off and trip count will become zero. 

Trip time will start from zero for next time when the fault current exceeds the set value again.

After a healthy trip, Start LED will be turned off and again if fault current exceeds threshold, start LED will be turned ON again.

In case of healthy trip, after trip time get elapsed relay generates the trip command which operates the Trip relay contacts as per user selected

configuration. Two LED indications on front plate of relay i.e. Trip (common trip indication) and Trip Ip and one signaling contact (XK2.3 –

XK2.4) will also be activated for user as Trip indication.