Protection Function

Three Phase Current Protection

Functionality

The three-phase overcurrent protections is used as single-phase, two-phase

or three phase non-directional overcurrent and short-circuit protection for feeders.

The function starts when the current exceeds the set limit. 

The operate time characteristics for low stage is both DMT and IDMT and high stage is definite time (DT) definite minimum. 

The instantaneous stage always operates with the DT characteristic.

In the DT mode, the function operates after a predefined operate time and resets when the fault current disappears. 

The IDMT mode provides current-dependent timer characteristics.

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.