The directional or non-directional earth-fault relay REJ 527 is a secondary relay which is connected to the voltage and current transformers of the object to be protected. The earth-fault current and the zero-sequence voltage unit continuously measure the zero-sequence voltage, earth-fault current and phase angle of the object. On detection of a fault, the relay will start, trip the circuit breaker, provide alarms, record fault data, etc., in accordance with the application and the configured relay functions.
The voltage unit includes low-set stage U0b> and the earth-fault current unit low-set stage I0 > and high-set stage I0 >>. The earth-fault stages can be replaced by two additional voltage stages, low-set stage U0 > and high-set stage U0 >>.
The protection functions are independent of each other and have their own setting groups and data recordings. The voltage and current functions use conventional transformer measurement.
An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact.