The combined overcurrent and earth-fault relay REJ 525 is a secondary relay which is connected to the current transformers of the object to be protected. The overcurrent unit and the earth-fault unit continuously measure the phase currents and the neutral current 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 overcurrent unit includes low-set stage I> and high-set stage I>> and the earth-fault unit low-set stage I0 > and high-set stage I0 >>. If the high-set stage is given a setting value within the lower part of the setting range, the relay module will have two nearly identical stages. In this case, the relay can be used in two-stage load shedding applications.
The protection functions are independent of each other and have their own setting groups and data recordings. The overcurrent protection function uses conventional current transformer measurement.
An output contact matrix allows start or trip signals from the protection stages to be routed to the desired output contact.