• A Eberle GmbH & Co KG

Transient Earth Fault Relay

Transient earth fault relays monitor each feeder of the bus bar and signal transient earth faults and transient earth faults with continuous earth faults. The different features of the relay and the easy change of parameters offer an optimal adaptation to the system. The chosen acquisition principle follows the proven technique of the transient earth fault relay EWR 2 and EWR 20/21. For the detection of an earth fault and its direction the zero sequence voltage UNE and the zero-sequence-current are measured and their polarities are compared immediately after an earth fault event. To prevent an accidental reaction of the transient earth fault relay this comparison is only carried out in a very small time slot. The zero sequence voltage is used as a reference quantity for the direction of the zero-sequence-current. If both measured quantities have the same polarity the earth fault lies in the direction of the feeder, in case of an unbalanced polarity towards the bus bar.
Adjustable trigger value of the zero sequence voltage and the measured current, suppression of the transient earth fault signals depending on the selected minimum time of the zero sequence voltage, suppression of earth fault signals towards the bus bar (optional), in case of a new earth fault the choice for retention or reset of the previous status and indication of actual direction of the earth fault is possible, signal status remains in case of power supply failure (bi-stable relay), manual reset of the indication by an external signal or automatically after a selectable time and signal for zero sequence voltage UNE>U as LED and relay output are the special characteristics of the relay.