Industrial earth leakage relays
- Network monitoring and protection
The electronic residual current relays allow monitoring and protection of low voltage distribution network through the use of toroidal transformer. - Carrying out the protection
Thanks to the residual current relays it is possible to measure the leakage current to earth.These relays work in conjuction with separete external toroid. The active conductors that pass through the toroid create a magnetc field proportional to the current flow. Under normal conditions and in the absence of leakage current, the vector sum of the current is zero. Any fault conditions causes an unbalance in the vector sum proportional to the value of the leakage current. The value of the fault current is constantly detected by the toroid; when the residual current relay receives a signal from the toroid, it switches its output contacts. Then the shunt-trip opens the circuit breaker.
Characteristics
- Adjusting sensitivity and tripping times
The sensitivity IΔn can be set from 0.03 to 30A while the tripping times from 0 to 5 seconds, thus ensuring flexibility for many applications. - Alarm
If the alarm function is ON, the alarm contact switches when the fault current exceeds 60% of the threshold IΔn selected. - Fail safe
The new range of ELR residual current relays allows, through a selector switch, to enable or not the fail safe function. If Fail safe is OFF, the relay activates the shunt-trip once the fault current is detected and also when there is no connection between the relay and toroid. If Fail safe is ON, the relay activates the shunt-trip also when there is lack of supply to the residual current relay. The Fail safe prevents the line from not being protected when there is no auxiliary power to the device. - Remote reset
The output contacts of the ELR residual current relays can be reset remotely, using push buttons. - Autoreset
When the fault will be removed from the network, the relay contacts will switch automatically, without the need to press the reset button from a local or remote position. - Frequency filtering
This feature makes the relay stronger in presence if currents with harmonic components that are not due to an effective fault in the circuit but they are typically caused by the presence of electronic filters (e.g. when using frequency converters driving motors) - Fault memory
The fault memory turns on in case of a fault and is only resettable manually. In this way it is possible to know if the relay has tripped even if the fault is no longer present and the contacts have returned into the standard position thanks to autoreset. - Digital display
The digital display allows instant reading of the value of earth leakage current. It is possible, through a minidip, to block the display on the residual current value that has generated the intervention of the circuit breaker.
