Shunt trip breakers essentially provide an off switch remotely or a direct link to a system outside the main breaker. Remote manual switches allow for human control while direct link automatically shuts off the breaker.

3.3. 2 (Safety Code for Elevators and Escalators) and the NEC 620.51(B) require power to an elevator be shut down prior to the release of water in the elevator shaft or machine room. This is typically accomplished by a shunt-trip device. Surge protection is required per NEC 620.51.

Whereas Designated and Alternate Elevator Recall captures and sends the elevator cab to safe floors, elevator shunt trip works a little different. Elevator Shunt Trip is a function that involves shunting the breaker that controls the elevator equipment prior to the release of the automatic sprinkler systems.

Emergency Shunt Relay. By Lighting Controls & Design. Normally-closed electrically-held relay to be wired in parallel with a wall switch. Manually controlled emergency lighting will be automatically shunted on during a power outage.

Earth Leakage relays (ELR’s) or also known as ground fault relays are residual current monitors (RCM’s) that are used to detect potentially dangerous ground fault currents before they cause any hazard. Causes for ground fault currents: Inadequate insulation due to mechanical damage of cables and devices.

Earth leakage relay vs Earth Fault relay Earth leakage relays are used to sense small magnitude of currents. Any leakage to the earth causes an imbalance between the phase and neutral currents. Earth fault relay senses this current and trips the circuit breaker.

Earth-fault relay is used to protect feeder against faults involving ground. Typically, earth faults are single line to ground and double line to ground faults. For the purpose of setting and coordination, only single line to ground faults are considered.

If there is no earth fault present, the vector sum of the currents in a three-phase supply is zero. If current from any phase flows to earth the toroid flux becomes unbalanced. The toroid produces an output, which trips the relay.

Operation. An ELCB is a specialised type of latching relay that has a building’s incoming mains power connected through its switching contacts so that the ELCB disconnects the power when earth leakage is detected. The ELCB detects fault currents from live to the Earth (ground) wire within the installation it protects.

Core Balance Current Transformer or CBCT is a ring-type current transformer through the center of which a three core cable or three single core cables (forms the primary winding) of three phase system passes. This type of current transformer is normally used for earth fault protection for low and medium voltage system.

TESTING PROCEDURE FOR EARTH LEAKAGE RELAYS (ELR)

1. Record all particulars of relay to be tested and its working settings.
2. Check that auxiliary supply voltage connected to the relay corresponds to rated.
3. Connect output of the test set to input terminals of ELR.

ELR (Earth Leakage Relay) ensures the protection of electrical installations and person against direct and indirect contacts. ELR is designed on an electronic basis, which ensures the monitoring of earth fault currents.

The 10 position trip current switch offers selectable earth leakage current settings from 30mA to 10 amps and the 16 position time delay set point switch offers additional delay for fault discrimination, selectable from 0 to 10 seconds. When the 30mA trip current leakage is selected, the time delay is disabled.