Earth leakage relays (also known as ELRs or by the alternative name of differential relays) are specialised latching relays that are used to monitor the leakage of current to earth on 3-phase electrical systems, interrupting the circuit in the event that a dangerous voltage leak is detected. Earth leakage relays can be found in domestic distribution boards and are used to sense insulation failures, preventing electric shocks. At RS, we supply a range of earth leakage relays from trusted brands, including Broyce Control, IME and Socomec.
Earth leakage relays monitor a circuit for significant leakage between the electrical supply and the earth by tracking the current that flows through both the phase conductor and neutral conductor of the electrical circuit. If the phase and neutral currents are equal and balanced, the relay will not interrupt the circuit as there is no difference between the two and therefore no signs of voltage leakage. However, if there is a difference, the relay will interrupt the flow of the current and trip the breaker, switching the circuit off to prevent any injury via electric shock.