EARTH LEAKAGE RELAY

Description of Earth Leakage Relay :

This relay is used on AC systems and is a sensitive electronic protective device. Its operation on Earth fault is independent of the system voltage imbalance. This relay can detect Earth fault currents as low as 1 amp. This is 0.25% in a 400 amps feeder system. This can be used on a single phase or on a three-phase network.

Principle of operation :

This relay operates on the core balance principle wherein the currents in the three phase of the system are summed by a core balance C.T. which for normal conditions equates to zero. In case of a leakage current to earth this balance is disturbed causing the electronic circuit to operate a relay within the unit. In this event the relay that is generally connected to circuit breaker operates thus tripping the main circuit. The electro mechanical relay operates on fault. The Earth Leakage Relay is provided with a TEST push button for checking its operation and a RESET button to reset the relay on operation. This helps in checking the proper functioning of the relay.

Construction :

The relay is housed in a robust insulated enclosure. The electronic circuit has a voltage developer, a level detector and a static switch which drives an electro-mechanical relay, the terminals of which are connected to a switch gear.

The electro-mechanical relay operates on a fault. The Earth Leakage Relay is provided with a TEST push button for checking its operation and a RESET push button to reset the relay on operation. This built-in test feature enables the quick check of the proper functioning of the Earth Leakage Relay.

The relay is also offered in a flush mounting design of standard, 96 sqmm.

Type ELR Relay can be used to detect earth leakage currents upto three feeders simultaneously. However it will not indicate in which feeder the fault has occured. The relay contacts can be connected to give an alarm or otherwise made to initiate tripping of all the terminals.

On set of N/O and N/C change over contacts can be provided.

Mounting :

The Earth Leakage Relay can be supplied in base mounting (Projection type) or 96 sqmm (door mounting). We can also supply the relays with DIP Type switches for leakage and time delay selection.

Specifications of Earth Leakage Relay :

Leakage Current Setting
From 15mA upwards as desired.
Core balance C.T.
Toroidal core, bar primary
Auxiliary supply
110/220/415/550 V Ac, 50 Hz, 1 Phase
Built-in relay contact
5 amps (resistive) 415 V AC or 220 V DC
Number of contacts
One N/O and One N/C.
Mounting
Base, 96 sqmm & DIN rail mounting

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