Earth Leakage Relay Wiring and Connection Diagram

In this article, we are going to see the Earth Leakage Relay Wiring Diagram. Earth leakage relay is a sensing device that senses the earth leakage current and sends signals to the circuit breaker to trip the circuit or disconnect the main power supply. Earth Leakage fault occurs due to improper connection, insulation failure, moisturization in electrical circuits, human electric shock, etc.  Generally, in most of the industrial electrical wirings, panels earth leakage relay is used to protect electrical devices and equipment. Earth leakage relay is always used with a circuit breaker(MCCB, ACB, etc). So when an earth leakage fault occurs, the earth leakage relay can sense the fault and send the signal to the circuit to trip the main power supply.

Earth Leakage Relay Wiring Connection

Terminals of the Earth Leakage Relay(ELR)

• The A1 and A2 terminals are for the auxiliary power supply to operate the Realy. It generally requires a 230V AC supply.
• T1 and T2 are the terminals to connect the CBCT or core balance current transformer or any other sensor.
• 31, 32, and 34 are the terminals of common, NC, and NO respectively.
• Terminals 11 and 14 are basically NO contact terminals they are used for voltage presence.
• Terminals 25, 26, and 27 are for remotely RESET.

Here we do not require all terminals to connect for this wiring. Some of them are only required, discussed in the connection procedure.

Connection Procedure

1. First, place the CBCT in such a way that all power cables should go through that. You can see in the above figure, all phases and neutral are going through the CBCT.

2. Connect the CBCT to the T1 and T2 terminals of the earth leakage relay as shown in the above figure.

3. Connect phase and neutral to the A1 and A2 terminal to provide the auxiliary power supply to the relay.

4. Connect the shunt trip coil of the MCCB through the 31 and 34 terminals of the earth leakage relay as shown in the above figure.

5. Also connect the neutral to the shunt trip coil.

How this circuit works?

The working principle of this circuit is very simple. In normal conditions, current in all phases and neutral are equal or balanced so the CBCT does not produce any current. But when the earth leakage fault occurs an unbalanced current will flow through the phase and neutral so the CBCT will produce a current and send a signal to the earth leakage relay. Once the ELR gets the signal from the CBCT it will make its NO contact into NC so the shunt trip coil of the MCCB will get the power supply and it will trip the MCCB.

This circuit will work when an earth leakage fault occurs anywhere in the load circuit. The advantage of this earth leakage relay is, we can adjust the current setting and timing setting. The adjustment of the current setting provides the facility at which the amount of leakage current the MCCB will trip. The adjustment of the timing setting allows us to set the time to trip the MCCB after the fault occurs.

Read Also: 

• Working and connection diagram of Single Phasing Preventer.
• MPCB Uses, Advantages, Connection | Motor Protection Circuit Breaker
• Contactor Interlocking Circuit and Wiring Diagram
• Proper RCCB connection Diagram with MCB
• Motor Control Circuit Forward Reverse | Wiring and Connection

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