Difference between Earth Fault Relay and Earth Leakage Relay

Earth leakage relay and earth fault relay both are electrical protective devices used to protect humans or electrical equipment from earth leakage or earth fault. The main difference between the earth fault relay and the earth leakage relay is earth fault relay is designed to sense high earth fault current which occurs due to the direct contact of any live conductor to earth. On the other hand, the earth leakage relay is designed to sense low earth leakage current which occurs due to the indirect contact between the live part and the earth or grounding such as insulation failure, moisturization, etc. Let's know the earth leakage relay and earth fault relay in detail.

Earth Leakage Relay

Before going to know about earth leakage relay, you must have to know what is earth leakage. When a few amount of leakage current flows from the live part of an electrical circuit to the ground or earth then it is called Earth leakage and the current is called earth leakage current. Earth leakage relay generally works on the current sensing principle. Because here the flow of current is very low so there is a potential difference also very low, so here voltage operated relay cannot work. Earth leakage relay uses core balance current transformer arrangement to sens the earth leakage current.

Earth leakage relay mostly gives protection against electric shock, overheating due to earth leakage, etc. Earth leakage relays are mostly used in domestic electrical circuits, and wiring where earth leakage happens due to improper wiring, insulation failure, loose connections, electrical shock, etc.

Earth leakage relay sens the earth leakage current from the unbalancing of current in phase and neutral. for a single-phase circuit, it continuously monitors if the current in both phase and neutral same or not. When an earth leakage fault occurs there will be an imbalance in the phase and neutral current. Thus the earth leakage relay can sense the leakage current and sends the signal to the main circuit breaker to trip or disconnect the main power supply.

Earth Fault Relay

When the live conductor accidentally touches the earth or ground part of an electrical circuit or equipment then a huge amount of current will flow from the live conductor to the earth. This is called Earth Fault and the fault current is called Earth fault current. Earth fault relay is voltage operated device. Generally, the earth fault relay is installed in series with the earth or grounding wire. So when an earth fault occurs a potential difference occurs across the earth fault relay, and it sends the signal to the circuit breaker to trip the circuit or disconnect the main power supply.

Earth fault really is a voltage-operated device so they only work when a big amount of fault occurs. Earth fault relays are generally used in electrical substations, and transformer installations where the chances of a big earth fault.

Earth Fault Relay VS Earth Leakage Relay

1. Earth fault relay is a voltage-operated device that senses the magnitude of the voltage that occurs due to the flow of earth fault current whereas the earth leakage relay is a current-operated device that senses the actual earth leakage current flows in the circuit.

2. Earth fault relay works when a large earth fault occurs. On the other hand, the earth leakage relay works when small earth leakage occurs.

3. Earth fault relay cannot give protection against electrical shock but an earth leakage relay can give protection against electrical shock.

4. Another important difference between Earth Fault Relay and Earth Leakage Relay is, the Earth fault relay can work only when the Earth fault current flows through the earthing or grounding conductor but the Earth leakage relay can work for Earth leakage current flowing from anywhere in the electrical circuit.

5. Earth fault relay is less sensitive than and low-cost device than the earth leakage relay.

6. Earth fault relays are used in ELCBs whereas Earth Leakage Relays are used in RCCBs.

Read Also: 

• The List of Faults RCCB can Protect and Can't Protect
• Short Circuit Fault Causes, Effects, Protection
• Neutral Fault Causes, Effects, Example, Explanation
• ELCB and RCCB Difference, Advantages, Limitations, Diagram
• Main Purpose of Using Neutral Grounding Resistor
• Working and connection diagram of Single Phasing Preventer.

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