How to choose Earth Leakage Relay

1. Introduction

In practice, the ASJ series earth leakage relay is usually combined with the outgoing circuit breaker in the outgoing cabinet of the low-voltage distribution cabinet to form a ground fault protector. 

The ASJ series earth leakage relay is particularly suitable for the safety protection of electricity used in schools, commercial buildings, factory workshops, national key fire protection units, intelligent buildings and communities, subways, petrochemicals, telecommunications and national defense departments.

2. Classification

AC type earth leakage relay is only used to monitor the AC residual current action relay, and its symbol is:image.png

Type A residual current relay is used to monitor AC and pulsating DC residual current relay. Its symbol is:1717052987614.jpg

Type B earth leakage relay is a residual current relay used to monitor AC, DC and pulsating DC. Its symbol is:1717052996303.jpg

1) When the load of the protected line is a pure AC load and the loop current is less than 500A, an AC type relay can be used;

2) When the loop current load type is complex and diverse, and the loop current is large, an A relay should be used.Type A relay can replace an AC type relay.

3. Working principle

The schematic diagram is shown below. The residual current operated relay collects the residual current of the circuit through the residual current transformer passing through the four wires ABCN. When the residual current exceeds the action value set by the relay, the relay operates, closes the tripping coil of the circuit breaker, and trips the circuit breaker, thereby realizing the ground fault protection function.


Note: Residual current relays cannot be used in the following situations

1) Circuits or systems with voltage higher than 0.69kV;

2) Circuits or systems with frequency conversion equipment;

3) High-power motor circuits.

4. Networking

4.1 Collect the output status of the relay through PLC, and then judge the action status of the relay, as shown in the following figure:


4.2 Networking via RS485 communication


5. Q&A

5.1 The earth leakage relay does not light up when powered on

Check whether the power supply terminals of the earth leakage relay have power and whether the voltage between the terminals is normal. If there is no voltage, please check whether the wiring is wrong; if the voltage is normal, there may be a problem with the earth leakage relay itself, please contact after-sales personnel for communication and processing.

5.2 The residual current relay trips the circuit breaker

The earth leakage relay is actuated when the residual current in the circuit exceeds the actuation value. First check whether the wiring of the circuit is abnormal, whether there is insulation damage to the phase line or ground fault. If so, after troubleshooting, long press the reset button of the instrument to resume normal operation. If there is no obvious ground fault, the residual current in the circuit can be measured by a clamp-on transformer to see if the residual current in the circuit exceeds the setting value of the residual current relay. If it exceeds, it is necessary to check the cause of the excessive residual current.

If everything is normal after troubleshooting, there may be a problem with the earth leakage relay itself. Please contact after-sales personnel for communication and processing.

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