Residual Current Relay

Residual Current Relay

Residual current relay is a product used to take precautions against dangers such as fire that may arise from electrical leakage. Thus, in a risky situation, the electricity is automatically cut off by this tool and unwanted hazards can be avoided.

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Residual current relay is a product used to take precautions against dangers such as fire that may arise from electrical leakage. Thus, in a risky situation, the electricity is automatically cut off by this tool and unwanted hazards can be avoided.

Residual current relay price may vary depending on the technical details of the product. There are many product options according to mA values and phase numbers. Residual current relays are developed and marketed by many manufacturers. The aforementioned relays actually function as a switch. It has an extremely important function to prevent accidents that may occur due to energy leakage in electrical installations. Relays that prevent leakage current are also protective against electric shocks as well as fires.

What is Leakage Current Relay?

The electricity passing through the circuit reaches the desired channel through the cables. However, when leaks occur, the electricity is cut off when it is detected by the switch that the electricity does not reach where it should go. Thus, an accident can be prevented before it occurs. Electricity leaks can harm people, the environment or a different circuit.

Residual current fuse or relay allows you to use electricity safely. So how are residual current relays connected? First of all, the cover of the fuse box in the house is opened. Various cables will be seen inside the box. The neutral wire in the box must be connected to the place on the switch indicated by the N symbol. After the phase connection is made, the switch is placed in the fuse box and its cover is closed.

Working Principle of Residual Current Relay

What is leakage current? The unwanted current that occurs in the body of the devices that perform their functions with electrical energy is called leakage current in general. What are the factors that cause leakage currents?

  • insulation problems
  • Broken device usage
  • Errors during wiring

Such situations can lead to electrical accidents or fires. Devices that protect against leakage current prevent such situations and fulfill an important function in protecting human health. How do residual current relays work?

Current relays are activated when the energy reaches a level that can harm human health. These devices, which work by cutting off the energy, are important security products. An energy level higher than 30 mA is sufficient to cause harm to humans. For this reason, when the energy rises above 30 mA , it is automatically cut off by the relay.


Current relays can be used for many years due to their robust structure. Before the product selection is made, the needs should be clarified and products with appropriate Ampere values should be preferred. These products, which have a fuse-like appearance, can cut the electric current in a short time like one second.

Residual Current Circuit Breaker

Electrical energy exposure can cause serious injury to the human body. It is also dangerous for other living things. Current protection switches operate with a very simple working principle. The product is also known as a fire protection switch. It is frequently preferred due to its advantages such as ease of assembly and small footprint.

How many Amps should the residual current relays for the house be? Exposure to high electrical energy can lead to death in some cases. Single-phase residual current relays can operate at 40a / 30ma values. Monophase is a word meaning single phase. Single phase residual current relays , They are 4-pole devices. It can instantly detect and cut off leaks that cause energy release over 30 mA . Three-phase residual current relays work with three phases and one neutral line.

Why Does Leakage Current Fuse Throw?

Products that work to prevent leakage current are also called residual current switches or residual current fuses. Why does the residual current relay trip? There could be multiple reasons for this situation. For example, the resistance of the ground line may be high. Therefore, when a certain value is exceeded, the energy should be turned off automatically.

When the cable connected to the ground line contacts a different cable, it may cause a short circuit. In such a case, the leakage current preventer relays cut the electricity. The leakage current switch functions according to the principle of equality of currents entering or leaving the circuit. In general, the currents entering the phase come out of the neutral. Which relay/fuse is used for what purpose?

  • 30 mA : For the protection of people
  • 300 mA : For equipment protection
  • 500 mA : It is used in applications where selectivity is required.

Relays can be two- or four-pole. In addition, it can be examined by dividing into 3 according to their types. These; AC can be sorted as A and B type.