What are the leakage circuit breakers leakage leakage circuit breaker model selection principle

An earth leakage circuit breaker is a switch that automatically operates when a leakage current in a circuit exceeds a predetermined value. The commonly used leakage circuit breaker is divided into voltage type and current type two kinds, and the current type is divided into two kinds of electromagnetic type and electronic type. Leakage circuit breakers are used to prevent personal electric shock. They should be selected according to the different requirements of direct and indirect contact. What is the working principle of the leakage circuit breaker ? What are the models of the leakage circuit breaker ? What is the difference between the leakage circuit breaker and the leakage protection device? If you have this requirement, you may wish to follow me to learn about the model of the leakage circuit breaker and other related knowledge of the leakage circuit breaker.

Leakage circuit breaker working principle

The composition and working principle of the leakage circuit breaker The leakage circuit breaker has two functions, one is the function of the circuit breaker and the other is the function of leakage protection. The circuit breaker function is the same as a general low-voltage circuit breaker and serves as a switching device that is not frequently operated. The leakage protection part detects the residual current through the zero-sequence transformer, that is, by detecting the instantaneous value of the current in the phase and the neutral of the protected circuit, the change of the leakage current to the ground is judged.

When the circuit leakage current exceeds the specified value or when there is electric shock, it can automatically cut off the power within the safety time, to protect the electrical equipment, protect personal safety and prevent accidents caused by leakage current caused by the device. The leakage circuit breaker is operated by Mechanism, electromagnetic release, contact system, arc extinguishing chamber, zero-sequence current transformer, earth-leakage trip unit and test device, etc. All components are placed in an insulating housing, and the leakage of modularized miniature circuit breakers The protection function is provided by the structure of the leakage accessory and can be combined with a circuit breaker when needed.

The leakage release is divided into two types: electromagnetic (ELM) and electronic (ELE). The difference between them is that the leakage current of the former can directly operate the main switch through the release, and the leakage current of the latter is amplified by the electronic amplification circuit. Only then can the tripper be operated to operate the main switch.

Leakage Circuit Breaker Selection Principle

Choose according to the purpose of use and where the electrical equipment is located

1) Protection against direct contact with electric shock

Because the danger of direct contact with electric shock is relatively large and the consequences are serious, the leakage current circuit breaker with higher sensitivity should be used. For electric tools, mobile electric equipment and temporary lines, the operating current in the circuit should be 30 mA and the operating time is Residual current circuit breaker within 0.1s. For households with more household appliances, it is best to install them in the household energy meter.

If the electric shock is likely to cause secondary damage (such as high-altitude operation), an earth-leakage circuit breaker with an operating current of 15 mA and an operating time within US must be installed in the circuit. For electrical medical equipment in hospitals, an earth leakage circuit breaker with an operating current of 6 mA and an operating time within US should be installed.

2) Indirect contact with electric shock protection

Indirect contact with electric shock at different locations can cause different degrees of personal injury. Therefore, different earth leakage circuit breakers should be installed in different locations. For places with a high risk of electric shock, a leakage circuit breaker with a relatively high sensitivity is required. The risk of electric shock in wet places is much greater than that in dry places. Earth-leakage circuit breakers with an operating current of 15-30mA and an operating time of 0.1s should generally be installed. For electrical equipment in the water, install the action. Current leakage current breaker with 6-l0mA and operating time within US. For an electrical device where the operator must stand on a metal object or in a metal container, as long as the voltage is higher than 24V, an earth-leakage circuit breaker with an operating current of 15mA or less and an operating time within US must be installed. For a fixed electrical equipment with a voltage of 220V or 380V, when the grounding resistance of the housing is less than 500fZ, a single unit may be equipped with an earth leakage circuit breaker with an operating current of 30mA and an operating time within 0.19. For large-scale electrical equipment with a rated current above 100A or a power supply circuit with multiple electrical equipment, an earth leakage circuit breaker with an operating current of 50--100mA can be installed. When the electrical equipment has a ground resistance of 1000 or less, it can be installed. Current leakage circuit breaker 200-500mA.

Select according to the normal leakage current of the circuit and equipment

1) The leakage circuit breaker equipped with a single machine. The operating current should be greater than 4 times the leakage current during normal operation of the device.

2) For leakage circuit breakers for branch lines, the operating current should be greater than 2.5 times the leakage current during normal operation of the line, and also greater than 4 times the leakage current of the electrical equipment with the largest leakage current in the line.

3) Earth-leakage circuit breakers for total protection of the main line or the entire network should have an operating current greater than 2.5 times the leakage current during normal operation of the power grid.

If it is not easy to measure the leakage current of a line or an electrical device, estimate it according to the following empirical formula:

Lighting circuit or residential life electrical circuit: The operating current of leakage circuit breaker IDZ>ISJ/2000;

Power and lighting hybrid circuit: current leakage circuit breaker IDZ>ISJ/1000.

In the formula IDZ is the leakage breaker operating current and ISJ is the maximum current in the circuit.

1) Single-phase 220V power supply for electrical equipment should use two-pole two-wire or single-pole two-wire leakage circuit breakers.

2) Three-phase three-wire system 380V power supply of electrical equipment, should use three-pole four-wire or four-pole four-wire leakage circuit breakers.

The difference between leakage circuit breaker and leakage protector

Circuit Breaker: The circuit breaker is the switch that controls the electrical circuit. If the air is used as the extinguishing medium, it is called the air circuit breaker (switch). If the sf6 gas is the extinguishing medium, it is called the sulfur hexafluoride circuit breaker (switch). Circuit breakers are generally selected at the rated current (load) and used as the main switch of the electrical circuit.

Leakage protector and leakage protection switch:

Leakage protector and leakage protection switch: When an air switch has leakage protection function, it is called leakage protection switch. If it is an electrical device that is used solely for leakage protection, it is called a leakage protector. Leakage protector because it does not manually shut off and close the body.

The basic principle for determining whether or not to leak current is: leakage protector, which detects "inflow" and "outflow" for the power supply, because the current on the fire line is equivalent to the outflow point of the power supply, and the current in the neutral line is quite When the current of the power supply “flows in”, when the line is normally not leaking, the current values flowing into and out of the power supply are equal in magnitude and opposite in direction, but when there is leakage in the circuit, the current flowing back to the power supply on the zero line should be less than the power flowing in from the power supply. The current value of the circuit, when it reaches 30mA, the protector will act and cut off the zero and fire wires.

The current flowing in and out of the switch must be equal, otherwise it is judged as leakage. When the leakage current reaches and exceeds a certain degree, a protective action - tripping occurs. The decision threshold is settable because the circuit is designed. Only when different applications are used, different sensitivity protectors are selected. Residual current refers to the vector sum of the instantaneous value of the current in the main circuit (zero-sequence transformer) of the protection device through residual current operation. It is expressed by its effective value. For a single-phase line, the residual current is the current of the phase to ground leakage; For three-phase lines, the residual current is the vector sum of the instantaneous values of the currents of each phase, expressed as its effective value.

Leakage circuit breaker is essentially a plastic shell type circuit breaker installed with a detection leakage component. It is mainly composed of a plastic housing, an operating mechanism, a contact system, an arc extinguishing chamber, a trip unit, a zero-sequence current transformer and a test device.

Editor's summary: Current-type leakage circuit breakers are mainly used for low-voltage power distribution systems where the neutral point of the transformer is grounded. Its characteristic is that when the person gets an electric shock, a leakage current is detected by the zero-sequence current transformer, the relay is actuated, and the power switch is disconnected. For more information, please continue to pay attention to our website, follow-up will show more exciting content.

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