[Cautions for application and common fault treatment of leakage circuit breakers]: The main function of leakage circuit breakers is to provide indirect contact protection, which is often used in low voltage circuits to prevent personal shock and accidents caused by leakage. 1. The common types of leakage circuit breakers are divided into voltage type and current type, while current type is divided into electromagnetic type and electronic type. Voltage leakage
The main function of leakage circuit breaker is to provide indirect contact protection. It is often used in low voltage circuit as a way to prevent personal shock and accidents caused by leakage.
Types of Leakage Circuit Breakers
The commonly used leakage circuit breakers are divided into voltage type and current type, while current type is divided into electromagnetic type and electronic type.
Voltage-type leakage circuit breaker is used in low voltage network where transformer neutral point is not grounded. Its characteristic is that when a person is electrocuted, a relatively high voltage appears between the zero line and the ground, which causes relay action and power switch tripping.
Current leakage circuit breaker is mainly used in low voltage distribution system with transformer neutral grounding. Its characteristic is that when a person is electrocuted, a leakage current is detected by a zero sequence current transformer, which makes the relay operate and the power switch disconnect.
II. Selection Principles of Leakage Circuit Breakers
1. Choose according to the purpose of use and the place where the electrical equipment is located.
Leakage circuit breaker is used to prevent personal shock. It should be selected according to different requirements of direct contact and indirect contact protection.
1) Protection against direct contact electric shock
Because direct contact with electric shock is harmful and the consequences are serious, the leakage circuit breaker with high sensitivity should be selected. For electric tools, mobile electrical equipment and temporary lines, the leakage circuit breaker with action current of 30 mA and action time of 0.1 s should be installed in the circuit. For residential houses with more household appliances, it is better to install them after entering the electric energy meter.
If the contact capacitor is liable to cause secondary damage (such as high altitude operation), the leakage circuit breaker should be installed in the circuit with the action current of 15 mA and the action time within US. For electrical and medical equipment in hospitals, leakage circuit breakers with action current of 6mA and action time of US should be installed.
2) Indirect contact protection
Indirect contact electric shock in different places can cause varying degrees of personal injury, so different leakage circuit breakers should be installed in different places. Leakage circuit breakers with high sensitivity are required in places where electric shock is easily harmful. The danger of electric shock in wet place is much greater than that in dry place. In general, leakage circuit breakers with action current of 15-30 mA and action time of 0.1 s should be installed. For electrical equipment in water, action should be installed. Leakage circuit breakers with current of 6-l0mA and action time of US should be installed. For the electrical equipment that the operator must stand on the metal object or in the metal container, as long as the voltage is higher than 24V, the leakage circuit breaker with the action current below 15A and the action time within US should be installed. For fixed electrical equipment with voltage of 220 V or 380 V, when the shell grounding resistance is below 500 fZ, the single machine can install a leakage circuit breaker with action current of 30 mA and action time of 0.19. For large-scale electrical equipment with rated current above 100A or power supply circuit with multiple electrical equipment, leakage circuit breakers with action current of 50-100mA can be installed, and leakage circuit breakers with action current of 200-500mA can be installed when grounding resistance of electrical equipment is below 1000.
2. Choose according to normal leakage current of circuit and equipment
1) Leakage circuit breaker for single machine. Active current should be 4 times larger than leakage current of equipment in normal operation.
2) The operating current of the leakage circuit breaker for branch line should be 2.5 times larger than the leakage current of the normal operation of the line, and 4 times larger than the leakage current of the electrical equipment with the largest leakage current in the line.
3) The operating current of the leakage circuit breaker of the main line or the total protection of the whole network should be 2.5 times larger than that of the leakage current of the normal operation of the power grid.
If it is not easy to measure leakage current of line or electrical equipment, the following empirical formulas can be used to estimate the leakage current:
Lighting circuit or residential power supply circuit: action current IDZ of leakage circuit breaker > ISJ/2000;
Hybrid power and lighting circuit: action current IDZ of leakage circuit breaker > ISJ/1000.
IDZ is the action current of leakage circuit breaker and ISJ is the maximum current in the circuit.
3. Choice of power supply mode according to electrical equipment
1) Electrical equipment supplied by single-phase 220V power supply should choose two-pole two-wire or two-pole leakage circuit breaker.
2) Three-phase three-wire 380V power supply electrical equipment, should choose three-pole four-wire or four-pole four-wire leakage circuit breaker.
III. Installation Notes
1. Before installation, check whether the data on the nameplate of leakage circuit breaker is consistent with the requirements of operation.
2. Installation should not be too close to high current busbar and AC connector.
3. When the action current of leakage circuit breaker is greater than that of smart mA, the equipment shell protected by leakage circuit breaker should be grounded reliably.
4. Full consideration should be given to the power supply mode, voltage and grounding mode of the power supply line.
5. Installing leakage circuit breakers with short circuit protection must ensure sufficient arc distance.
6. Copper conductors shall be used in the external control circuit of combined leakage circuit breakers with a cross-sectional area not less than 1.5mmzo.
FONT face: The main function of leakage circuit breaker is to provide indirect contact protection, which is often used in low-voltage circuits to prevent personal shock and accidents caused by leakage. 1. The types of leakage circuit breakers commonly used are divided into voltage type and current type, and current type.
