1) direct contact with the protection of electrocution Because of direct contact with electrocution of the hazards are relatively large, caused by the consequences of the seriousness of the choice of higher sensitivity leakage circuit breakers, power tools, mobile electrical equipment and temporary lines, should be installed in the circuit of the action current of 30mA, the action time of 0.1s leakage circuit breaker. Leakage circuit breaker. For residential houses with more household appliances, it is best to install it after the household energy meter. If it is easy to cause secondary injuries once electrocuted (such as working at height), an earth leakage circuit breaker with an operating current of 15mA and an operating time within US should be installed in the circuit. For electrical medical equipment in hospitals, earth leakage circuit breakers with an action current of 6mA and an action time within US should be installed. (2) Indirect contact electrocution protection Indirect contact electrocution in different places can cause different degrees of personal injury, so different places should be installed in different leakage circuit breakers. For easy electrocution of the hazardous places, the requirements of the leakage circuit breaker with higher sensitivity. In the wet place than in the dry place of electrocution risk is much greater, generally should be installed for the action current of 15-30mA, action time within 0.1s of the leakage circuit breaker. For electrical equipment in the water, should be installed. Current 6-l0mA, action time within the US leakage circuit breaker. For the operator must stand on metal objects or metal containers in the electrical equipment, as long as the voltage is higher than 24V, should be installed with an action current of 15mA or less, the action time within US leakage circuit breaker. For fixed electrical equipment with voltage of 220V or 380V, when the shell grounding resistance is below 500fZ, the single unit can be installed with an action current of 30mA and an action time within 0.19 of the earth leakage circuit breaker. For the rated current of 100A or more large electrical equipment or power supply circuit with multiple electrical equipment, can be installed with an action current of 50-100mA earth leakage circuit breaker, the grounding resistance of the electrical equipment in the following 1000, can be installed with an action current of 200-500mA earth leakage circuit breaker.
Selected according to the normal leakage current of the circuit and equipment
1) single machine with leakage circuit breaker. Action current should be greater than 4 times the leakage current of the normal operation of the equipment. 2) for branch line leakage circuit breaker, the action current should be greater than the normal operation of the line leakage current of 2.5 times, but also to be greater than the line leakage current of the largest leakage current of electrical equipment leakage current of 4 times. 3) The earth leakage circuit breaker for the main line or the total protection of the whole network shall have an action current greater than 2.5 times the leakage current during normal operation of the grid. If it is not easy to measure the leakage current of the line or electrical equipment, can be estimated in accordance with the following empirical formulas: Lighting circuit or residential electricity circuit: leakage circuit breaker action current IDZ>ISJ/2000; power and lighting mixed circuit: leakage circuit breaker action current IDZ>ISJ/1000. The formula in the IDZ for the leakage circuit breaker action current, ISJ is the maximum leakage current in the circuit, ISJ is the leakage circuit breaker action current. ISJ is the maximum current in the circuit.
Selected according to the power supply mode of electrical equipment
1)Single-phase 220V power supply of electrical equipment should be selected two-pole, two-wire or single-pole, two-wire earth leakage circuit breaker. 2) three-phase three-wire 380V power supply of electrical equipment, should be used three-pole four-wire type or four-pole four-wire type earth leakage circuit breaker.
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