The high-voltage circuit breaker (or high-voltage switch) can not only cut off or close the no-load current and load current in the high-voltage circuit, but also cut off the overload current and short-circuit current through the function of the relay protection device when the system fails. Perfect arc extinguishing structure and sufficient current interruption capacity, can be divided into: oil circuit breaker (more oil circuit breaker, less oil circuit breaker), sulfur hexafluoride circuit breaker (SF6 circuit breaker), compressed air circuit breaker, vacuum circuit breaker 。
In order to ensure the safety of high-voltage electrical appliances under normal operation, maintenance, short-circuit and overvoltage conditions, high-voltage electrical appliances should be selected according to the following conditions:
① Choose according to normal working conditions, including voltage, current, frequency, mechanical load, etc.;
② Choose according to short-circuit conditions, including short-time withstand current, peak withstand current, closing and breaking current, etc.;
③ Choose according to environmental conditions including temperature, humidity, altitude, earthquake, etc.;
④ Choose according to overvoltage withstand capability including insulation level;
⑤ Choose according to the different characteristics of various high-voltage electrical appliances, including the operation performance of the switch, the protection characteristics of the fuse, the load of the transformer, and the accuracy level.
① For the high-voltage electrical equipment selected according to the operating voltage, its rated voltage should conform to the nominal voltage of the system where it is located, and its allowable maximum operating voltage Umax should not be less than the maximum operating voltage Uy of the circuit where it is located, that is, Umax ≥ Uy.
② Select the rated current In of the high-voltage electrical appliance according to the operating current, and should not be less than the continuous operating current Ig of the loop in various possible operating modes, that is, In ≥ Ig .
① General requirements for short-circuit stability verification
② Thermal effect of short-circuit current
③ Short-circuit stability verification
Post time: Sep-06-2021