Disconnector: At high voltages such as 10kV and 35kV, it is generally used in conjunction with circuit breakers. Disconnectors are usually turned off later and turned on first. Their main function is to form a visually visible breakpoint during electrical maintenance, ensuring that the lower maintenance line is not energized. Due to the presence of an arc extinguishing device for the circuit breaker, the switch contacts are all inside the arc extinguishing device, and the external part is invisible, and cannot be considered as an obvious breakpoint. Nowadays, high-voltage switchgear cabinets are all movable, and the circuit breaker can be directly pulled out of the switchgear like a drawer after opening, which is equivalent to having an obvious break point, eliminating the need to install an isolating switch. Although isolation switches can be defined to close no-load current, they are rarely used in high-voltage situations because they are too dangerous. In low voltage situations, there are many small motors that can be directly switched on and off between knives in rural areas, and there is no danger. However, this design cannot be used in formal situations. To sum up, the isolating switch function only forms an obvious breakpoint to ensure safety.
Load switch: It has a certain arc extinguishing ability, but it is not as strong as the arc extinguishing ability of the circuit breaker. It can switch on and off the normal working current. In the case of a short circuit, he can only silently withstand the short circuit current, and if this time the manual or electric opening may explode. Therefore, load switches are generally used together with current limiting fuses (load switch+fuse is not a standard configuration, nor can it be used without a fuse). In case of overload or short circuit, the circuit is disconnected by the fuse. To save costs, load switch+fuse can replace circuit breaker.
Circuit breaker: With strong arc extinguishing ability, it can open and close normal working current and fault current. The protection function of the high-voltage circuit breaker is realized through a relay protection device. The high-voltage circuit breaker does not have the thermal, magnetic, and undervoltage tripping devices of the low-voltage circuit breaker. Whether there is a fault in the circuit is determined by the relay protection device, and the circuit breaker only executes the division according to the instructions of the relay protection. Because load switches and disconnectors cannot break fault currents, there is no need to give them instructions in the event of a line fault. High voltage circuit breaker is a switch with strong arc extinguishing ability, which must be used together with relay protection devices.
