Outlet cabinet: circuit breaker, current transformer, comprehensive protection, intelligent control device, lightning arrester, grounding knife and zero sequence current transformer.
PT cabinet: isolating knife, high-voltage fuse, voltage transformer, comprehensive protection, intelligent control device and lightning arrester.
The inlet and outlet cabinets are mainly used for breaking, so the circuit breaker is necessary and the main component.
The current transformer converts the primary heavy current into a current signal of 1A or 5A for secondary use: metering-ammeter display, metering-watt-hour meter and protection-comprehensive protection.
The low-voltage circuit breaker is equipped with a thermo-magnetic trip for overload and short-circuit protection, while the high-voltage circuit breaker has no protection function, so it needs to cooperate with comprehensive protection to realize line protection. The comprehensive protection receives the current signal of the protected circuit breaker and the voltage signal of the PT cabinet, and some of them also receive the signal of the zero-sequence current transformer to monitor the fault of the system. When there is a fault, it will send an alarm or a disconnection command to disconnect the circuit breaker.
Intelligent control device is a dispensable thing. It integrates some auxiliary functions of the switch cabinet into one device, including: manually opening and closing the circuit breaker, indicating the position of the trolley-test position, working position and maintenance position, indicating the opening and closing of the grounding knife, indicating the opening and closing of the circuit breaker, indicating the completion of energy storage, indicating the temperature and humidity, automatic heating and dehumidification, and some voice functions-when people approach, they will remind the equipment of the danger of electrification. Without this device, switchgear manufacturers must realize these functions through buttons, indicator lights, etc. Now high-voltage switchgear is basically standard, and the old switchgear does not have this device.
All lightning arrester cabinets are equipped with overvoltage protectors to prevent lightning overvoltage and operating overvoltage.
The grounding knife is only needed in the outlet cabinet, so as to replace the grounding wire when repairing the lower equipment of the outlet cabinet. According to the safety and electrical regulations, the wire entry cabinet is not needed, because the lower port of the wire entry cabinet is called. After the outlet cabinet is pulled out, the lower port is generally not electrified, and after the inlet cabinet is pulled out, the lower port may still be electrified. For some outlet cabinets involving special control, if the lower port may be charged, the grounding knife is not installed.
The zero-sequence current transformer is special for the outlet cabinet, which is used to detect the zero-sequence current of the outlet cable, and the signal is sent to the small current grounding line selection device or comprehensive protection. The outgoing line of the incoming cabinet is a bus, and the grounding fault of incoming cable is detected by the superior circuit breaker.
PT cabinet converts the high voltage of bus into low voltage, generally100V. The high voltage fuse is used to prevent the short circuit of voltage transformer, and the isolating knife is used to replace the fuse. The high-voltage fuse can be replaced at any time, which will not cause bus power failure.