The core function of high voltage disconnect switch is to establish visible electrical breakpoints to open and close circuits in a current-free state, provide visually visible physical isolation, and strictly prohibit load operation, and cooperate with the grounding switch to ensure reliable grounding of the circuit during maintenance. The voltage level of high voltage disconnect switch is applicable to 72.5kV~800kV systems (126kV level is a typical benchmark).
The high voltage disconnect switch environment requires that the humidity be controlled at a relative humidity daily average value of ≤80%, and the condensation risk area must be equipped with a constant temperature heating device (to prevent condensation on the surface of the insulation parts), and the pollution area of level III and above (salt density ≥0.25mg/cm²) must use anti-fouling porcelain bushings, and the creepage distance ≥31mm/kV. The horizontal error of the embedded steel plate is ≤1mm/m, the surface flatness deviation is ≤0.5mm (detected by laser level), the anchor bolts are 8.8-grade M30 high-strength bolts, the tightening torque is 450~500N·m (tightened in diagonal order), the verticality deviation of the support insulator is ≤1‰ (calibrated by laser theodolite), and the tilt deviation will cause the operating torque to exceed the standard.
When operating the high voltage disconnect switch, pay attention to the five-protection interlocking, which means that when the circuit breaker is closed, it is forbidden to operate the disconnector (mechanical interlocking verification); when the grounding switch is closed, it is forbidden to close the disconnector (electrical interlocking verification).
The operation sequence is: power failure-circuit breaker opening → load side disconnector → power supply side disconnector; power supply-power supply side disconnector → load side disconnector → circuit breaker. It is strictly forbidden to operate with load (arc temperature exceeds 15000℃, which can melt the contacts and close the grounding switch without experience, and unauthorized release of the interlocking device.