High-voltage switchgear is a very important electrical equipment in the power system. The deterioration of the operating state of the switchgear is one of the reasons for the failure of the power system. Analyzing the causes of high-voltage switchgear faults, they mostly occur in insulation, conduction, and mechanical aspects.
(1) Refusal to operate and misoperation faults
This type of fault is the main fault of high-voltage switchgear, and its causes can be divided into two categories. One category is caused by mechanical faults in the operating mechanism and transmission system, specifically manifested as mechanism jamming, component deformation, displacement or damage, loose or jammed opening and closing iron cores, broken or loose pins, and tripping failure. The other category is caused by electrical control and auxiliary circuits, manifested as poor contact in secondary wiring, loose terminals, wiring errors, burning of opening and closing coils due to mechanism jamming or poor transfer switches, malfunctioning auxiliary switch switching, and faults in the operating power supply, closing contactor, micro switch, etc.
(2) Breaking and closing faults
This type of fault is caused by the circuit breaker itself. For low-oil circuit breakers, it mainly manifests as oil spray short circuit, burning of the arc extinguishing chamber, insufficient breaking capacity, and explosion during closing. For vacuum circuit breakers, it manifests as air leakage in the arc extinguishing chamber and bellows, reduced vacuum degree, re-ignition when switching capacitor banks, and cracking of ceramic tubes.
(3) Insulation faults
The insulation level is to correctly handle the relationship among various voltages acting on the insulation (including operating voltage and various overvoltages), various voltage limiting measures, and insulation strength. Strive to make the product both safe and economical, achieving economic benefits. Faults in insulation mainly manifest as external insulation flashover to ground breakdown, internal insulation flashover to ground breakdown, phase-to-phase insulation flashover breakdown, lightning overvoltage flashover breakdown, flashover of porcelain bushings and capacitor bushings, pollution flashover, breakdown, explosion, flashover of lifting rods, CT flashover, breakdown, explosion, and porcelain bottle fracture.
(4) Current-carrying faults
The main cause of current-carrying faults at the 72-12KV voltage level is poor contact of the switchgear isolation plug, leading to melting of the contacts.
(5) External forces and other faults
Including impacts from foreign objects, natural disasters, short circuits caused by small animals, and other unknown external forces and unexpected faults.
