Faults related to switching‑on and switching‑off frequently occur on the circuit breaker body and operation control system of high‑voltage switchgear, which can be divided into three categories: circuit‑breaker body faults, mechanical faults of mechanism and transmission system, as well as faults of electrical control and secondary circuit.

Circuit‑breaker body faults: For low‑oil circuit breakers, common problems include oil‑injection short‑circuit, arcing‑chamber burnout, insufficient breaking capacity and explosion during closing. For vacuum circuit breakers, typical faults cover air leakage of arc‑extinguishing chambers and bellows, vacuum degree reduction, re‑ignition when switching capacitor banks, and ceramic tube rupture.

Mechanical faults of mechanism and transmission system: They may result in mechanism jamming, deformation, displacement or damage of components, loosening and jamming of opening‑closing iron cores, loose shaft pins and tripping failure, which directly lead to failure‑to‑operate and malfunction.

Faults of electrical control and secondary circuit: These include poor contact of secondary wiring, loose terminals and wrong wiring; burnout of opening‑closing coils caused by mechanism jamming or defective transfer switches; failure of auxiliary‑switch switching, and damage of components such as operating power supply, closing contactors and micro‑switches, which further give rise to abnormal switch actions.