Complex methods to diagnose the technical state of the medium and high voltage circuit breaker after short-circuit events

The paper presents the methods of modal identification and off-line diagnosis for circuit breakers. The modal identification refers to lower frequency domain and point out the material wear, weakening of joining and porcelain cracks. Modal shapes mark out places where a fault yields. The off-line diagnosis methods refer to the circuit breaker current carrying ability, making or breaking of high currents quality, contacts degradation and mobile contact travel quality. The vibration analysis, included in these methods, refers to higher frequency domain. These methods must be applied after every serious short-circuit event with a view to assure a good operation of a power system. Tests carried out on a high voltage SF₆ circuit breaker of 420 kV/2500 A are presented