Online non-invasive evaluation of arcing time for condition assessment of high-voltage gas circuit breakers

Online non-invasive methods to assess circuit breaker condition have been under consideration in recent years. The combination of the arcing time and the short-circuit current recorded by protective relays can be utilized to assess the degrading impact of current interruption on arcing contacts. In many previous investigations, an integral over arcing time of different functions of current and voltage has been proposed to predict the erosion rate of arcing contacts. Although the arcing time is a crucial parameter for these indices, no easily adaptable method to online condition assessment is available. This paper proposes a method for online determination of arcing time based on the measurement of the switching time of the auxiliary contacts. Several experiments have been performed under no-load conditions as well as during short-circuit current interruption, on two circuit breakers with different trip coil excitations (AC and DC). The results show that the delay time between the contact separation instant of the arcing contacts and the switching time of the auxiliary contacts has a very low jitter. This enables precise determination of the arcing time by measurement of the switching time of the auxiliary contacts, which is accessible during the online operation of circuit breakers.