Monitoring of HV Generator Circuit Breaker Contact Ablation Based on Acoustic Emission

High-voltage (HV) generator circuit breaker (GCB) is a key protective element for isolating HV generators in case of faults, or operational reasons. GCB typically has a double contact system. During the breaking operation process of the GCB, at first the nominal contact opens; after a while, the arcing contact opens with a minimum time-elapse between the two operations. An arc ignites when the arcing contact opens. This arc should concern the arcing contact only because the nominal contact is not designed to withstand arcs. However, after each operation the arcing contact is slightly ablated because of the arc. The ablation due to arcing makes the contact shorter and shorter. Therefore, the time interval between the two opening operations also gets shorter. For proper operation of the GCB, a minimum time interval for the commutation of the current from the nominal contact system to the ablation contact system has to be assured. In this paper, a noninvasive direct ablation measurement method based on acoustic emission is presented. This is aimed at monitoring the delay in the time instant of the start of arcing contact touch as it gets shorter due to ablation, from the acoustic emission signals. Test results carried out on real breakers substantiate the proposed approach.