Contact Erosion at High Currents in High-Voltage Gas Circuit Breakers—Part I: Experimental Research and Material Testing

Abstract

The arcing environment at high current levels in high-voltage circuit breakers is severe and complex. The energy injected into the electrode is mainly through the arc root attachment during the arcing process. Analysis of high current (∼40 kA peak) AC arc images of the contact surface shows that the contact is heated non-uniformly and that a molten pool may be formed at arc extinction. It has been found that the molten pool can be divided into central and edge heating areas. The characteristics of non-uniform heating cause the thickness of the molten layer to be thick in the center and thin on both sides. After high-current arcing erosion, the material on the contact surface changes from Cu-W to pure tungsten. During the separation process of the arcing contacts, the electrode-fall voltage under different working conditions (CO₂ or SF₆) can be obtained through the voltage jump signal. The parameters measured in this paper will be used to evaluate the energy balance of arc-electrode under these conditions.