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

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 (similar to 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.