Evaluation of Electrode Conditioning Method of Applying AC Voltage for Vacuum Interrupters

This work describes an efficient conditioning method to achieve 400 kV of lightning impulse withstand voltage for the vacuum interrupter rated at 84 kV by applying ac voltage. As the first step, we measured the floating electric potential of the arc shield by reproducing the electric field when the interrupter was installed in gas-insulated switchgears. The electric potential was about 40% of the applied voltage. Using the measured potential, the electric field of the vacuum interrupter was calculated with axisymmetric 2-D finite element method. Then, the dimensions of the vacuum interrupter were designed so as to satisfy the insulation design criteria. The intermittent discharge during voltage application was stopped within 1 min. With this conditioning, we succeeded in withstanding lightning impulse voltage of 400 kV or more. Also, we confirmed that 400 kV could be achievable by this conditioning even for the contact electrode with welded traces. The results support the effectiveness of this conditioning method. As a result, this design and conditioning process enabled to eliminate conventional conditioning processes by switching arc and applying lightning impulse voltage in order to achieve 400 kV of lightning impulse withstand voltage.