Research and development on 145 kV/40 kA one break vacuum circuit breaker

145 kV and 40 kA one break vacuum interrupter has been developed. To achieve the high current interrupting capability, axial magnetic field type electrode was used. In addition, some designing techniques were applied to enhance the current interrupting and electrical insulation performance. Temperature rise simulation on the contact surface, magnetic and electric field analysis were key techniques. Also, the basic researches on the magnetic field distribution, vacuum breakdown characteristics under nonuniform field condition were carried out. The knowledge from these results has contributed to improve the performance. As a result, the advanced vacuum circuit breaker successfully interrupted the 40 kA symmetrical current at 145 kV and withstood impulse voltage of 650 kV.