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Recovery of dielectric strength after DC interruption in vacuum

In order to investigate the influence of the electrode separation, arc time and frequency of the reverse current on the breaking capacity of vacuum breakers in a DC interrupting process, the dielectric recovery strength was measured after the interruption of a breaker. A high speed actuator mixed with a permanent magnetic actuator and a repulsion actuator was designed. And a circuit which can produce a high voltage pulse was set up to measure the dielectric recovery strength after the extinction of arcs. By the method of forced current-zero, experiments were carried out to interrupt a small DC current in a synthetic test circuit. Then the dielectric recovery strength under conditions of different electrode separations, different arc time and different frequencies of the reverse current was measured with the method of monopole discharge. The experimental results indicated that there existed a critical electrode separation in the DC interrupting process. Within this electrode separation, the dielectric recovery strength can be enhanced by increasing the electrode separation and decreasing the arc time. In addition, decreasing the frequency of the reverse current can also improve the dielectric recovery strength.