A rotating spark gap for double impulse experiments

The switching gap is the most important circuit component in a high-voltage high-current generator. Usually these switching devices are in the form of triggered spark gaps. It is well known, that following high current sparking, the gap between the electrodes stays "hot" for some time, which affects the recovery time of the spark gap. Improving recovery time has been the subject of several investigations and various techniques have been suggested. The effect of gas type and the pressure of the gas were extensively researched. In addition, the insertion of a rotating dielectric perforated disc between the spark electrodes was found to improve the recovery of the gap at high repetition rates. When simulating multiple lightning strikes on power system equipment, there is a need for a generator which is able to output several kiloamps at high voltages with a variable time period between the successive impulses. This time interval varies from seconds down to the millisecond range. At these small intervals, the normal recovery time of the conventional spark gap becomes inadequate. Moreover, if successive opposite polarity impulses are required, capacitive type generators with standard spark gaps cannot be used. In this paper, a novel design of rotating spark gap is described. This design allows improvement of the recovery time and more importantly the generation of successive impulses of opposite polarity. In this programme, these impulses have been applied to high voltage surge arresters in nonstandard tests.