Interaction phenomena between PD pulses in SF6 and SF 6/water vapour mixtures

While partial discharges (PD) in SF₆ have been extensively studied there has been little attention given to the interaction between successive PDs. Repetitive discharges may affect the characteristics of subsequent PDs in the same general location so that theoretical simulations of the waveforms may be difficult to use and any investigations of impurity species may also be affected. This paper outlines some such interaction effects recorded in tests. There are two different kinds of interactions. One is caused by the space charge, and lasts about several tens of nsec. The other is caused by the PD energy accumulation in and around the previous PD channel. This latter effect is not significant for the first fifty or so (in the conditions here) pulses. However, after hundreds or thousands of pulses, the effect of this interaction becomes obvious and has to be taken into account