Comparison between discharge patterns in solid and liquid insulating materials

Many papers have reported the experimental results of partial discharges in solid as well as liquid insulating materials. However, there is almost no report deals with the comparison between the two and particularly concerning the phase resolved partial discharges in solid and liquid insulation. This paper reports the comparison of phase-resolved partial discharge characteristics in solid and liquid insulating materials. The phase resolved partial discharge distribution from the two materials are presented. The role of applied voltage on the partial discharges is discussed. The phase shift on discharge occurrence which relates with the role of the space charge around the discharge sites in solid and liquid materials is also investigated. The experimental results indicated that partial discharges in solid are different with partial discharges from liquid material. The discharge magnitude in solid as well as in liquid is strongly affected by applied voltage. The discharge probability in solid is strongly dependent on the time derivative of the applied voltage but discharge probability in liquid is strongly affected by the instantaneous applied voltage. F-q-n patters showed that discharges in solid are strongly affected by the space charges and thus phase shift was clearly observed. However, there is no evident role of space charge in the occurrence of discharges in liquid insulating materials.