Effect of particles on partial discharge inception in oil immersed insulating system

The behavior of a spherical metallic particle was observed with a high speed camera at the instance of partial discharge inception in an oil immersed insulating system. The polarity of the metallic particle charge was evaluated by the behavior of the particle and the direction of the electric field. A positively charged particle moves to the pressboard located on a negative electrode to initiate the partial discharge. The charge quantity of the particle can be calculated by the behavior of particles and electric fields. The movement of particle is notable in an AC peak voltage so that the partial discharge initiation can be observed on the peak voltage. A mechanism of partial discharge inception is proposed.