Discharge structure and dielectric strength of long oil gaps in the presence of an insulating barrier

This work is devoted to the influence of insulating barriers on the trajectory of the discharge structure, the breakdown voltage and the time lag to breakdown in a point-plane electrode arrangement for long oil gaps. It is shown that the barrier parameters (nature, dimensions and position) play a significant role in the improvement of the dielectric strength of the system. It was observed that the discharge goes from the point electrode to the barrier edge and then from this edge to the plane electrode. The discharge trajectory between the point and the edge of the barrier can be direct (the shorter distance) or tortuous. The presence of the barrier elongates the discharge length. In results, the time lag to breakdown and the breakdown voltage will be increased. The breakdown voltage of a given gap length in presence of an insulating barrier is roughly equal to that of a gap without barrier the length of which is equal to the sum of the distance from the point electrode to the edge of the barrier and from the edge of the barrier to the electrode plane