The effect of viscosity on streamer propagation in insulating oil under impulse conditions

In previous studies the influence of viscosity on predischarge initiation and propagation was investigated using fluids with different viscosity numbers. However, this procedure has the disadvantage that the influences of fluid composition and viscosity cannot be separated. In this work only one fluid (transformer oil Shell Diala D) was investigated. The viscosity was adjusted by keeping the oil at the correlated temperature. The experiments were carried out varying the viscosity over a wide range. The predischarge behavior was explored in the strongly non-uniform field of point-plane geometries with gaps up to 10 mm and impulse voltages of both polarities up to 250 kV