Experimental Arrangement for Investigating the Surface Dielectric Strength of Insulating Materials

An experimental arrangement for laboratory investigation of surface discharges along insulating specimens is presented. A sphere-ring and a needle-plane air gap bridged by PA insulating surfaces were stressed by positive slowly-varying high voltages with variable waveform parameters and by positive standard lightning impulse voltages. A flexible digital measurement and control system allowed for simultaneous monitoring of the applied voltage and discharge current, as well as of the UV radiation and temperature rise of the insulating surface associated with surface discharge activity. With the aid of the introduced experimental set-up, measurement procedures and analyses, the various surface discharge modes including flashover are easily identified, providing valuable information on their inception and spatial-temporal growth characteristics.