Kelvin probe for surface potential measurements on epoxy insulators for HVDC applications

Surface charging is one of the key problems in HVDC insulation development and the accumulated surface charge on insulator has thus to be quantified. The use of a vibrating Kelvin probes for this purpose became quite common in the last years according to literature. With a Kelvin probe the surface potential due to the accumulated charges can be measured without contacting the surface. Due to its working principle, the measured surface potential distribution is a convolution of the actual surface potential spatial distribution and of the -rather broad- response function of the probe. This imposes some limits on the smallest detectable features on an insulator surface.In this paper we present a measurement system built for the characterization of insulators in air environment and investigate the limits in respect of resolution of a Kelvin probe and its suitability for measurements mapping the whole surface of epoxy insulators.