Accuracy of surface potential measurements of HVDC spacers

Stationary DC electric fields are determined by the resistivity distribution of the used insulation materials. In the presence of interfaces between different insulation materials, charge accumulation at these boundary layers may have a significant influence on the electric field distribution and with it on the breakdown strength of the arrangement. To investigate and understand these charging processes, measurements of the accumulated surface charges have to be performed. In our research we measure the electric potential, as it is a consequence of the accumulated surface charges, close to the surface with a Kelvin Probe like it is widely done in this field of research. In this paper we show the limits and influencing factors on this measurement.