HVDC flashover performance of fibreglass reinforced (FRP) hot sticks considering space charges

In high voltage direct current (HVDC) electric power systems, live-line maintenance methods are being used to enhance their reliability and avoid costly outages. Live-line working standards presently do not consider the impact of charge on the surface of live line tools. Electric field stresses produced due to surface charging of polymeric materials under HVAC and HVDC operating conditions are different in distribution and magnitude. Recently, more attention has been given to the study of surface charging characteristics of polymeric materials and its impact on DC flashover voltage. In this work, two sources for generating space charges on a sample of FRP tool are used; a corona ring of needles and pre-stressing from one electrode with the other electrode grounded. Before flashover testing, the samples are firstly charged, and then the applied DC voltage is ramped until flashover occurs. The DC flashover voltage and leakage current are monitored at every test to identify the effect of surface charges. The effects on the flashover voltage due to the presence of surface charge are investigated by applying both polarities of voltage when charges pre-existed on the surface. This paper aims at providing an understanding of DC flashover characteristics of FRP hot-sticks due to surface charging by direct contact and/or corona discharge of nearby energized parts.