Investigation of space charge profile on the flashover characteristics of fiberglass reinforced plastic (FRP) tools under HVDC conditions
In high voltage direct current (HVDC) electric power systems, live-line maintenance methods, using fibreglass reinforced plastic (FRP) tools, are being applied to enhance their reliability and avoid costly outages. The effects of direct current (DC) space charges are not well understood or accounted for in live-line working standards. Surface charge is generated by a ring of needles, pre-stressing and wiping. Surface potentials are measured using a vibrating Kelvin probe and converted to charge densities using a probe response matrix. Surface charging characteristics of FRP are compared to silicone rubber (SIR) and wood hot stick insulator samples. The effects on flashover voltage due to the presence of surface charge are investigated by applying both polarities of voltage when charges pre-existed on the surface. It is discovered that the presence of surface charge does impact the flashover voltage of FRP insulator samples. Mitigation methods are investigated and discussed.