Potential and electric field calculation along a FRP live-line tool under cold and icing conditions

Two clean live-line tool flashovers in Manitoba at 500-kV line voltage and two recent ones in Saskatchewan at 230 kV during freezing conditions led to extensive laboratory tests to reproduce some of these flashover conditions in a controlled laboratory environment to understand the underlying mechanisms and to assess mitigation measures. This paper improves on the three-dimensional finite element method model developed in our previous study to compute the potential and electric field along and around a fiberglass-reinforced plastic hot-stick in a series of “true” cold fog tests at the UQAC. In the previous study, the simulations were carried out with a dry surface and non-uniform wetting. In simulating the non-uniform wetting conditions, since a non-continuous water film was considered to be on the hot-stick surface, there was no leakage current. However, in the flashover and cold fog tests at the UQAC, leakage current activities were observed between the HV and ground electrodes on the surface of the hot-stick. In the present study, the mathematical equations of the model were modified to allow for the presence of leakage current flowing through a continuous thin layer of ice on the surface of the hot-stick in freezing and cold conditions, as was the case for the flashover incidents experienced in Saskatchewan. The potential and electric field distribution along and around the hot-stick were calculated and compared with those in dry surface conditions.