Calculation of minimum approach distances for tools for live-line working under freezing conditions

IEEE Std. 516-2009 and IEC 61472-2013 present Minimum Approach Distance (MAD) requirements for tools to perform live maintenance safely, provided that the tool has no continuous film of moisture or measurable contamination present on its surface. However, four separate "clean" FRP hot-stick flashover incidents occurred in Canada under steady-state system conditions at the peak of the voltage negative half-cycle during cold and freezing conditions. This paper investigates IEC and IEEE methods of calculating MAD for tools employed for live working done on the geometry of the Manitoba site incidents at 500-kV. Based on cold fog tests carried out at CIGELE to reproduce these incidents, guidelines for calculating MAD in cold and freezing climate regions are proposed.