Switching overvoltages and risk of flashover on Yugoslav 400 kV transmission lines

A brief presentation of the results of experimental investigations of phase-to-earth and phase-to-phase switching overvoltages on Yugoslav 400 kV transmission lines is given, as well as the results concerning the reliability of their operation for different insulation levels. Investigations of switching overvoltages were performed on four 400 kV network subsystems. Only experimental results obtained on the 400 kV transmission lines of Yugoslavia are presented: at the time they were switched on and off, unloaded or loaded with a transformer, itself at no-load, or with an autotransformer with or without reactor on the tertiary. On the basis of the measured amplitudes of phase-to-earth and phase-to-phase switching overvoltages, the risk of flashover on 400 kV transmission lines was analysed.