Lightning Overvoltages Suppression for the 35-kV Cable Section Insulation with the Frequency-Dependent Device

Abstract

Lightning strokes are considered to be the one of the most serious factor impacting the electrical equipment insulation and leading to the high overvoltage level that has to be reduced. The paper deals with the analysis of unrestricted lightning overvoltages impacting the 35-kV cable line insulation that was carried out for the case when the chopped impulse is formed as a result of the line insulation flashover. Following the preliminary results, dangerous lightning overvoltages that exceed the permitted impulse strength of the cable line insulation can occur when the overhead line with the 35-kV nominal voltage is arranged in a 110-kV line frame. In some cases, the traditional protection devices are not effective in the high-frequency overvoltage restriction. So the new method of suppression is considered for the 35-kV cable line protection. The effectiveness of the frequency-dependent device at lightning strokes is analyzed for different simulation modes and variable protection device characteristics. As a result, recommendations for the appropriate frequency-dependent device parameters are given.