Switching voltages in MV networks: their natures, characteristics and methods to prevent their occurrence or to limit their values

In MV cable networks as applied in the Netherlands, insulation co-ordination is in principle defined by the potential occurrence of switching overvoltages. These overvoltages have different origins. Harm can be caused to the installation by either the amplitude or rising time or both. In this article, the basic phenomena are reviewed, such as normal current chopping, virtual current chopping, multiple restrikes and pre-ignitions. The probability of their occurrence in practice is discussed and possible precautions are mentioned. The authors include a description of a special method to prevent the most severe overvoltages