Oscillatory overvoltage in compact medium voltage switchgear during impulse surge tests

All power network components have to be designed in such a way that they are able to withstand all stresses during their normal operating life including transient impulse voltages. For this purpose, all power network components including switchgears have to pass high voltage impulse tests. Although the amplitude, rise and fall time of applied voltage impulses are given in standards, there is no guarantee that the voltage imposed to all internal parts of components is the same. If the spectrum of an applied voltage pulse is in the range of the Eigen frequencies of a system, resonance effects may occur. Such resonances may lead to overvoltages on internal elements of the system. Medium voltage switchgear is one of those complex systems, where different energy storing elements are…