Medium voltage distribution power grids mostly operate with ungrounded neutral points of transformers. The philosophy of these electrical grids is based on the assumption that they are more reliable than grids with grounded neutral. However, transient currents during single phase or multiple faults to ground, depending mostly on the phase to ground capacitances of the used cables connected to power grid substation buses, frequently have intermittent nature due to arising arc. Moreover, this kind of arc ground fault on the ungrounded system causes transient overvoltages significantly higher than the nominal value. In the consequence, it may be dangerous for the electrical devices connected to the power system. The article focuses on the transient overvoltages on the adjustable speed drives due to ground faults within the industrial grid. The Matlab/Simulink Software was used for modeling system transients during intermittent faults.
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