A novel method to reduce the harmonic currents in the residual earth fault current during a single phase to ground fault in compensated grids

This paper presents a new approach to reduce the harmonic currents during a single phase to ground fault in a compensated grid. The reduction of the harmonic component in the fault current improves network stability and possibly prevents a blackout. A model has been simulated in Matlab-Simulink with multiple current sources working as compensation system in a 20 kV medium voltage example grid. The simulation results show that the harmonic distortion of the grid voltage has a significant influence on the magnitude of the fault current. That may lead to exceeding the extinguishing limit if the distortion is too high. With the presented method it is possible to significantly reduce the harmonic current without intervening the grounding of the transformer and the zero system. Furthermore, it is possible to place the system anywhere within the grid, which leads to a high degree of flexibility and facilitates upgrading.