Location of the Earth Faults in MV Compensated Networks

The MV networks are not construct as transposed that means they are non-symmetrical. This factor causes the unbalancing of the phase voltages and the zero component of voltage appears there. The distribution networks with overhead lines are operated as compensated with the arc-suppression coil connected to node of transformer. The operation with the arc-suppression coil out of tune is accompanied by higher values of the fault currents during the ground faults and the natural frequency of the course of recovery voltage in the network after switching off or interrupting the ground fault. These disadvantages can only be removed by efficient elimination of the phase asymmetry. This paper describes new method of elimination phase capacitance asymmetry by ancillary suppression coils. This method has favorable effects on the network operation during the ground fault and do not reduce the protecting elements sensitivity to high-ohm ground faults. By improving the accuracy of the arc-suppression coil tuning the safety of the compensated networks operation can be enhanced. The new method of elimination of the phase asymmetry opens the secondary advantage like new method of fault location. This location method starts from idea of fault location using inter-harmonic signal [1,3,7] or remote control signal [6] and is based on injection of higher inter- harmonic frequency signal to the secondary windings of ancillary suppression coil which is connected to affected phase. With Ohm law application it is possible to determine the impedance of fault-loop and from this the distance of fault too.