Possible Solutions to Problems of Voltage Asymmetry and Localization of Failures in MV Compensated Networks

The compensated networks are affected by the phase capacity asymmetry of wiring, which causes the unbalancing of the phase voltages in the tuned condition of the arc-suppression coil. In the especially unfavourable cases this effect reduces the possibility of network operation with the tuned arc-suppression coil. 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. The new methods of eliminating the phase capacity asymmetry allow for controlling the phase asymmetry size (its reduction as well as its possible increase), they keep it within a specified tolerance band (Uo value in the tuned condition of the arc-suppression coil is typically maintained at levels from 1% to 4% of the network voltage phase value). The new methods of elimination of the phase capacity asymmetry have favourable 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 other properties of the whole system of phase capacity asymmetry elimination designed to increase the compensated networks operation safety, to improve the reliability of ground- fault protections and to locate the fault areas, can be fully utilized