Research Of Detection Of Phase-to-ground Fault In Petersen-coil-protected Networks By Wavelets Analysis

The Petersen-coil grounding in which a reactor is connected between the neutral of the power system and the ground is widely used in medium voltage power system in our country. Among all the faults likely to occur in a power networks, earth-phase faults are the most frequent ones. Accurate and fast selection of the fault line could increase power-supply reliability. In this dissertation, the investigation of the earth-phase fault circuit selection based on wavelets are involved. The main contributions are as follows:(1) A novel method of fault circuit selection is presented. In this method the transient fault signals are analyzed with wavelets transform to obtain the transient fault information, and the fault circuit is selected by the synthetic phase comparison method.(2) The analysis procedure of the fault circuit selection is developed and a fault circuit selection device is designed.(3) The validity of the method is confirmed by a large amount of the experiment results from a Petersen-coil protected 10kV simulation system with three outgoing lines. The experiments also show that the method can enhance the reliability of the relaying greatly.