A Novel Technique For Single Phase High-Impedance Fault Detection

Generally, the transmission line fault can cause high phase current. Proper grounding protection set can trip reliably and cut off the fault. However, some unique geographical characters, such as fire grounding, bamboo grounding and treetop grounding, can cause single phase high-impedance grounding fault frequently, which cause low level current in practice. Especially in the case of the high-voltage transmission lines, high impedance faults (HIF) are characterized by an intermittent Arc-type nature and low level of the fault currents. The detection of the low-level ground currents with the conventional over-current relays is difficult and sometimes inaccurate. To analysis the fault component, wavelet transform can be seen as a well-developed mathematical tool. It can be formulated to describe signals in a localized time and frequency format. Analysis results show that when a single phase fault happens in the transmission line, wavelet transform modulus maxima of the zero-sequence current and the fault phase current will present special characteristics. A new scheme based on the characteristics is presented to detect the HIF.Furthermore, the changes of current and voltage caused by the normal...