Small Current Grounding System Based On Wavelet Analysis Of Single-phase Fault Line Selection

Neutral non-grounded and Petersen-coil grounded systems are widely used in 6-35kV distribution network in China. Single phase earthed fault is the common fault in this system. To select the fault line accurately is of great importance to improve the operation reliability. However, the current theories and apparatus cannot select the fault line accurately and satisfy the requirement of fault line selection.The transient components of grounding capacitance current are several times even ten times higher than the steady state value in several cycles after happening fault. The frequency of inductance current high-quency components that the extinguishing coil produces is not correspondence with the frequency of capacitance current. The characteristic components can not only improve the currency of line selection, but also ignore the influence of extinguishing coil. The wavelet theory can accurately analyse the discontinous, weak and nonstationary fault signal. In power system, it can analyse the transient process and draw the fault characteristic. This paper analyses the transient character of line fault when the neutral point connects to ground in different ways. From the perspective of signal processing, the...