Research Of The Location Of Power Cable Earth Fault In Distribution System Based On Hilbert-Huang Transform

With the development of society, the use of power cables is more extensive in the distribution network. However, due to mechanical damage, insulation aging, water tree and other factors, a long-time running power cable may be breakdown. When the power cable is breakdown, it is required to detect the fault point exactly and quickly in order to exclude the fault and restore the power supply. This is important to improve the reliability of power supply.Identify the type of fault accurately is the prerequisite for fault location. The Paper established a fault type identification system including preliminary classification module, earth fault classification module and two-phase fault classification module. The preliminary classification module uses the energy the signal's lowest frequency of the wavelet coefficients of as the input vector of the support vector machine network. The earth fault classification module and two-phase fault classification module use the wavelet singular entropy of three phase voltages as the input vector of the support vector machine network. The simulation results show that this method can identify various fault types rapidly and accurately and immune to the fault resistance,and fault location.After identify the fault type accurately, the paper locates the ground fault(including single-phase ground fault and two-phase ground fault) which is most common in distribution system. The aerial mode component and zero mode component of traveling wave propagate to the detecting point at different speed whenults occur. The fault distance can be calculated by the propagation gap of the grounding faaerial mode component and zero mode component. So identifying and detecting fault-generated wave signals are vital for the location system. The paper presents a new method for time-frequency analysisfault-generated wave signals. We obtain the instantaneous frequency of the fault signal through Hilbert-Huang Transform(HHT) and detect the arrival time of traveling wave exactly through the instantaneous frequency.