Simulation Research Of Distribution Network Fault Location Method Based On Intelligent Signal Analysis

Most of distribution networks in China are resonance grounding system. In various types of overhead line failures, single-phase ground fault takes the largest proportion. Online fault detection and location are the basis of self-healing function of smart grid, It aimed at quickly identifying, eliminating single-phase ground faults while ensuring the electricity supply. The ultimate goal is to improve power supply 62 reliability. So the research of fault location in distribution network has important practical significance.Traveling wave fault location is the main method for fault location of HV transmission line. Because with plenty of branches, the topological structure of distribution network is quite complex, the travelling wave fault location method cannot be directly applied to the fault location in distribution network. So this paper improves the travelling wave fault location method in distribution network, proposing the method of multi-measuring-point piecewise travelling wave fault location in order to solve the problem of complex topological structure, plenty of branches and the difficulty of fault point location in distribution network. The method of multi-measuring-point piecewise travelling wave fault location presented, firstly divides the distribution network into a plurality of sections, arranges the detection devices on both ends of each segment of line and locates the fault section through the arrival time of the fault travelling wave. Then the method of double side distance measure is used in the fault section to calculate the position of the fault. The piecewise fault location method can shorten the length of the line in fault location, effectively reduce the attenuation of the travelling wave and improve the accuracy of the travelling wave fault location.The double terminal travelling wave fault location method locates the position of the fault through the difference of distance converted from the difference of time between when the wave heads of the inceptive fault travelling waves propagate to each end of the line at the speed of signal propagation velocity(close to the speed of light). As a result, the accuracy of the wave head detection determines that of the fault location. At present, wavelet transform and Hilbert-Huang transform are commonly used wave head detection methods. Wavelet transform is not self-adapting, and it requires the appropriate wavelet basis function and decomposition scale has been chosen for the signal to be analyzed. When the characteristic of the signal changes, the chosen wavelet basis functions and decomposition scale will not be able to analyze the signal correctly. Hilbert-Huang transform is self-adapting, which is suitable for both stationary and nonstationary signals. However, there are less envelope and over envelope problems in EMD algorithm, while the IMF component has the deviation, both of which affect the decomposition results. Simultaneously, the calculation of Hilbert transform is of a large mount, so that it fails to meet the requirements of real-time in fault location.Aiming at the problem of the difficulty of accurately detecting the fault travelling wave head in travelling wave method, this paper puts forward the method of combining EEMD and Teager energy operator to improve the detection accuracy of the travelling wave and greatly reduce the computational complexity. This paper uses Hermite interpolation algorithm to fit the envelope, which brings an effective solution to the less envelope and over envelope problems and makes the catastrophe point of time of the fault component in IMF component more accurate. Moreover, the computational complexity of Teager energy operator(TEO) is much smaller than that of Hilbert transform, thus more in line with the requirements of real-time in travelling wave fault location.In this paper, the wave head detection method of multi-measuring-point piecewise travelling wave fault location method and EEMD combined with TEO are tested respectively with PSCAD simulation. The result shows that, the measuring points get the detection time of the travelling wave head that is more accurate and the shorter computing time, The fault location precision than the common traveling wave ranging method improves the precision of 100 meters.