Fault Location For Power Line Based On Single-end Transient Traveling Wave Time-frequency Analysis

With the accelerated construction of power grid, it is becoming increasingly prominent for power transmission and distribution network being the pivotal roles, which have important economic value and social benefits to quickly and accurately locate fault and restore power.Distribution network fault in the 80% above is the single phase grounding fault, and most of them transient fault and the steady current weak feature is not obvious after single phase to ground fault occurred, the traditional fault location methods based on steady-state information are limited. However, the fault location methods based on transient information using abundant fault transient information, not easily influenced by system operation condition and so on, has advantages of fast response speed and higher accuracy. Especially the traveling wave method, but there still have difficulty in identify wave-front and determine wave velocity,which influence its accuracy and reliability of location.Therefore, further studying analysis the time-frequency characteristics of the fault transient travelling wave, developing excellent performance location method, and improving traveling wave fault location technology,is of great theoretical significance and practical value.This paper firstly analyzes the transient traveling wave characteristics of the radial overhead distribution network after the single-phase ground. Secondly, based on the distributed parameter line image function model, voltage or current after fault is derived as a function of expression, and by solving the expression formula of characteristic line get mathematical relation between the frequency and fault distance.At the same time, this paper briefly introduces the frequency characteristics of the circuit parameters and the travelling wave dispersion, laid the theoretical basis for the later fault location.In this paper, considering the influence of frequency characteristics of transient current traveling wave on the wave propagation velocity and the arrival of the first wave-front, it presents a single-terminal fault location method based on time domain features for distribution circuit of the single phase ground fault location: according to the modulus of cross transmission characteristics of traveling wave in the fault point to realize the criterion of fault section; Lipschitz exponent of the continuous wavelet transform is used to link the transient wave-front time and the wave propagation velocity, complete fault location;the sampling frequency is limited by the fault distance is analyzed and the fault location of truncation error, optimize distance measuring results. This paper built a simulation model in EMTDC and calculated by MATLAB, to verify the correctness of the method.Meanwhile, this paper compares the extracted the characteristic frequency of fault transient traveling wave by the DFT method, the complex wavelet transform and matrix pencil in transmission line single-ended fault location on the applicability and advantages and disadvantages, and according to the theory of singular values difference spectrum,matrix pencil method is improved.Further presents a single-terminal fault location method for the distribution network considering the characteristic of special frequency bands(SFB) of its zero mode network.By improved matrix pencil method, extracted the frequency inside the SFB from sample information, to realize the distribution circuit of single-phase ground fault location. Similarly, simulation experiments in EMTDC to verify the correctness of this single-ended fault location method.