Double-ended Traveling Wave Fault Location Method In-depth Study

The theory of using traveling wave in transmission line fault location has existed for a long time. But fault traveling wave signal is considered to be a kind of singular non-stationary signal and has complex frequency distribution and high traveling velocity. In addition, under the influence of the electromagnetic coupling between phases of the single-circuit and double-circuit parallel transmission line, the imbalance and frequency characteristic of the transmission line parameters, different component of traveling wave has different grade of attenuation, aberration and traveling velocity. All of these characters bring difficulties to choose the velocity and measure the traveling wave arriving time. Based on the exist theories, this paper focus on the resolution of all the difficulties mentioned above and illustrates a more integrated and reliable method to locate the traveling wave fault, by using wavelet analysis and phase-mode transformation as research tools. The majority of work in this study is listed as follows:Analyzing and summarizing the capacity of TA and TV to transform high frequency traveling wave signal; theoretically analyzing and simulated comparing the single-ended and double-ended traveling wave measure methods in aspect of reliability, precision and adaptability. Based on this paper's researches, the double-ended measure method using current traveling wave is considered to be more feasible and reliable.For the electromagnetic coupling between phases of the transmission line, different components of traveling wave have different traveling paths, different grades of attenuation and aberration and different traveling velocities. Hence it is important to choose suitable traveling wave components for faulting location. Based on the phase-mode transformation of single-circuit transmission line, phase-mode transformation of double-circuit transmission line is emphasized in this paper. The suitable modes of current traveling wave for fault location are chosen according to the researches in parameters' characteristic of every mode.Fault traveling wave on transmission line is a kind of singular non-stationary signal. Wavelet analysis is widely used to detect singular point of this kind of signal, profit from its favorable localization performance in both time and frequency domain. Traveling wave has high velocities and frequencies; tiny error in singular point position will cause big error in fault location. So it is important to choose suitable wavelet functions. In this dissertation, according to the characteristic of traveling wave, the principles of choosing wavelet function and scale are summarized and the fault location performance of two kinds of Gauss wavelet function, Morlet wavelet function and two kinds of B-spline wavelet function are analyzed and simulated. And the derivation of equivalent filter coefficients of B-spline wavelet is presented.The researches in choosing traveling wave velocity and acquiring arriving time only make sense when they are banded together. Wavelet transforms in different scales match different frequency segments of signal. The traveling wave signal has complex frequencies. Signals with different frequencies of different modes travel in different velocities. In this dissertation, the calculation methods of mode velocities under different scales are presented.The theoretical analysis and simulation results indicate that the studies in this dissertation can improve the accuracy, reliability and adaptability of traveling wave fault location.