Research On The Traveling-wave Fault Location Method Of HVDC Transmission Line

HVDC transmission system has broad prospects in our country. The direct current transmission technology will play vital roles in transmitting electric power from the west area to the east in China as well as in the electrical power system nation networking projects. Therefore, the precise location of HVDC transmission line fault is of great significance and practical engineering value. Fault location based on fundamental components is easy to be affected by transition resistor, fault type, bus configuration and TA saturation, thus, its location accuracy is not satisfactory. Nowadays, with the development of computer, correspondence and measure technology, transmission lines fault location based on traveling–wave is rapidly developing. The wavelet transform simultaneously has the good attribute of showing partial signal in the time domain and the frequency domain, and the ability of eliminating noises. The signal singular point contains most important information, and the Wavelet Modulus Maxima can portray the signal singular point and the irregularity of traveling-wave. Therefore, picking-up the high frequency transition signal with the wavelet transform can realize the precise fault location.Firstly, the characteristics and the issues of two fault location methods respectively based on traveling-wave and fundamental components are analyzed in details in this thesis.Secondly, the wave process and the double terminal traveling-wave fault location principle are described. A traveling-wave fault location system is proposed and its structure is introduced.Thirdly, the wavelet transform theory is introduced, in which most commonly used is Dyadic Wavelet Transform. In Dyadic Wavelet Transform, the wavelet transform can change focus through changing scale J. In fault location systems, the Cubic B-Spline Wavelet is chosen as basic wavelet and the head of traveling-wave can be accurately distinguished by use of the wavelet Modulus Maxima theory.Finally, the HVDC systems are simulated and analyzed with PSCAD and MATLAB software, and the precise time of the initial current traveling-wave head that arriving at both sides of the bus are obtained after fault happened. Then, the distances between the fault location and the both sides of the bus can be computed. The result indicated that, the head of the current traveling-wave can be accurately distinguished with the wavelet transform method, so, the highly precise fault location of the HVDC transmission line can be realized.