A Single-ended Travelling Wave Fault Location Method Of High-voltage Cable Based On Natural Frequencies

With the constant expanding of economic scale of cities and the raising of power consumption in various industries, power cable, especially the high voltage cable over110 k V, has became arterial transmission line in cities, which has supplanted overhead line.In order to ensure the reliability as well as security of power supply and to reduce operational costs, the high-voltage power cable fault need to be located quickly and accurately once it occurred. Therefore, a single-ended travelling wave fault location method of high-voltage cable based on natural frequencies is presented in this paper,especially the high-voltage cable over 110 k V, by analyzing various domestic and foreign cable fault location method. The paper includes the following parts:(1)The basic structure of high-voltage power cable and the main forms of faults have been analyzed. The travelling wave propagation of single-line fault as well as the reflection and the refraction of travelling wave are discussed, particularly included the effects of different impedance at terminal and diverse busbar scheme on waveform.(2)The reason and characteristics of fault induced travelling wave natural frequencies are derived by using the ideal input-state-output model of power cable. Using the power cable terminal voltage and current functions in Laplace domain, the relations of natural frequencies, fault distance and angle of reflection are derived in different reflectance. The fault induced travelling wave natural frequencies extraction is completed by Fourier transform. Then the modified formula for lossy power cable is presented.(3) In order to identify the accuracy of travelling wave fault location method based on natural frequencies, when metallic short circuit happens, PSCAD is used to simulate the main insulation fault and to obtain the fault information, as the same time, MATLAB software is also used to program the algorithm. The simulations of different short circuit condition and system terminal impedance are conducted in order to verify the applicability of algorithm. In addition, the effects of different busbar scheme on this algorithm are verified by simulation.The single-ended travelling wave fault location method based on natural frequencies,presented by this paper, is immune to the interference of wavefront which is superior to time-domain method. The experimental results indicate that this method is much accurate and has a great potential in practical application.