Transmission Line Fault Model For Electromagnetic Transient Analysis Of Traveling Wave Fault Location Application Research

Long term operation statistical results showed that trip accident due to lighting striking form a big share of all transmission line accident. So identification of interference of lightning and fault generated by lightning and short-circuit of HVDC transmission line is one of essential subject especially for the coming construction of UHVDC system in China.In case of lightning stroke on±800kV UHVDC transmission line but not generating fault, the voltage traveling-wave fluctuate around the original DC component value. After several refractions and reflections, it gradually declines to zero due to dispersion. Because of the electromagnetic coupling between bipolar transmission lines, the variations of voltage traveling-wave on two polars are consistent in the short time after lightning stroke.Under the condition of transmission line fault by lightning stroke or short-circuit, the fault is equivalent to superpose a fault driving source at fault point which cut off the voltage traveling-wave suddenly. The transient after fault is similar to dynamic process of DC source driving switching circuit. After the short fault time by lightning stroke, the voltage traveling-wave of fault polar will decline, while the sound polar will rise.The traveling-waves generated by lightning stroke or short-circuit and lightning stroke without fault contain abundant fault information. The information is the key of identification of interference and fault of HVDC transmission line.The traveling-waves are signals of great singularity, and the singular points indicate the arrival of the wavefronts at the detecting end. The time-frequency characteristic of wavelet transform suits the analysis of traveling-wave very well. With the module maximum theory, identification of interference and fault can be transformed to the detection of wavelet transform modulem aximum.There is a characteristic that the waveform of the traveling-waves generated by lightning stroke or short-circuit is cut, but the waveform of lightning stroke without fault is not.When the UHVDC transmission line is struck by lightning, the traveling wave, which is caused by lighting stroke with fault, will decline while the sound polar will rise. So the polarity of correlation coefficient is opposite. The traveling wave, which is caused by lighting stroke without fault, the variations of voltage traveling-wave on two polars are consistent in the short time after lightning stroke. So the polarity of correlation coefficient is consistent.According to above analyse, criterion can be formed to identify the interference of lightning and faults generated by lightning and short-circuit by wavelet transform modulem aximum and coefficient.In this paper, relevant researchs are different from the overvoltage researchs. In view of protection point, analyse of the electromagnetic character of UHVDC system, identification and location of interference of lightning and fault help to shorten detection scope, enhance efficient, accelerate power reconfiguration and improve reliability of DC power transmission. Meanwhile research will facilitate forming of new protection. The studies will promote the new protection principle to produce.A new electromagnetic transient recorder and analyse prototype with high speed and high accuracy is introduced。Up to now, it has been tentative operation on the Hongzhan line in yunnan power grid. Practice shows the device has high accuracy and adaptability.The physical concept of the method presented in this paper is clear and lots of EMTP simulations shows that the method is feasible.