| As China’s energy base and “wind of the construction of the three gorges”, InnerMongolia are facing the historical opportunity of country’s implementingdevelop-the-west strategy, project of transmission of electricity from the western to theeastern region and calling"green energy", so there is broad space in the development ofthe power electricity. Inner Mongolia"three horizontal grids also provids500kV fourlength wise"preliminary already built. But500kV transmission lines are mainly locatedin mountainous and wild areas, transmission line failure rate is high. High voltagetransmission line fault on the entire power system has a larger threat to the safe operationand maintenance personnel on the line brought about by the heavy burden.After the linefault, fast and accurate positioning can be repaired in time lines and rapid restoration ofpower supply, not only for the rapid repair of fault line,to ensure supply reliability andreduce power losses, but also to ensure the safety and stability of the entire system andthe economy are very important.Now, the high voltage transmission system only has travelling wave fault locationdevice, there are two main factors influencing the accuracy and reliability of travelingwave fault location, namely the determination of traveling wave velocity and the timewhen the reflected wave fronts arrives.In the aspect of fault location,t his thesis proposestwo kinds of fault location methods based on the time-frequency characteristics oftransient traveling wave to improve the accuracy of current fault location methods usingtraveling wave and traveling wave natural frequency.One of them is a new fault location method based on the travelling wave combiningwith natural frequency.It uses method based on natural frequency to calculate roughlyfault distance, and the time regions of reflected waves from fault point to detective busare confirmed through the distance. Ensemble empirical mode decomposition isemployed to extract the high-frequency component from traveling wave, recognize thereflected wave fronts and avoids the influence of traveling wave speed. Then adouble-ended traveling wave location method that doesn’t need to identify the travelingwave is presented, which avoids the influence of traveling wave speed and transmissionline arc in theory, thereby both of the location reliability and accuracy are improved.Ensemble empirical mode decomposition is a new method of signal analysis.it hasan obvious predominance in dealing with the break transient signal and the weaksignal.EEMD has a good self-adaptability, which helps to improve the accuracy of signalanalysis, therefore it can be used to detect the transient traveling wave and determine thetime when the head of wave arrives.This thesis proposed applying EEMD to detecting the frequency discontinuity pointof travelling wave so as to pick up the inceptive travelling wave and achieve faultlocation. Meanwhile, this thesis made a rough introduction on algorithm of EEMD andthe method to catching the inceptive travelling wave, and conducted a lot of simulation test on the algorithm.Based on the main parameters of500kV Transmission system in Inner Mongolia,this paper uses power system simulation software PSCAD/EMTDC to build a model, andthe two novel fault location algorithm is used to make simulation analysis of faultlocation when line fault has happened on different positions and with different resistanceson the transmission line. A large number of simulation results show that the locationaccuracy of the two methods raised in this thesis have a significantly improvement overexisting traveling wave method. Moreover, their reliability and accuracy will not beaffected by fault resistance, fault distanceor fault type. It also has a good adaptability tonoise interference.This research has important practical value for the design of fault location method,itwill play theoretical and applicable role in extended industry application of500kVTransmission system in Inner Mongolia. |
PDF Full Text Request