| At present,China’s power construction is at an important stage,and the government also proposed a long-distance transmission strategy.Researching and developing corresponding transmission technology has become a hot spot at this stage.As the core equipment of power system transmission,the operation of the electric power cable will directly affect the safety of the system,consequently,how to locate the fault point quickly and accurately is more and more concerned by power workers.On the basis of travelling wave method,this paper put forward a fault location algorithm to remove wave speed limitation,and deduce the corresponding calculation formula in detail,and use wavelet transform to search modulus maximum sequence of fault signal so as to locate the line fault point,which provides maintenance basis for the operation and maintenance staff,and it is significant in the early prevention of cable line fault.The main research contents of this thesis are as follows:Firstly,this thesis introduces the basic theory of cable line fault location,including the fault reason,judgement of the type,and the comparative analysis of advantages and disadvantages of various fault location methods.According to the propagation characteristics of travelling wave in the line,the transient travelling wave signal in the fault cable is further analyzed and studied,and its corresponding mathematical model is established.Then the cable line is divided into three sections according to the time when the fault point refraction reflected wave and the terminal reflection wave reach the detection bus and the polarity combination of each travelling wave head,separately deduce the corresponding location algorithm for removing the wave speed limit of each section.Through MATLAB modeling and simulation,the corresponding high-frequency signal is obtained by wavelet four-level decomposition,and the corresponding modulus maximum sequence is obtained by further analysis and search,and finally the location result is obtained by the algorithm.Finally,this thesis designs cable fault location system based on simulation model,and the system is divided into three parts:pulse signal source,signal receiving circuit and input and output module.Build the system hardware circuit and debug the system,set short circuit and open circuit faults at the cable line respectively and carry out the location test through system,the waveform obtained by test is processed by improved threshold denoising method,and then the fault distance is calculated by using the location algorithm that remove the wave speed limitation.In the end,the results meet the expected requirements,which verify the feasibility of the system. |
