Research On Fault Diagnosis Method Of High-voltage Cable Based On Lissajous Graph And Temperature

As the State Grid has issued a number of documents successively to vigorously promote the construction of UHV lines and substations,it recognized that UHV has the advantages of a long industrial chain,strong motivation,and significant economic and social benefits;clarified the increase in the investment scale of UHV projects.High-voltage,ultra-high-voltage,and ultra-high-voltage,they all show a huge potential for growth.Cable plays an important role in the power network.Nowadays,urban zone can’t develop alone without high-voltage AC cable lines.With many of urbanized high-level transmission channels overhead lines have been transmitted to the ground through cable transformation,the difficulty of maintenance is far beyond that in the past.There’s not many effective ways to assess the statues of cable but sending staffs to inspect the cable locally.Due to the high uncertainty of cable line faults,and the types of faults are complex,how to quickly implement online fault diagnosis has become a major problem.In view of the above problems,thesis makes the following main research contents.Firstly,the present domestic and foreign situation of HV AC cable fault studies were analyzed.Then the goal of this thesis has been set,which is the diagnosis of hv AC cable faults.From the perspective of the sheath current,the relation between cable faults can be found.In chapter 2,the mechanism of current generation in the sheath of HV AC cables is analyzed in detail.Secondly,a fault analysis method for high-voltage cables based on the principle of locus method is proposed.The locus method is used to draw the locus map by integrating the sheath current,and calculate the locus characteristic parameters.By using the ATP-EMTP simulation software,a high-voltage AC cable model is built.Different fault locus diagrams are generated via this model,by simulating different kind of fault.Different operating states can be directly reflected in the locus diagrams and there are significant differences.Meanwhile,measuring the cable temperature via distributed optical fiber system.Then use the Pettitt Detection to anaylse the probabilities of each phase’s fault.Combining those informations,the result of diagnose can be bring out.Finally,the diagnostic system is introduced,including the main control chip,the field data acquisition and processing circuit,the power supply,etc.The slave computer collects the currents of key points in real time.Once the currents change suddenly or beyond the normal range in a long time,the upper computer judges the fault.The slave computer records the signal and send it to the upper computer.The upper computer diagnose the fault via the method of this paper.