| The high frequency overvoltage in the power system can be divided into three categories according to its waveform characteristics.The fast wave front overvoltage(frontwave time 0.1~20μs)is mainly caused by lightning strike.Although the action time is short,its amplitude is much higher.The normal working voltage of the equipment poses a great threat to the safe operation of the equipment in the power system.It is necessary to analyze the transient process of the corresponding equipment under the fast wave pre-voltage.Among the devices acting on the fast wave pre-voltage,there is a class of typical electrical structures whose transient analysis process is complicated.This is the core-tube type electrical structure,which is characterized by two inner and outer conductive parts,and the representative equipment is a wind power generator tower.The tube and the GIS sleeve,the fast wave front overvoltage acts on one of the conductive parts and the corresponding overvoltage is generated by the coupling on the other layer,because the accurate modeling of the core tube electrical structure is the equipment the key to the transient process under fast-wave over-voltage.In view of the transient process analysis of the electrical equipment of the core tube structure under the fast wave pre-voltage,the main research work of this paper is divided into two parts.One is to explore the modeling method of the core tube electrical structure in the electrical equipment;The second is to have the overvoltage of the electrical equipment of a typical core tube structure is simulated and analyzed.The main work content and results are as follows:(1)The equipment modeling method with core tube structure in electrical equipment is studied.The vertical and horizontal core tube electrical structures are divided according to the different ground arrangement.The two types of core tube structures are equivalent circuits according to their respective characteristics.The method of the network is modeled,and the calculation method of the main parameters in the corresponding model is given.(2)Transient response analysis of electrical equipment with typical horizontal core tube structure.The wind turbine is used as the research object to model various parts including fan blades,sliding contact parts of the nacelle shaft,tubular tower and internal power cable and grounding system.The grounding system is equivalent according to the actual structure using a multi-conductor π-type circuit.The electrical parameters of each component are calculated according to the actual fan structure,and the overall simulation model of the transient over-voltage distribution parameter under the over-voltage of the wind turbine before the fast wave is established.Based on the model,the overvoltage distribution of the overvoltage wave propagation path is analyzed,and the effects of different grounding resistance,lightning current parameters,grounding mode and arrester configuration scheme on overvoltage distribution are discussed.(3)Transient response analysis of typical horizontal core tube structure electrical equipment: A GIS test field containing GIS equipment and GIL transmission line is taken as the research object,and the segmented conductor wave impedance model is modeled by GIS and GIL according to the horizontal core tube structure modeling method.And construct the transient grounding grid and the equivalent model of the impulse voltage generator used in the test,and calculate the transient ground potential rise of the outer casing under the fast wave front overvoltage during the impact withstand voltage test.The analysis results show that the ground potential of the GIS shell is affected by the grounding lead parameters of the equipment,the surface condition,the connection conditions of the GIS equipment and the grounding grid,and the suppression measures of the GIS transient ground potential rise in the lightning impulse test are discussed in detail. |
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