| EHV mixed lines have both economy and reliability advantages on electricity transmission to city center and crossing-river place.Therefore,mixed lines have been widely applied and popularized in the construction of modern power system.Aiming at stable operation of the system and quick recovery of the load centre power supply,study on accurate fault location and adaptive reclosing technology of mixed cable-overhead line is of great theoretical and practical value.Firstly,the fault location method and adaptive reclosing of EHV mixed line are conducted in-depth research.The current research status of fault location method and adaptive reclosing of EHV mixed line are summarized.The parameters and electrical characteristics of mixed line are analyzed,and the inhomogeneity of circuit parameters and the characteristics of transient electric capacity after the fault are revealed.Combined with the characteristics of the parameters of mixed line,the frequency dependent model is introduced and based on the model a mixed line model is built.Based on the analysis of the electrical boundary conditions in the typical grounding modes of power cable,for the parameters calculation of power cable segment of the EHV mixed line,the equivalent core impedance and admittance calculation method of different conductor layer grounding modes are presented.Aiming at asymmetric fault and symmetrical fault of mixed line,the distribution of sequence voltage variation along the line is analyzed.The magnitude of the sequence voltage variation calculated from the two ends of the mixed line is equal at the fault point.Then,a fault location algorithm for EHV mixed line is proposed based on variation of sequence voltage and verified by the simulation of mixed line model.By analyzing the characteristics of recovery voltage under single-phase fault for mixed line,an adaptive reclosing technology based on the improved Prony algorithm is proposed and verified by the simulation of mixed line with shunt reactors model. |
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