| China's power grid has a wide distribution range and its transmission lines and distribution lines are all over the country.Transmission lines with high insulation level and erection height are more vulnerable to direct lightning hazards.However,due to the low insulation levels and low relative heights,distribution line is more hit by the induced lightning.In the transmission line,the annual trip accident caused by lightning strikes is about 50%.In the distribution line,the number of flashover faults caused by the induced lightning overvoltage in the 10 kV distribution line in some areas is as high as nearly 10,000 times a year,which seriously affects the power supply.Reliability,so the analysis and research on lightning overvoltage in transmission lines and distribution lines is of great significance.Therefore,this paper mainly studies transmission and distribution lines suffered by different lightning strikes and derives lightning protection measures for transmission and distribution lines.Firstly,the mechanism of lightning discharge and the type of lightning strike in nature are elaborated.This paper introduces the mathematical model and various electrical equipment models in the calculation of lightning intruding waves on transmission lines and calculates the equivalent model parameters based on the actual line parameters.Select the appropriate base current model and the backlash model as the mathematical model of the lightning induced lightning in the distribution line.The Maxwell's equations are used to solve the induced electric field and magnetic field generated by the lightning current return current of any point in space.The finite difference time domain method is used to solve the time domain of the Agrawal lightning strike electromagnetic field and transmission line coupling model.An iterative formula for the scattered voltage and induced current on the distribution line.Secondly,according to the basic parameters of the UHV substation,the typical single-line-out-circuit breaker open circuit and single-line-single-single-single operation modes of the GIS substation are used as the calculation conditions.The substation is subjected to the counter-thunder and the lightning strike.The lightning intruding wave overvoltage is calculated,and then the arrangement of the arrester is proposed.The substation after the lightning arrester is subjected to the lightning strike and the lightning overvoltage caused by the lightning strike in the station is calculated,and the arrester scheme is verified to determine the arrester.Arrange the plan to ensure the safe operation of the substation.Finally,the feasibility of the inductive lightning overvoltage calculation method is verified.While the single variable is changed,the induced lightning overvoltage on the 10 kV distribution line is simulated by the earth resistivity,lightning current waveform and lightning distance from the conductor distance to the induction lightning.The suppression effect of different ground wire installation positions on the induced overvoltage is analyzed on the three-phase wire of the line.Then,in order to study the lightning protection effect of the entire distribution line,the lightning strike rate of the lightning strike rate is used to compare the lightning protection effect of the overhead ground line and the coupled ground line.The reasonable position of the installation ground line is obtained.Referring to the differences in lightning activity in different regions,the lightning protection effect of the line is analyzed by using different ratios of inductive lightning and direct lightning.At last,the reasonable lightning protection methods for distribution lines is obtained. |
PDF Full Text Request