Research On Calculations For Lightning Performance Of Multi-circuit Transmission Lines

Line trip caused by lightning stroke is the most frequent accident in the electricalpower system. Thus, the accurate assessment of lightning performance is of greatsignificance for the safety and stability operation of electrical power system.At present, the main methods assessing the shielding failure of a transmission line are:regulation method, electrical geometric model （EGM）, leader development method（LPM）, Monte Carlo method and so on. This paper analyses the main influencing factorson electrical geometric model, such as striking distance, striking distance factor, workingvoltage, slope angle of ground and so on. Meanwhile, in order to solve the calculationproblem caused by the complex structure of multi-circuit transmission lines, a scanneddiscrete electrical geometric model is proposed. This paper studies the application of MonteCarlo method in shielding failure calculation. This method could consider the influencecaused by different random variables in the lightning stroke procedure and reflects therandomness of the discharge procedure in some degree. Besides, based on the existingliteratures, this paper considers the impact of leader incidence angle.And the paper gives areasonable simulation number by repeatedly simulation to minimize the dispersivity of theresult.The methods of assessing transmission line counterattack are: regulation method,wave impedance, electromagnetic computation and so on. This paper analysescounterattack performance by multilayer wave impedance. Multilayer Wave impedancemodel of the tower is established in the simulation software such as EMTP/ATP. Andintersection method is used as flashover criterion. By the validation with the calculatingresults of the referencing literature, the correctness of the model is confirmed in this paper.Based on above research, a software which can calculates the lightning performanceof the transmission line is developed The software uses C++as the platform, applyingMatlab, ATP to have a secondary development tools. The software can calculate shieldingfailure flashover rate and counterattack flashover rate for a variety of tower which havedifferent voltage level. Shielding calculation uses regulation method, electrical geometric model and Monte Carlo method, and counterattack calculation uses regulation methodandmultilayer wave impedance model.