Lightning Electromagnetic Transient Analysis Of 500kV Double-circuit Transmission Lines On The Same Tower Considering Unbalanced Insulation

Lightning strike is one of the main causes of tripping faults on transmission lines.For the double-circuit transmission line of the same tower,the lightning strike can not only cause the single-trip trip of the transmission line,but also cause the double-circuit transmission line to trip at the same time.The damage caused by lightning strikes to the power system is far greater than the damage caused by single tripping of the line.In particular,the higher the voltage level of the line,the greater the impact on the power system caused by lightning strikes,and even the vicious events such as power interruption.For the power system,the 500 kV ultra-high voltage transmission line is like the aorta of the human body.It can safely and stably operate,which directly affects whether the entire power system can operate safely and stably.Unbalanced insulation is a method to effectively cope with the lightning strike problem of the double-circuit transmission line on the same tower.Therefore,it is necessary to conduct an in-depth analysis of the lightning strike and jump problem of 500 kV doublecircuit transmission lines on the same tower under unbalanced insulation conditions.It is also necessary to analyze the lightning strike process according to the lightning current transient waveform collected by the station,and provide feasible suggestions for the unbalanced insulation setting mode.In this paper,the electromagnetic transient simulation model of 500 kV double-circuit lightning strike transmission line on the same tower is built by PSCAD/EMTDC electromagnetic transient simulation software.The double exponential lightning current model,the pulsed lightning current model and the Heidler lightning current model are analyzed respectively.For the case of unbalanced insulation and balanced insulation,the effects of double-exponential lightning current model,pulsed lightning current model and Heidler lightning current model on lightning transient electromagnetic simulation are analyzed.When the line is running,there is a complex coupling relationship between the doublecircuit transmission lines on the same tower.This paper decomposes it into the same vector network and ring traffic network,and analyzes the ring traffic unique to the double-circuit transmission line on the same tower.Starting from the definition of the circulating current traveling wave of the double-circuit line on the same tower,the law of the deflection of the circulating current traveling wave is studied.Finally,for the 500 kV double-circuit transmission line on the same tower under unbalanced insulation,the lightning current transient waveform collected at the station end protection installation is analyzed,and fault line selection,phase selection and fault location are respectively performed,which can achieve imbalance.Degree of verification.The simulation results show that the unbalanced insulation enhances the lightning resistance level of the insulated circuit.By letting the power transmission line first flashover,the flashover probability of the other transmission line is reduced,and to avoid the flashback of the two transmission lines to some extent.Case.However,when the peak of the lightning current is large,there will still be two flashovers of the transmission line.The insulation voltage of the unbalanced insulation can be modified,and the flashover voltage setting value that maintains the high insulation level is 20% higher than the flashover voltage setting value of the low insulation level,and it can ensure that one line is not affected by the lightning current when the lightning strikes.