| To adapt the need of power load for the quick development of economy, the development of power system is turning for the higher voltage and larger capacity direction. Using double-circuit transmission line is the developing tide for 500kV main configuration to reduce line holding ground. For just a few years, the 500AC power transmit system breakdown accidents caused by lightning often occurred in our country and others, the research on ultra-high-voltage power transmitting line lightning protection performance also have been paid attention in the worldwide range, but the reports on research deeply and systemically on the subject are of scarce. The design of lightning preventing by existing model is not in accord with the running results for ultra-high voltage transmission line. So it is important significance and applied value for 500kV transmission line lightning protection performance designing by exploring a new model of lightning shielding failure that be the same with lightning protection performance of ultra-high voltage transmission line and analyzing the lightning protection performance of 500kV double circuit transmission line By studying deeply the lightning protection performance for ultra-high voltage transmission line, the main contents of the paper include: ①On considering the ascending forerunner effects on the lighting and the back-head lighting cases, the variable step-length method should be applied to the model of the descending lighting forerunner, firstly putting forward the lightning simulation model that adapt to ultra-high voltage transmission line. The calculating on the example and the simulation testing show that the simulation model can reflect the basis rule of lightning striking transmission line and accord with the running experience. The model can be applied to the evaluation and calculating on characteristics of lightning striking the high altitude transmission lines.②Through analyzing deeply the lighting protection performance of back striking for 500kV double circuit transmission line, the distributed parameter model of tower is built when analyzing the back stroking lightning protection performance for 500kV double circuit line and applied the statistical method to analyzing the lightning protection performance of back stroke with considering the randomness of working voltage's phase when lightning stroked the top tower. Aiming at the view of that those nations, such as USA, Japan and Europe: the means of unbalanced insulation can not be applied to double circuit transmission line, the author concludes that unbalanced high insulation can sharply decrease the simultaneity rate of lightning back striking as well as not increasing the rate of the single line' breakdown by theory and simulator analysis,③Through analyzing deeply the lighting protection performance of shielding failure for 500kV double circuit transmission line, the EGM is improved by considering the effect of wind speed. The calculation result is compared and analyzed by EGM with the simulation model.④After the systematic research of factors that influence the lightning protection performance of shielding failure on 500kV double circuit transmission line, a good advice had also been put forward for the considerable and effective means of lightning shield protection. These factors are the height of tower, leaning angle of ground, insulation manner, surge impedance of tower, the array style of conductor and so on.⑤According to deep researches on the effects on the electric performance of lines arrangement in double circuit transmission line, the best lines arrangements should be in conversed phases order and be replaced, it not only meet the electric power quality requirement but also reduce the line operation over-voltage.
|
PDF Full Text Request