Simulation And Protection Research On The Lightning Over-voltage Of Substation Secondary Side

It is well known that lightning activity is easy to cause equipment failure which will affect the safe and reliable operation of the substation. Therefore, it is very important to master the over-voltage propagation mechanism. In this paper, lightning over-voltage in a substation is analyzed by using time domain finite element method(TDFEM) and ATP-EMTP simulation. Hereby, a new measure for lightning over-voltage protection is put forward. The principal content and achievements of the dissertation is listed as following:Firstly, based on traveling wave equation of multi-conductor transmission line, under the condition of considering bus residual voltage, the propagation process of lightning over-voltage was analyzed. The equations for several units including distribution parameter and lumped parameter were derived and the propagation process of substation secondary over-voltage were calculated. Compared with ATP-EMTP, the trapped charge distribution characteristics of the transmission line under TDFEM could be taken into account, the voltage and current distribution at any point along the transmission line could be obtained.Subsequently, by using ATP-EMTP software, transmission line model, tower model, tower grounding resistance model, arrester model, insulator string flashover model, earth potential model and other electrical equipment models, were analyzed and chosen. In the case of Hongahipo substation which was suffered from lighting strike seriously, an integral simulation of the whole substation was built and all the simulation parameters were setup. According to the simulation, the lightning over-voltage's propagation laws of bus bar, transformer, arrester, head of secondary cable, earth connection point were quantitative studied.Thirdly, a new type of over-voltage protection measures, which combines inductor with zinc oxide lightning arrester(MOA) that series with transient suppression diodes and a LC low-pass filter circuit, was put forward and the corresponding simulation was carried out by using ATP-EMTP based on Hongshipo substation's lightning accident. According to the simulation analysis on single point grounding and multipoint grounding, a reasonable and effective grounding type was drawn. Finally, the new over-voltage protection measures and reasonable grounding type were applied into lightning strike on tower. By simulation, it is found that secondary over-voltage level could be suppressed to an acceptable level. Accordingly, the correctness of the new over-voltage protection measures and reasonable grounding type is verified.