Study On Lightning Transient Of Double Circuit DC Lines And Its Effect On Traveling Wave Protection

The issue of transmission line corridor tension is getting more apparent as the increasingly development of power grid in these years. The common-tower double circuit dc liens has the advantage of narrow transmission line corridor, fast construction, and has already applied in our country. As the common-tower double circuit include two circuits dc system, its safe and stable operation is very important. In recently, the common-tower double circuit lines still using traveling wave protection as its main protection, then it deem to be influenced by thunder lightning and other transient process. Moreover, the common-tower double circuit has the complex and unfair multi-pole lines’ coupling, the propagation characteristics of lightning traveling-wave in double circuit lines and its effect on traveling wave protection would be more complicate. Therefore, study on lightning transient characteristics of common-tower double circuit dc lines and its effect on action performance of traveling wave protection is significant to make sure the safe and stable operation of common-tower double circuit dc lines.According to the parameter of real project, this paper firstly build the PSCAD/EMTDC simulation model of common-tower double circuit dc project. Then the lightning transient characteristics of common-tower double circuit dc system lines in various lightning situations are analyzed, and find that the upper pole lightning has an worse influence on stricken pole, in contrast with lower pole lightning; the positive pole in non-stricken circuit is mainly influenced by non-fault shielding failure of 1-P pole, while the non-stricken negative pole is mainly influenced by non-fault shielding failure of 2-P pole; the back flashover of 1-P pole and 2-P pole all have little effect on non-flashover pole.Study the lightning response characteristic of main existing protection criterion which based on pole line travel-wave and modulus travel-wave respectively. For the analysis of protection criterion based on pole line travel-wave, it can be realized that incorrect action risk of stricken pole under non-fault shielding failure of upper pole is higher than under non-fault shielding failure of lower pole. In the traveling wave protection of non-stricken pole, the incorrect action risk of positive pole in non-stricken circuit is high when struck by non-fault shielding failure of 1-P pole; the incorrect action risk of 1-N pole and 2-N pole is high when struck by non-fault shielding failure of 2-P pole. According to the lightning response characteristics of modulus traveling wave protection variables, its risk of incorrect action of stricken pole is higher than pole line protection for non-fault shielding failure; the incorrect action risk of non-stricken pole in lightning circuit is high for shielding failure, while the incorrect action risk of traveling wave protection in the non-lightning circuit is relative low.Above all, the corresponding lightning identification improved scheme is put forward for the different protection criterion respectively, the Simulation based on PSCAD/EMTDC show this improved scheme could effectively decrease the incorrect action of traveling wave protection as dc lines struck by lightning.