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Experimental study on lighting shielding performance of “b500 kV HVDC transmission lines

This paper is to investigate the lightning shielding performance of the HVDC transmission line when taking the dc operation voltage into account. Firstly, the equivalency of the scale experiment is discussed from the following aspects: (a) the determination of test scale factor; (b) the electric field simulation of downward leader; (c) nominal field simulation of the HVDC transmission line. Secondly, a test circuit is established taking into account of the isolation of the dc charge circuit and surge generator. The exposure space distribution of the HVDC transmission line is obtained from a large amount discharge experiments. The total number of recorded discharge is over 7500 times. The competition between upward streamers originating from the grounded wire and polar conductor is observed by using the high-speed digital camera. Finally, the effectiveness mechanism of the dc operation voltage on the lightning shielding performance of HVDC transmission line is analyzed according to the recorded phenomenon. Based on the EGM conception, the qualitatively effect of the dc operation voltage is calculated. It reveals that the shielding failure flashover rate of the 500kV positive polar is 4.84 times than that not taking account of the dc operation voltage.