Study On Lightning Protection Performance Of UHV DC Transmission Line

UHVDC transmission line is shouldered the task of optimal allocation of power resources and the development of West of China. Due to the long distance, wide distribution, complex geographical, complicated regional climate and irregular lightning activity, the transmission line is offen struck by lightning. Therefore, studing lightning protection of UHVDC transmission line has important significance to improve its reliability.This thesis analyzed the development of DC power transmission at home and abroad and the influence of thunder. On the basis of summarizing the domestic and foreign research achievements about performance of lightning protection, the thesis built the model of UHVDC transmission line. The results of simulation and calculation show that the larger grounding resistance, soil resistivity, wind speed and the ice thickness, the smaller current of back strike lightning that lead to insulator flashover, and the larger insulator flashover rates suffered back strike lightning. When improving the tower height, insulator flashover rates of back strke lightning increases exponentially. By wind loads, insulator distance is redused that increace the insulator flashover rates suffered back strike lightning. Thickness of the ice also reduces the insulation distance. With the wind influnce, the lager thckness, the larger protected angle, and the larger insulator flashover rates suffered back strike lightning.The results of simulation and caculation with EGM model show that redusing the protected angle help to decrease the insulator flashover rates suffered shieldong failure especially when the protected angle is negative value. When ground tilt angle is exist, the insulator flashover rates suffered shielding failure when lateral conductor is positive polar is lager than when is negtive polar. With the tilt angle increace, the insulator flashover rates suffered shielding failure is larger The shielding effect is selled at a discount greatly while the tilt angle is much bigger. With the influnce of wind, the shielding effect of the earth wire is redused. The thickness of the ice exacerbated rates. Improving the heigh of the ground vegetation helps to improve the shielding effect of the wire.The thesis calculated theflashover rates of the Yun-Guang+800kV UHVDC transmission line finally. The results show that the line flashover 3.5812 times a year, including back strke lightning flashover 0.2152 times and 3.366 times a year occurred shielding lightning with fault. The differentiate rates are 6% and 94%. Back strike flashover is mainly concentrated in the line of the tall mountains region, especially in Guangxi section. Shielding lightning flashover is mainly concentrated in region of general mountains and tall mountains. It is hardly occurreds insulator flashover in plain erea of Guangxi province and swamp of Guangdong province.