Test and Observation of Lightning Shielding Characteristics of ± 1100kV Transmission Lines

Lightning damage is the one of the main causes of faults in transmission lines. At present, the design of lightning shielding system for $\pm1100\text{kV}$ UHV DC transmission lines mainly draws on the operating experience of lower voltage transmission lines. Therefore, it is necessary to carry out model tests to study the lightning shielding performance of ±1100kV UHV DC transmission lines. Negative switching impulse of 250/2500μs has been used according to the amplitude and rate of electric field intensity at the surface of the tower. The lightning shielding simulation test is carried out in the plain case with a model ratio of 1:12.5 for the Z38102AL type tower of $\pm1100\text{kV}$ UHV DC transmission line, and the photography observation with high speed was carried out at the same time. The test results show that the probability curve of the shielding failure spatial region shows an inclined parabola curve, and the lightning shielding failure space of the negative conductor is significantly smaller than that of the positive conductor. The negative polarity conductor on the other side of the tower has a certain weakening effect on the lightning inducing ability of the positive polarity conductor close to the high voltage electrode, but has little effect on the shielding performance of the lightning conductor and the ground. The discharge process is analyzed based on the observations of high-speed cameras, and the synchronous analysis of voltage waveform is carried out. The inhibition of the negative polarity voltage of the conductor on the initiation and development of the upward streamer and the development of the downward leader is explained.