Research And Analysis On Lightning Protection Performance Of UHV DC Transmission Lines

UHV DC transmission has a large capacity, long distance, low loss power transmissio n advantages. It meets the needs of China's basic national conditions and energy development strategy, and its safe operation is extremely important. Its transmission lines are widely distributed across the region and more failures may occur. According to statistics, a variety of factors of line failure, lightning accounts for a large part. Therefore, research on lightning protection of line is very valuable and meaningful.In this paper,,the use of electromagnetic transient simulation software ATP-EMTP, Based on the research results at home and abroad,Creating relevant lightning current model, tower model, transmission line model, the impact of grounding resistance model and insulator string flashover model. Using the established models to simulate lightning situation, get the line back strike and lightning shielding failure level.Based electrical geometry model(EGM), Considering a variety of factors,including the line voltage, lightning strike angle, wind speed, topography of the line, which affect performance of lightning shielding failure. Article proposed an improved EGM, To verify the accuracy of the model and the method applied to practical examples. In the calculations, considering the effect of lightning strike angle, it closer to the actual situation, more accurate in theory.Using software ATP-EMTP simulates the line of back strike and lightning shielding failure and Using the improved EGM simulates and researches Lightning Performance of UHV DC transmission line. The results show that: UHV DC transmission line back flashover level is very high, less prone to back strike flashover rate. Positive polarity line flashover easier than the negative line. With the decrease of the tower grounding resistance, lowering the height of the tower, and improve the line insulation levels, back strike lightning protection of UHV DC transmission lines increase, back strike flashover rate decrease. soil resistivity is no significant effect on back strike flashover rate. Reducing ground resistance can usually be reduced back strike flashover rate. Tower height is too high makes back strike lightning protection levels are drastically reduced,so flashover rate is probability significantly higher. lightning protection level of lightning shielding failure is low, so it is the main lightning flashover way. With the wind speed, steep hill degree, nominal tower height, ground line protection angle become large, flashover rate of lightning shielding failure increase. After the wind speed reaches 10 m / s, flashover rate of lightning shielding failure rise soon. With the increase of the lightning strike angle, flashover rate of lightning shielding failure begins to rise then reduced to 0.when lightning strike angle at 15 ° ~ 30 °, the line has a maximum rate of strike flashover.flashover rate of lightning shielding failure affect emphasis should consider lightning strike angle in this angular range. Line voltage for the back strike and lightning shielding failure are relatively large impact.so its impact can not be ignored. Recommended that the actual operation of the line, using negative protection angle. For a high tower, the ground is very steep slope areas, you can add another protection of measures to reduce flashover rate. In wind speed larger areas, it is recommended to add measures to prevent line dancing.