| Since China entered the 21 st century,the scale of power grid development has gradually expanded.In most areas,500 k V grid structure has been built,and 1000 k V UHV transmission lines are also under construction.Although the improvement of power grid voltage level improves the transmission efficiency to a great extent,it also increases the probability of lightning accidents.Relevant statistical data show that: 40%-70% of the trip rate is caused by lightning,if the substation suffered from lightning,it will continue to cause the phenomenon of power supply interruption,lightning disaster has become the primary factor endangering the security of China’s power grid system.At present,the construction of UHV transmission is developing rapidly in China.Taking Hebei as an example,the UHV AC double landing point of Southern Hebei Power Grid has initially formed.In order to ensure the smooth progress of UHV construction and operation and maintenance management,it is necessary to systematically study the issues related to UHV transmission construction.Based on the practical application,this paper analyzes the trip prediction and lightning protection of the 1000 k V Changzhi Nanyang Jingmen UHV transmission project,and makes in-depth discussion and research.From the technical point of view,this paper analyzes the importance of UHV transmission line lightning protection to promote the steady-state performance of power grid,and hopes that the research can provide reference for improving the lightning protection line structure of regional power grid;the main research results of this paper are as follows.(1)Changzhi-Nanyang-Jingmen line after engineering testing confirmed that the transmission line 90 km of the area belongs to the lightning frequency zone,the average thunderstorm day reached 40.72 d.The electrical geometry model method is used to calculate the lightning form in this area as the winding method for lightning bypass tripping rate.(2)Analysis of the results calculated by predictive model: When the dual loop protection angle of Changzhi-Nanyang-Jingmen transmission line is-3 degrees and-5 degrees,the lightning trip rate of the line is in line with the recommended value,so the set double-return line protection angle can be referenced GB50665-2011 "1000k V overhead transmission line design specification",the plain hilly area of the dual-return line protection angle is suitable for the choice of equal to or less than-3 degrees,the mountainous area of the dual-return line protection angle is suitable for the choice of equal to or less than-5 degrees At the same time,combined with the design specification,the single-return line protection angle in plain hilly areas is suitable for the choice of-6 degrees,and the single-back line protection angle in mountainous areas is suitable for the selection of-4 degrees.(3)In the Changzhi-Nanyang-Jingmen line lightning performance analysis shows that,because the type of grounding device is affected by soil resistivity,therefore,based on economic and feasibility considerations,different soil resistivity should be used in the grounding device selection Type should be considered comprehensively:(1)combined with the project line in addition to lightning frequency area outside the area of soil resistivity is relatively small,so choose the built-in ground size method to set the lightning protection device;(2)Combined with the project lightning frequency area soil resistivity is high,usually up to p>2000f>m,for this reason,in order to effectively avoid may cause a certain degree of corrosion of the soil,it is recommended that the project actually install ion grounding device to reduce soil resistance. |
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