| As the main frame of power grid,the safe and stable operation of transmission line is of great significance to ensure the reliability of power grid.The survey results of transmission line operation data of Henan power grid in recent ten years show that lightning stroke is the most likely cause of transmission line tripping in addition to external force damage,among which lightning stroke of overhead transmission line mostly occurs on 220kV transmission line.Therefore,this paper focuses on the research and application of lightning protection measures for 220kV transmission lines in Henan Province.Firstly,this paper analyzes the basic situation and operation of the existing 220kV transmission lines in Henan by using the method of investigation and statistics,and finds out the lightning fault characteristics and lightning protection problems of Henan power grid.According to the analysis,lightning strikes often occur at the junction of large span and different soil resistivity;There are some problems in lightning protection measures,such as inaccurate fault monitoring,single lightning protection design measures and difficult operation and maintenance.According to the characteristics of lightning fault and existing problems of lightning protection,this paper studies and applies comprehensive lightning protection measures based on 220kV new line project.Then,This paper chooses the route based on the principle of avoiding mountains and rivers as much as possible.The vulnerable sections of rivers,highways and line intersections are found by on-site investigation,and the poles and towers with high soil resistivity are found by quadrupole method,so as to determine the key protection areas of line lightning protection design.According to the actual situation of the new line,the combination of conventional lightning protection measures and new lightning protection measures is adopted for lightning protection of vulnerable sections and vulnerable towers.The conventional lightning protection measures include strengthening insulation,reducing the protection angle of lightning wire,installing lateral lightning rod,etc;New lightning protection measures include adding resistance reduction cage,installing adjustable parallel clearance,etc.The feasibility of the resistance reduction cage is verified by theoretical calculation and finite element model simulation.Then,this paper carries out the lightning protection simulation calculation of the incoming section of the substation.The incoming section of the transmission line is directly connected with the substation.Lightning strike on the incoming section will impact the substation equipment,and its lightning protection is more complex and important.Based on the 220kV new line project,referring to the transmission line and substation equipment parameters,this paper establishes its simulation model by using ATP-EMTP software.Then,the factors affecting the overvoltage level of equipment in substation such as lightning point location,line arrester configuration and tower grounding resistance are simulated and analyzed.The analysis results show that when lightning intrudes from 2#tower,the overvoltage level of equipment in substation is the highest;Installing lightning arrester on the tower outside the station has no impact on the overvoltage level of equipment in the substation;Reducing the tower grounding resistance can significantly improve the overvoltage level of equipment in substation.Finally,according to the actual statistics,after the comprehensive lightning protection measures are applied to the new 220kV line,the annual average trip times are reduced by 82%,and the lightning protection effect is greatly improved,which verifies the effectiveness of the comprehensive lightning protection measures.The research and Practice on lightning protection of 220kV transmission line in this paper has strong reference value and popularization and application value for lightning protection design of transmission lines with similar voltage levels in other areas. |
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