Research On Refined Lightning Risk Assessment And Protection Technology Of Wind Farm Collection Line In Mountainous Area

A large number of onshore wind farms in China are distributed in mountainous areas with complex natural environment conditions.The operation experience shows that lightning trip of collecting lines has become the primary factor causing power loss of wind farms in mountainous areas,threatening the safe operation and stability of power grid.To accurately grasp the lightning risk level of the collection line under the influence of complex terrain factors can provide technical support for the lightning protection transformation of the collection line.Therefore,it is urgent to carry out the refined lightning risk assessment and protection technology research of the collection line of mountain wind farm.In this paper,the shielding failure trip calculation model of the collector line in mountain wind farm considering the influence of three-dimensional terrain factors is established,the refined lightning risk assessment is carried out,and the lightning protection technical scheme of the collector line in mountain wind farm is proposed:1)In this paper,a three-dimensional electrical geometry model is established,which can consider the complex terrain,tower structure and line sag in mountainous area.A calculation model of lightning withstand level of collector line considering tower multi wave impedance and line frequency variation characteristics is established.The risk factors of shielding failure and counterattack trip of collector line are analyzed,and the trip rate of collector line in Shiputang wind farm of a company in Yunnan Province is calculated,The trip rate calculation result is 5.41 times / 100 km · year,which is consistent with the wind farm operation statistics result of 5.02 times / 100 km · year,which verifies the effectiveness of the calculation model;2)The risk assessment method of lightning stroke trip out for collecting lines of wind farms in mountainous areas is studied.The risk of lightning stroke trip out for collecting lines of wind farms in mountainous areas and the characteristics of the ratio of shielding strike and counterattack are analyzed.The risk assessment method of lightning stroke for collecting lines considering the ratio of lightning stroke trip out and the ratio of shielding strike and counterattack is studied,the principle of classification and classification of lightning trip risk of collecting lines is proposed.The refined assessment and risk classification of lightning trip risk of 400 towers of collecting lines in two wind farms are completed,and the weak links of lightning protection of collecting lines are proposed;3)This paper studies and compares the suppression effects of strengthening insulation,reducing tower grounding resistance,erecting coupling ground wire and installing line arrester on lightning risk of collection line,and comprehensively considers the lightning risk level,the ratio of shielding and counterattack and the technical economy of transformation under the existing measures of wind farm collection line,This paper puts forward the methods and principles of lightning risk differential transformation mainly based on grounding transformation and installation of line arrester,carries out the research on the comprehensive protection technical scheme for the collection line of Shiputang wind farm and Nanhuashan wind farm,and puts forward the differential lightning protection technical scheme for two wind farms.The research work in this paper is helpful to improve the operation reliability of the collection line of wind farms in mountainous areas,and to protect the development of wind power and power transmission.