Research On Lightning Protection Technologies For Multi-voltage Transmission Lines

With the continuous development of power grid,the accidents of multi-voltage transmission lines caused by lightning strike are increasing.Among them,the production equipment of petrochemical enterprises has the particularity of continuous production,flammability and explosion.Requirements for reliability and power quality of continuous power supply are very high.The tripping caused by lightning strikes on transmission lines can cause the outage of important electrical equipment such as motors,which can lead to the interruption of continuous production,easily lead to fire and explosion accidents,and cause huge losses.Through understanding the operation status and problems of lightning strike in multi-voltage transmission and transformation system of petrochemical enterprises.Finding the Causes of Lightning Stroke Disasters on Multi-voltage Transmission Lines and the Weak Links.It is of great social and economic significance to study the key technology and equipment of lightning protection for transmission lines.In order to quantitatively analyze the lightning protection capability of 35 k V transmission lines,combining with the real lines of petrochemical enterprises and considering lightning model,tower,arrester,transformer and other information,the direct lightning stroke and lightning induction simulation calculation model of 35 k V transmission lines is established by electromagnetic transient simulation software ATP-EMTP.The infuences of tower grounding resistance,spacing and lightning arrester on lightning protection are calculated and analyzed.In order to quantitatively analyze the harm of lightning shielding to transmission lines,a miniature model of 110 k V transmission lines is constructed.The test parameters such as tower height,spacing and diameter of miniature poles used in the test are all reduced in the same proportion,and the shielding failure test of transmission lines is carried out.A multi-needle bypass lightning rod for line shielding protection is developed.The lightning rods made of pure aluminium and tungsten-aluminium are tested by using A+C wave.In order to solve the disadvantage of traditional zinc oxide arrester which is easily damaged by lightning strike,based on the principle of thermal expansion of gas and the theory of magnetohydrodynamics(MHD),assuming that the arc gap plasma obeys the conservation of mass,momentum and energy expressed by Navier-Stokes equation,a mathematical model of arc gap is established.The distribution of conductivity of arc gap is calculated,and the temperature when the radius and spacing of electrode are adjusted.And the change of electrical conductivity.A multi-gap self-extinguishing arc line arrester based on gap discharge is developed,and high voltage and current impact tests have beencarried out.Taking 220 k V,110 k V and 35 k V transmission lines of typical petrochemical enterprises as examples,the lightning resistance level of 220 k V and 110 k V transmission lines before and after installing lightning arresters is calculated by electromagnetic transient simulation software.According to the simulation results,the installation phase and number of arresters are determined,and the lightning protection transformation scheme of high voltage transmission lines in petrochemical enterprises is formulated,which effectively reduces the shielding failure rate and lightning protection level of lines.The installation scheme of self-extinguishing arc line arrester in 35 k V transmission line is formulated,the lightning protection effect after installing gap self-extinguishing arc line arrester is calculated and lightning trip rate of line is reduced.