Based On ATP-EMTP Research On Multi-pulse Lightning Response Of Transmission Lines

Electricity is a special industry which is related to a country whether can function normally,as a basic driving force and the normal operation and development for industry,agriculture,modern science and technology,and national defense.In the power industry,overhead transmission lines play a pivotal role in the power system,connecting power plants to power users.However,overhead transmission lines usually span from tens to hundreds of kilometers.Lightning strikes on transmission lines,causing their voltages to rise,causing circuit breakers to become the main cause of power system failure.According to the analysis of the accident data of the power system over the years,the lightning trip caused by the lightning trip accounted for 40%~70% of the total trip accident of the line.With the improvement of modern lightning protection technology and information technology,the collected data shows that multiple flash strikes are common sites of lightning in nature,and 80% of lightning has multiple flash strikes.Therefore,it is necessary to analyze the response of transmission lines under multi-pulse lightning impulses.In this paper,the optical electric field sensor is used to measure the lightning data from the field,and the multiple pulse lightning data is obtained.The multi-pulse lightning is tested by using the calibration of the lightning location system and the lightning current accumulation probability,which justify the reliability of the measured data.MATLAB is used to obtain the corresponding parameters according to the wave front time,tail time and rising steepness defined by the double-index standard lightning wave recommended by IEC.Equivalent models of various parts of the transmission are established by using ATP-EMTP.When establishing a multi-pulse lightning power supply model,the multi-pulse lightning interval is converted from 20 to 200 ms to 20 us,then the accumulation of energy of the multi-pulse lightning to the electrical equipment is converted into the accumulation of voltage.Hence,the multiple impulse lightning power model is established,as well as impact corona model and Jmarit model of line impedance variation with frequency,multi-wave impedance model of pole tower,insulator string model and arrester model.The simulation analyzes the response of direct lightning and shielding failure under single and multiple pulses.Considering whether the line equipped with the lightning arrester or not,difference of line overvoltage between mono-pulse lightning and multi-pulse lightning are compared.A lightning overvoltage data acquired from 220 kV online monitoring system is used to confirm the reference of the simulation for its similarity of the overvoltage value with the lightning arrester is simulated in this paper.Simulation results show that when the lightning arrester is not installed on the line,whether it is a single-pulse lightning impulse or a multi-pulse lightning impulse,a high overvoltage will occur,causing the insulator string to flash;Under multi-pulse lightning strikes,the line will have a higher overvoltage than single-pulse lightning.At the same time,under multi-pulse lightning strike,the arrester can still effectively limit the overvoltage amplitude,and the overvoltage time of the line will be greatly extended.The arrester will continuously receive multiple over-voltage surges in a short time.All the energy is concentrated on the arrester valve plate,and the heat energy of the valve plate will not be able to occur,leading to failure of protection of the arrester,and even extreme conditions such as explosion.Aiming at the new form of lightning protection under multi-pulse lightning,the series-space zinc oxide arrester with a certain resistance of the gap body is used as a lightning protection measure under multi-pulse lightning impulse from the perspective of conservation of energy and theoretical calculation.