Lightning Protection Mechanism And Experimental Research Of Double Jet Arc Extinguishing

This paper proposes a new kind of arc-extinguishing lightning protection device of 110 k V transmission line which parallels on both sides of the insulator-Double Jet Arc Extinguishing Gap(DJAEG).The gap ensures the arcing gap discharges preferentially when the lightning strikes.the high-speed airflow is generated to cut the arc instantaneously until it is extinguished when the gas pellet is triggered by the lightning pulse.The basic characteristics of the arc are introduced firstly to point out the diameter and temperature which equal to the arc energy.The characteristics of the arc under the impact of airflow are analysed to derive the criterion of arc extinguishment,and the rule of arc extinguishment in the process of arc suppression by airflow is determined.On the basis of theoretical analysis,a high-speed airflow coupled arc model is created according to the MHD.The geometric model of the DJAEG is built by COMSOL MUTIPHYSICS to analyse the 50 k A lightning pulse coupled with 10 k A power frequency current and the arc extinguishing process after the high-speed airflow,to solve the distribution of electromagnetic characteristics,and monitor the changes of conductivity,speed,and temperature in the arc-extinguishing device.It is proved that the airflow can extinguish the arc within 4 ms without power frequency current occurred.The arc extinguishing device is designed under the results of the simulation.Arc-extinguishing response time、50% breakdown voltage、power frequency withstand voltage、high current impulse withstand、high frequency high current arc ignition test and power frequency follow current interruption test are carried out on test platform with the arc-extinguishing device.Test conclusions: 1)the air pellet reaction time is about 0.2 ms,the delay two pellets is about 0.15 ms,the arc development can be interfered at the beginning;2)The parallel gap distance is controlled at 800 mm-890 mm,which not only meets the installation characteristics of the device,but also guarantees the DJAEG can discharge preferentially;3)The DJAEG can withstand power frequency voltage of 185 k V for 1 min under rainfall conditions without flashover;4)The arc extinguishing device can withstand 2 times with an interval of 1 min Value of 66.7 k A impulse current without damage;5)The internal flash electrode of the device can withstand continuous 100 ms amplitude 40 k A power frequency burning without damage;6)The device can interrupt 2.3 k A power frequency follow current in 4ms,Which meet the requirements that the power frequency follow current is interrupted within 1 /4 cycle.The actual application of the device was selected in 110 k V transmission line of Guangxi.The trip-out rate model is established to compare the trip-out rate before and after installation.After DJAEG was installed on the line,the trip-out rate dropped from 1.8 to 0.04,which verify the effectiveness of the DJAEG.