Mechanism And Experimental Research On Arc Extinction Characteristics Under Detonation Air Flow In Confined Space

Lightning disaster seriously threatens the safe and stable operation of power system.Although the existing"blocking"and"Dredging"lightning protection technologies alleviate the lightning damage to a certain extent,their safety,effectiveness and economy still need to be solved.Therefore,aiming at the technical bottleneck and deficiency of lightning protection measures for110kV transmission line,a detonation gas arc extinguishing lightning protection device with active arc extinguishing function is proposed.The device uses the lightning pulse signal to trigger the arc extinguishing gas shot synchronously at the moment when the arc is formed,so as to generate the detonation gas flow and quickly extinguish the arc before the relay protection action,so as to realize the lightning non tripping.In this paper,the characteristics of arc extinction under the action of detonation flow are studied from three aspects:theoretical analysis,simulation modeling and experimental research,the specific research contents are as follows:Firstly,the structure,installation and working principle of the device are introduced.Based on the physical characteristics of AC arc,the energy balance process of arc column under the action of detonation flow is studied.The results show that whether the AC arc is extinguished or not depends on the competition between the arc gap dielectric strength and the recovery speed of the arc gap voltage,the process of de dissociation and thermal dissociation.The detonation gas can accelerate the energy dissipation of the arc,strengthen the de dissociation of the arc,and promote the rapid recovery of the arc dielectric strength.The chain arc model under the action of detonation flow is established,and the parameters of arc velocity and diameter are obtained.Then,based on the C-J model of detonation wave,the physical meaning of Rayleigh line and Hugoniot line of detonation wave is analyzed,and the influence of arc extinguishing gas charge diameter on detonation velocity is also analyzed,That means the detonation velocity increases with the increase of the diameter of the gas shot,and it is suggested that the diameter of the arc extinguishing gas shot should be kept in a reasonable range.Based on the MHD equation,the arcing process of detonation flow was simulated by COMSOL Multiphysics software,The simulation results show that 10k A arc can be extinguished in 6ms,the flow can deeply inhibit the restricking of arc.Finally,the experiments about the response time related to the trigger,Lightning impulse test,insulation coordination,power frequency withstand voltage test,power frequency continuous current interruption,air velocity and arc construction suppression are carried out for 110kV arc extinguishing device,meanwhile,the running condition of the device is analyzed.Considering that the device will develop to a higher voltage level line in the future,lightning impulse test and power frequency withstand voltage test are carried out for 220kV arc extinguishing device.Now comes to the point:1)The response time,related to the trigger,of the device is 200μs,and the response time decreases with the increase of lightning amplitude;2)Under the same spacing,the flashover voltage of negative polarity U_50%is higher than that of positive polarity U_50%;3)When z/z₀is limited from 0.7 to 0.85,the V-s curve of 110kV device is located below the V-s curve of insulator,which can form a good insulation coordination,so as to ensure that when lightning strikes,the device can be prior to breakdown the arc-over.But when z/z₀equals to 0.9,the V-s curve of the two has intersection point,and the two can not form insulation coordination,that means the arc extinguishing device can not protect the insulator;4)The experiments show the U_50%of 220kV device is 837.7kV.The V-s curve of 220kV device is below the V-s curve of insulator,and there is good insulation margin between the two;5)The 110kV and 220kV devices withstood power frequency voltage of 180.3kV and 361.2kV for 1min,respectively,without breakdown and flashover;6)The110kV device successfully cut off the power frequency continuous current arc of about 5.1k A in 2.6ms and did not reignite;7)The average air velocity of 110kV device is 250m/s,and the peak value of air velocity can reach more than 300m/s.At the same time,the arc restricking rate and arc build-up rate decrease with the increase of flow velocity,and the arc extinction rate increases with the increase of flow velocity;8)The lightning protection effect of 110kV arc extinguishing device is obvious,which can effectively prevent the occurrence of trip.