| Due to Chinese vast territory and complex topography,none of the current lightning protection technologies can achieve ideal results.Nowadays,the lightning protection technologies at home and abroad can be divided into "blocking type" and "draining type",of which the "blocking type lightning protection technology" is the main one.This paper proposes an overhead line lightning protection scheme with type Multiple&Zigzag Channels Arc-extinguished Lightning Protection Gap(ALPG)as the core.The lightning protection scheme centered on the ALPG device has the advantages of both "blocking" and "draining" lightning protection technologies.That is: during lightning strikes,the appropriate insulation ratio is used to avoid arcover at both ends of the insulator,and guide the arc movement path to the inside of the device,thereby suppressing the development of the arc through the special structure of the ALPG device.The specific work of optimization research on this device is as follows:The theoretical part analyzes the status of MZAC to the arc existence.First,by analyzing the motion state of the arc in the MZAC,it can be seen that the structure can compress the arc,thereby reducing the arc radius and increasing the current density of the arc axis,and having the maximum airflow velocity at the boundary of the arc column.Then,from the perspective of thermodynamics,the heat is used as a characterization of arc energy.The analysis of MZAC as an open energy system shows that the Joule heat generated by the arc causes the working fluid to expand and do work on the arc.This process promotes the exchange of medium in the MZAC and accelerates the heat dissipation in the system.The simulation part is a confirmation of the theoretical part,and a simulation model of MZAC is established based on the COMSOL Multiphysics software for coupling analysis.In this section,the airflow velocity is used to characterize the medium exchange rate and the amount of work done of expansion work,the temperature is used to characterize the development state of arc energy,and the electrical conductivity is used to characterize the conduction state of the arc flashover channel.According to the simulation results: the peak air velocity can reach 700 m/s and decrease to 350 m/s within 3.3 ms.The existence of air velocity indicates that the medium exchange in the MZAC is still continuing;the peak temperature is greater than 7000 K and decreases within 3.3 ms,which is much lower than the critical ignition temperature of the arc.The time for the flashover channel in the MZAC arc extinguishing unit from on to off is 3.3 ms.The 10/35 kV ALPG device is subjected to an impulse voltage test to obtain the corresponding U50% and volt-second characteristic curve;according to the result of the impulse current test: the device will not fall off or not damage after being subjected to a 16 k A impulse current,and has a suppressive effect on the impulse current.According to the power frequency interruption test,the power frequency arc can be blocked after the air gap is broken down by the impulse current when the device is connected to the network.Taking the actual operation of a 10 kV distribution line in Yunnan and a 35 kV collection line of a wind farm in Fujian as examples,the author's design of ALPG fittings and installation methods suitable for different operating conditions are introduced.According to the line parameters before and after the installation of ALPG,the lightning trip rate was calculated and compared with the actual operation.The results show that ALPG reduces the lightning trip rate by about 90%. |
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