Impacts Of Forest Fire On Streamer Discharge Of Transmission Line GAP

In recent years,with the development of ultra-high voltage and extra-high voltage,more overhead high voltage lines are bound to pass through various complex landforms,and more and more frequent forest fires seriously threaten the safe and stable operation of power grid.Although the experimental and theoretical study of streamer discharge at home and abroad has obtained certain achievements,but limi ted testing technology,discharge microscopic physical quantities can't be measured in the experiments.In addition,as the physical model is not yet perfect,it can only describe the discharge under ideal conditions.For some special environments,the fac tors are single and the research is scattered,and the combined effects of different factors on the discharge are not noticed.Therefore,in view of the existing problems in the current study,in-depth study of the transmission line discharge process under conditions of forest fires(high temperature,solid particles)is not only conducive to the perfection of the theory of gas discharge,but also can reveal the transmission line discharge mechanism caused by forest fires.In this thesis,fluid mechanics model is adopted to conduct simulation research on the streamer discharge process.The main calculation part is implemented on COMSOL software.The calculation accuracy and efficiency are taken into account through reasonable grid subdivision.The maximum mesh element size in the streamer channel area should be 0.004 mm.Outside this area,the maximum mesh element size in the area away from the streamer can be increased to 0.04 mm.Under various conditions,the microphysical quantities that cannot be measured experimentally,such as electrons,positive and negative ions,and spatial electric field distribution,are calculated,and the reliability of the model is verified by comparison with existing research results.The temperature increases gradually from 273.15 K to 673.15 K without solid particles.The streamer radius gradually increased from 0.39 mm to 0.79 mm.The general trend of the evolution of all kinds of particles is basically the same,but its maximum value has declined.The maximum electric field intensity at the head of the streamer gradually decreased from 17.4MV/m to 8.89MV/m,decreasing by 48.9%.The E/N at the head of the streamer slightly increased,which is the opposite of the head electric field change.The development rate of the streamer increas es obviously,which is mainly affected by the change of the E/N at the head of the streamer.The solid particle were added at room temperature of 273.15 K.The polarization effect of the solid particle on the electric field,the electric field near the top and bottom poles is enhanced,and the electric field near the equator is weakened.With the strong electric field of the streamer head near,the electric field at top poles of the solid particle is constantly weakened to intercept the original streamer,the electric field at bottom poles of the solid particle is constantly enhanced to cause a new streamer.The electron density at the top pole of solid particles(the change of positive and negative ions is roughly the same as that of electrons)significantly decreases,and the electron density at the bottom pole significantly increases,which is the result of the strong electric field at the head of the stream gradually close to the polarization electric field of the solid particle with the development of discharge.The radius and the rate of development of streamer have no obvious change.The combined action of high temperature and the solid particle is analyzed.The electric field at the head of the new streamer restarted by the solid particle was higher than that of the original streamer without the solid particle,and the solid particle weakened the inhibiting effect of temperature on the electric field at the head of the streamer.Also increased from 273.15 K to 673.15 K,the electric field at the head of the new streamer restarted by the solid particle only decreased by 39.6%.Compared to the situation without the solid particle,with the increase in temperature,the enhancement of the E/N at the head of the new streamer is more obvious.The solid particle stronger the influence of temperature on the E/N.The growth rate of the E/N can be seen that the higher the temperature,the stronger the expanding effect of the solid particle.This combined effects are directly reflected in the change of the development rate of the streamer.The development rate of the new streamer generated by the solid particle under high temperature is significantly increased,and the fastest is about 3mm/ns.