| In recent years,my country has adopted a series of measures to protect natural resources and achieved outstanding results.The coverage of green plants in various places has increased significantly,and the types of vegetation have become increasingly diversified.In order to realize the cross-regional transmission of electric energy,a large number of transmission lines have been built in vast mountainous and forested areas.However,due to the intensification of the greenhouse effect and the increase of nonstandard human use of fire,the probability of large-scale wildfires has greatly increased.Wildfires have typical characteristics such as ash,high temperature,and multiple charged particles.Under the action of these factors,the gap discharge phenomenon of transmission lines occurs frequently,and even causes large-scale line outages,which seriously threatens the safe and stable operation of the power grid.Aiming at the problem of gap discharge caused by frequent wildfires,scholars at home and abroad have achieved a series of results through experiments.However,due to the limited technical means,it is difficult to observe the changes in the microscopic physical quantities of the discharge under the influence of the flame,so it is impossible to explain the interaction law of the wildfire and the air gap discharge from the mechanism.In this paper,the method of numerical simulation is used to study the influence of three typical characteristics(burning particulate matter,flame temperature,charged particles)on the gap discharge when the mountain fire erupts.It not only reveals the micro-physical law of the gap discharge under the conditions of the mountain fire,but also expands the new idea of using numerical simulation methods to study the mechanism of gap discharge under extreme conditions such as wildfires.The main contents are as follows:(1)The mechanism of streamer discharge under the condition of wildfire is analyzed firstly.Then,three typical characteristics of burning particulate matter,flame high temperature and charged particle in wildfire are introduced,and the influence means of each characteristic on line discharge characteristics are discussed respectively.(2)According to the interaction mechanism of fluid field,temperature field,electric field and particle motion,a multi-physical field coupling model is established,and the motion state and distribution of particles in flame are reflected by numerical simulation.Furthermore,the influence of solid particles on the electric field distribution in gap is analyzed,and the relationship between the properties of particles and the electric field distortion is discussed,thereby the influence mechanism of burning particulate matter generated by the mountain fire on the gap discharge is explained.(3)Based on the plasma hydrodynamics model,a rod-plate air gap discharge model is established to simulate the gap discharge under the condition of wildfire.The governing equations and boundary conditions of the model are given.Then,the characteristics of streamer discharge under normal temperature and ideal air environment are analyzed.In order to verify the effectiveness of the proposed model,simulation results are compared with the results calculated by the empirical formula.(4)The influence of two typical characteristics of high temperature and multicharged particles of wildfire on streamer discharge is analyzed.The streamer propagation rate,electric field intensity and electron density of the discharge at different temperatures are calculated,and the influence of temperature on streamer discharge is analyzed.Combined with the distribution characteristics of charged particles in flame gap,the relationship between the number density of charged particles and discharge characteristics such as streamer propagation velocity and head electric field are investigated. |
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