棒_板长空气间隙击穿电场稳态条件的仿真

棒—板长空气间隙击穿电场稳态条件的仿真

洪　川,胡建林,孙才新,莫登斌,张仁民

(重庆大学高电压与电工新技术教育部重点实验室,重庆400044)

摘　要:为推动以放电理论为基础的高电压与外绝缘学科从半物理到物理研究方向的发展,基于有限元数值计算

方法,对棒-板长空气间隙的电晕云模型进行了仿真研究。结果表明:带电离子和外加电压同时影响空间电场分布,空气分子的电离率α对电场分布影响较大,附着率η、结合率β、解离率γ对电场影响较小;不同电晕云长度对空间电场分布的影响都具有相同规律性;空气相对湿度对击穿电压影响较大,空气湿度越小,空气越容易击穿;正极性棒-板长空气间隙击穿的电场条件为:放电起始后,电晕头部最高场强达到1110kV/cm ,电晕云内部最低场强达到310kV/cm ,在该条件下对应的击穿电压计算值与实验值误差<11%。以上计算结果可为超特高压外绝缘的设计提供可靠的理论依据。

关键词:棒-板间隙;长空气间隙;电场计算;有限元分析;先导放电;电晕云模型中图分类号:TM853文献标志码:A 文章编号:100326520(2007)1120075205

基金资助项目:国家自然科学基金重大计划重点项目

(90210026)。

Project Supported by National Natural Science Foundation of China (90210026).

Simulation of the Steady 2state Breakdow n Field

in Rod 2plane Long Air G ap

HON G Chuan ,HU Jian 2lin ,SUN Cai 2xin ,MO Deng 2bin ,ZHAN G Ren 2min (The Key Laboratory of High Voltage and Elect rical New Technology of Minist ry

of Education ,Chongqing U niversity ,Chongqing 400044,China )

Abstract :For the cross of multi 2discipline and the lack of advanced apparatus to measure the parameters of air dis 2charge ,the research on high 2voltage and insulation technology was mainly based on experiments.To accelerate the development of discipline of high 2voltage and insulation f rom semi 2physical research into physical research ,this arti 2cle studies the breakdown field strength in the corona cloud model in rod 2plane air gap on the basis of the finite ele 2ment method (FEM ).The corona cloud models of different lengths were created in different rod 2plane electrodes to find out where and how the long air gap s were breakdown.The results indicate that the charged ion and applied volt 2

age affect the space electric field distribution together ,the ionizing rate αaffects the electric field distribution mostly compared to the combination rate η,the attachment rate βand the dissociation rate γ,the attachment rate βis most affected by the ion temperature and the others are most affected by the electric field.The corona cloud models of dif 2ferent length have the same regularity to affect the field distribution that the electric field has the same maximal and minimal values between rod and corona cloud ,when the maximal electric field in head of the corona reaches 1110kV/cm and the minimal electric field between the rod and corona cloud reaches 310kV/cm ,the air gap breakdown.The maximal error between the simulation values and experimental U 50%is below 11%,and the dampness of air af 2fects the breakdown voltage significantly and the small dampness leads to lower breakdown voltage.The above re 2sults provide a reliable theoretical basis for the design of air insulation.

K ey w ords :rod 2plane air gap ;long air gap ;electric field calculation ;FEM ;leader discharge ;corona cloud model

0　引　言

气体绝缘设计的前提是要有大量和精确的空气间隙的放电参数,这就需要进行长空气间隙放电的实验研究和理论计算分析。因目前电场测量存在许多困难,故实验数据主要记录的是长空气间隙的击穿电压。若能先将击穿电压与空间电场强度、带电离子浓度等建立起较准确的对应关系,再通过仿真

中得到的电场强度、离子浓度参数来推断不同空气间隙模型下的击穿电压,则对于大量节约实验成本,为空气间隙击穿实验提供理论指导具有重大意义。

本文基于有限元计算方法[1,2],将空气电离的瞬态过程简化为电晕云生长模型以消除时间变量,仿真研究了气体放电中产生的电荷对空间电场强度的影响,并结合空气击穿电压实验数据,得出了电晕云模型的空气击穿所需的电场强度条件。1　棒-板间隙的电晕云生长模型

棒-板电极物理模型见图1[3,4]:仿真中采用的长空气间隙距离d 为015～012m ;圆板电极(阴极)

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57・ 第33卷第11期

2007年 11月

高　电　压　技　术

High Voltage Engineering

Vol.33No.11

Nov.　2007