Modelling and Simulation of Air and SF6 Switching Arcs in High Voltage Circuit Breakers

层流 湍流 机械 断路器 弧(几何) 电气工程 电压 物理 工程类 机械工程
作者
J Liu
标识
DOI:10.17638/03003675
摘要

This thesis is concerned with the modelling of switching arcs in air in high voltage circuit breakers and with a comparative study of interruption capability of air and SF6 switching arcs. Emphasis is given to the identification of dominant energy transport processes for arc interruption and the material properties associated these processes. There have been renewed interests in air arcs because of its possible use in a mixture with other gases as a replacement for SF6 in circuit breakers for environment protection. Computer simulation of the switching air arc has been carried out using arc models based on laminar flow and on turbulent flow for the experimental set up of Fang et al [41] under DC current and that of Frind and Rich [66] for the current zero period. DC arc voltages predicted by arc model assuming laminar flow (LAM) are much lower than those measured. Thus, turbulence is introduced to account for additional power loss mechanism not included in the laminar flow model. Two turbulence models have been used to take into account of turbulence enhanced momentum and energy transport: the Prandtl mixing length model (PML) and the standard k-epsilon model or its modified version. For the DC air nozzle arc of Fang et al [41] the value of the turbulence parameter, c= 0.06, in PML has been chosen to match the predicted arc voltage with that measured at 1 kA DC and a stagnation pressure of 10 bar. PML can give satisfactory agreement with experiments over a DC current range from 250 A to 3 kA. When the standard k-epsilon model is used, the predict arc voltage is much higher than that measured indicating that turbulence cooling is too strong. One of the turbulence parameters of the standard k-epsilon model which controls the dissipation rate of turbulent kinetic energy is adjusted to match the predicted arc voltage with the experimentally measured arc voltage under the same discharge conditions as those for finding the value of c in PML. With this chosen value of 1 = 1.62, the modified k-epsilon model (MKE) gives similar results to those of PML. Three arc models (LAM, PML and MKE) are used to compute the critical rate of rise of recovery voltage (RRRV) for the air nozzle arc of Frind and Rich [66]. The presence of the shock inside the nozzle in the presence of the arc prevents the optimisation of the value of turbulence parameter for PML due to numerical convergence problems. RRRV predicted by PML and LAM are much lower than the experimental value. MKE with 1 = 1.65 is successful in predicting satisfactorily the RRRV at di/dt= 13.5 A/μs for several stagnation pressures. However, it has been found that a single value of 1 chosen for one value of di/dt cannot give satisfactory prediction of RRRV for other values of di/dt. A comparative computational study of SF6 and air switching arcs based on MKE has been carried out for the experimental conditions of Frind and Rich [66] for di/dt= 13.5A/μs at several stagnation pressures. Under the same discharge conditions RRRV of SF6 switching arc is one order of magnitude higher than that of air switching arc. Such large difference in the interruption capabilities of SF6 and air is due to the different dominant energy transport processes responsible for the arc cooling during current zero period. Two material properties of the arc plasma, the product of density and specific heat at constant pressure (ρCP) and that of density and enthalpy (ρh) are responsible for the distinctive arc features for SF6 and air. SF6 switching arc has a distinctive arc core surrounded by a thin region with steep temperature gradient. Under the same discharge conditions as those of SF6 air switching arc has no distinctive core structure. Its radial temperature profile is very broad and arc radius is much bigger than that of SF6. Such broad radial temperature profile of air arc is due to the peaks of turbulent thermal conductivity at 4,000 K and 7,000 K produced by the corresponding peaks of the material property of ρCP of air. For SF6 ρCP has a peak just below 4,000 K, which ensures rapid temperature decay above 4,000 K and a gentle temperature tail below 4,000 K. In comparison with SF6 under the same pressure difference across the nozzle the velocity inside air arc is much higher than that of SF6. With ρh of air being greater than that of SF6 for temperature higher than 7,000 K together with higher velocity enthalpy transport capability of air arc is much higher than that of SF6. Energy balance calculation for the current carrying core indicates that after the breakdown of quasi-steady state turbulent thermal conduction is the dominant energy transport process for SF6 while for air arc axial convection is dominant. As a consequence the rates of decay of arc temperature and arc radius for air arc a few microseconds before current zero are much slower than those of SF6, thus resulting in a large difference between RRRVs for the two gases under the same discharge conditions. To find an alternative arc quenching gas with similar interruption capability to that of SF6 one should aim at ρCP and ρh of the alternative gas with similar features to those of SF6.
最长约 10秒,即可获得该文献文件

科研通智能强力驱动
Strongly Powered by AbleSci AI
更新
大幅提高文件上传限制,最高150M (2024-4-1)

科研通是完全免费的文献互助平台,具备全网最快的应助速度,最高的求助完成率。 对每一个文献求助,科研通都将尽心尽力,给求助人一个满意的交代。
实时播报
杜贺满发布了新的文献求助10
刚刚
666完成签到 ,获得积分10
1秒前
1秒前
2秒前
wlqc完成签到,获得积分10
3秒前
mufcyang完成签到,获得积分10
3秒前
Mango完成签到 ,获得积分10
4秒前
铁柱xh完成签到 ,获得积分10
5秒前
汉朝老橙完成签到,获得积分10
5秒前
含蓄含烟完成签到,获得积分10
5秒前
安静如冬发布了新的文献求助10
6秒前
活泼火水完成签到,获得积分10
6秒前
炸炸呦发布了新的文献求助10
6秒前
6秒前
Joanna完成签到,获得积分10
7秒前
独特的半芹完成签到,获得积分10
7秒前
GD完成签到,获得积分10
8秒前
自觉松完成签到,获得积分20
8秒前
蔓越莓给蔓越莓的求助进行了留言
8秒前
娃haha完成签到,获得积分10
8秒前
栗子应助优雅逍遥采纳,获得10
9秒前
传统的松鼠完成签到 ,获得积分10
9秒前
晚晚完成签到 ,获得积分10
9秒前
打打应助CC采纳,获得10
10秒前
10秒前
小可完成签到,获得积分10
10秒前
研友_8DoPDZ完成签到,获得积分10
11秒前
11秒前
hcd12138完成签到,获得积分10
12秒前
lisa完成签到,获得积分10
13秒前
丑麒完成签到,获得积分10
14秒前
15秒前
chd完成签到 ,获得积分10
15秒前
沉静的万天完成签到 ,获得积分10
15秒前
果粒儿完成签到 ,获得积分10
15秒前
卿莞尔完成签到 ,获得积分10
16秒前
甜蜜寄文发布了新的文献求助10
17秒前
LingYing完成签到,获得积分10
17秒前
木马不旋转完成签到,获得积分10
17秒前
Crisp完成签到,获得积分10
18秒前
高分求助中
The late Devonian Standard Conodont Zonation 2000
The Lali Section: An Excellent Reference Section for Upper - Devonian in South China 1500
Nickel superalloy market size, share, growth, trends, and forecast 2023-2030 1000
Smart but Scattered: The Revolutionary Executive Skills Approach to Helping Kids Reach Their Potential (第二版) 1000
Mantiden: Faszinierende Lauerjäger Faszinierende Lauerjäger 800
PraxisRatgeber: Mantiden: Faszinierende Lauerjäger 800
A new species of Coccus (Homoptera: Coccoidea) from Malawi 500
热门求助领域 (近24小时)
化学 医学 生物 材料科学 工程类 有机化学 生物化学 物理 内科学 纳米技术 计算机科学 化学工程 复合材料 基因 遗传学 催化作用 物理化学 免疫学 量子力学 细胞生物学
热门帖子
关注 科研通微信公众号,转发送积分 3244993
求助须知:如何正确求助?哪些是违规求助? 2888606
关于积分的说明 8254294
捐赠科研通 2557053
什么是DOI,文献DOI怎么找? 1385683
科研通“疑难数据库(出版商)”最低求助积分说明 650212
邀请新用户注册赠送积分活动 626403