摘要
探究气体绝缘母线在超高压大电流工况下的温升特性对设备的正常运行以及监测维护意义重大。然而,在长期大电流负荷运行下,因接触异常等原因导致母线在较小封闭空间内产生大量热量,极易造成局部过热严重威胁设备安全运行。针对这一问题,本文以550kV气体绝缘母线为研究对象,构建了考虑接触电阻的3维电磁-温度-流体多场耦合模型,计算其在1.1倍额定电流(8800A)、气压0.3MPa条件下的母线温度分布,并搭建了大电流温升试验平台进行验证,试验测量结果与仿真结果吻合度高。基于验证后的可靠模型,进一步探究了通流水平、SF_(6)气压及接触状态对母线温度分布的影响规律。结果表明:母线最高温度位于盆子凹面处电接触部位顶部(约为54℃),该端触头上方SF_(6)温度比导杆上方高近15℃,凹面处触头径向温度梯度明显低于凸面处触头径向温度梯度;在非等温自然对流的情况下,母线温度整体呈径向上高下低、轴向端部高中间低的规律分布;母线温度随通流水平提高呈非线性上升、随SF_(6)气压增大呈近似线性下降,可在一定范围内提高设备绝缘气体压强以降低设备运行温度;异常电接触处温度随阻值增大近似线性增加,而电接触异常往往是母线过热的主要风险点。研究结果可为超高压大电流气体绝缘设备产品设计及状态监测提供参考。
Objective This study focuses on the temperature rise characteristics of ultra-high voltage,high-current gas-insulated busbars.It investigates the temperature and flow rate distribution of the busbar under 1.1 times the rated current(8800 A)and 0.3 MPa gas pressure.Additionally,a highcurrent temperature rise test platform is built to verify the model's validity.Based on this,the study examines the influence of the through-current level,the SF_(6)gas pressure,and the contact state on the temperature distribution of the busbar.Methods In this study,the 550 kV gas-insulated busbar is taken as the research subject.The contact resistance is calculated through direct current(DC)low resistance measurement.Electrical and thermal conductivities are the determined using the resistance formula and the Wiedemann-Franz law.These calculations are incorporated into the development of a three-dimensional electromagnetic-temperature-fluid multi-field coupling model of the busbar.The temperature and flow velocity distribution under 1.1 times the rated current(8800 A)and 0.3 MPa air pressure are calculated,considering factors such as contact resistance,skin effect,natural convection,and thermal radiation.The temperature differences between the busbar conductor,the maximum hot spot,and the shell are analyzed and compared with the temperature difference at the axial section where the basin convex and concave contacts are located.A high-current temperature rise test platform is built to validate the model's results,and the test measurements align closely with the simulation results.Based on the reliable model verified by the test,the influence of the throughcurrent level,SF_(6)air pressure,and contact state on the temperature distribution of the busbar is further investigated.Additonally,a variation diagram showing the maximum hot spot temperature of the busbar with each factor is obtained.Results and Discussions To calculate the bus temperature distribution,it is first necessary to determine its loss size.Considering the skin depth of the conductive rod and basin insert,the total loss of the bus is calculated to be 695.786 W.The primary heat sources are the conductor rod and electrical contact components.The maximum magnetic induction intensity occurs at the basin insert edge,and the current density is mainly concentrated on the surface of the conductor.This loss is mapped to the temperature field to calculate the bus temperature and gas flow rate distribution.The rise in bus temperature is mainly concentrated in the through-flow conductor components.The temperatures at both ends of the contact are significantly higher than at the middle of the guide rod.The highest temperature of the bus,approximately 54℃,is located at the concave surface of the basin at the top of the electrical contact part.This temperature is about 15℃higher than the SF_(6)temperature at the end of the contact.The temperature rise in the SF_(6)is mainly concentrated in the upper part of the cavity.Additionally,the radial temperature gradient of the contact at the concave surface of the busbar is significantly higher than that at the convex surface.Hot air buildup around the shell at the concave surface of the basin is noticeable,showing a radial pattern of higher temperature at the top and lower temperatures at the bottom,with a left-right symmetrical distribution pattern.The location of the busbar conductor hot spot corresponds to the shell,with a clear difference in the temperature gradient at different x-axis locations.The temperature gradient difference between the conductor and the heat near the shell causes the internal SF_(6)gas and air to move upward.The external air flow velocity is approximately 0.23 ms^(−1),creating a circulation along the boundary of the solution domain due to non-isothermal natural convection.The influence of different factors on the bus temperature distribution law is further explored through simulation.As the load current increases,the highest temperature trend for the conductor and electrical contact is almost identical and significantly increases,while the shell temperature increase is much smaller than that of the through-flow conductor.The three highest temperatures rise with the current increase nonlinearly;SF_(6)gas pressure per 0.05 MPa shows a roughly linear decreasing trend for both bus conductor and shell temperatures,with the conductor temperature being more sensitive to changes in SF_(6)gas pressure than the shell.The abnormal electrical contact temperature increases approximately linearly with the resistance value.The normal electrical contact temperature rise is about 15℃.Even when the contact resistance value reaches approximately 70μΩthe highest shell temperature exceeds the normal temperature of the electrical contact.Finally,the high-current temperature rise test platform validates the constructed model,providing data support for the temperature rise characterization discussed in this study.Conclusions This research delineates the temperature rise characteristics of the electromagnetic-thermal-fluid multi-field coupling model of a 550 kV gas-insulated busbar,considering the influence of contact resistance on the thermal characteristics.It analyzes the temperature rise characteristics under high-current conditions and investigates the influence of current level,SF_(6)pressure,and contact state on the temperature distribution of the busbar.These findings have considerable engineering implications,offering valuable references for product design and condition monitoring of gas-insulated equipment,and helping to reduce the occurrence of overheating faults.
作者
侯世英
罗澳
杨帆
王鹏博
权帅峰
孙帅
HOU Shiying;LUO Ao;YANG Fan;WANG Pengbo;QUAN Shuaifeng;SUN Shuai(College of Electrical Eng.,China Chongqing Univ.,Chongqing 400044,China;Xi'an XD Switchgear Electric Co.,Ltd.,Xi'an 710077,China;Guangdong Key Lab.of Electric Power Equipment Reliability,Electric Power Research Inst.of Guangdong Power Grid Co.,Ltd.,Guangzhou 510080,China)
出处
《工程科学与技术》
EI
CAS
CSCD
北大核心
2024年第5期76-85,共10页
Advanced Engineering Sciences
基金
国家重点研发计划项目(2021YFB2401700)。
关键词
气体绝缘母线
多物理场耦合
温升特性
接触电阻
影响因素
gas-insulated busbar
multi-field coupling
temperature rise characteristics
contact resistance
influencing factors
作者简介
侯世英(1962-),女,教授,博士.研究方向:电力装备多物理场计算.E-mail:Houshiying@cqu.edu.cn;通信作者:杨帆,教授,E-mail:yangfan@cqu.edu.cn。
