Statistical characteristics of transient enclosure voltage in ultra-high-voltage gas-insulated switchgear

Transient enclosure voltage（TEV）,which is a phenomenon induced by the inner dielectric breakdown of SF_6 during disconnector operations in a gas-insulated switchgear（GIS）,may cause issues relating to shock hazard and electromagnetic interference to secondary equipment.This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage（UHV）substations.In this paper,the statistical characteristics of TEV at UHV level are collected from field experiments,and are analyzed and compared to those from a repeated strike process.The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first.Then,statistical characteristics,such as the pulse number,duration of pulses,frequency components,magnitude and single pulse duration,are extracted.The transmission line theory is introduced to analyze the TEV and is validated by the experimental results.Finally,the relationship between the TEV and the repeated strike process is analyzed.This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage.The results contribute to the definition of the standard testing waveform of the TEV,and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.

Overview of development, design, testing and application of compact gas-insulated DC systems up to ±550 kV

The development of high-voltage direct current gas-insulated switchgear assemblies(DC GIS)of rated voltages up to±550 kV has been completed.DC GIS provide a compact technical solution with a high functional density,optimized for projects with limited space as in offshore HVDC converter platforms,onshore HVDC converter stations and transition stations between different transmission media.Up to now,no standards for testing of gas-insulated DC systems are available,although pre-standardization work is in progress within CIGRE.Some tests can be performed as required in AC GIS standards.Special aspects of DC voltage stress,like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution,must be considered by additional electric and thermoelectric tests.For DC GIS,the experience of long-term performance is limited today.Although ageing is expected to be of lower importance,tests are recommended.This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology.It explains the developed modules of the substation and gives an overview of the performed tests.Furthermore,it provides an insight in the on-going standardization activities and describes applications in converter and transition stations,showing its space-saving characteristics.

China’s 10-year progress in DC gas-insulated equipment:From basic research to industry perspective

The construction of the future energy structure of China under the 2050 carbon-neutral vision requires compact direct current(DC)gas-insulation equipment as important nodes and solutions to support electric power transmission and distribution of long-distance and large-capacity.This paper reviews China's 10-year progress in DC gas-insulated equipment.Important progresses in basic research and industry perspective are presented,with related scientific issues and technical bottlenecks being discussed.The progress in DC gas-insulated equipment worldwide(Europe,Japan,America)is also reported briefly.

特高压GIS设备现场标准雷电冲击耐压试验技术的应用

气体绝缘金属封闭组合电器(GIS)在电力系统中应用广泛,其运行安全可靠对电力系统至关重要。现场雷电冲击耐压试验受制于设备体积和回路电感,难以在GIS变电站,尤其是特高压GIS变电站应用。本文分析了目前GIS设备冲击耐压试验现状,并从波形参数、电压极性和加压间隔时间等方面阐述了GIS设备冲击电压绝缘缺陷检出影响因素。基于研发的特高压GIS变电站现场冲击耐压试验用的可移动式气体绝缘标准雷电冲击试验成套设备,成功在1000 kV南京站和苏州站开展了现场标准雷电冲击耐压试验。

温度对GIS绝缘子表面金属异物局部放电及闪络特性的影响

表面金属异物是造成气体绝缘全封闭组合电器(gas-insulated switchgear,GIS)绝缘子故障失效的重要原因。运行中的绝缘子不仅承受强电场作用,还承受温度场的作用,研究电–热耦合下绝缘子表面金属异物的局部放电和闪络特性,具有重要的实际意义。鉴于此,该文建立GIS绝缘子电场和温度场耦合试验平台,开展不同温度作用下绝缘子表面金属异物缺陷的局部放电和闪络特性研究。结果发现,绝缘子表面最高温度从25℃升高至75℃时,绝缘子表面2.5cm长金属异物缺陷的局部放电起始电压降低约16%;平均放电量从0.55pC增加至1.45pC;最大放电量从9.1pC增加至11.5pC;放电频次也从不足200次/s增加至近400次/s。不同电压下,不同尺寸金属异物局部放电特性随温度变化的规律基本一致;而温度对绝缘子表面金属异物缺陷的工频闪络电压的影响不显著。研究结果有助于进一步认识实际运行中在电–热耦合作用下,温度变化对绝缘子表面金属异物缺陷的局部放电和闪络特性的影响规律。

Environment-friendly Insulating Gases for HVDC Gas-insulated Transmission Lines

Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line(GIL)electric field condition is the key to the next generation of Environment-friendly HVDC GILs.In this paper,we review the literature on sulfur hexafluoride(SF6)alternatives including the scientific understanding,control,and implementation of gas-solid systems in this type of power transmission.First,the structure-activity relationship between the molecular structure and physico-chemical properties of Environment-friendly insulating gases is presented.Then,the search and prediction of important physicochemical properties of gases are summarized.Subsequently,in view of the potential of environmental friendly insulating gases,the swarm parameters of gas discharge and breakdown properties in a quasi-uniform field,inhomogeneous field,and at the gas-solid interface,that need to be taken into account with industrialized DC GILs are discussed.The latest research progress on insulation characteristics,especially the polarity effect in DC gas-solid insulation systems,the sensitivity to the electrode surface state,and the non-uniformity of the electric field,and the influence of metal particles and their variation with air pressure,is highlighted.In addition,the heat transfer characteristics of insulating gases,related to DC GIL transmission with a large current-carrying capacity and the influence of alternative gases on the heat transfer characteristics are described.Finally,aiming at solving the contradiction of low environmental impact,high dielectric strength and low liquefaction temperatures in the selection of alternative gases,an coordinated regulation model for Environment-friendly gases in DC GILs is established.Considerations for future work on this topic are also presented.

六氟化硫组合开关设备在鲁新煤矿的应用

六氟化硫负荷开关是一种开断能力比较强的开关.普通的负荷开关采用的是空气灭弧,而六氟化硫负荷开关触头密封于六氟化硫气仓内,利用六氟化硫的高绝缘性能灭弧.。随着国民经济的发展需要,高压配电SF6的装置广泛应用于城区变电站、工业变电站。做好SF6的安装、维护,能保证电力系统的安全运行。

220kV GIS设备出厂试验探讨

GIS是Gas-insulated metal-enclosed Switchgear中主要单词首字母缩写即气体绝缘金属封闭开关设备通常成为高压开关设备。本文对核电站用220kV GIS设备出厂试验包含的试验项目、试验目的、试验实施等进行了较详细的论述。220kV是电网系统标称电压,设备一般以最高电压Um的有效值命名产品型号,这也符合国标GB/T11022《高压开关设备和控制设备标准的共用技术要求》中4.2.1、GB311.1-2012《高压输变电设备绝缘配合》表2中的规定。电压等级220kV和252kV为同一等级,某核电站220kV GIS设备主要的出厂试验项目有:回路电阻测量、SF6水份测量、SF6气密试验、雷电冲击试验、耐压及局部放电测量。

Photon count technique as a potential tool for insulation microdefect detection:Principles and primary results

The requirements for the construction of a new power system inevitably pose significant challenges and changes to the operation and maintenance of the power grid.To ensure the safe and stable operation of ultra-high voltage(UHV)transmission equipment,this work reports on the principles and preliminary results of using electroluminescence(EL)-based photon counting(PC)methods for early detection of micro-defects in GIS/GIL insulation spacer.In this study,the impact of voltage,gas pressure,and gas composition on the photon response of insulation is examined.Furthermore,the corresponding relationship between defect status and photon response characteristics is explored,along with the discussion of the EL mechanism and its evolution induced by defects.The research results demonstrate that PC measurement exhibits high sensitivity to variations in millimeter-scale defect size,position,and morphology at lower electric fields before partial discharge(PD)initiation.With this regard,this paper reveals promising prospects for the early detection of micro-defects in UHV transmission equipment using PC measurement-based methods.

Eco-friendly gas insulating medium for next-generation SF_(6)-free equipment

Gas-insulated equipment(GIE)that utilizes the most potent greenhouse gas sulfur hexafluoride(SF_(6))as insulation and arc-quenching medium has been widely used in the power industry.Seeking eco-friendly insulating gas with advanced performance for next-generation SF_(6)-free GIE is significant for the“net-zero”goal and sustainable development.In this paper,the utilization,emission,and reduction policies of SF_(6)around the world were summarized first.Then,we systematically reviewed the latest progress in comprehensive performance evaluation of eco-friendly insulating gas in terms of molecular design,dielectric insulation,arc-quenching,stability and decomposition,materials compatibility,biosafety,etc.Further,the representative applications of eco-friendly insulating gas in medium-voltage,high-voltage GIE as well as relevant maintenance-related technologies were highlighted.Accordingly,the existing challenges and future perspectives were proposed,presenting a roadmap to hopefully steer the development of eco-friendly insulating gas and GIE.

Experimental and Theoretical Studies of C_(3)F_(7)CN/CO_(2) Mixture Decomposition Under Overheating Fault

Heptafluoroisobutyrontrile(C_(3)F_(7)CN)performs well in dielectric properties and environmental protection,which has the potential to replace SF6 gas.The decomposition characteristics of C_(3)F_(7)CN mixture under fault conditions directly affect the possibility of its replacement for SF6 gas.However,the number of studies on the decomposition characteristics of C_(3)F_(7)CN mixture under overheating fault is less.In this paper,the decomposition characteristics of C_(3)F_(7)CN/CO_(2) mixture under an overheating fault are studied by gas chromatography-mass spectrometry(GC/MS)and quantum chemical calculations.Byproducts CO,C_(3)F_(6) and HF are detected at 200℃.At 550℃,the C_(3)F_(7)CN molecule begins to decompose and produces CHF_(3),C_(2)F_(4),CF_(3)CN and CNCN.Moreover,the results of GC/MS show that the insulation medium C_(3)F_(7)CN contains an impurity,which is C3HF7(HFC-227ea).Combined with the results of GC/MS and quantum chemistry calculations,it can be concluded that the decomposition by-product C_(3)F_(6) at 200℃ mainly comes from the decomposition of C_(3)HF_(7).C_(3)HF_(7) reduces the decomposition temperature of the C_(3)F_(7)CN/CO_(2) mixture.Therefore,it is very important to improve the purity of the insulation medium C_(3)F_(7)CN.