Development of 72‐kV high‐pressure air‐insulated GIS with vacuum circuit breaker

SF₆ gas has excellent dielectric strength and interruption performance. For these reasons, it has been widely used for gas‐insulated switchgear (GIS). However, use of SF₆ gas has become regulated under agreements set at the 1997 COP3. Thus, investigation and development for GIS with a lower amount of SF₆ gas are being carried out worldwide. Presently, SF₆‐free GIS has been commercialized for the 24‐kV class. Air or N₂ gas is used as the insulation gas for this GIS. On the other hand, SF₆‐free GIS has not been commercialized for the 72‐kV‐class GIS. The dielectric strengths of air and N₂ gas are approximately one‐third that of SF₆ gas. To enhance the insulation performance of air and N₂ we have investigated a hybrid gas insulation system which has the combined features of providing an insulation coating and suitable insulation gas. We have developed the world's first 72‐kV SF₆‐free GIS. This paper deals with key technologies for SF₆‐free GIS, such as the hybrid insulation structure, a bellows for the high‐pressure vacuum circuit breaker, a newly designed disconnector and spacer, and prevention of particle levitation. Test results of the 72‐kV high‐pressure air‐insulated GIS with the vacuum circuit breaker are described. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 13–23, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20451     

Breakdown characteristics of gas‐insulated switchgear for nonstandard lightning impulse waveforms under nonuniform electric field

To improve the insulation specification of gas‐insulated switchgear (GIS), it is necessary to recognize the insulation characteristics of SF₆ gas during actual surges (called nonstandard lightning impulse waveforms) occurring at field substations. The authors observed the insulation characteristics of SF₆ gas gap under various types of nonstandard lightning impulse waveforms and compared them quantitatively with those obtained with standard lightning impulse waveforms. The experimental results were used to derive an evaluation method for real surges, which was applied to typical surges for various UHV and 500‐kV systems. In the preceding study, therefore, only the case of a quasi‐uniform electric field (with a typical range of field utilization factors in the bus of a GIS) was investigated. In the present investigation, the insulation characteristics of an SF₆ gas gap for a nonuniform electric field were observed experimentally and an evaluation method for converting nonstandard lightning impulse waveforms equivalently to the standard lightning impulse waveform was investigated. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(1): 11–18, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21144     

Development of a high‐pressure air‐insulated 72/84‐kV disconnecting switch corresponding to bus‐transfer current switching

SF₆ gas has excellent dielectric strength and current interruption performance. For these reasons, it has been widely used for gas‐insulated switchgear (GIS). Today, such global environmental problems as global warming are important issues of concern. SF₆ gas is known as a greenhouse gas with a long atmospheric lifetime, and has global warming potential of 23,900. SF₆‐free 72‐kV GIS was recently developed by using high‐pressure air and a gas/solid hybrid structure. But an alternating current disconnecting switch (DS) has yet to be developed thus making this type of SF₆‐free 72‐kV GIS unsuitable for double bus‐bar application. Consequently, the development of a high‐pressure air‐insulated DS corresponding to bus‐transfer current switching has been expected. The bus‐transfer current is the highest among all current interruption requirements for the DS. To develop an alternating current DS, efforts must be made to reduce arcing damage to the electrode. This paper describes the fundamental characteristics of current interruption in the plain break type and the magnetic field driven type. Then, average arcing time of the magnetic field driven type was estimated by magnetic flux density. Finally, two types of DS, which were a high‐speed plain break and a low‐speed magnetic field driven, were confirmed to comply with bus‐transfer current switching requirements on JEC standard. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 48–55, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20595     

Development of insulation technology in compact SF6 gas‐filled bushings: Development of compact 800‐kV SF6 gas‐filled bushings

Efforts of designers of gas‐insulated switchgear (GIS) are currently focused on such features as smaller installation area and economical efficiency. Circuit breakers (CB), disconnecting switches (DS), and earthing switches (ES) have been redesigned in more compact configurations. Compactness and light‐weight requirements are applied also to bushings used in GIS. GIS bushings can be divided in three general types: capacitor, gas‐filled, and molded bushings. Requirements of the light weight and the economical efficiency of gas‐filled bushings can be satisfied by improvements in insulation technology. Size reduction can be effectively achieved by moderation of the electric field strength on the outside surface of the hollow insulator in the area of the inner grounded electrode tip. We devised a new inner grounded electrode structure consisting of a cylindrical electrode and a ring electrode supported by column electrodes. This paper describes the effect of reduction of the maximum value of electric field strength on the outside surface of the hollow insulator by a new type of grounded electrode. Then, improvement of insulation performance for electrodes with insulation coating in SF₆ gas is described as the composite insulation technology. Finally, the efficiency of these insulation technologies is described by the basic insulation test results of a prototype compact 800‐kV SF₆ gas‐filled bushing. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(1): 19–27, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20898     

Insulation characteristics of vacuum interrupter for a new 72/84 kVC-GIS

This paper describes insulation technology for 72/84 kV vacuum interrupter for a new cubicle-type gas insulated switchgear (CGIS). The insulation performance has been increased significantly by a multi-gap shield configuration around the ceramic surface, which resulted in a 40% volume reduction of the vacuum interrupter. The CGIS housing the vacuum interrupter also reduced by 40% in volume. In the paper, the authors describe the basic characteristics on surface insulation and the area effect on surface insulation and their application to an new 72/84 kV CGIS     

A study on hybrid insulation composition joint using gas and solid insulator for gas‐insulated power equipment

SF₆ is used as the main insulation gas for gas‐insulated switchgear (GIS), but it has recently become a gas that must be restricted because of its greenhouse effects. To date, we have studied the insulation characteristics of compressed N₂ and CO₂ as possible alternatives for SF₆. We have reported that N₂ or CO₂ must be pressurized to 2.0 MPa when it is used as a substitute for SF₆ at 0.5 MPa. Therefore, we have proposed a hybrid installation composition that uses gas and solid insulators. Because the central conductor of GIS is covered by a solid insulator in this composition, a high‐pressure gas at 2.0 MPa is not needed. However, the joint of the solid insulator becomes a weak point for discharge development. In this paper, we describe an effective configuration for improvement of the withstand voltage based on experiments. The most effective connector was made of resin without an implant electrode and the most effective configuration was one without a solid–solid interface between the solid insulator of the central conductor and the resin connector. In this experiment, the improvement of breakdown electric field of the hybrid composition was 44% or more compared with the case of only gas insulation (conventional method). In addition, further improvement can be expected by optimizing the insulation creepage distance and configuration. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 11–20, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21107     

Solid insulated switchgear and investigation of its mechanical and electrical reliability

SF₆ gas is widely employed in medium‐voltage switchgear because of its high insulation reliability and down‐sizing ability. However, SF₆ gas was placed on the list of greenhouse gases under the Kyoto Protocol in 1997. Since then, research on low‐SF₆ or SF₆‐free insulation has been carried out actively. Therefore, we focused on solid materials with higher dielectric strength than SF₆, and we have now developed solid insulated switchgear (SIS) that uses molding of all main circuits. A new epoxy casting material is used which contains a large amount of spherical silica and a small amount of rubber particles. This new material has high mechanical strength, high thermal resistance, high toughness, and also high dielectric strength because of direct molding of the vacuum bottle, as well as reduced size and high reliability. This paper describes the technology of the new epoxy casting material which makes possible SIS. In addition, mechanical and electrical reliability tests of SIS using a new epoxy resin were performed, and the effectiveness of the developed material and the mechanical and electrical reliability of the SIS were verified. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(4): 28–36, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21057     

基于SF6混合气体绝缘性能的设备补气策略研究

随着电力需求的增长和环境保护要求的提高,SF₆气体的使用逐渐受到限制。SF₆混合气体在一定程度上减少了SF₆气体用量,目前已经在电气设备中应用。文中针对SF₆混合气体在220 kV气体绝缘组合电器（GIS）中发生泄漏引起的绝缘变化展开研究,通过改变微量的气压值和混合比,探究混合气体的绝缘性能变化,分析气压、混合比因素对工频击穿电压的影响规律,获取各气压下各比例混合气体的绝缘强度曲线图,从而得到保证设备安全稳定运行的补气策略。研究发现,混合气体击穿电压的变化规律呈现出随着压强和混合比的提高,非线性程度增大的特点,并且得到了设备安全运行的混合比和气压的边界值。文中的研究可以为SF₆/N₂混合气体绝缘设备提供运维规程和技术标准,同时为制定混合气体的检测技术标准奠定基础。     

A study on condition assessment method of gas‐insulated switchgear. part II. influence of moisture in the SF6, detection of a partial discharge on a spacer,repetition discharge and overheating by incomplete contact

Rationalization of the maintenance of gas‐insulated equipment under operation and lifetime extension based on the results of appropriate diagnosis are necessary to reduce the cost of gas‐insulated equipment. Therefore, condition‐based maintenance (CBM) is required and accurate methods for observing the inside of equipment are important. In this report, we describe a diagnosis method that can be used for actual gas‐insulated equipment, such as to assess the deterioration of the spacers made of epoxy resin and to detect loose connections in the central conductor. The principal results are summarized as follows: (1) The quantity of decomposition gases depends on the moisture and magnitude of the partial discharge. However, decomposition gases were detected even if SF₆ had low moisture content (less than 100 ppm) similar to that used in actual equipment. This means that our method can be applied to actual equipment. (2) It became clear that CF₄ is a typical gas generated by partial discharge on the spacer surface. Therefore, it is possible to diagnose spacer deterioration by monitoring CF₄. (3) Decomposition gases (SF₄, SO₂, SO₄, SO₂F₂) were generated by impulse breakdown, which was assumed to be due to repetition discharge caused by insulation failure and loose connections. (4) SF₆ gas was assumed to be exposed to a loose connection and was heated from room temperature to 800 °C, and the generated decomposition gases were analyzed by FTIR in real time. As a result, the decomposition gases were generated at temperatures above approximately 500 °C in a heating time of 1.5 minutes. Therefore, a loose connection can be detected by analyzing the decomposition gas. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(2): 22–30, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21108     

News from Japan

In an attempt to reduce global warming, much research and development work has been done on electric power equipment in which SF6 gas insulation is not used. Mitsubishi Electric Corporation, Tokyo, which released 24-kV-rated dry air insulated switchgear in 2000, has completed more than 1,000 switchgear installations in the 12-, 24-, and 36-kV classes. Recently, the company developed 72-kV-rated switchgear which features low-pressurized dry air (gauge pressure < 0.2 MPa-g) insulation, improved electromagnetic actuators and condition-based maintenance (CBM) functions.     

Insulation characteristics of CO2 gas for nonstandard lightning impulse oscillations: Evaluation method of nonstandard lightning impulse waveform for CO2 gas insulation

SF₆ gas is widely used in electric power apparatus such as gas‐insulated switchgears (GIS), because of its superior dielectric properties; however, it has been identified as a greenhouse gas at COP3 in 1997, and alternative insulation gases to SF₆ have recently been investigated. One of the candidates is CO₂ gas, which has lower global warming potential (GWP). However, CO₂ gas has a lower withstand voltage level than SF₆ gas; therefore, it is necessary to rationalize the equipment insulation level and reexamine the insulating test voltage for electric power apparatus as low as possible. From our previous investigation, in SF₆ gas insulation system, we obtained that the insulation requirements of the real surges (called nonstandard lightning impulse waveform) are not as severe as those of the standard lightning impulse waveform. This paper describes the evaluation method for real surges, based on insulation characteristics of CO₂ gas gaps. Furthermore, the method was applied to typical field overvoltage waveform in the lightning surge time region for 500‐kV systems and it is obtained that the equivalent peak value of the standard lightning impulse waveform is possibly reduced by 10 to 15%. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 1– 9, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20560     

Optimization on the internal insulation system of gas‐insulated bushing for 1100‐kV GIS based on multiobjective optimization method

In this paper, we first study the voltage and electric field distribution characteristics under the basic lightning impulse level (BIL) of 2400 kV by finite element method (FEM) calculation which are affected by the internal shielding structure of the gas‐insulated bushing for the 1100‐kV gas‐insulated substation (GIS). On this basis, four parameters of the shielding structure are determined to be the decision variables in the optimization process. Four electric field objective functions and four potential objective functions are also proposed. Using a multiobjective optimization method, we then construct an evaluation function with the eight objective functions mentioned above, which are used to evaluate the electric field and potential distribution synthetically. Furthermore, a combination of FEM and the evolution strategy is used to construct the stochastic optimization objective function with the multiobjective evaluation function. The electric field and potential distribution of the gas‐insulated bushing are greatly improved after optimization, and the electric field strength at key spots is effectively reduced. The insulation system of gas‐insulated bushing for 1100‐kV GIS designed by this method has passed type tests and worked well nearly 3 years. So, this optimization provides a constructive method and useful basis for the design of gas‐insulated bushings for 1100‐kV GIS and other electrical equipment. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

10 kV高压开关柜的故障在线检测方法

为提高１０ｋＶ高压开关柜的可靠性，提出了母线连接处温度、动作时间、弹簧储能时间与真空灭弧室等真空度测量方法。     

72.5kV空气绝缘HGIS关键技术开发

介绍了一种空气绝缘的72.5 k V HGIS设备,对比研究了空气、N2、CO2的绝缘特性,设计开发了72.5 k V单断口真空断路器,研发了HGIS样机,并通过了型式试验。该机无污染气体或温室效应气体排放,使高压开关设备真正实现了环保,符合国家环保要求。     

Development and design of DC‐GIS

In order to realize a reliable, compact, and economical converter station for HVDC transmission, applications of gas insulated switchgear (GIS) for dc transmission lines are considered. The characteristics of dc gas insulation differ from those of ac. The behavior of metallic particles left in the enclosure is one of the largest differences. The accumulation of electrical charges on solid insulators is another essential factor in designing a DC‐GIS. Also, degradation of metal oxide arrester blocks under dc stress must be deliberated. Based on the fundamental studies, we developed the components of ± 500‐kV DC‐GIS. Electrical and mechanical performances of these components have been tested and proven to be satisfactory. Finally these components have been assembled into a full DC‐GIS and subjected to a long‐term voltage endurance test. In this paper, the design philosophy of ± 500‐kV DC‐GIS, details of the components, and the test results are described. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 51–61, 1999     

户外真空断路器绝缘强度的分析

应用ANSYS软件分析计算了支柱式12kV户外真空断路器真空灭弧室外表面的电场强度,得出在不同填充材料、气泡和不同外绝缘材料时的电场强度及分布曲线;分析得出不同条件对真空灭弧室外表面电场强度的影响,用以提高户外真空断路器灭弧室外表面的绝缘性能。     

Application and monitoring of SF6 gas‐insulated NGR (neutral grounding resistor) using ceramic resistors

About 15 years have passed since ceramic‐resistor NGRs (Neutral Grounding Resistors) were developed as new materials for power equipment. This paper describes the cumulative numbers of applications of ceramic‐resistor‐type SF₆ gas‐insulated NGRs and the typical construction of the 22‐, 66‐, and 110‐kV NGRs, and also describes monitoring methods for measuring the residual leakage current of the 110‐kV NGR that depend on the neutral unbalance voltage of power transformers, and the use of thermal detection devices for the ceramic resistors of the 66‐kV NGRs. © 2001 Scripta Technica, Electr Eng Jpn, 137(4): 32–37, 2001     

基于红外的GIS内部导体温度检测技术研究

为预防气体绝缘金属封闭开关设备(GIS)触头过热缺陷,解决传统测温技术无法实现GIS设备内部触头温度准确检测的难题,提高GIS设备内部触头温度的测量精度,提出一种基于红外热成像GIS内部导体温度检测技术。通过不同光程和气压条件下SF_6吸收率试验,对影响红外测温精度的光程和SF_6气体压力进行分析,得到光程、气体压力与温度修正值的关系,并计算得到温度补偿算法;将该温度补偿算法应用在红外测温装置中,能够根据被测物的光程和SF_6气体压力准确测得GIS内部导体实际温度。最终的试验结果显示,该红外测温仪在加入补偿算法后能够较准确地测量出GIS设备气室内触头的实际温度。     

内陆核电500 kV配电装置型式比选

根据浙江省西部某核电项目的工程实际情况,对500 kV配电装置的多种型式,如空气绝缘敞开式配电装置(AIS)、SF6气体绝缘全封闭组合电器(GIS)和混合式配电装置(H-GIS)等,从技术、经济等方面进行详细的分析比较,并综合考虑核电厂的可靠性、安全性等因素,推荐500 kV GIS作为内陆核电的配电装置选型方案。     

中压真空断路器在保障城市电网供电可靠性中的应用

真空断路器技术的发展取决于两个技术的发展:真空灭弧室技术和操动机构技术。单稳态永磁操动机构真空断路器在这两方面研究取得的进步使中压真空断路器实现了小型化、高可靠性、长寿命和完全免维护。它是一种空气绝缘的全封闭型真空断路器,集操动机构和灭弧室于一体。它本身不含有任何有害气体,且尺寸小和免维护,可使空气绝缘的固定柜做到非常紧凑的程度。文章对这项出自前苏联军事试验室的研制成果及其应用作了介绍,并对其应用前景进行了评估。