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     

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     

Insulation technology in dry air and vacuum for a 72‐kV low‐pressure dry‐air insulated switchgear

A new 72‐kV rated low‐pressure dry‐air insulated switchgear applying electromagnetic actuation and a function that supports CBM has been developed. First, the dielectric characteristics in dry air under lightning impulse application were investigated for bare and insulator‐covered electrodes. The dependence of the breakdown electric field strength on the effective area was found in order to apply it to the configuration design of the insulation mold for the vacuum interrupter. In addition, the dependence of the moisture volume on the surface resistance was found in order to decide the moisture volume in the gas pressure tank. Next, a new vacuum circuit breaker (VCB) was designed. To keep the dimensions the same as in the previous 72‐kV SF₆ gas insulated switchgear, the distance between contacts in the vacuum interrupter must be shorter than in the previous switchgear. The voltage withstand capability between electrodes practically designed for the vacuum interrupter was investigated under DC voltage application, in a small capacitive current breaking simulation. The gap configuration, including contacts and slits, was optimized and the distance was shortened by 11% from the previous switchgear. As a result, the new low‐pressure dry‐air insulated switchgear was designed to be comparable in external size to the previous SF₆ gas insulated switchgear. Using dry air as an insulation medium with low pressure makes it possible to reduce the environmental burden. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(1): 18–24, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21058     

高海拔地区500 kV电缆户外终端用复合空心绝缘子的设计

对高海拔地区500 kV电缆户外终端用复合空心绝缘子进行设计,复合空心绝缘子爬电距离为32000 mm,结构高度为7990 mm.通过材料选择和生产工艺控制,保证复合空心绝缘子的优异性能;弯曲试验破坏值为设计值的1.24倍,验证设计的产品能够承受电缆户外终端运行时的外力影响.     

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     

Re‐ignition surge and high‐frequency arc extinction phenomena at 550‐kV shunt reactor current interruption

At substations connected with transmission lines and cables, shunt reactors are sometimes installed to compensate the capacitive current of these lines and cables. It is known that re‐ignitions occur and high‐frequency currents flow during interruption of the shunt reactor currents by switches. When the high‐frequency currents are interrupted immediately after the re‐ignitions (which is called high‐frequency arc extinction), the result is often repetitive re‐ignitions or voltage escalations that produce dangerous overvoltages. The authors investigated the occurrence of high‐frequency arc extinctions in a 550‐kV one‐break SF₆ gas circuit breaker during interruption of a 550‐kV shunt reactor current. Computations for a real 550‐kV substation gave a minimum frequency of 290 kHz for the high‐frequency current. However, 550‐kV reactor current interruption tests showed that high‐frequency arc extinctions did not occur even when this frequency was lowered to 26 kHz. Since high‐frequency arc extinction is generally likely to occur at lower frequencies, it was concluded that high‐frequency arc extinction will not occur in a 550‐kV one‐break SF₆ gas circuit breaker during interruption of shunt reactor current in real substations. © 2001 Scripta Technica, Electr Eng Jpn, 136(2): 18–25, 2001     

500kV吊串复合绝缘子断裂原因分析

通过对500 kV潍崂线277号铁塔故障吊串复合绝缘子的检查,并和该线路同周期运行的2支非故障吊串进行对比试验,原因为硅橡胶护套由于电蚀、外力等长期作用下护套穿孔,导致芯棒与外界接触,芯棒长期腐蚀作用下断裂,提出了相应的预防措施。     

1000kV交流复合绝缘子均压环参数设计

为了将1000kV交流特高压输电线路复合绝缘子沿面电场分布控制在合理的范围内,根据复合绝缘子的特点,采用场域分解的方法将三维无界场域分解成有界子区域,选择使用有限元法进行1000kV交流输电线路复合绝缘子串沿面电位、电场分布计算及均压环参数优化设计。应用ANSOFT软件建立1000kV交流线路带杆塔、导线的全三维模型,研究了均压环的管径、环径和抬高距离对绝缘子电场分布影响的规律,从控制电场强度的角度出发得到了均压环结构参数的配置方案。三维计算结果表明,安装了均压环后,复合绝缘子护套、金具、均压环表面最大电场强度均可以满足要求,绝缘子沿面电位分布的均匀性也得到了提高。金具可见电晕和无线电干扰试验的结果表明,高压端金具和均压环的起晕电压、无线电干扰均符合国家标准要求。     

220 kV同塔双回线路钻越500 kV线路的方案选择

针对220 kV同塔双回线路钻越500 kV线路的方案选择问题,分析了钻越方案的制约因素,采用改变地线悬挂形式、导线排列方式、跳线绝缘子串型式等措施,进行了钻越塔的设计和优化,设计了双回鹰嘴蝶型耐张塔。经工程实际应用证明,该型耐张塔具有良好的推广前景,为220 kV同塔双回线路钻越500 kV线路提供了一种可行的解决方案。     

500KV线路自然积污规律试验研究

本文介绍了一种测量５００ｋｖ线路绝缘子串自然污盐密串平均值测量的新方法，总结了各种号绝缘子的积污规律，以及塔高；电压等级对绝缘子积污的影响。为５００ｋＶ线路绝缘、绝缘子选型，污秽研究和线路清扫等提出了科学依据。     

Development of Y‐branch joint for 275‐kV XLPE and fluid‐filled cable

When a new UHV substation is built in an urban region, generally, an existing underground transmission line will be diverted and drawn into the new substation. Compared with the latter construction method, enormous cost reduction of switching facilities and cable construction is expected when applying a Y‐branch joint (YJ) which is able to serve as a three‐way joint. The YJ has already been applied for 154‐kV‐class circuit, but it has not been investigated for 275‐kV‐class circuit. Since both XLPE and oil‐filled cable are presently used in 275‐kV‐class underground cable line, a universal design YJ for both cables has been investigated. The YJ was applied in a compact design which was based on our sophisticated electrical stress control technology for 500‐kV prefabricated‐type joint. Furthermore, the design was based on its prefabricated assembling technology. The YJ was verified as to its electrical and mechanical performance as 275‐kV cable joint by completion of its assembling test and a long‐term electrical test. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 18–24, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20514     

4‐kV 100‐Mbps monolithic isolator on SOI with trench isolation for wideband networks

Two types of monolithic isolator on a silicon‐on‐insulator (SOI) with trench isolation have been fabricated. One is a multitrench isolator with polysilicon resistors in which two circuit areas are isolated using thirty‐four 0.4‐µm‐wide trenches on an SOI. The inequality in the voltages applied to the trenches is reduced by using polysilicon resistors parallel to the trenches, which increases the isolation voltage from 2.6 to 4.0 kV. The other is a spiral wide‐trench isolator in which two circuit areas are isolated using two spiral 10‐µm‐wide trenches. Monocrystalline silicon is used as a resistor to reduce the inequality in the trench voltages. Signals are transmitted between the two circuit areas through two series of high‐voltage capacitors: silicon on buried oxide and a third metal are used as electrodes. A network interface large‐scale integration (LSI) with a four‐channel isolator was fabricated using multitrench isolation. It provides 4‐kV isolation and supports 100‐Mbps transmission. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

±800 kV同塔双回直流输电工程绝缘配合研究

随着特高压电网的不断建设,可供特高压输电线路经过的通道逐渐变得有限,线路走廊的矛盾日益突出。为提高现有输电走廊的利用效率,有必要研究±800 kV特高压线路同塔双回输电技术。对换流站电气设备和架空输电线路的绝缘配合研究认为,换流站电气设备的绝缘水平,可与以往单回线的相同。对于±800 kV同塔双回输电线工程,由于线路之间的互感作用,其参数会有所改变,对线路上的过电压水平产生一定的影响。±800 kV同塔双回输电线路采用V形绝缘子串的悬挂方式,与中国以往±800 kV单回V形绝缘子串水平排列的悬挂方式有较大的差别。分析研究表明,±800 kV同塔双回输电线工程的空气间隙,决定于操作过电压。依据±800 kV同塔双回输电线工程操作过电压仿真计算,以及±800 kV同塔双回真型塔放电特性试验研究结果,进行了绝缘配合研究,推荐了±800 kV同塔双回直流线路最小空气间隙距离。     

Development of pre-molded normal straight joint for 66 kV XLPEcables for short-term use

A premolded normal straight joint for 66 kV cross-linked polyethylene (XLPE) insulated power cables that requires less time and skill in jointing was developed for temporary applications. This plug-in type ethylene-propylene rubber (EPR) normal straight joint has an expected useful life of one year. In various tests carried out on the developed joints, it was shown that the joint can be assembled quickly (in about one hour) without requiring much skill. The initial characteristics tests revealed that these joints are satisfactory for 66 kV XLPE cables. The expected performance of the joints are confirmed in long-term tests and in subsequent residual performance tests     

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     

Observation of lightning at 500‐kV transmission lines (part 1)

We investigated the phenomenon of lightning strokes on 500‐kV transmission lines from 1984 to 1993. The investigation covered the recording of lightning paths by still cameras and measurements of lightning current at the lower part of transmission tower on 31 towers, over a 12.7‐km‐long section of the transmission line. We also observed lightning on an isolated tower at a nuclear power station. In the course of lightning observations spanning a 10‐year period, we have confirmed the suitability of the lightning protection design on transmission lines. The distribution of lightning incidence angle (θ) expressed in terms of (cos^mθ) was characterized by exponent m = 2 for the three‐dimensional observations and m = 3.5 for the two‐dimensional observations. No cases of shielding failure on 500‐kV transmission lines were observed. The ratio of lightning current at the top of the isolated tower to the lower part was about 11 to 1. In addition, the lightning current waveform at the top of the isolated tower was similar to that at the lower part. © 1999 Scripta Technica, Electr Eng Jpn, 130(2): 59–67, 2000     

110 kV输电线路不挂绝缘子复合材料绝缘横担的研制与应用

随着电网建设的发展,深化纤维增强聚合物（fiber reinforced polymer,FRP）复合材料在输电线路上的应用与研究十分必要。在前期绝缘横担研究的基础上,完成了110 kV不挂绝缘子复合材料绝缘横担的设计和制造工作,并实现安全挂网运行。测试结果证明,该横担改变了传统横担需要悬挂绝缘子的特点,降低了风偏闪络的风险;改善了硅橡胶伞裙绝缘横担不可走人,易受虫鸟侵蚀的缺点;同时又不像瓷绝缘横担那样容易脆裂受损。因此,这种新型复合横担更具研究前景。     

Application of the AC Superposition Method to Degradation Diagnosis of 22/33‐kV Class XLPE Cables

Water trees in the insulator of XLPE cable may considerably reduce the dielectric breakdown voltage, thus being an important lifetime‐governing factor. The ac superposition method we have investigated is a new technique for hot‐line diagnosis of 6.6‐kV XLPE cables, and the diagnostic apparatus using this technique is now widely used in the distribution line field. In order to study the application of the ac superposition method to degradation diagnosis of 22/33‐kV class XLPE cables, we measured deterioration signals of the cables with water trees by a modification of the above diagnostic apparatus. The deterioration signals, hereafter called “ac superposition current”, were generated by an amplitude modulation effect due to the nonlinear resistance of water trees. Moreover, we evaluated the relationship between the ac superposition current and the ac breakdown voltage. It is difficult to judge whether a correlation between then is present or not because of the uneven distribution of the measured data. However, the ac superposition current tends to increase linearly with a decrease in the residual thickness of the insulator. For example, the ac superposition current was about 40 nA when the residual thickness decreased to 3 mm. Thus, we consider that the ac superposition method is effective for degradation diagnosis of 22/33‐kV class XLPE cables.     

1 000 kV交流双回路单柱组合耐张塔型式规划

针对在1000 kV交流特高压双回输电线路中使用鼓(伞)型耐张塔的不足,设计了一种全新的耐张塔型——单柱组合耐张塔,其特点是分塔挂线、无导线横担、水平布置跳线、灵活性好、施工方便等,与鼓(伞)型塔相比,在杆塔高度、塔重、横担长度、跳线等方面的技术经济性较为优越。最后提出了该塔在电磁环境、跳线、防雷等设计方面需要进一步探讨的技术问题。     

带电更换±800kV直流输电线路直线塔V串合成绝缘子方法研究

研究带电更换±800 kV直流输电线路直线塔V串整串绝缘子方法。研制出了六联板专用夹具,选定承力工具的吊点为导线正上方的横担上梁主材交汇处。合理的吊点确保了绝缘承力工具的有效绝缘长度大于6.6 m,成功实现了带电更换±800kV直流输电线路直线塔V串整串绝缘子,大大提高了供电可靠性。