太赫兹时域光谱技术在绝缘纸板微水含量检测中的应用分析

水分是电力设备油纸绝缘寿命的首要劣化因素。将太赫兹时域光谱系统（THz-TDS）引入到油纸绝缘微水含量测试中,利用太赫兹时域光谱系统对不同微水含量绝缘纸板样品进行测试,得到了不同太赫兹时域及频域响应信号结果并进行拟合,从而获得了可以初步估计纸板中水分含量的计算公式;最后结合太赫兹成像技术对纸板平面的水分不均匀分布情况进行了检测。由于水分子中的氢键在太赫兹波照射下会产生强烈的共振与吸收,在太赫兹透射波中产生明显的反馈作用,基于此原理可以将太赫兹检测技术运用于对绝缘纸板水分含量与分布的评估中。     

Mechanism of increase of electrostatic charging tendency in insulating oil for oil‐immersed transformer

The mechanism of the increase in the electrostatic charging tendency (ECT) of insulating oil and causative compounds were investigated by accelerated deterioration tests with the addition of various compounds. Although the ECT of the insulating oil was almost constant when only sulfoxide compounds were added, a marked increase was observed when either hydrochloric acid or moisture, which was considered to be generated by the aging of insulating oil, was also added to oil containing sulfoxide compounds. It is assumed that the sulfonium ion, which is generated by the reaction between sulfoxide compounds and hydrogen ion, is the compound that directly contributes to the increase in the ECT. Hydrogen ions can be supplied from organic acids generated by the oxidation of hydrocarbons in aging insulating oil. It is considered that the increase in the ECT of insulating oil is caused by the generation of sulfoxides by the oxidation of sulfide, which are present in fresh oil (originating compounds), and the generation of sulfonium ions by a reaction between sulfoxide and hydrogen ions, which are formed during aging. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 26–33, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21113     

Quantitative Evaluation of Corrosive Sulfur in Electrical Insulating Oil

This paper presents quantitative evaluation method of corrosive sulfur in insulating oil. The level of corrosion on copper strip which was aged in insulating oil is expressed numerically by the amount of sulfur on it. Since X‐ray strength by wave length dispersive X‐ray (WDX) and measurement value of sulfur on copper strip by titration show good correlation, the amount of sulfur can be obtained rapidly only by WDX. The performance of passivator such as BTA or Irgamet39 was quantitatively evaluated by WDX. The evaluation of life of passivator was also achieved. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Effects of antioxidants and acids on copper sulfide generation and migration induced by dibenzyl disulfide in oil‐immersed transformers

This study aims to explore the effect of the antioxidant 2,6‐di‐tert‐butyl‐p‐cresol (DBPC) and acids on the generation and migration of copper sulfide on insulating windings as a result of the reaction of dibenzyl disulfide (DBDS) and copper in oil‐immersed transformers. The heating experiments were conducted by adding different amounts of DBPC and different kinds of acids to the naphthenic mineral oil. The result indicates that acids can accelerate the generation of copper sulfide and that DBPC cannot effectively consume DBDS to reduce the corrosion phenomenon, but rather accelerates the deposition of copper sulfide onto the insulating paper. In particular, when the DBPC concentration is approximately 0.9% (w/w) at 130 °C for ten days, the amount of copper sulfide deposited on the insulating paper reaches its maximum. Moreover, excessive use of the antioxidant DBPC accelerates the aging of insulating oil, on the contrary, which adversely affects the mineral oil. Although the addition of DBPC can improve the antioxygenic property of mineral oil, too much of it is inadvisable because the transformers that contain DBPC and DBDS may be at high risk and suffer from breakdown. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

纳米绝缘油交流击穿特性分析

绝缘油填充于各型变压器、电力电容器等充油电力设备中,起绝缘、导热、灭弧等作用,在电力系统中有着广泛地应用。随着输电电压等级的不断提高,对绝缘油提出了更高的要求,因此提高绝缘油性能,对中国特高压发展具有重要意义。由于纳米粒子的尺寸效应,传统的小桥击穿理论可能将不再适用,为改善绝缘油的性能提供了新的途径。笔者研究了纳米绝缘油的制备方法,并对不同质量分数纳米粒子的绝缘油进行了交流击穿电压实验。研究结果表明,适当质量分数的纳米粒子能有效地改善绝缘油的交流击穿特性。应用纳米粒子球形介质极化模型,计算了粒子表面产生的势阱,并指出了纳米粒子改善绝缘油击穿特性和添加纳米粒子过多导致绝缘油的击穿性能降低的原因。     

Application of a novel polypropylene to the insulation of an electric power cable

Cross‐linked polyethylene (XLPE) has been widely adopted as insulating material for high‐voltage power cables up to 500 kV. Further improvement of electrical and thermal properties on insulating material is required in order to increase cable operation efficiency. Therefore, the development of novel insulating material possessing high thermal properties will be necessary. Recent progress of catalysis technology contributes to obtain new polymeric materials which may be applied to electrical insulation. The authors investigated the basic properties of newly developed stereoregular syndiotactic polypropylene (s‐PP) which is synthesized with homogeneous metallocene catalyst. Though recycling of cross‐linked polymers such as conventionally used XLPE may be difficult because of their poor heat deformation, the s‐PP which is not cross‐linked must be suitable for recycling. A series of experiments on its physical and electrical properties gave the following results.

• (1) s‐PP has sufficient flexibility compared with isotactic polypropylene (i‐PP ).
• (2) Both AC and lightning impulse breakdown strength of s‐PP in spite of no cross‐linking are superior to those of XLPE in the temperature range from 25 to 90 °C.
• (3) Degradation by copper of s‐PP is less than that of i‐PP.
• (4) s‐PP/VLDPE blend shows sufficient brittleness temperature for use.

These results suggested that s‐PP should serve as insulating material for power cables at higher‐temperature operation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 18–26, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002//eej.10210     

不同场强下新型绝缘聚合物的变色特性及其介电特性

为了依靠绝缘材料在电场下的颜色变化判断电力设备带电状态,制备了等规/无规聚（3-己基噻吩）（poly(3-hexylthiophene),P3HT）共混薄膜。研究发现,等规P3HT纳米微晶在共混薄膜顶部均匀分布。随无规P3HT含量的上升,共混薄膜沿厚度方向表现出更好的绝缘性能。在无规P3HT含量为95%时,共混薄膜的工频介电常数为5.86,电阻率为3.2 T Ω·cm,直流击穿场强达到113 kV/mm。通过空间电荷积累光谱发现,当电场强度大于40 kV/mm时,电荷主要积累在绝缘的无规P3HT中,且共混薄膜吸收光谱450 nm处峰强度随电场强度的增加而升高,实现了空间电荷驱动的绝缘体系电致变色,为电力设备绝缘带电状态检测提供了新方法。     

High Dynamic Range Measurement with Arrayed Frequency Converter

When measuring multicarrier communication systems such as an orthogonal frequency division multiplexing (OFDM) or UWB wireless signal, there is a problem that the effective measuring dynamic range of the measuring instrument may be reduced, since the peak‐to‐average power ratio (PAPR) of the measured signal is significantly high. In order to solve this problem, we propose a technique that maintains the measuring dynamic range by dividing the measured signal into multiple bandwidths to decrease the measured signal power. We made a prototype of the measuring equipment, confirmed the operation of the algorithm, and verified the effectiveness of dynamic range improvement is 5 to 8 dB in relation to a conventional circuit. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(2): 28–35, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22367     

Influence of Measurement Parameters on Frequency Response Analysis Diagnosis of Oil‐Immersed Transformer

Appropriate monitoring and maintenance become important as an oil‐immersed transformer ages. Generally, dissolved gas analysis (DGA) is effective for the online diagnosis, and if an abnormality is detected, frequency response analysis (FRA) is effective for the offline diagnosis to localize the failed part. FRA diagnosis detects a slight change of waveforms; however, external factors may influence the results. Here, we discuss the influence of an insulating oil presence, tap position, and measurement lead wire length as possible parameters that influence the FRA characteristics. We confirmed that the measurement parameters examined here greatly influenced the FRA characteristics. In the actual diagnosis, it is important to remove these external parameters as much as possible, and keep a detailed record of the measurement parameters. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 18–25, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22313     

Application of Kalman filter to hot‐spot temperature monitoring in oil‐immersed power transformer

Winding hot‐spot temperature (HST) is an important factor that affects the insulation life of an oil‐immersed power transformer. Thus, precise prediction and close monitoring of HSTs are necessary to avoid thermal damage. In this paper, a differential equation for HST prediction is presented, which takes into consideration the effects of the top‐oil temperature variations and thermal dynamics of the load. A discrete form of this equation based on the framework of the Kalman filter (KF) algorithm was used to establish a real‐time estimation model for the HST. The KF‐based model was validated by a sample heat‐run test involving a transformer setup in the laboratory. Moreover, the proposed model was applied to a real, large power transformer and compared with the classical IEEE‐Annex G method. Results show that the HSTs estimated by the KF‐based model are closer to the measured values. The exhibited potential applicability and generality in real‐time prediction for HST demonstrate that the proposed model can be employed for online monitoring of HSTs for large power transformers. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Breakdown characteristics of oil and paper insulation for a very fast transient voltage

This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043     

Control of fault current limiter by series‐connected voltage sag compensator

This paper describes a control scheme of fault current limiter by series voltage injection. The current limiter proposed in this study is based on the use of a SMES‐based series‐connected voltage sag compensator, which has been previously studied by the authors, for controlling fault current caused by short circuit on the load side. An algorithm for fast discriminating between power system voltage sag and load‐side short circuit is proposed for the equipment to correctly function either for voltage sag compensation or for fault current limiting purpose. Furthermore, a new control strategy based on output voltage phase control of the series compensator is proposed for current limiting with good waveform characteristics and low active power absorption. Experimental results demonstrated the validity of the proposed strategy. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(2): 64–72, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20128     

Energy Conservation in Urban Areas

This article outlines the energy conservation measures in the civilian sector from a few different viewpoint regarding energy conservation in cities. First, the energy consumption trends in the business and residential sectors are discussed, focusing the importance of energy conservation measures in applications such as home heating, water heating and specific power demand. Second, as a measure to reduce energy demand itself, energy conservation by way of applying heat insulating materials to buildings and changing the life style of residents is considered. And from the viewpoint of improving the energy system efficiency, additionally discussed here are the measures to improve the efficiency of each energy equipment such as air‐conditioners and co‐generation equipment, and the characteristics of District heating and cooling systems such as the local energy infrastructures. Lastly, from the knowledge obtained through model analyses by the authors, a scheme is recommended that would be one of the most efficient city‐energy schemes where the energy systems including heat pumps, co‐generators or equipment using solar power are utilized for their best‐suited applications for business and residential customers. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Influence of various compounds on electrostatic charging tendency in insulating oil

The influence of various compounds on the increase of the electrostatic charging tendency (ECT) in insulating oil was investigated. Sulfide compounds, which are contained in new mineral oil, are identified for the first time as the original materials involved in the increase of the ECT. This is verified by heating tests of alkylbenzene with the addition of various compounds. Coexistence with copper and injection of oxygen enhance the increase of the ECT. Some sulfide and sulfoxide compounds increase the ECT markedly. On the other hand, the influence of sulfones, which are oxidation products of sulfoxides, is negligible. Although sulfonic acids, which are oxidation products of sulfones, markedly increase the ECT, the polarity is reverse. Thus, the ECT is influenced by the kinds and the molecular structures of additive sulfur compounds. The influence of nitrogen compounds and that of oxygen compounds are confirmed to be smaller than that of sulfur compounds. Since the amounts of nitrogen compounds and oxygen compounds are much smaller than those of sulfur compounds in mineral insulating oils, the influence of these compounds is considered negligible. Since the ECT of oils with the addition of sulfides or sulfoxides increases after heating, the other compounds should be created from these compounds that increase the ECT directly. Thus, the increase of the ECT is mostly caused by the oxidation of sulfides, which creates sulfoxides. Then certain compounds, which directly increase the ECT, are created from sulfoxides. If sulfones or sulfonic acids are created by the oxidation of sulfoxides, the ECT decreases because of the influence of these compounds on the ECT. It is most likely that some process other than oxidation occurs in the creation of the compounds that increase the ECT directly. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(3): 29–36, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21112     

Estimating Power Outage Costs Based on a Survey of Industrial Customers

Thousands of factories in Japan responded to a survey on power outage costs for industrial customers. From across the country, 5139 facilities designated as energy management factories answered questions about their power consumption and the loss of production value due to a hypothetical hour‐long power outage on a summer weekday. Using their responses, we estimated the median unit cost of a power outage across all sectors to be 672 yen/kWh. The service sector of amusement and hobbies and the manufacturing sector that makes electronic information and communication equipment have relatively high unit costs for power outages. The direct cost of damage from a specified power outage across all sectors totaled 77 billion yen. Using input–output analysis, we estimated the indirect damage costs caused by the repercussions of halting production. Indirect damages across all sectors totaled 91 billion yen. The wholesale and retail trade sector had the largest direct damage costs, while the transportation equipment manufacturing sector has the largest indirect damage costs. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(4): 25–32, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22306     

Technologies for Energy Saving in Industrial Field

This paper summarizes practical and developed techniques and technologies for energy saving in the industrial field. Newly developed high‐efficiency electrical equipment or combined technologies, which are about ‘power electronics’, ‘microcomputers’ and ‘motion control’ in addition to the progress of sensing devices and monitoring systems, bring both energy saving and high productivity in the factory. The technology trend of new factory facilities is concerned about changing power sources from pneumatic (compressed air) or hydraulic power (oil system) to electrical direct‐driven servomotor systems, which have the technical characteristics of fine‐grained and regenerative control. These technologies are able to reduce and recover idling (standby) power consumption during the holding period at the production stage in the factory. The items in this paper were published as Technical Report No. 988 in January 11, 2004 by IEEJ, and that report is reviewed and updated in this paper. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

TLM simulation of microwave hybrid sintering of multiple samples in a multimode cavity

Microwave heating technology is a powerful mean to ensure successful sintering of ceramic materials. In sintering experiments, low loss insulators, conductors and high‐loss ceramics are microwaved so as to get optimal mechanical and structural properties. It is known that low‐loss ceramic materials such alumina and zirconia exhibit long waiting time before reaching a critical coupling temperature at which microwaves can be readily absorbed. On the other hand, some ceramics such as silicon carbid have a high loss factor and therefore can be used as a process stimulus for microwave sintering of microwave transparent ceramics. Furthermore, successful sintering experiments often require the use of carefully designed insulating structure in order to minimize thermal gradients caused by heat loss from surfaces. All these problems have led to the introduction of microwave hybrid heating (MHH) schemes using higher dielectric loss susceptors, insulation or coating. Since MHH depend mainly on human expertise, the optimization of sintering experiments will certainly benefit from numerical simulations. The transmission line matrix (TLM) is used to study two MHH schemes where both a susceptor and an insulating matrix were, respectively, used as process stimulus for microwave heating of multiple alumina samples within a three‐dimensional multimode cavity. The effects of such MHH schemes and target settings on electric field distribution and power absorption rates are reported in this paper. Copyright © 2003 John Wiley & Sons, Ltd.     

Development of a DC −1 MV insulating transformer for neutral beam injectors

A DC −1 MV insulating transformer has been developed for the power supply of the neutral beam injector (NBI ) at ITER (International Thermonuclear Experimental Reactor) . A DC long‐pulse −1 MV insulation structure between the primary and secondary windings, considering potential variation in the insulator for DC long pulse, has been designed. Simultaneous development of a compound bushing, which consists of an AC 500 kV condenser bushing inside a cylindrical fiber‐reinforced plastic tube, has been carried out. The DC −1 MV insulation design has been verified by high‐voltage insulation tests of AC 50 Hz 1300 kV peak for 1 min, DC −1200 kV for 1 h, and a long‐duration test of DC −1060 kV for 5 h. The results showed that the insulating transformer satisfies the power supply requirements for the ITER NBI . Copyright © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Measurement of topcoat thickness of thermal barrier coating for gas turbines using terahertz waves

The topcoat thickness of thermal barrier coating (TBC) samples was measured using terahertz (THz) waves. The index of refraction of yttria‐stabilized zirconia (YSZ), which is the topcoat material, is necessary to obtain the topcoat thickness from time domain re?ectometry. Time domain THz spectroscopy was applied to YSZ samples, and the index of refraction was measured to be 4.8 in the frequency region 0.1 to 1.2 THz. The topcoat thickness of six di?erent TBC samples, which varied from 300 to 600 µm, was measured using THz waves. The results were in agreement with microscope observation results to within measurement error. In addition, the topcoat thickness pro?le of a turbine blade sample was measured with a resolution of 2.4 µm. The pro?le showed a standard deviation of 4 µm, which re?ects the actual variation in the topcoat thickness. The results showed that THz waves are e?ective for high‐resolution measurement of the topcoat thickness. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 1–9, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22385     

Research on influencing factors of corrosive sulfur attacking copper in insulating oil and prevention

The influencing factors (temperature, electric field, and oxygen) of sulfur attack in transformer oil are studied through comparative tests on new oil, oil in service, and these two oils with the deactivator additive BTA (benzotriazole, C₆H₄N₃H). The influence of these factors on the chemical reaction between copper and corrosive sulfur is analyzed in further. The results show that temperature, electric field, and oxygen can promote the reaction between copper and corrosive sulfur. Moreover, oxygen also accelerates the aging of the insulating oil. On the contrary, recharging nitrogen can remove oxygen and reduce sulfur's corrosive activity. Adding the BTA deactivator can also prevent corrosion, even during the accelerated aging of oil with oxygen. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.