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As the deregulation of the electric power industry moves forward, there is an increasing need for cost cutting and it is becoming exceedingly important to keep track of the residual life and identify the timing of replacement for power transmission equipment that has aged for several tens of years in the field. This paper, taking up the theme of 'insulation degradation phenomena and lifetime evaluation for power transmission equipment', conducted cross-sectional comparison of different types of equipment although this kind of evaluation was made independently for these equipment types so far. This paper covered six types of equipment: gas insulated switchgear (GIS), gas insulated transformers, oil filled (OF) transformers, OF cables, crosslinked polyethylene (XLPE) cables, and power capacitors. As a result of examining the characteristics such as electric, thermal, mechanical, and hygroscopic degradations, each of these equipment types was found to have distinctive Voltage-time (V-t) and Voltage-number (V-N) characteristics, which sometimes greatly varied from those of others. Since thermal degradation is dominant for gas insulated transformers and oil filled transformers, their lifetimes depend on the reduction of mechanical strengths of Polyethylene Terephthalate (PET) or insulating paper. Therefore, it is effective to diagnose decomposition products such as CO, C[O.sub.2] and furfural generated in the thermal degradation mechanism. On the other hand, the influence of electric degradation has more significant impact on the other equipment types except OF cables. Such GIS components as epoxy spacers, XLPE cables, and power capacitors for which long-term ac voltages are dominant, are commonly characterized by the long-term V-t characteristics with a large gradient (small n-value). In terms of insulation structures, there is a possibility of reducing the degree of degradation by improving solids or the interface between solids and electrodes. Index Terms--Power transmission equipment, insulation degradation, lifetime evaluation, cross-sectional comparison.

Because of the excellent high insulation performance, vacuum is expected to be one of the alternatives of [SF.sub.6] gas. In order to reduce the use of [SF.sub.6] gas in substation equipment, the applicability of vacuum circuit breakers (VCB) and vacuum interrupters (VI) should be extended to higher (typically 145-300 kV) voltage. For the high voltage VI, the role of electrical insulation design becomes more important. For accurate insulation design of the VI, we developed an optimization technique to improve the electrical insulation performance. We evaluated several design variables necessary, for optimizing the electrode contour of the main contactor and center shield in VI. The electrode area effect on vacuum breakdown characteristics as well as the electric field distribution was considered in the optimization process. In order to verify the accuracy and the efficiency of the proposed technique, we applied it to a practical model of VI. In addition, we examined the influence of the parameters of the area effect, arrangement of VI in VCB on the optimization result. From the calculation results, we confirmed that the optimization based on the area effect had higher availability and higher accuracy than the electric field optimization from the viewpoint of the improvement of the electrical insulation performance of vacuum insulated equipment. Index Terms--Numerical optimization, vacuum interrupter (VI), vacuum insulation, area effect, center shield electrode.

Gas insulated Switchgears (GIS) are widely used as major substation equipment because of their excellent insulation and interruption performance. However, while a GIS is highly reliable, it is a concealed device, meaning diagnostic technology using various sensors is required to detect any insulation abnormality. Among various potential defects inside a GIS, the most problematic is caused by the existence of fine metallic particles, and thus the ability to detect harmful particles in tests at a factory and on site as well as in operation is becoming an important subject. This paper examines, on an experimental basis, the UHF sensor's characteristics of detecting partial discharge (PD) signals generated from particles inside the GIS with those placed freely on the bottom surface of the tank, having adhered to the insulating spacer's surface, and fixed on the center conductor, respectively. Based on previous reports, breakdown characteristics with the existence of particles were arranged in terms of the particle length, and the harmful particle length was estimated. Both results were compared with each other to evaluate the possibility of detecting harmful particles in each location with the UHF sensor. Consequently, it emerged that free particles were detected comparatively easily. However, while those having adhered to the spacer's surface and fixed on the center conductor could be detected in insulation tests at 2 pu at a factory, detection was difficult in many cases in the field. Index Terms--Gas insulated switchgear, GIS, metallic particle, harmful particle length, partial discharge, PD, UHF sensor.

Partial discharge (PD) measurement allows detection of insulation defects in various electric power apparatus before an insulation failure occurs. It can also improve the reliability of the insulation performance of apparatus, and support rational and economical design, lifetime prediction, and nondestructive inspection. Historically speaking, PD detection methods have evolved in each category of apparatus and power cables. However, there does not seem to exist what we call universality in PD detection technology that is available to all kinds of power equipment. This article specifically describes features, similarities, and differences of partial discharge measurement and diagnosis technologies for electric power apparatus used in transmission and distribution. The main task of this article lies in not simply reviewing PD measurement and diagnosis techniques but trying a cross-equipment evaluation. First, this article deals with similarities and differences among partial discharge detection techniques for typical power apparatuses including gas insulated switchgear, oil-immersed transformers, and power cables. In particular electrical measurement technology and electromagnetic measurement technology are compared selectively. The second subject is to describe signal-processing technologies, and discuss similarities and differences among equipment in terms of noise removal, location identification, and foreign particle identification. Finally, judgment methods and judgment criteria for equipment diagnoses as a whole are analyzed and described. These discussions are expected to clarify the positioning of the partial discharge measurement technologies for various equipment among all electric power apparatus, and support technological development in the future. Index Terms--Electric power apparatus, partial discharge measurement, total assessment, partial discharge detection technology, signal processing, judgment criteria.

This paper reviews the up-to-date research activities on electrical insulation techniques under repetitive surge voltages with steep wavefront for low voltage inverter-fed motors. Partial discharge (PD) inception, propagation, ageing and breakdown characteristics of magnet wires, including recently developed PD-resistant wires such as nanocomposite enameled wires, are described. PD measurement techniques under the steep-front voltages and IEC activity toward their standardization are also introduced. Index Terms--Inverter-fed motor, inverter surge, partial discharge, lifetime, ageing, PD-resistant wire, nanocomposite, standardization, IEC.

From the viewpoint of mitigating global warming by S[F.sub.6] gas, this paper discusses breakdown (BD) characteristics of different electronegative gas mixtures with [N.sub.2]O gas as S[F.sub.6] gas substitutes for quasi-uniform electric field under lightning impulse voltage applications. Experimental results revealed the positive synergism in breakdown strength of binary [N.sub.2].O/C[O.sub.2] and ternary [N.sub.2].O/C[O.sub.2]/[O.sub.2] gas mixtures, respectively. Furthermore, [N.sub.2] gas as a retardant gas was also mixed with the electronegative gas mixtures in order to reduce the electron energy into the effective levels of electron attachment ability by the electronegative gas mixtures. As the result, ternary [N.sub.2].O/ C[O.sub.2] / [N.sub.2] and quaternary [N.sub.2].O / C[O.sub.2] / [O.sub.2] / [N.sub.2] gas mixtures could exhibit the significant synergistic effect in breakdown strength. The optimum mixture rate of quaternary [N.sub.2].O /C[O.sub.2]/[O.sub.2]/[N.sub.2] gas mixtures was consistent with that estimated by assuming the independent contribution of component gases to the improvement of impulse BD characteristics. Index Terms--GIS, impulse breakdown, [N.sub.2].O gas, S[F.sub.6] substitutes.

The thermal runaway properties of a conduction-cooled Bi2212 High Temperature Superconducting (HTS) coil are examined. Findings reveal the effectiveness of monitoring the coil temperature and current for the diagnosis of the thermal runaway under the compensating operation for load fluctuations.

We investigated the charging characteristics of alumina in vacuum with varying surface roughness, and the electric field distribution. The charging on the alumina surface in vacuum is, in general, strongly influenced by field electron emission (FEE) and secondary electron emission avalanche (SEEA). We varied the surface roughness and the electric field distribution on the alumina surface in order to control the FEE and the SEEA. Under these conditions, we measured the 2-dimensional distribution of surface charging potential on the alumina surface. From the measurement results, we quantitatively discussed charge polarity and charge density on the surface for various types of electric field distributions. Finally, we successfully propose a concept of a charging control technique on the alumina insulator in vacuum for the improvement of electrical insulation performance on the alumina surface. Index Terms--Charging characteristics, vacuum, surface roughness, alumina insulator, electric field distribution, secondary electron emission avalanche (SEEA).

S[F.sub.6] gas has been widely used in electrical power equipment such as circuit breakers and transformers due to its superior insulation and interruption characteristics. However since 1997, S[F.sub.6] gas has been designated a greenhouse gas subject to emission restrictions at COP3 (The 3rd session of the Conference Of the Parties to the United Nations Framework Convention on Climate Change) so a new insulating gas is needed as a substitute for S[F.sub.6] gas. This research considers the use of high-pressure C[O.sub.2] gas as an insulator while stressing the environment aspects. Fundamental insulation data for the insulating gas acquired supposing gas insulated switchgears (GIS) consists of; (1) insulation breakdown characteristics under clean conditions and, (2) insulation breakdown characteristics with metallic particle contamination. The parameters in this case were assumed from an actual apparatus viewpoint, to be a high gas pressure up to 2.0 MPa, an electrode size capable of determining the surface area effect, the electrode surface roughness, and metallic particle length, etc. at the base electrode of the 72 kV GIS. As a result, experiments using these parameters revealed insulation characteristics for high-pressure C[O.sub.2] gas and that negative lightning impulse decided the insulation design, as well as the present S[F.sub.6] GIS. The need for taking measures to suppress PD under ac voltage and also the need for restricting metallic foreign particles around the central conductor and insulating spacer were recognized. Index Terms--Insulating gas, S[F.sub.6] substitute, C[O.sub.2] gas, gas insulated switchgear (GIS), insulation breakdown characteristics, clean condition, metallic particle.

In inverter-fed motor coils, surge voltages with the rise time of several tens or hundreds of nano-second may cause partial discharge (PD) and degradation of electrical insulation performance of the inverter-fed motor coils. This paper discusses PD inception characteristics as well as PD propagation characteristics after PD inception for magnet wire of inverter-fed motor under surge voltage application. Experimental results firstly revealed that PD inception voltage (PDIV) decreased with the increase in the length of enamel-coated wire, which was evaluated in terms of the stressed wire contact length under surge voltage application, i.e. size effect. We proposed a regression line for the size effect on PDIV for the electrical insulation design of inverter-fed motor coils. Secondly, PD propagation characteristics were also investigated under the higher voltage application, and their mechanisms were discussed in terms of generation probability of initial electrons, space charge behavior in the wedge-shaped air gap, charging on the enamel surface and so on. Index Terms--Inverter-fed motor, inverter surge, partial discharge, inception voltage, initial electron, charge behavior.

This paper describes the propagation characteristics and mechanisms of partial discharge (PD) leading to breakdown (BD) in electronegative gases such as S[F.sub.6]/[N.sub.2] and [C.sub.2][F.sub.6]/[N.sub.2] gas mixtures for ac voltage application. An established PD measuring system of highly time-resolved PD current and light intensity waveforms, streak and light emission images enabled us to discuss the physical mechanisms of PD generation and propagation in terms of space charge behavior. Experimental results revealed that the time-resolved PD generation was divided into different groups composed of the first large PD and the subsequent small PDs; the former was identified as the leader discharge, and the latter corresponded to the streamer discharges. The successive generation of the streamer and leader discharges was interpreted by the change of critical volume size. The time-resolved PD generation characteristics leading to BD were also measured and discussed. The leader discharge would be obliged to take a detour along the periphery of the positive space charge area in the vicinity of the needle electrode, and finally result in BD in electronegative gases. Index Terms--Electrical insulation, electronegative gas mixtures, partial discharges, breakdown, streamer, leader, space charge, corona stabilization effect.

This paper deals with cross-apparatus comparisons of an insulation design of electric power apparatus. Focusing on a gas insulated switchgear (GIS), an oil-filled transformer, a cable, and a capacitor, we summarize the different and common features of their insulation design on the basis of not only referring literatures but also the authors' experiences. The insulation design process has three evaluation steps. Each step optimizes its evaluation subject by considering the nature of an insulation medium or an insulation component, and the optimization result is different. However, it is common that the insulation design process has three steps without exceptions. The technology supporting the three steps is also common. Index Terms--Electric power apparatus, insulation design, gas insulated switchgear, power transformer, power cable, power capacitor.

Functionally graded materials (FGM) have spatial distribution of a material property in order to achieve efficient stress control. An application of the FGM to a solid insulator (spacer) for a gaseous insulation system, like gas insulated switchgear, is expected to improve electric field (Efield) distribution around the spacer. In this paper, we describe the applicability of the FGM spacer to gas insulated power equipment. In the FGM spacer, we gave spatial distribution of dielectric permittivity to control the E-field distribution inside and outside the spacer. This paper includes following key results for the applications of the FGM. Firstly, E-field simulation results when applying the FGM by a finite element method are presented, in which we show the effective reduction of the maximum field strength by applying the FGM. Next, a fabrication technique of the FGM spacer sample with not only step-by-step but also continuous changes of permittivity is presented by use of centrifugal force. Finally, dielectric breakdown tests using FGM samples which are accurately controlled the spatial distribution of permittivity are carried out under lightning impulse voltage applications. The test result indicates the increase of breakdown voltage (BDV). From these results, we verified the applicability and the fabrication technique of FGM spacer for improvement of the dielectric strength in the gaseous insulation system. Index Terms--Functionally graded material (FGM), Permittivity, Electric field (E-field), Spacer, Epoxy resin, Filler, Centrifugal force, Gas insulated switchgear (G1S)

Insulating materials exist in a variety of different forms, including gas, liquid, solid, and vacuum, and different forms of insulating materials have significantly different dielectric strengths and insulating properties. Power transmission/substation facilities for UHV AC and 500 kV DC power transmission and 500 kV underground power transmission facilities have been designed and constructed by taking advantage of the insulating properties of various insulating materials and structures so that they conform to the demanded insulation specifications. Conventionally, insulating material technology has been developed by making a close study of apparatuses and insulating materials individually. In this paper, as a new attempt, the insulating properties of various insulating materials/apparatuses are cross-sectionally compared and examined from an entirely new viewpoint through the assessment of commonalities and differences between them. A listing of lightning impulse and AC dielectric strength data is prepared and systematically positioned from the standpoint of material and structure, and compared and evaluated in a unified way from the viewpoint of typical indices of insulating properties including the 'n' value of the V-t characteristic, Weibull parameters, and impulse ratio. Further, an insulation assessment of apparatuses is systematically made with consideration given to their sizes and structures as well as the insulating materials themselves. As a result, it was found, for example, that the design field strengths of power capacitors were high and those of generators were not, and there was a noticeable difference in design field strength between S[F.sub.6] gas insulated apparatuses and oil-immersed transformers. It is expected that the analysis conducted from an entirely new angle may provide a new approach to the development of apparatus insulation technology and to the rationalization of insulation design. Index Terms Common insulating properties, cross-sectional comparison, lightning impulse, AC dielectric strength, Weibull parameter, impulse ratio.

We have investigated impulse partial discharge (PD) and breakdown (BD) characteristics of a needle-plane gap in [N.sub.2]/S[F.sub.6] gas mixtures under positive lightning impulse voltage application, and discussed their physical mechanisms. The 50% probability PD inception voltage (PDI[V.sub.50]), leader discharge onset voltage (LOV) and BD voltage (BD[V.sub.50]) were measured and analyzed as a function of gas pressure and S[F.sub.6] content. Experimental results revealed the stepwise propagation process of the impulse PD and enabled us to classify the impulse PD in [N.sub.2]/S[F.sub.6] gas mixtures into two types, the streamer discharge and the leader discharge. We also discussed the impulse PD propagation mechanisms in terms of PD parameters such as propagation length, time interval and current pulse magnitude, and suggested a sequential relationship in the PD propagation process under non-uniform electric field. Index Terms--[N.sub.2]/S[F.sub.6] gas mixtures, lightning impulse voltage, partial discharge, streamer, leader.

A novel technique for partial discharge (PD) measurement and analysis (PD-CPWA: PD Current Pulse Waveform Analysis) is developed and introduced in this paper. PD-CPWA is expected to be utilized to discuss PD mechanisms and physics in electrical insulating materials, focusing on the PD current pulse waveform and its time transition from PD inception to breakdown (BD). In this paper, the concept and principle of PDC-PWA are described, and the applications of PD-CPWA to (1) epoxy spacer samples under thermal and electric combined stresses in GIS, (2) creepage PD on epoxy spacers in S[F.sub.6] gas and (3) liquid nitrogen / polypropylene laminated paper composite insulation system for high temperature superconducting cables are introduced and discussed. Index Terms--Electrical insulation, dielectric materials, partial discharges, breakdown, current measurement, waveform analysis.

In order to investigate the charging mechanisms of solid dielectrics in vacuum, we constructed real-time and high-speed measurement systems for charge density, current pulse, light emission and applied voltage. By applying a negative dc ramped voltage to an electrode with a cathode triple-junction (TJ), we measured the temporal variation of surface charge accumulation and current pulse waveforms expressing the electron emission from TJ, by electrostatic probes. From the measurement results, we explain the step like charging process and propose an electron emission model by taking the electric field and its relaxation by charging into account. In addition, we elucidate the relationship between the charging process and the location of electron emission. Index Terms--Vacuum, charging, dielectrics, triple-junction, electron emission

The strategy for the synthesis of higher cyclic amides employs the compound (P) containing one (P)-helicene moiety and one dianiline moiety as a building block. The reaction involves coupling, two-directional chain elongation, and cyclization to obtain cycloamides.

Research discusses the process of selective aromatic polyfunctionalization by regioselective nitration of helicenes. Results indicate that the tetranitrohelicenes form charge-transfer complexes with chiral diaminohelicene. The chiral recognition suggest that helicenes of the same configuration form more stable complexes than the enantiometric helicenes.

The spreading behavior of the optically active series of macrocycloamides composed of helical chiral components at the air-water interface was investigated. The objective of the experiment is to produce a novel chiral Langmuir-Blodgett film by synthesizing the optically active chiral compounds. Results showed that all of the pi-A isotherms had a relatively significant increase in surface pressure and collapse pressure even without a long alkyl chain. In addition, an optically active Langmuir-Blodgett film based on helical chirality was created for the first time.