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Gas-insulated switchgear (GIS) has widely been used for AC power distribution because of its high reliability and compactness. Recently, DC GIS has been developed with various investigations for dielectric breakdown characteristics of DC gas insulation. GIS insulation is composed of SF6 gas and solid spacers, and it has been recognized that the dielectric performance of DC GIS is mainly influenced by solid spacers. Under DC stress, the electric field is directed one way, the effect of electrification for charges to be accumulated in the spacer must be taken into account and also the effect exists in AC GIS because the switching operations may leave the remnant DC charge on the AC GIS spacer. This paper first describes the effective resistivity (the bulk or the surface) of the solid spacer under the DC stress from the experimental investigation, and the critical factor on the solid spacer that causes reduced dielectric performance of the GIS insulation is studied. Second, the present paper deals with the electrification on the GIS with various levels of surface roughness of the epoxy insulator and metallic electrode. Finally, the DC insulation characteristics of GIS insulator are investigated based on the experimental results. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(4): 6–13, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20788 [ABSTRACT FROM AUTHOR]

Power capacitors are highly reliable equipment due to their completely enclosed configuration. They have usually worked with very little trouble for a long time. Their dielectric strength can, however, be reduced due to some stresses such as overvoltage application or thermal degradation of the insulation material during their long period of operation, and these events can result in the dielectric breakdown of the capacitors in extreme cases. Power capacitors with oil-impregnated paper/film are commonly used in substation. Therefore, it is very important to diagnose the deterioration and predict the remaining service life of such equipment, to assist in plant maintenance. To establish the diagnostic method of the deterioration of the capacitors with oil-impregnated paper/film, we have conducted thermally and electrically accelerated deterioration tests and investigated the changes of their characteristics. Based on the experimental results obtained, it can be concluded that the behavior of the oil-dissolved gases can be used as a useful index to diagnose the insulation deterioration of these capacitors. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(2): 1–9, 1997 [ABSTRACT FROM AUTHOR]

To improve the insulation specification of gas-insulated switchgear (GIS), it is necessary to recognize the insulation characteristics of SF gas during actual surges (called nonstandard lightning impulse waveforms) occurring at field substations. The authors observed the insulation characteristics of SF 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 SF 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 (). DOI 10.1002/eej.21144 [ABSTRACT FROM AUTHOR]