Hirokuni Aoyagi

Measurement of Transient Voltages Induced by Disconnect Switch Operation

This paper describes a proposed method of measuring disconnect switch surges and introduces some data derived from applying this method.

V-T Characteristics of Epoxy Mold Insulation for Sustained AC Voltage

This paper describes experiments conducted to determine the cause of epoxy mold insulation breakdown under sustained applied AC voltage. It can be readily understood that epoxy mold insulation, widely used as solid insulation in gas-insulated switchgear, is subject to breakdown under sustained applied voltage when the mold insulation contains large voids. However, epoxy mold insulation which is practically void-free also deteriorates under sustained applied voltage. It has been clarified by conducting experiments using various embedded electrode materials that the deterioration of this void-free epoxy mold insulation is primarily caused by an electric field concentration due to micro-protrusions on the embedded electrode surface and a small partial discharge which occurred at minute debonded portions around the micro-protrusions.

DC Dielectric Characteristics and Conception of Insulation Design for DC GIS

In order to discuss the dielectric performance of DC GIS, the flashover characteristics of gas-insulated bus were studied under conical- and disk-type spacers. The test involves the investigation on effect of electrification for charge to be accumulated in spacers and the effect of metallic particles. As the result, it was found that the dielectric characteristics of conical-type spacer are better than disk type. Moreover, the dielectric performance of DC GIS is more affected by the characteristics of coaxial electrode system than spacer surface with regard to metallic particle. On the basis of the results of these tests, this report presents the conception of insulation design for DC GIS.

Metallic Particle Motion in 3-Phase SF 6 Gas Insulated Bus

To investigate the behavior of metallic particles in 3-phase gas insulated buses (3-phase GIB), we conducted a test by using a 3-phase 275kV, ac, 60Hz full-scale model. The test results revealed that in a 3-phase electric field, unlike in a single-phase field, metallic particles were trapped on and around the high-voltage conductors and revolved circumferentially. Computer analysis shows that it was closely related to locational and periodic changes in the electric field provided by the 3-phase GIB, and that there were points on the high-voltage conductors in which metallic particles were readily trapped. It also was proved that phenomena peculiar to the 3-phase GIB could be reproduced very well by computer simulation.To investigate the behavior of metallic particles in 3-phase gas insulated buses (3-phase GIB), we conducted a test by using a 3-phase 275kV, ac, 60Hz full-scale model. The test results revealed that in a 3-phase electric field, unlike in a single-phase field, metallic particles were trapped on and around the high-voltage conductors and revolved circumferentially. Computer analysis shows that it was closely related to locational and periodic changes in the electric field provided by the 3-phase GIB, and that there were points on the high-voltage conductors in which metallic particles were readily trapped. It also was proved that phenomena peculiar to the 3-phase GIB could be reproduced very well by computer simulation.

VOLTAGE-TIME CHARACTERISTICS OF PARTICLE-INITIATED BREAKDOWN IN SF6 GAS

ABSTRACT This paper describes experiments which were conducted to determine the relationship between ac breakdown voltage and time to breakdown (V-t characteristics) when conducting particles are present in SF6 gas. The experimental results indicate that: (1) Time dependence of ac breakdown voltage under contaminated conditions is a little more than that under uncontaminated conditions. (2) V-t characteristics under contaminated conditions depend on the length of the particle and the gas pressure. (3) The presence of an insulator makes no significant difference.