Fundamental insulation characteristics of high-pressure CO₂ gas for gas-insulated power equipment - effect of coating conductor on insulation performance and effect of decomposition products on creeping insulation of spacer -

Abstract

Currently, environmental problems such as global warming are important issues, and SF 6 has been identified as a greenhouse gas with a long atmospheric lifetime. Therefore, in the long term, it is preferable to reduce the amount of SF 6 used as an insulating gas. It is thus important to discuss the possibility of using more environmentally friendly gases as alternative insulation for gas-insulated apparatus. In this paper, we describe the fundamental insulation breakdown characteristics of high-pressure CO 2 gas at gas pressures of up to 1.0 MPa under simulated practical conditions, including the insulation breakdown characteristics of a high-voltage conductor with an insulating coating and the effect of decomposition products on the creeping insulation of a spacer. With the aim of enhancing insulation performance, we discuss the effect of the type of insulating coating on insulation performance. The breakdown electric field was increased by 20% by coating the conductor. It was verified that the application of an insulating coating is a practical method for enhancing the insulation performance of high-pressure CO 2 gas. It was also verified that the decomposition products have only a slight effect on the creeping insulation of the spacer except for when there is heavy pollution on the insulating spacer. However, if a large amount of decomposition products is expected to be deposited on the insulating spacer during operation, which may cause a severe interruption to the current, it will be necessary to consider this factor in the insulation design.

Study on oxygen/nitrogen gas mixtures for the surface insulation performance in gas insulated switchgear

“…This study [38] also suggested that the dew point of moisture in SF 6 gas was less than -10 °C for the surface insulation performance and that the maintenance level of moisture decreased with gas pressure. Moreover, the insulation resistance of a spacer decreased because of the absorption of moisture in air [39]. These results suggest that the candidate gases require a low moisture content to ensure the surface insulation performance and to preserve the insulation resistance of a spacer.…”

“…Nitta et al [38] and Goshima et al [39] presented the aforementioned mechanism on the degradation of surface insulation performance and the decreasing insulation resistance of a spacer because of moisture in the insulation gas respectively. However, this mechanism was investigated on the flashover characteristics on moisture content and temperature variations in SF 6 .…”

Surface Discharge Mechanism on Epoxy Resin in Electronegative Gases and Its Application

“…In addition to selecting the insulating gas, engineering techniques can be applied to an insulation design method, and these techniques should be integrated into high-voltage apparatus with a selection method of insulating gas that considers the electron swarm parameters. The engineering techniques are improvements in electrodes and solid dielectrics, details of which can be found in references [11,[32][33][34][35][36]. The theoretical principles governing the engineering techniques are the suppression of electron generation and relaxation of the concentrated electric field.…”

“…Their dielectric strength and characteristics have been compared with those of SF 6 [9]. In addition to gas insulation, composite insulation has been applied to SF 6 -free gas-insulated switchgear (GIS), instead of simple dielectric insulations by vacuum, gases, or solid dielectrics [10,11]. Composite insulation is a method of using a solid dielectric and an insulating gas together.…”

Dielectric Properties of HFC-227ea (Heptafluor-Opropane) and its Mixtures With HFC-125 (Pen-Tafluoroethane) as a Substitute for SF6

“…The SF 6 alternative gases consist of conventional gases (N 2 , CO 2 , air, etc.) [7]- [9], CF 3 I gas [10], PFC gases (c-C 4 F 8 , etc.) [11], perfluoroketone gases (C 5 F 10 O) [12], perfluoronitrile gases (C 4 F 7 N) [13], refrigerant gases (HFO-1234ze and R-134a) [14], [15], and so on [16], [17].…”