A Study on Dielectric Properties of High Temperature CO₂ Gas Contaminated with PTFE Vapor at 0.8MPa

抄録

Carbon dioxide (CO₂) is considered as one of the sulfur hexa-fluoride (SF₆) alternatives for arc-quenching gas. In this paper, polytetrafluoroethylen (PTFE) was assumed as the nozzle material of the gas circuit breaker. The dielectric properties in the hot CO₂ gas contaminated by PTFE vapor were calculated in the temperature range of 300K to 4,000K at a pressure of 0.8MPa. In this calculation, not only 48 gaseous phase species but also the carbon in solid phase one (graphite) were adopted as component species. It is derived that at temperatures below 2,000K, the critical reduced electric field strength of the hot CO₂ gas contaminated with PTFE vapor becomes higher than that of pure CO₂ as the PTFE vapor concentration increases. By contrast, in the high temperature region exceeding 2,000K, the critical reduced electric field strength is less than that of pure CO₂ when PTFE contamination is 20% or 40%. The dominant reactions governing the critical reduced electric field strength are discussed and listed in the Tables. It is concluded that the dominant reactions are brought about by the dominant particles or particles having large electron collision cross sections.