Insulation characteristics of gas mixtures including perfluorocarbon gas

Abstract

This paper describes discharge properties of N 2 and CO 2 -based gas mixtures including a perfluorocarbon (PFC) gas such as CF 4 , C 3 F 8 and c-C 4 F 8 under non-uniform field. The mixture ratio between a base gas of N 2 or CO 2 and the additive PFC gas was fixed as 9:1; namely, 90%N 2 /10%PFC or 90%CO 2 /10%PFC gas mixture. The PFC gases have even smaller global warming potential (GWP) than SF 6 gas and have good insulation properties as SF 6 gas. Thus, PFC gas mixture is expected to be a SF 6 substitute without highly pressurizing the gas over the conventional pressure of 0.5 to 0.6 MPa. In this study, in order to compare the partial discharge (PD) inception voltage V PD and breakdown voltage V B properties between N 2 and CO 2 -based gas mixtures, as well as between the additive gas of PFC and SF 6 gas, we investigated these properties of the gas mixtures with a needle to plane electrode under ac high voltage application. The gas pressure was changed from 0.1 to 0.6 MPa. As a result, it was found that V PD and V B characteristics of N 2 and CO 2 -based gas mixtures differed considerably, especially the gas pressure dependence of V B (so-called the N shape characteristics). V B characteristics of N 2 -based gas mixture including c-C 4 F 8 proved to be excellent within the test conditions over the wide gas pressure region, showing the maximum breakdown voltage. In terms of V PD properties, CO 2 -based gas mixture had an advantage over N 2 -based gas mixture due to higher V PD . Furthermore, we discussed the synergy effects of V PD and V B for N 2 and CO 2 -based gas mixtures using the index R n which was defined to quantify the degree of the effect. R n for CO 2 -based gas mixture was higher than that of N 2 -based gas mixture.Index Terms -SF 6 gas, perfluorocarbon (PFC) gas, partial discharge, breakdown voltage, non-uniform field.

Partial discharges and breakdown in C3F8

“…Intense research on PFCs started in the early 80s. Thus, many contributions can be found concerning the characteristics of C 3 F 8 (and other PFCs) on the molecular level [18,19,20,21,22,23,24,25,26,27] and on the phenomenological level [16,28,29,30]. Although C 3 F 8 was proposed as replacement candidate in several contributions, it still has a high global warming potential compared to CO 2 .…”

Optimization of the separation of sulfur hexafluoride and nitrogen by selective adsorption using monte carlo simulations

“…3,4 Besides, there are numerous research studies aimed at finding an alternative gas for insulation of electrical equipment, but a suitable substitute for SF 6 for some key applications is yet to be found. [5][6][7] One of the main options to diminish SF 6 emissions is mixing it with other gases to reduce the overall amount of SF 6 used, while keeping the desired properties of the pure fluid. Nitrogen is the preferred gas for these mixtures, for two main reasons: mixtures of SF 6 and N 2 with a low concentration of SF 6 still maintain the high dielectric strength of pure SF 6 ; and nitrogen is a cheap gas, making the overall process cheaper and environmentally friendlier.…”

Experimental Study on Performance of SF6+N2Mixed Gas Insulation

“…It seals high-voltage components, such as circuit breakers, disconnectors, grounding switches, in a metal pipe, uses SF 6 as insulating medium [1] . SF 6 has a strong adsorption ability of electrons, the strong electronegative indicates its excellent properties of insulation and arc extinguishing [2,3] , another feature of the SF 6 gas is having a high thermal conductivity [4] . Till now, SF 6 gas is the best insulation and arc extinguishing medium.…”

“…Solves practical application problems of SF 6 alternative gases. 6 and SF 6 /N 2 gas mixture According to the experimental research literature and research institutions [2][3][4] . In frequency AC voltage, SF 6 gas gap electric strength (peak) can be represented by the following empirical formula:…”