Production rates for oxyfluorides SOF2, SO2F2, and SOF4 in SF6 corona discharges

Abstract

The most abundant, long-lived stable gaseous species generated by corona discharges in SF 6 gas containing trace levels of 0, and H,0 are the oxyfluorides SOF,, SOF, and SOF 4 . Absolute energy and charge rates-ofproduction of these and the minor products SO,, OCS, and CO2 have been measured at different total gas pressures from 100 kPa to 300 kPa and for discharges of different current, power, and polarity. Oxyfluoride yields for SF6/02 mixtures containing up to 10% 0, have also been measured. The results indicate that oxyfluoride production is not controlled by the concentrations of either 0, or H,0 at levels below about I%, and the rate controlling factor is the dissociation rate of SF 6 in the discharge. The discharge current and time dependence of the production rates are discussed in terms of gas-phase mechanisms that have been proposed to explain previous observations of electrical, thermal, and laser-induced decomposition of SF 6 and SFs/O, mixtures. Upper limits on the total SF 6 decomposition rate in low-current discharges have been estimated. Details of the chemical analysis procedures are given, and application of the results to the design of chemical diagnostics for SF 6 -insulated, high-voltage apparatus is discussed.

Research for electric energy systems - an annual report

“…(17) that the time rate-ofproduction for S 2 F 10 is proportional to the discharge current. The fact that the production appears to be linear suggests [31,56] that secondary S 2 F 10 production and destruction processes are relatively unimportant.…”

“…Calculated (lines) [31] and Sauers and coworkers [25]. Figure 16 shows a comparison between the measured and calculated oxyfluoride yields for a fixed discharge current and water vapor concentration and the two different indicated relative 0 2 concentrations.…”

“…The ceiling limit for human exposure is recommended by the American Conference of Governmental and Industrial Hygienists [30] to be 10 parts per billion, making this chemical 300 times more toxic than other known gaseous by-products of SF 6 decomposition in electrical discharges [28,31]. There are previous reports of S 2 F 10 formation under various electrical discharge conditions which include spark [32][33][34][35], corona [33] and arc [36, 37] discharges.…”

“…Model for Corona Discharge-Induced Decomposition of SF 6 In this section we discuss a chemical-kinetics model for oxidation of SF 6 [31], [55][56][57][58][59]; 2) The yields for SOF 4 can exhibit nonlinearities that suggest a destruction process for this species with a rate proportional to the amount of SOF 4 present in the gas at any given time [56] [25,31].…”

Decomposition Characteristics of SF6 and Partial Discharge Recognition under Negative DC Conditions

“…Eventually, the safe and reliable operation of the equipment and the entire power grid is compromised. SF 6 gas component analysis (GCA) is a non-electrical detection method, which can effectively avoid the complex electromagnetic interference of substations and has become a popular research topic in recent years [13][14][15][16]. In [17][18][19], the SF6 decomposed products under arc, spark, and corona discharges were studied.…”