I. Coll et al., Sparking-induced decomposition of 10% SF6-90% N-2 mixtures: effect of a solid organic insulator, oxygen and water, J PHYS D, 33(11), 2000, pp. 1348-1359
The chemical stability of 10% SF6-90% N-2 mixtures (100 kPa pressure) has b
een studied under sparking in the presence or absence of an organic insulat
or (teflon, kel'F, polyethylene, polypropylene. nylon. megelit), and/or add
ed impurities (0.2%; O-2 or H2O). The study was carried out experimentally
and numerically.
The production rates of the main decomposition products of SF6: (SF4 + SOF2
), S2F10, etc, and of products containing nitrogen, NF3, N2O, were evaluate
d. The results from the model led to trends similar to those observed exper
imentally concerning the effects on gas phase composition, of the presence
of atoms such as O, H, C, etc, from the vaporized Insulator and/or the adde
d impurities.
A comparison of the chemical stability of the SF6-N-2 mixture with that of
pure SF6 has also been made. The results can be summarized as follows:
in all cases, the major byproducts formed were (SF4 + SOF2) and S2F10;
the use of the SF6-N-2 mixture instead of SF6 led to the decreased formatio
n of degradation products:
vaporization of an organic insulator caused an increase in the production o
f degradation products which was less intense for the mixture than for pure
SF6;
the study carried our with nitrogen-diluted SF, showed the importance of fo
reign atoms (C. H. O. etc) on the proportion of SF6 that is not regenerated
. Owing to their tendency to trap fluorine atoms. the impurity atoms preven
t SF6 from recombining and can thus lead to the deterioration of the dielec
tric qualities of the gas mixture.