Dielectric composition based on polyarylalkanes which have improved dielectric properties
AssigneeElf Atochem S.A.
InventorsNoelle Berger, Raymond Commandeur
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Abstract
The invention relates to a dielectric composition including at least one polyarylalkane oligomer of formula: ##STR1## in which n.sub.1 and n.sub.2 =0, 1 or 2, with the proviso that n.sub.1 +n.sub.2 =1 or 2, x=0, 1, 2, 3, 4, 5 or 6 and that the said composition has, in particular, a breakdown voltage increasing with the temperature.
Claims15
In an electrical distribution high temperature power transformer, the improvement wherein said power transformer contains an insulating oil consisting essentially of a dielectric composition comprising at least one polyarylalkane oligomer which consists essentially of an isomer or an isomeric mixture of the formula:
- ##STR10## in which n.sub.1 and n.sub.2 =0, 1 or 2, with the proviso that n.sub.1 +n.sub.2 is equal to 1 or 2, x=0, 1, 2, 3, 4, 5 or 6 and that the said composition has
- a) a vapor pressure not exceeding 1 torr at 150.degree. C.,
- b) a thermal quality coefficient, defined as the product of the specific heat at 100.degree. (J/l/.degree.C.) and of the thermal conductivity at 100.degree. C. (W/m/.degree.C.), divided by the viscosity at 100.degree. C. (mm.sup.2 /s) and multiplied by 100, of at least 3,
- c) a rate of formation of volatiles at 260.degree. C. during 500 hours not exceeding 3 g/kg,
- d) a breakdown voltage at 20.degree. C. of at least 60 kV and at 80.degree. C. of at least 110 kV, measured in 50 Hz alternating current in a cell equipped with an electrode consisting of a rod of 0.6 mm diameter and with an electrode consisting of a Rogowski disc with a rounded edge 40 mm in diameter, the said electrodes being separated by a distance of 40 mm.
A dielectric composition comprising at least 60% by weight of at least one polyarylalkane oligomer which consists essentially an isomer or an isomeric mixture of the formula:
- ##STR14## in which n.sub.1 and n.sub.2 =0, 1 or 2, with the proviso that n.sub.1 +n.sub.2 is equal to 1 or 2, x=0, 1, 2, 3, 4, 5 or 6 and that the said composition has
- a) a vapor pressure not exceeding 1 torr at 150.degree. C.,
- b) a thermal quality coefficient, defined as the product of the specific heat at 100.degree. (J/l/.degree.C.) and of the thermal conductivity at 100.degree. C. (W/m/.degree.C.), divided by the viscosity at 100.degree. C. (mm.sup.2 /s) and multiplied by 100, of at least 3,
- c) a rate of formation of volatiles at 260.degree. C. during 500 hours not exceeding 3 g/kg,
- d) a breakdown voltage at 20.degree. C. of at least 60 kV and at 80.degree. C. of at least 110 kV, measured in 50 Hz alternating current in a cell equipped with an electrode consisting of a rod of 0.6 mm diameter and with an electrode consisting of a Rogowski disc with a rounded edge 40 mm in diameter, the said electrodes being separated by a distance of 40 mm.
Dependencies are inferred from the claim text.