Electrical Insulating Materials

Abstract

As part of a study to determine which of the types of products that may be formed by the service degradation of insulating oils cause serious dielectric losses in insulating oils at 60 cycles and which do not, properties of systems composed of liquid paraffin and a cupric or lead soap of the following acids have been investigated: 1,10-hydroxystearic, stearic, palmitic, myristic, lauric, capric, pelargonio, caprylic, cyclohexanecarboxylic, undecylenic, erucic, and abietic acids. In the preparation of these soaps, some of which were crystalline, possible adsorption of alkali ions was avoided by treating the acetates with the above acids rather than with their alkali soaps.Most of the systems containing lead soaps, in concentrations of 0.15 per cent by weight, became cloudy as they were being cooled. At temperatures immediately above the point of separation, the systems had high power factors and dielectric constants.Certain mixtures of lead soaps set to translucent gels or greases on cooling.The systems containing cupric soaps of individual acids had low power factors and conductivities at all temperatures, including those near which the soaps separated from solution. Systems containing mixed soaps, prepared from cupric abietate and certain acids or other soaps, however, had high power factors, conductivities, and dielectric constants at certain temperatures, even though these systems did not become cloudy on cooling. The dielectric properties of the systems are believed to be related to the state of dispersion of the soaps in the oil. THE work here described is part of an investigation to determine which of the types of products that may be formed by the serviced degradation of insulating oils cause serious dielectric losses in insulating oils at 60 cycles, and which do not. The types of deterioration products considered in this paper are certain lead and copper soaps.

Liquid Dielectrics

“…Inasmuch as all the systems with higher power factors than solutions containing equimolecular proportions of acid or base became heterogeneous upon cooling (whereupon their power factors increased), an alternative explanation seems possible. Previous work with soaps (8) and with oxidation products (11) showed that systems appearing to be homogeneous but becoming visually heterogeneous at lower temperatures often exhibit dielectric behaviors resembling those of heterogeneous rather than of homogeneous systems. Tri-n-butylamine From consideration of the data obtained it is believed that, although the presence of sufficiently high proportions of soluble salts resulting from reaction between nitrogen bases and carboxylic acids can cause high power factors in insulating oils, the presence of such compounds in proportions equivalent to the low nitrogen content of insulating oils does not appreciably affect the power factors of the solutions.…”

“…To minimize the number of variables, the authors prepared numerous systems consisting of liquid paraffin and one or more highly purified compounds selected to represent types of products that might be found in or formed in insulating oils during deterioration, and investigated the power factors and related properties of these systems. The systems investigated were prepared to simulate deteriorated oils containing oilsoluble oxidation products (IS, IS), sparingly soluble oxidation products (11), copper and lead soaps such as are formed by oxidation of oils in contact with these metals (8), and products resulting from corona discharge on insulating oils (16). For concentrations of contaminants that could reasonably be expected to be formed in service, significantly high power factors have been found only when one component of the contaminant is by itself incompletely soluble in the oil.…”

Properties of Organic Solutions of Heavy Metal Soaps.

“…This involves treating an aqueous solution of the appropriate sodium or potassium soap with a solution of a metal salt, filtering off the precipitate, washing with ethanol and acetone and drying. Copper and lead dodecanoates and octadecanoates can be obtained from the acetates (77); zinc, cadmium, magnesium and aluminum, etc., carboxylates can be obtained from the corresponding chlorides (65,87).…”

Oil-Paper Dielectrics

“…In other cases additives have been selected to resemble certain properties of deterioration products whose structures are unknown. Up to the present the classes of additives have been: oil-soluble oxidation products in oil (11) and in impregnated paper (IS); copper and lead soaps (7); sulfur and nitrogen compounds (8); and products resulting from subjecting oil to corona discharge (IS) in oil.…”