This review outlines the charging tendency test methods that have been used in the electricity supply industry especially as applied to large transformers. Methods that have been used to generate charge and to measure charge are discussed and the results of various experiments are presented. >

Electrostatic charging in transformer oils. Testing and assessment

A noise analyzer for monitoring static electrification current

The author presents a novel measurement system for testing electrification of transformer oil when moving a solid phase in a liquid-phase environment. The system is based on hydrodynamic phenomena occurring for a rotating disc in liquid. It is concluded that the spinning disc system is useful for examining the electrification of transformer oil. The results obtained, particularly those concerning the effect of oil aging electrification, agree with the results obtained by means of A. Klinkenberg's (1958) system. >

Investigation of transformer oil electrification in a spinning disk system

The results of an investigation of the changes induced in transformer oil under the influence of thermal aging are presented. The investigations were carried out on various types of oil in order to study their electrostatic properties as a function of the aging process. A measurement system with a rotating disk developed by the author was used. It was discovered that the aging process causes quantitative and qualitative changes in oil electrification. These changes depend on the type of oil. >

Electrostatic properties of aged transformer oil

: The breakdown voltage and time to breakdown for electrodes in water has been measured. Reports in Russian journals describe increases of a factor of three in the holdoff voltage for water subjected to some treatment which is not described. Several electrode treatments and water treatments were tried in an effort to uncover the secret. Electrode treatments included: anodizing aluminum electrodes, coating electrodes with polyethersulfane and polycarbonate, and coating the electrodes with black wax. Electrodes with integral magnets were tried. Water treatments included: dissolved SF6, solutions with HCl and solutions with the surfactants dodecylamine and laric acid. None of these schemes produced a large increase in holdoff voltage although some did produce small but statistically significant increases. Some produced significant decreases. This report also includes an extensive bibiliography of articles and electrical breakdown and conduction in water.

High Voltage Water Breakdown Studies

In this paper the results of aging-oriented examinations of static electrification in transformer oil flowing through pressboard, glass and bras pipes are reported. Samples of transformer oil under examination have various degrees of aging. Changes in static electrification of oil are compared to classical aging indices. As a result, strong relation is found between the electrification of oil and degree of aging.

J. Kedzia

Papers

Static Electrification in Transformer Oil as a Measure of its Aging