Abstract
A power transformer outage has a dramatic financial consequence not only for electric power systems utilities but also for interconnected customers. The service reliability of this important asset largely depends upon the condition of the oil-paper insulation. Therefore, by keeping the qualities of oil-paper insulation system in pristine condition, the maintenance planners can reduce the decline rate of internal faults. Accurate diagnostic methods for analyzing the condition of transformers are therefore essential. Currently, there are various electrical and physicochemical diagnostic techniques available for insulation condition monitoring of power transformers. This paper is aimed at the description, analysis and interpretation of modern physicochemical diagnostics techniques for assessing insulation condition in aged transformers. Since fields and laboratory experiences have shown that transformer oil contains about 70% of diagnostic information, the physicochemical analyses of oil samples can therefore be extremely useful in monitoring the condition of power transformers.
Highlights
Today’s power transformers constitute a major part of the capital equipment of power utilities all over the world
The content of dissolved decay products in the insulating oil consists of a variety of compounds, such as peroxides, aldehydes, ketones, and organic acids each of which is partially adsorbed onto the large surface of the of the insulation paper leading to premature aging of transformers
This review summarizes the main physicochemical diagnostics techniques and demonstrates their usefulness in transformers
Summary
Today’s power transformers constitute a major part of the capital equipment of power utilities all over the world. Any improved preventive maintenance procedures should help extending their life In these important machines, the Achilles heel is the insulation system, i.e.,: (a) insulation between the high voltage (HV) winding and the tank; (b) insulation between the HV and the low voltage (LV) windings; and (c) inter-phase insulation. The diagnostic methods that give useful information on transformation insulation condition are chemical and electrical tests [3]. The life of the transformer being connected with that of its insulation, the evaluation of the insulation system condition is essential to assess the condition of the transformer when new and after several years of use This evaluation necessarily involves both electrical and physicochemical techniques/diagnostic methods. In addition to electrical methods, the physicochemical diagnostic methods are very important for the condition monitoring or for studying the degradation of electrical insulation in power transformer. Oil condition based on color comparisons [9]
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