The diagnostic power of oil analysis for power transformers: New developments
As blood tests provide information about a person’s state of health, oil analyses provide information about the condition of a transformer. Transformer oil testing has proven to be an excellent tool for early defect identification in preventive maintenance of oil-filled transformers. It has permitted extended service life by giving a measure of both oil and solid insulation condition, and by identifying the presence of incipient thermal and dielectric faults. When performed regularly, oil analysis will help the asset manager run a cost-effective maintenance program for transformers.
This column addresses some recent developments in oil analysis, such as sustainable alternatives for mineral oil, an alternative marker for analysis of paper degradation, and online transformer oil monitoring.
Keywords: oil analysis, ester, cellulose paper, degree of polymerization
Over the last decades a large variety of oil analyses techniques have been developed and standardized. These techniques involve physical or chemical oil properties, electrical and environmental properties, and DGA (Dissolved Gas Analysis). The application of oil analysis may be linked to maintenance, lifetime extension, and establishing the status of ageing and corrosion for replacement and refurbishment issues. In the majority of oil-filled transformers mineral oil is used, and physical oil samples are taken in service for analysis in the laboratory. This column addresses some recent developments in oil analysis. The first one is related to sustainable alternatives for mineral oil, in particular esters. The second one deals with methanol as an alternative marker for analysis of paper degradation, and the third one with the benefits and drawbacks of online transformer oil monitoring.
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