engleski

Experience with biodegradable liquids in instrument transformers with an emphasis on dielectric testing

There is little thorough experience regarding the use of alternative, biodegradable insulation liquids in high-voltage instrument transformers while extensive research exists for power and distribution transformers. Implementation of the mentioned dielectric liquids requires an extensive testing sequence to verify its expected performance. This is why the first aim of the paper is to detail the referent testing sequence which consisted of routine and type tests including increased partial discharge requirements, multiple chopped test, lifetime expectancy test, insulation breakdown test and additional tests such as: temperature rise, cold weather performance, internal arc and material compatibility tests. Each step of the testing sequence was also accompanied by DGA testing. In addition to presenting the proposed testing sequence for qualification of new dielectric liquids, the main emphasis of this paper will be on aspect of dielectric performance. The body of this paper will be presented through actual testing performed on several prototypes. Two biodegradable dielectric liquids were used for this effort: MIDEL 7131, a synthetic ester and Nynas NYTRO BIO 300X, a bio-hydrocarbon based isoparaffinic oil. The main parameters considered include but are not limited to: tgδ, insulation capacitance, partial discharge inception voltage, gas increases, etc.

Instrument transformers, Biodegradable liquids, Dielectric performance, Simulated aging, Partial discharge, Impulse testing, Paper-liquid insulation systems

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