M/DBT, new alternative dielectric liquids for transformers

J. Walker, A. Valot, Z.D. Wang, X. Yi, Q. Liu

    Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


    Mono/dibenzyltoluene (M/DBT) is based on synthetic aromatic hydrocarbons. It is an insulating liquid with specifications meeting standard IEC 60867 where it is defined as methylpolyarylmethane derivatives. M/DBT has been used in high voltage capacitors for over 25 years. It has also been approved for other electrical equipment such as capacitive voltage transformers and bushings.Today, mineral oils are highly refined to meet health and environment requirements (carcinogenic poly-aromatic hydrocarbons content must be less than 0.1%) and more stringent requirements for eliminating the issue of corrosive sulphur. Highly refined oils contain less aromatic compounds due to the hydrogenation process. As a consequence the gassing tendency of mineral oils becomes more positive, which could affect the electrical behaviour of the oil and also the technical performance of transformer. In theory using M/DBT as complement to mineral oils will restore the original gassing performance of the mineral oil.This paper reports the experimental studies made on a mineral oil, a natural ester and a M/DBT. AC breakdown voltages and the resulting 1% withstand voltages through statistic analysis, gassing tendencies and partial discharge behaviours are discussed. In addition, the above characteristics of the insulating liquids with certain percentages of M/DBT are also studied. The results confirm that by adding 3-10% of M/DBT, a gas-evolving mineral oil can become gas absorbing. Partial discharges of both mineral oil and natural ester, particularly those occurring at negative half cycles, can be suppressed by adding the M/DBT. Both AC breakdown voltages and 1% withstand voltages of the investigated liquids and their mixtures are comparable.
    Original languageEnglish
    Title of host publicationCIGRE D1-107 colloquium , 2012
    Number of pages10
    Publication statusPublished - 2012


    • Transformer
    • gas absorbing
    • gas evolving
    • gassing tendency
    • partial discharge
    • AC breakdown voltage
    • mono and dibenzyltoluene (M/DBT)
    • mineral oil
    • natural ester


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