This mechanism was proposed to explain the ECT of oil
containing octyl sulfonic acid where insulating oil is
negatively charged [8] without heating. Compared to octyl
sulfonic acid that is a strong acid, on the other hand, the
hydrogen-ion dissociation property of BTA is weak. Thus
almost no variation occurs in the ECT of oil with the addition
of BTA. However, when positively charged ions such as
sulfonium ions are generated, the hydrogen-ion dissociation of
BTA occurs and the charge unbalance in oil is compensated.