The ECT of alkyl benzene with octyl sulfide and that with octyl sulfoxide exceeded 500 pC/ml. The values of ECT of alkyl benzene with octyl sulfone were lower than 100
pC/ml. The ECT of alkyl benzene with octyl sulfonic acid
exceeded 500 pC/ml with reverse polarity. Sulfide compounds
contained in mineral insulating oil in the brand-new condition
are transformed to produce sulfur compounds including
sulfoxide, sulfone and sulfonic acid compounds. The effects of
these compounds on the ECT are different with each other.