Ageing characteristics of synthetic liquids

Synthetic liquids have been developed as substitutes for the PCB's in electrical applications in transformers, capacitors and switchgear equipment. These liquids are tailor made to meet the requirement of specific applications. Pentaerthritol esters of oleic acid and caprylic acid, methyl oleate, silicone oil, iso propyl biphenyl, alkyl benzene and liquids derived from vegetable oil were studied for electric strength, tan delta and resistivity before being subjected to accelerated ageing. These liquids were subjected to accelerating ageing as per the procedure outlined in ASTM D1934. The deterioration of the electrical properties due to the oxidation products like acids and sludge formation are evaluated and discussed.