Abstract :
Static electrification due to oil now causes many field failures of large forced-oil cooled power transformers. Also, in practice under normal operating conditions, the oil volume in these power transformers is reduced due to the internal heat generated (from the energized windings) which accelerates the chemical processes occurring inside. To complete filling of the oil tanks of such transformers, either new oil of the same or different type is used. Laboratory analogs of these transformers; namely a closed and an open cycle, have been used for investigating this phenomenon. Such tests have been performed upon different types of fresh and aged oils and oil mixtures to measure the electrification current. Investigations of the effect of oil temperature, oil velocity, frequency and type of the applied voltage, type of the solid-phase material, and the length of the oil gap are introduced. Also, a 200 kVA, 3.3 kV/380 V distribution power transformer is used where the oil is forced and heated externally to examine and demonstrate this phenomenon for unenergized and energized cases and for both fresh and aged oils
Keywords :
ageing; power transformer insulation; static electrification; transformer oil; 200 kVA; 3.3 kV; 380 V; aged oils; chemical processes; closed cycle; distribution power transformer; electrification current; forced-oil cooled power transformers; internal heat; oil gap length; oil mixtures; oil temperature; oil velocity; oil volume; open cycle; power transformers; solid-phase material; static electrification; Acceleration; Aging; Chemical processes; Filling; Fuel storage; Laboratories; Petroleum; Power generation; Power transformers; Testing;
