Heater treater is a hor izontal chamber inside which the oil-water emulsion is treated. the water is separated from the oil by treating chemically, thermally and electrically. the electrical treatment is done in this heater treater chamber. this paper presents one of the component and its fault analysis, the component being the heater treater transformer. the htt is a three winding transformer viz .primary, secondary and tertiary.htt provides the required high voltage for electrolysis of the oil-water emulsion.