INFLUENCE OF CO-FIELD MOTION ON THE CONDUCTION CURRENT IN OIL UNDER NONUNIFORM DC FIELDS

The effect of enforced co-field motion on conduction current in transf ormer oil was studied using a point-to-plane electrode geometry. Tests were carried out on degassed oil and gas-saturated oil for negative a nd positive point polarities using both a solid and a mesh-plane elect rode, and gaps ranging from 200 to 900 mum. For stationary oil the pre sence of oxygen decreased the conduction current for both polarities o f the point electrode. For degassed and O2 saturated oil the axial flo w produced a significant reduction in the conduction current; the fast er the flow the larger the reduction in current. With oxygen in soluti on, current fluctuations were much larger than for degassed oil. An un expected result was the consistent finding that for gas-saturated oil an increase in pressure produced an increase in the conduction current , but only for a solid plane electrode. There is an excellent correlat ion between the effect of flow on conduction current and on the breakd own voltage.