Effect of temperature on flow electrification under dc electrical field

An oil–pressboard insulation system has been built to simulate converter transformer turn-to-turn insulation structure. Streaming current in the oil was measured while applying high dc voltage on the insulation at different temperatures. Flow electrification was also researched at low flow velocity of 0.2 m/s and at high flow velocity of 1.2 m/s. The streaming current increases exponentially with temperature when the high dc voltage is not applied on the insulation. However, at the same temperature, the streaming current is much smaller than that with the dc voltage been applied. The streaming current is in an inverted U-shaped development with the increase of temperature, when the insulation withstands the dc voltage. The peak value of the streaming current was observed at a lower temperature when the dc voltage is higher. A mathematic model has been developed to describe the electrification characteristics of insulation under the dc voltage