No abstract

No abstract

Abstract-A simulation model of a continuous disc type 6.6kV transformer winding was used to study the propagation behaviour of partial discharge (PD) pulses. The model based on multi-conductor transmission line theory uses a single turn as a circuit element with the capacitance, inductance, and losses calculated as distributed parameters. Transfer functions that describe how the location of the PD source affects the current signals measured at the terminals of the winding were calculated. The paper shows how the position of the zeros in the frequency response of the measured current signals can be used to locate the source of the discharge. Sensitivity studies on the parameters of the model were used to investigate the effect of inaccuracies in the model on the position of the zeros and hence the location of the discharge.

This paper investigated the motion of a metallic cylinder particle of mm size under uniform AC field in three transformer liquids, including a mineral oil, a synthetic ester and a natural ester. The clean transformer liquids were also artificially contaminated by copper particles of μm size, and the relationship between the AC breakdown strengths and the amount of copper particles was determined. It is found that the breakdown voltages of esters are influenced by metallic particles to a less degree than mineral oil. The slower motion of metallic particles in esters of higher viscosities than mineral oil reduce the chance of breakdown, and this might account for the better performance of esters under AC stresses with the existence of metallic particles.

No abstract