Experimental Study of Cellulose Particles Effect on Impulse Breakdown in Transformer Oil

This paper conducts an experimental research about the effect of cellulose particles on impulse breakdown in transformer oil. The hemispherical electrodes immersed in the bulk of the transformer oil are used to form a quasi-uniform electric field. The breakdown tests are carried out and the breakdown voltages for three cellulose contamination levels oil under four kinds of impulse, 1.4/50 μs, 14/220 μs, 80/850 μs and 250/2600 μs, are obtained. The results show that both the impulse waveshape and cellulose contamination level exert an effect on the breakdown voltage of transformer oil. Specifically, longer impulse duration or higher cellulose contamination levels of transformer oil lead to the decrease of impulse breakdown voltage. It is noted that the effect of the high level cellulose contamination for U50% becomes much more significant under the impulses of 80/850 μs and 240/2400 μs. Another relevant experiment is finally conducted under the impulses of 1.4/50 μs and 240/2400 μs on cellulose particles motion in transformer oil gap submitted to a divergent electric field, and the suspension and aggregation of cellulose particles are observed under the impulses of 240/2400 μs. It is concluded that the particle can play a catalytic role in the impulse breakdown of the oil gap. © 2018, Electrical Technology Press Co. Ltd. All right reserved.