A comparative study of the particle accumulation in natural ester and mineral oil under DC electric field

The cellulose particles bridging phenomenon under the DC electric field needed to be analysed. This is useful for further understanding the insulation failure and guiding the structure design of transformer using natural ester in the future. The images of cellulose particles accumulation and leak current for contaminated mineral oil and natural ester were compared under different DC electrical field strength using plate-plate electrode system. Results show that the formation process of cellulose particles bridge in mineral oil is much easier to its formation in natural ester, and the bridges in mineral oil were thicker than that in natural ester. The leak current in both types of oil increase with the rising of electrical field strength, however, the contaminated mineral oil has much higher leak current than the contaminated natural ester at the same electrical stress. The completed bridge contributes a lot to the leak current. The effect of cellulose particles on the conduction property of natural ester is weaker than that of mineral oil.