Effect of Different Particles on Breakdown and Conductivity Properties of Mineral Oil under Non-uniform DC Electric Field

Mineral oil is widely used in transformers, whose security decides the safety and even lifetime of transformers. With the increase of the volume of high-voltage and largecapacity transformer, the quality of particle pollution source increases, which makes the influence of particle pollution on insulation performance more significant. This paper mainly focused on the breakdown and conductivity properties of mineral oil contained cellulose particles or metal particles under non-uniform DC electric field, as well as the motion characteristics of different types of impurities. Results show that with the increasing of contamination level, oil breakdown strength decreased. Metal particles is more destructive. Moisture of cellulose particles and aging of mineral oil also play a significant role in motion characteristics of cellulose particles. With the aging of oil and the increasing of moisture in cellulose particles, not only the velocity of motion of cellulose particles and bridging increased, but also bridges became thicker. Meanwhile, the saturated conductivity current is higher.