AC Breakdown Voltage and Partial Discharge of Palm Oil As Insulating Liquid with The Presence of Cellulose Particles

The transformer oil and impregnated paper are widely used as electrical insulation design of power transformers. The dielectric strength of the oil paper insulation in transformers may reduce with the high contamination level of cellulose particle in the transformer oil. Furthermore, it may generate partial discharge or even breakdown with particle accruement. This paper presents experimental studies on the effect of cellulose particles on AC breakdown voltages and Partial Discharge (PD) characteristic of palm oil (PO). A mineral oil (MO) was also tested and used as comparison. In total, liquids with three cellulose particle contamination levels, i.e. low, medium, and high were investigated. Results show that the AC breakdown strength of PO is comparable to that of MO at clean condition. Meanwhile, the presence of cellulose particles reduce the AC breakdown strength of both PO and MO. It is summarized that the particle effect on liquid breakdown is associated with increase of cellulose particle concentration and the viscosity of the liquid itself. Due to higher viscosity of PO, AC breakdown voltage of PO is less significant than that of MO. The analysis of PD data was conducted by utilizing Partial Discharge Inception Voltage (PDIV) and Phase resolved partial discharge (PRPD) patterns. The influence of cellulose particles on PD activity does not show much change, but there is slight increase the PDIV value. When subjected to particle, results from PD test show that the PD activity is mainly due to void discharge.