Influence of Cellulose Fiber Contamination and Bridging on Breakdown Voltage of PFAE under Lightning Impulse Stress

This research investigates the effect of cellulose fiber contamination and its bridging skeleton on the breakdown voltage of Palm Fatty Acid Easter (PFAE) under Standard Lightning Impulse Voltage (SLIV). An industrial microcrystalline cellulose fine fiber (particle size: 20 µm,) is selected as artificial contaminants with 0.004wt% fiber concentration level. A single stage of test transformer completed with auxiliary circuit is generated to deliver a standard impulse waveforms of 1.2/50 µs and it is applied according to the outlined of IEC60897 to obtain breakdown voltage test. The cylindrical test cell fitted with a needle-plane configuration of 0.5mm gap electrodes are utilized to create the strong non-uniform field crossed the gap. A 10kV DC power supply is connected between the electrodes in order to create and retained the cellulose bridge skeleton artificially. The microscope fitted with the digital camera responsible to monitor and capture the optical images of bridging formation between the electrodes gap. The breakdown voltage obtained from the experiment is analyzed using Weibull Cumulative Breakdown Probability. In this analysis, the Clean Oil is used as the reference. Based on the experimental results, the cellulosic fiber contamination has reduced nearly 3% breakdown voltage of PFAE. The cellulose fiber contamination with bridge formation is prominently influencing lower breakdown voltage to 16% lower than clean PFAE oil.