Partial Discharge Activity of Al2O3 Nanofluid Impregnated Paper Insulation System

Oil-impregnated pressboard (OIP) is preferable insulating medium in power transformers because of its excellent electrical and physical performances. However, under non-uniform fields the degradation of such binary material can be accelerated by partial discharge (PD). In this study Al
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O
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oil-based nanofluid is used as a replacement to base oil aiming at improving its PD resistivity. The PD characteristics for both nanofluid impregnated paper (NIP) and OIP were investigated. First, the investigated samples were prepared using a commercially obtained pressboard with a thickness of 1mm. The nanofluid sample was prepared using both stirring and ultrasonic processing. Then, the dried pressboard pieces were impregnated into the nanofluid and base oil inside the vacuum oven. Second, the PD measuring system was manufactured using a needle-plane electrode with a gap spacing of 1 mm. The PD inception voltages (PDIVs) were measured for each sample and were analyzed using Weibull distribution. Then, the PD propagation was estimated at different levels of applied voltage higher than the calculated average inception. The estimation was based on calculating the number of PD pulses for both negative and positive polarity of applied AC voltage. In addition, the time transition of PD pluses for 10 min time domain was depicted for both NIP and OIP. Moreover, the current magnitude of PD pulses and their phase appearance were analyzed. It was found that PD pulses appear around the peaks of the applied AC voltage for both NIP and OIP with a corresponding higher number of pulses for OIP. Based on the obtained results, the role of nanoparticles in PD activity is discussed.