Precise thermo-fluid dynamics analysis of corrugated wall distribution transformer cooled with mineral oil-based nanofluids: Experimental verification

Abstract

Corrugated wall distribution transformers (CWDTs) are one of the momentous and expensive equipment for power systems, and their failure has a negative impact on the security of the grid. The continuous operation of the transformer strongly depends on its insulation status and then on the hotspot temperature (HST). In this paper, a comprehensive and precise 3D computational fluid dynamic (CFD) based modeling is proposed for HST prediction. In this modeling, the conservator, which has a remarkable impact on the HST, is thoroughly modeled. Optical fiber sensors (OFSs) in the studied 500 kVA CWDT are employed to validate the precision of the proposed HST prediction method via a 3D CFD-based modeling during the temperature rise test (TRT). The experimental results indicate that the proposed 3D CFD-based model for HST prediction is very precise and there is suitable proximity with the practical values. The error percentage of the proposed 3D CFD-based model is 0.76 % (0.7 °C) compared to the OFSs results, which indicates the accuracy and efficiency of the proposed modeling. Also, a thermal camera is employed to verify the results of 3D CFD-based modeling in top-oil temperature (TOT), bottom-oil temperature (BOT) and conservator oil temperature (COT) during the TRT. According to the obtained results, temperatures of 3D CFD-based simulation and thermal camera in the aforementioned three points are in good agreement with each other. In this case, the error percentage is less than 2.7 %, which indicates the precision and proficiency of the proposed 3D modeling. Finally, the utilization effect of multi-walled carbon nanotubes (MWCNTs) and diamond nanoparticles on CWDT' HST reduction and loading capacity increment (LCI) has been studied and verified via the proposed 3D CFD-based modeling. The results show that the lowest effect is for MWCNT with 0.005 % concentration, where HST reduction and LCI are 3.3 °C and 5.6 %, respectively, and the highest effect is for diamond nanoparticle with 0.01 % concentration, where HST reduction and LCI are 5.1 °C and 7.8 %, respectively.