Statistical Investigation of Lightning Impulse Breakdown Voltage of Natural and Synthetic Ester Oils-Based Fe3O4, Al2O3and SiO2Nanofluids

Abderrahmane Beroual,Usama Khaled

doi:10.1109/access.2020.3003246

Abderrahmane Beroual, Usama Khaled

Open Access

https://doi.org/10.1109/access.2020.3003246

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Abstract

The characteristics of lighting impulse breakdown voltage (LI-BDV) constitute key performance indicators of insulating materials, especially in insulations based on liquids and liquid-paper for high voltage applications. Encouraged by environmental policies worldwide, new insulating liquids have been developed in recent years. Among these are natural and synthetic esters that are currently considered as potential substitutes for traditional mineral oils due to their environmentally friendly properties. Recent technological advances have shown that the addition of specific nanoparticles (NPs) to insulating liquids can improve both the dielectric withstand voltage and the thermal behavior of liquid insulations. This paper examines the effects of some NPs on the negative LI-BDV of natural and synthetic ester liquids, namely MIDEL 1204 and MIDEL 7131, respectively. The used NPs are Fe3O4, Al2O3 and SiO2. The LI-BDV measurements are executed in accordance with IEC 60060 standard, and the breakdown voltage with 1% probability risk (i.e., the lowest possible breakdown voltage) was also estimated. The experimental results showed that these NPs improved the LI-BDV of both synthetic and natural ester liquids and an optimal concentration of NPs can be determined. Statistical analysis was also performed to check the compliance of the experimental results with the most common probability distributions, normal and Weibull distributions.

Highlights

Natural and synthetic esters are increasingly used in oil-filled apparatus, especially in high voltage (HV) transformers, to replace the commonly used mineral oil (MO)
Similar results are found with natural ester (NE), where the U50% of the lighting impulse breakdown voltage (LI-breakdown voltage (BDV)) value of pure NE is almost twice that of the mean value of the AC breakdown voltage (AC-BDV) (i.e., 129.34 kV against 68.77 kV) [10]
Note that for each type of NP, there is an optimal concentration that gives the highest value of U50% lightning impulse (LI)-BDV for both ester liquids

Summary

Introduction

Natural and synthetic esters are increasingly used in oil-filled apparatus, especially in high voltage (HV) transformers, to replace the commonly used mineral oil (MO). As well as some of their interesting properties from an environmental point of view, such as biodegradability and non-toxicity [1]–[4], these insulating liquids have a high flash point and low sensitivity to water content. These characteristics qualify them for use in devices installed near urban areas. The addition of some NPs considerably improve the thermal properties of liquids; nanofluids (NFs) are commonly used for cooling of various devices and systems [6]–[8]. In the case of esters, the AC-BDV can be improved, but to a lesser degree than that of MO [10], [11]

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