Nanodielectric Fluids for Power Transformer Insulation and Cooling: A Review Identifying Challenges and Future Research Needs

It is becoming increasingly common for many oil-immersed power transformers (PTs) in many countries, including USA, to reach the end of their designed service life. Insulation issues fundamentally cause transformer failure. Due to the significant capital cost, customized design, and long lead time for delivery, it is less desirable to replace these essential element assets, especially for large ones. Instead, exploring novel insulation systems that may be used to upgrade existing oil-immersed transformers is considered. On the other hand, novel insulation systems that improve electrical insulation and thermal management are also attractive for new PTs, which lead to higher density designs. This review investigates nanodielectric fluids (NDFs) as alternatives to transformer oils. NDFs are nanofluids (NFs) wherein the base fluid is dielectric. Adding different nanoparticles (NPs) to the dielectric liquids will result in nanodielectric liquids. Choi and Eastman in 1995 revolutionized the area of PT oil research by inventing NFs that are said to have enhanced thermal transport properties. Similar investigations on PT oils led to the discovery that NPs are capable of enhancing the dielectric properties as well. This revolutionary research field has piqued the interest of many researchers, scientists, and industrialists all over the world. However, it is not easy to synthesize an NDF just by mixing any NP with PT oils. Several factors, such as NDF stability, NP concentration, size, shape, NDF viscosity, choice of surfactant, concentration of surfactant, time of ultrasonication, and cost, should be considered while synthesizing an NDF. Although many studies have been conducted using various base fluids and NPs, commercial NDFs for PTs have yet to be realized. This article critically reviews investigations done on NDFs for PTs, identifies technical gaps, and highlights future research needs. As a result, it can be a valuable source for further research.