Читать книгу Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems - Группа авторов - Страница 55

Viscosity of an oil is defined as the measure of the internal friction of the flowing liquid. The viscosity of an insulating fluid influences its ability to transfer heat from the interior of the transformer to the environment. With a higher viscosity, it becomes difficult for the liquid to flow and transfer heat quickly, which results in rise of the hot‐spot temperatures within the transformer. Generally, at operating temperature of a power transformer, NEOs show lesser viscosity value than silicone oils but higher than MOs. The natural esters having higher viscosity may indicate that their cooling capability is lesser than MOs. But this is not the case, as it is observed from many studies, that a high specific heat capacity and high thermal conductivity upgrade natural esters to exhibit better cooling performance [68]. As seen from Figure 2.8, the viscosity values of pongamia, jatropha, and palm oil are comparable to MO. However, more research is required when using high‐viscosity fluids in power transformers designed for MO insulation.