Читать книгу Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems - Группа авторов - Страница 52

The growing demand of increased fire safety requires a fluid with high flash and fire points. Flash point can be defined as the temperature at which a combustible liquid can be heated to give off sufficient vapor to momentarily form a flammable mixture with air when a small flame is applied under specified conditions. This is determined by employing a Pensky–Martens closed cup apparatus as per ASTM D93. The NEOs tend to have higher flash points when compared with the MO as seen in Figure 2.7b. The fire point is defined as the temperature at which the liquid itself catches fire. The primary benefits of NEOs are their higher flash and fire points than the conventional MO. Fire point plays a key role during shipment of oils and installation of transformers in indoor as well as outdoors, with lesser concern about the fire safety protocols. Natural esters have fire points of above 300 °C and meet the requirements of “K” class insulators. These oils are widely used in many practical installations and have regulatory advantages in many sites [65].