Conduction and Breakdown in Liquid Dielectrics

Conduction and Breakdown in Liquid Dielectrics:

Characteristics of Liquid Dielectrics : Essential Characteristics of Liquid Dielectrics should possess good dielectric properties, excellent heat transfer characteristics and must be chemically stable under the range of conditions under which the equipment operates. These are briefly discussed below. (a) Electrical Properties The electrical properties that are essential in determining the dielectric performance of a Characteristics of Conduction and Breakdown in Liquid Dielectrics Dielectrics are its capacitance per unit volume or its relative permittivity its resistivity its loss tangent (tan δ) or its …


Classification of Liquid Dielectrics : In recent years, a substitute to mineral oils, other polyester oils have been developed which are extensively used in transformers in Europe and other countries. One such oil is the halogen free Penta-Etythrite-Tetra Fatty Acid. Polyester oil (PETFP oil) which has very good electrical, physical and thermal properties. It is also biodegradable, i.e. when decomposed has almost negligible toxicity and does not contribute to pollution. The Conduction and Breakdown in Liquid Dielectrics …


Conduction and Breakdown in Commercial Liquids : As already mentioned, Conduction and Breakdown in Commercial Liquids are not chemically pure and have impurities like gas bubbles, suspended particles, etc. These impurities reduce the breakdown strength of these liquids considerably. The breakdown mechanisms are also considerably influenced by the presence of these impurities. In addition, when breakdown occurs in these liquids, additional gases and gas bubbles are evolved and solid decomposition products are …


Conduction and Breakdown in Pure Liquids : When low electric fields less than 1 kV/cm are applied, conductivities of 10-18-10-20 mho/cm are obtained. Conduction and Breakdown in Pure Liquids are probably due to the impurities remaining after purification. However, when the fields are high (> 100 kV/cm) the currents not only increase rapidly, but also undergo violent fluctuations which will die down after some time. A typical mean value of the conduction …


Liquid Dielectrics : Liquid dielectrics, because of their inherent properties, appear as though they would be more useful as insulating materials than either solids or gases. This is because both liquids and solids are usually 103 times denser than gases and hence, from Paschen’s flaw it should follow that they possess much higher dielectric strength of the order of 107 V/cm. Also, Conduction and Breakdown in Liquid Dielectrics …


Pure Liquids and Commercial Liquids : Pure liquids are those which are chemically pure and do not contain any other impurity even in traces of 1 in I09, and are structurally simple. Examples of such simple pure liquids are n-hexane (C6H14), n-heptane (C7H16) and other paraffin hydrocarbons. By using simple and pure liquids, it is easier to separate out the various factors that influence conduction and breakdown in them. On the other hand, …