Diagnosis of Dissipation Factor and Breakdown Voltage of Alternative Insulating Liquids

Summary

Trouble-free operation of electroinsulating subsystems is necessary for proper operation of the power system. Insulation systems are one of the most important elements of power system. For a power transformer is used insulating liquid as a filling that serves as a cooling and dielectric medium. The most commonly used insulating liquid is mineral oil. Mineral oil is characterized by high flammability and poor biodegradability. On the other hand, this oil has very good electrical properties. For reasons of environmental protection is an effort to replace the mineral oil by alternative insulating liquids. These alternative insulating liquids may be vegetable or synthetic oils. In this paper are investigated the different kinds of vegetable oils, which are modified in various ways. This paper aims to compare the electrical properties of these alternative insulating liquids with mineral oil. The first part of the experiment aims to finding the best alternative insulating liquids based on natural esters. Commercially available sunflower and rapeseed oil were selected as alternative insulating liquids. Mineral oil Shell Diala DX and insulating liquid based on synthetic organic esters MIDEL 7131 were selected as a comparison sample. These samples were aged in hot air ovens at 140°C of accelerated aging. Dissipation factor was chosen as an important parameter, which was measured at temperatures from 25°C to 90°C. The whole measuring of dissipation factor was performed according to standard CSN EN 60247. The second part of the experiment follows the above-defined aims. Besides the dissipation factor is one of the diagnostic parameters dielectric strength. Alternative insulating liquids were tested to breakdown voltage according to CSN EN 60156 and mutually compared. Since the electric strength is dependent on the moisture content, the samples of insulating liquids were dried to the minimum limit moisture. This paper focuses on the alternative insulating liquid in terms of the two most frequently used electrical parameters for diagnosis of insulating liquids.

Additional informations

Authors

Mauro Marco Aurélio Siqueira, Suñé Jaime, Suresh, Surges Benjamin, Morais Cláudio