A CIRCUIT MODEL FOR THE BEHAVIOUR OF THE DISTRIBUTION TRANSFORMER

摘要

Transformers are key points of power networks. Preventive diagnosis and maintenance of transformers are necessary in order to improve the reliability of power systems. An extensive research has been developed on transformer insulation condition assessment. A clear understanding of the physical behaviour of the insulation system in response to the various stresses and contaminations allows for better understanding and analysis of the test and measurement results. In this paper a transformer equivalent circuit is proposed, that facilitates the study of the various phenomena that are presented during its operation. Except for the current and voltage transformation other phenomena related to the main insulating system of the transformer are for example those of polarization of the insulation, the thermal puncture observed at low field values, the electrical puncture, the electrochemical breakdown of the insulation due to partial discharges, as well as phenomena presented at field values much higher than 0,2MV/cm.