Совершенствование методов расчета изоляции силовых трансформаторов

Abstract

Degradation of the internal insulation electrical strength is one of the main factors leading to failures of high-voltage oil-filled transformers. To a certain extent, this is due to structural shortcomings laid down at the design stage. Correct calculation of the transformer main insulation will help ensure their reliable operation within the standard service life. The experience gained with design, manufacture and operation of high-voltage oil-filled transformers, as well as new modern manufacturing technologies generate the need to develop new methods and approaches to the calculation of their insulation structures. An approach to calculation and design of transformer insulation is proposed, which takes into account the influence of the oil channel volume on the breakdown field strength at various points of insulation, as well as electrical strength statistical characteristics when exposed to various voltage waveforms under operating conditions. Using the ANSYS MAXWELL software package, the insulation structures of power transformers were calculated. A model of a 110 kV two-winding three-phase transformer's main insulation is constructed in two 2D projections. The model takes into account the design features of the main insulation of oil-barrier type power transformers: the distance between the windings and the distance from the windings to barriers and capacitive rings. By using the proposed approach it becomes possible to achieve better calculation accuracy and take into account the transformer design features and significantly larger number of influencing factors in designing the transformer insulation.