Axial internal forces in power transformer active part elements under windings clamping, variation of temperature and insulating materials moisture content
Keywords:
transformer, winding, axial forces, operation, shipment, moisture contentAbstract
The paper examines core type transformers in which windings clamping and magnetic system end yokes clamping is accomplished by means of the same yoke beams. With regard to forces of friction between the yoke beams and the yoke there were obtained expressions for internal forces in the active part elements under variation of their temperature and insulating materials moisture content. Based on numerical analysis, there was studied influence of variation of active part elements temperature and insulating material moisture content upon the internal forces in windings. It was demonstrated, that internal axial forces in windings reduce after clamping as the transformer cools to room temperature. Subsequent heating in operation compensates for this drop. Windings clamping forces may reduce to dangerous levels during shipment at low temperatures causing the windings to shift due to accelerations. If left for a prolonged period in a relatively humid environment, the windings in the active part may build high internal axial forces due to moisture content increase in insulation materials causing damage to the clamping structure.
References
Lazariev, I. (2010) 'Axial internal forces in power transformer windings under clamping, variation of temperature and moisture content in the case of block assembly', Collected works of the Institute for electrodynamics of the National Academy of sciences of Ukraine, vol. 25, pp. 97—105.
Lazariev V., Lazariev I. (2005) 'On the cause of reduction of axial clamping forces of transformer windings under short circuit', Electronics and Electricity, vol. 1, pp 18—22.
Lazariev V., Zubkova I. (2005) 'Determination of internal forces in the active part elements of a single-phase shunt reactor with side yokes under variation of temperature, active part lifting and shipment', Collected works of the Institute for electrodynamics of the National Academy of sciences of Ukraine, vol. 3, pp 124 – 132.
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