Simulation of the Mechanical Vibrations in a High Voltage Transformer
Winding fault is one of the components that cause more problems in the transformer. The main faults of transformer winding are irreversible changes in the mechanical structure of winding under the action of electromagnetic force or mechanical force. Common faults include loosening, warping, bulging and dislocation of winding. The live detection technology of transformer winding deformation based on noise and vibration is of great significance. In this paper, the mechanism and characteristics of transformer vibration are studied firstly. The vibration of transformer is caused by the vibration of its main body (core, winding, etc.) and the vibration of cooling device. The core vibration mainly comes from magnetostriction of silicon steel sheet, which is expressed by magnetostriction ratio. Through mathematical deduction, it is found that the vibration acceleration is based on two times of the power supply frequency, and the amplitude is proportional to the square of the voltage. Winding vibration is closely related to structural stiffness and dynamic characteristics. When the transformer winding coil flows through the load current, due to the existence of leakage magnetic field, dynamic electromagnetic force is generated between windings, wire cakes and turns, which causes winding vibration. In the study of the mechanism and characteristics of transformer vibration, the axial structure of winding coil is simplified to MASS-SPRING-DAMP model. The upper and lower pressure plates are considered as rigid bodies and fixed constraints. Each layer of wire cake is equivalent to a mass module, and the insulation pad is equivalent to an elastic element. The distributions of radial and axial electromagnetic force and acceleration are obtained by dynamic simulation analysis.