Influence of the Power Factor on the Vibration Behavior of Transformers for Primary and Secondary Distribution

Vibration analysis is a powerful tool for transformer assessment. Knowledge about functional relationships between vibration and influence factors is essential for a successful assessment. One of these influence factors is the power factor, which may vary due to day-dependent changes in the electric load. In this paper, the functional relationship between the power factor and the vibration is investigated. First, a theoretical analysis is conducted on the superposition of core-and winding vibrations in dependence of the power factor. The theoretical analysis concludes that the highest 100 Hz vibration amplitude is measured when the phi angle of the load current equals the phi angle of the transformer in open-circuit test. The results from the theoretical analysis are then experimentally investigated in single-phase loads for different power factors and apparent power scenarios. The laboratory experiment is conducted with a transformer for primary and secondary distribution. The results from the laboratory experiment support the findings from the theoretical analysis.