Session: 01-03-01: General topics in vibrations and acoustics

Paper Number: 165199

Detailed Design of Vibration Reduction Through the Tank Reinforcement of the Transformer 

Recently, the importance of low-noise design on transformers has been growing. This is due to increasing requirements from customers whose substations are being installed nearby downtowns. The acoustic emissions of large power transformers, being a source of environmental noise pollution, are of concern to communities near power substations. Increasingly stringent noise emission limits are therefore being placed on transformers by both regulators and utility operators. 

To reduce transformer noise, vibration reduction methods, such as reinforcing the tank, are generally selected and incorporated into the manufacturing design. However, due to the lack of detailed design standards at the manufacturing design stage, it is challenging to effectively implement these measures in actual production.

This paper presents numerical analyses to identify the vibration characteristics based on the shape and dimensions of internal stiffeners at the tank corners and predicts the sound pressure level for load and no-load noise in large power transformers. The numerical analyses involves the vibro-acoustic finite element model of a transformer including the excitations of the forces present in a transformer active part. Subsequently, an optimal design solution effective in noise reduction is selected. Load noise in transformers is generated by the interaction between the electric and magnetic fields when a load is applied, producing electromagnetic forces known as Lorentz forces. These forces induce vibrations in the winding structure, leading to noise generation. No-load noise, on the other hand, occurs due to magnetostriction in the transformer core when the transformer is in a no-load state. Magnetostriction results from microscopic expansion and contraction of the core caused by flux variations when an alternating voltage is applied. The characteristics of the transformers assembly's oscillatory motion resulting from the applied forces then interact with external acoustic elements, allowing sound pressure levels to be determined.

It is of note that all key structural and fluid elements impacting a transformer's vibro-acoustic response have been included in the finite element model presented in this paper. Structural components within the model therefore includes core, windings, tank of the a transformer, as well as parts connecting the aforementioned assemblies. Furthermore, the insulation oil of a transformer and the bi-directional fluid-structure interaction between the active part, oil and tank have been considered. Such detailed modelling has enabled the prediction of vibration and acoustic response characteristics of a transformer under nominal operating conditions.

Additionally, no-load and load vibro-acoustic analysis results indicates that the vibration and acoustic behavior of the transformer is influenced by the size, spacing, quantity, and centerline placement of the internal stiffeners.
In conclusion, the optimal design of the internal stiffeners at the tank corners, selected in this paper, was validated through appropriate experimental measurements. These measurements were conducted on multiple manufactured transformers. Notably, the experimentally determined noise reduction trends in sound pressure levels showed favourable agreement with the numerical analysis results. Through this process, the numerical analysis results and the optimal design proposed in this paper have been validated.

Through numerical analysis-based predictions of transformer vibration and noise characteristics, the proposed optimal design of internal reinforcements at the enclosure corners enables transformer manufacturers to establish detailed design standards at the manufacturing design stage. Consequently, this approach improves design efficiency and reduces material costs. Furthermore, it is possible to continuously produce transformers that meet the acoustic targets. As a result, the likelihood of incurring significant nonconformance costs due to exceeding the guaranteed noise level during manufacturing is reduced.

Presenting Author: Minok Yun HD HYUNDAI ELECTRIC

Presenting Author Biography: Minok Yun is a senior researcher at HD Hyundai Electric. Their research focuses on vibro-acoustic analysis and structural analysis with power transformers.

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