Novel Method for dielectric Integration of Integrated Tap-Changer based on 3D-FEM Simulation for compact transformer design

Integrated on-load tap-changers (OLTCs) are pivotal in enhancing the performance and sustainability of power transformers. These OLTCs utilize optimized materials, eliminate various components on the transformer, and feature a space-efficient design. When optimizing the size of a transformer, dielectric considerations are of utmost importance to maintain the highest possible reliability. Integrated OLTCs consist of a diverter switch and a tap selector placed on one board per phase, located directly in the main tank of the transformer without a separate diverter switch compartment. In conventional OLTCs, the connection between transformer regulating windings and the selector of the OLTC is realized using leads that are bent around the OLTC. This configuration defines the electric field strength between the OLTC and surrounding elements, such as the transformer tank. In the case of integrated-type tapchangers, the connection points of the selector are aligned with the regulating winding, avoiding the need to bend the regulating winding leads. This alignment opens up possibilities for transformer design optimization during the design stage but also introduces new dielectric challenges when integrating this type of OLTC into the transformer. To ensure the most efficient dielectric integration of OLTCs and achieve the most compact transformer design, this paper presents a novel method that supports electrical engineers at transformer manufacturers.

The proposed approach is based on dielectric finite-element-method (FEM) simulation, utilizing a simplified 3D geometry of the respective OLTC provided by the OLTC manufacturer. In addition, proof is provided that the transformer manufacturer can concentrate on its expertise in insulation strength between the tank and OLTC and that the internal insulation strength of the OLTC is not influenced by it. With applying this method, it is possible to maximize the reduction in transformer size, saving space, steel and oil, thereby best serving the goal of sustainability.

This novel dielectric simulation method not only enhances the reliability and performance of integrated OLTCs but also contributes significantly to the overall efficiency and sustainability of power transformers. As the demand for renewable energy continues to grow, the adoption of such innovative solutions will be essential in meeting future energy needs while minimizing environmental impact.