Why Are Holes Drilled in the Lower Ends of Conductive Rods in Some European Standard Transformer Bushings?

Transformer bushings play a crucial role in the safe and efficient operation of electrical power systems. Among the various designs and standards, European Standard transformer bushings are known for their rigorous quality and performance criteria. One notable feature in some of these bushings is the presence of holes drilled in the lower ends of the conductive rods. This design element may seem minor, but it serves several important functions.

1. Pressure Equalization and Venting

· Technical Background: In bushings filled with insulating oil or air, holes at the lower ends of conductive rods help balance internal pressure and provide venting pathways. This prevents the formation of air bubbles during manufacturing or operation, which can impair insulation performance.

· Verification: This is a common practice in transformer design and manufacturing, especially in oil-filled transformers.

2. Oil Flow Channels

· Technical Background: In oil-filled transformers, holes in the lower ends of conductive rods improve oil circulation, ensuring thorough impregnation and cooling of the insulation materials.

· Verification: Enhanced oil flow and cooling are critical for the long-term stable operation of transformers, and this design is widely adopted.

3. Stress Relief

· Technical Background: Holes in the conductive rods can help distribute mechanical stress, preventing stress concentration that can lead to material fatigue or failure.

· Verification: This concept is well-established in materials science and mechanical design, improving the durability of components through structural optimization.

4. Manufacturing Process Requirements

· Technical Background: In some cases, holes are part of the manufacturing process, such as during electroplating or insulation layer application, ensuring uniform treatment.

· Verification: Optimizing the manufacturing process is essential for ensuring product quality.

Conclusion

The holes drilled in the lower ends of conductive rods in some European Standard transformer bushings are a thoughtful design feature that enhances pressure equalization, oil flow, stress relief, and manufacturing efficiency. These benefits contribute to the reliability, safety, and efficiency of transformer systems, ensuring stable and durable performance in various operational conditions.