Short answer: transformer bushings should be selected by rated voltage, rated current, insulation level, mounting flange, creepage distance, conductor interface and transformer drawing.
| Low-voltage bushing | Used on distribution transformer LV side. Confirm current rating and terminal connection. |
|---|---|
| Medium-voltage bushing | Used on HV side of distribution transformers. Confirm voltage class, creepage distance and oil interface. |
| Porcelain bushing | Common for transformer tank connection where ceramic insulation is specified. |
| Epoxy or composite bushing | Used where design, weight or pollution performance requires non-porcelain material. |
Transformer bushings should be matched to the transformer drawing. Similar voltage bushings can have different flange, thread and terminal dimensions.