Those plastic caps are not sufficient. When you have unused deadfront wells, you should be using a bushing well insulated plug. If you have unused inserts in the wells, you should be using the appropriate insulating cap. Some applications use arrestors instead of the protective caps. As...
If the transformer is tripping on hi temp at 56% rated load, there is something definitely going on. Everyone above makes some good suggestions.
Suggestions:
1) Verify liquid level. Is the level too low? Transformer have leaks?
2) Check liquid temp gauge/winding temp gauge to make sure...
