Hi First the hydrogen seems to be quite elevated comparing to other gases , What is the transformer age and size? Before any significant conclusion, I suggest to send an oil sample to a laboratory for DGA tests. The portable device used for these measurement may be less accurate for those...
Your questions are very good and is a real situation appearing in many transformers in past 10 years. The gas concentration especially of hydrogen is quite high and you should be concern. They are few possibilities, stray gas indeed but they appear usually before oil treatment not after. The...
