Regular electrical tests of power transformers include ratio tests for all three phases as well as for all taps, static winding resistance tests for all three phases and taps for both HV and LV as well as a short circuit impedance test. Interpretation of such test results and comparing the results against factory acceptance tests, commissioning results – or other transformers of the same type – are a good diagnostic tool to decide if a transformer is still fit for service or has failed – and what the reason of the failure is. A portable, easy and fast to use test solution covering all the above tests is presented.

Overview: https://youtu.be/eEvIyvewrbY
Tutorial on transformer testing: https://youtu.be/UHURqRR6-LQ