Power transformers are widely considered the most critical components in electrical transmission and distribution networks. Due to the aging of transformer fleets in the field, regular diagnostic testing and condition assessment become increasingly relevant. Transformer designs can be very complex and, thus, measuring the variety of different parameters can be a time- and cost-intensive job. In order to perform the different diagnostic tests, multiple devices and a frequent change of test leads are required. Individual phase measurements and multiple tap changer positions further increase the testing effort and the outage time. On average a whole working day needs to be scheduled for the full range of routine tests, usually making it the most time-consuming asset to test in the substation.