This paper describes the design and setup of different measuring systems for the calibration of commercial voltage and current transformer test sets for non-conventional instrument transformers. The calibration systems are recently developed at the national metrology institutes VSL, PTB, METAS and TUBITAK within the frame of the European project “FUTURE GRID - Non-conventional voltage and current sensors for future power grids”. The attained uncertainty of the calibration systems is in the order of 10 ppm and 10 μrad for testing the analogue non-conventional input and 20 ppm and 80 μrad for testing the digital (IEC 61850-9-2) input of the test set.