The increasing integration of power electronics and renewable energy sources in modern electrical grids has introduced new challenges in medium voltage transformer calibration, particularly in the frequency range from 9 kHz to 150 kHz. Accurate and traceable calibration methods are essential to ensure reliable voltage measurement in electrical grids, where power quality and compliance with IEC 61869-1:2024 standards are critical. This study presents advancements in the development of traceable calibration techniques for medium voltage transformers operating within this frequency range. The approach includes the design of generators capable of simulating real world grid disturbances and the establishment of reference measurement systems at National Metrology Institutes. The study further explores generator configurations, such as parallel and series source arrangements, to extend calibration capabilities beyond existing limits. The proposed calibration methodology incorporates precision voltage dividers with high resolution, filtering and amplification techniques, and advanced data acquisition methods to achieve measurement uncertainties below 0.01% for fundamental components and between 0.2 % and 1 % for harmonic components. A key challenge is the ability to measure a fundamental voltage as high as 50 kV while superimposing harmonics with amplitudes as low as 5 V in the 9 kHz to 150 kHz range. These developments aim to enhance power system reliability, improve voltage measurement accuracy, and support the transition to more efficient and resilient electrical grids. The presented results lay the foundation for future calibration services. © The Authors, published by EDP Sciences.