Society’s increasing use of switching devices (inverters, bulky power electronic converters, active filters, etc.), both as loads and as part of generators, especially for renewable energy sources, has driven consequent proliferation of conducted disturbances on grid voltage and current, also at MV level, up to hundreds of kilohertz, due to the harmonics of the components around the switching frequency. Consequently, standardised methodologies, procedures and infrastructures for calibration, characterisation and testing ITs beyond frequencies covered by presently available infrastructures are needed. Characterisation of ITs used for MV HFM in AC and DC MV grids is one of the three priority topics submitted by CEN/CENELEC for this call.

Suitable parameters to define the accuracy and the performance requirements of ITs up to 150  kHz are not available. There is an urgent need to standardise procedures to test ITs up to this range of frequency. Indeed standards, which are currently in force, include requirements only up to 20  kHz and test procedures only for 50/60 Hz. New calibration methods for AC and DC ITs, with high accuracy class, at frequencies up to 150  kHz are needed. High voltage and high current metrological infrastructures, capable to ensure the traceability for this extended range of frequency are missing.

The development of setups to generate realistic test voltages (AC or DC up to 36  kV) and test currents (AC or DC up to 2 kA) will promote new calibration services for the electrical industry and deposit new calibration services for NMIs. Indeed, the achievements of NMIs during previous or ongoing European projects and the present available capabilities and facilities, among all actors combined, do not cover this topic since frequencies higher than 20  kHz and up to 150  kHz represent new issues for the AC electrical networks.

The overall objective of the project is to develop traceable measurements and characterisation methods of instrument transformers used for high frequency measurements in AC and DC medium voltage grids.

The specific objectives of the project are:

1. To identify performance requirements both for Instrument Transformers as well as for the measuring instruments connected to them, based on disturbances in AC and DC MV grids (system voltage < 36  kV) and on future measurement needs in the frequency range up to 150  kHz.
2. To establish suitable parameters for the definition of the accuracy of voltage and current transformers in the frequency range up to 150  kHz. To define suitable calibration conditions and procedures for the accuracy evaluation.
3. To facilitate the laboratory set up to generate test voltage (AC or DC at <36  kV system voltage) and test current (AC or DC at <2 kA). Preference should be for generation of the power frequency quantity with superimposed components with frequencies up to 150  kHz, but at a fraction of the magnitude of the power frequency components.
4. To develop reference measuring systems for the calibration of Instrument Transformers in the frequency range up to 150  kHz at voltage level up to 36  kV system voltage and current levels up to 2 kA and to develop traceable calibration chains for these new systems.
5. To contribute to a revision of written standards by providing the data, methods, guidelines and recommendations, which are necessary for the accuracy verification of Instrument Transformers used up to 150  kHz, to IEC TC 38 Instrument Transformers. Outputs should be in a form that can be incorporated into standards (IEC 61869 standard family) at the earliest opportunity and communicated through a variety of media to the standards community and to end users (Transmission System Operators, Distribution System Operators, customers). In addition, to interact with the European Metrology Network on Smart Electricity Grids.