Instrument transformers (ITs), or transducers, are used to accurately reduce the relatively high levels of voltage and current used in the electrical power grid to lower levels that are useable by instruments such as energy meters or system monitoring instruments. The ratio error and phase error of the instrument transformers are the figures of merit for performance and these are sometimes obtained from calibrations of the ITs and used to correct results. 

Fitting or removing ITs from the power system is often disruptive and expensive as it may require a system interruption. Some technologies of current transducers can be split and fitted around the conductor in a non-invasive manner.

National Metrology Institutes (NMI) provide calibration facilities for voltage transformers (VT) using high voltage facilities in the range of tens of kV.  High current facilities are used to calibrate current transformers (CT).  Traditionally, grid ITs are optimised for accurate performance the 50 Hz power frequency, however recent interest in power quality, requires acceptable accuracy at higher frequencies leading to the ned for increased frequency calibration facilities.

On-site calibration facilities are also available at some NMIs which have the advantage that the IT can be calibrated in-situ without the extra inconvenience and expense of transporting a heavy and large transformer, that for some VTs can be filled with pressurised gas that must first be emptied.

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Projects

Metrology for the next-generation digital substation instrumentation

Short Name: FutureGrid II, Project Number: 17IND06

Measurements for next-generation digital substation instrumentation...

Loss Measurements on Power Transformers and Reactors

Short Name: TrafoLoss, Project Number: 17NRM01

 

Metrology for smart energy management in electric railway systems

Short Name: MyRailS, Project Number: 16ENG04

Non-conventional voltage and current sensors for future power grids

Short Name: FutureGrid, Project Number: ENG61

 

Journal Papers

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

Crotti, G., D’Avanzo, G., Giordano, D., Letizia, P.S. and Luiso, M.

Document type: Article

Project title: 19NRM05: IT4PQ: Measurement methods and test procedures for assessing accuracy of instrument transformers for power quality measurements

Name of Call / Funding Programme: EMPIR 2019: Pre-Co-Normative

High-Frequency Current Transformer Design and Implementation Considerations for Wideband Partial Discharge Applications

Klüss, J., Elg, A-P. and Wingqvist, C.

Document type: Article

Project title: 19ENG02: FutureEnergy: Metrology for future energy transmission

Name of Call / Funding Programme: EMPIR 2019: Energy

Research Project EMPIR 19ENG02 Future Energy

Elg, A-P., Garnacho, F., Agazar, M., Meisner, J., Merev, A., Houtzager, E., Hällström, J., Lahti, K., Mier Escurra, C., Platinero, C., Micand, T., Steiner, T. and Voss, A.

Document type: Proceeding

Project title: 19ENG02: FutureEnergy: Metrology for future energy transmission

Name of Call / Funding Programme: EMPIR 2019: Energy

A simplified procedure for the Accurate Frequency Response Identification of Voltage Transformers

Crotti, G., Giordano, D., Letizia, P.S., Delle Femine, A. and Luiso, M.

Document type: Article

Project title: 19NRM05: IT4PQ: Measurement methods and test procedures for assessing accuracy of instrument transformers for power quality measurements

Name of Call / Funding Programme: EMPIR 2019: Pre-Co-Normative

Measurement Methods and Procedures for Assessing Accuracy of Instrument Transformers for Power Quality Measurements

Crotti, G., van den Brom, H.E., Mohns, E., Tinarelli, R., Luiso, M., Styblikova, R., Agazar, M., Çaycı, H., Mazza, P., Meyer, J. and Almutairi, M.

Document type: Article

Project title: 19NRM05: IT4PQ: Measurement methods and test procedures for assessing accuracy of instrument transformers for power quality measurements

Name of Call / Funding Programme: EMPIR 2019: Pre-Co-Normative