Traceable test systems for digital instrument transformers
Real-time grid monitoring systems based on synchronised power quality (PQ) or phasor measurement units (PMUs) measurements require the development of calibration methods for digital Instrument Transformers (IT) and Low Power Instrument Transformers (LPIT) to assess their behaviour under steady-state, dynamic and transient events.
To address this, calibration systems for testing digital ITs up to 2 kA for current and up to 400/√3 kV for voltage, with basic uncertainties of 0.005 % and 0.005 crad are developed. They include generation and measurement of realistic sequences of PQ non-steady-state events, and accurate synchronisation of reference set-ups and digital IT output signals. The considered frequency range is up to 9 kHz for laboratory set-ups, and up to 2.5 kHz for on-site set-ups. Moreover, test procedures and metrics to quantify and evaluate the performances of ITs and sensors are provided. The uncertainties in the laboratory generation and measurement of the reference PQ events are from five times to one order of magnitude lower than the corresponding values for the IEC 61000-4-30 class A compliant measuring instruments. The uncertainties for the testing with typical PMU disturbances are more than one order of magnitude lower than accuracies specified in IEEE C37.118.1 for PMUs. Test waveforms reproducing one or a sequence of PQ stationary/dynamic/transient events are identified and accurately reproduced with specifically-designed supply systems, defining reference measurement systems.
These calibration systems are employed to test digital ITs, both commercial and laboratory-developed. New-technology current and voltage ITs, refined for digital conversion of the output, are characterised for their use in PQ measurements. From the experience gained, test procedures and quantitative evaluation criteria for the transformer/sensor performances when used in PQ/PMU measurements are defined, and three sets of new/extended CMCs entries are proposed.
For more information, see the project webpage >>
Short Name:FutureGrid II,Project Number:17IND06
Alma mater studiorum Università di Bologna (Italy)
ComSensus, komunikacije in senzorika, d.o.o. (Slovenia)
Fundacion Circe Centro de investigacion de recursos y consumos energeticos (Spain)
Ricerca sul Sistema Energetico – RSE S.p.A. (Italy)
Synaptec Ltd (United Kingdom)
Università degli studi della Campania Luigi Vanvitelli (Italy)
University of Strathclyde (United Kingdom)