Evaluation of Instrument Transformers in presence of multiple influence factors

Instrument transformers (ITs) used in power quality (PQ) measurements need to be calibrated over an extended frequency range to 9 kHz in order to make medium voltage PQ measurements.

Coordinator: Gabriella Crotti

Instrument transformers (ITs) used in power quality (PQ) measurements need to be calibrated over an extended frequency range to 9 kHz in order to make medium voltage PQ measurements.  Under real measurement conditions, ITs can be subjected to various influencing factors, which may affect their ratio and phase errors.

It is therefore necessary to evaluate the performance of ITs in PQ measurements in the presence of more than one influence factors and to define simplified test conditions and procedures for their evaluation.  This is recognised in the present version of international standards IEC 619869-X series for testing ITs, which individually takes into account the effect of several influence quantities such as burden, temperature, magnetic and electric field produced by adjacent phases, and proximity effect. In these standards, it is not considered that, in practical operating conditions, more of the above quantities can be present at the same time. However, there is no evidence that their effects can be simply linearly combined.

In light of this, the first task to be dealt with is the formulation of the test conditions for evaluating the effect of the main influence factors on a subset of PQ indices. Associated testing procedures and architectures will need to be defined and the existing reference measurement setups adapted accordingly.

To evaluate if and how the combination of more than one influence quantity affects the PQ indices measurement, the effects of each of them must be individually determined by applying the procedure reported in the international standards. Their outcomes will be compared with those provided by the application of the reference procedures previously defined for combined influence quantities by using the same make and model of IT.

The analysis of the above comparison will help in defining criteria for assessing if a given combination of influence quantities is significant and if so determine whether existing type tests in international standards need to be modified.  With the purpose of making simpler and affordable for manufacturers to implement such tests, simplified procedures and setups will be defined and applied for evaluating the effects of the most significant combinations of influence factors. These results will be validated by comparison with those obtained with the reference procedures, thus allowing the establishment of good practice for PQ measurement in presence of separate and combined influence factors.

For more information, see the project webpage >>

Parent project
Short Name:IT4PQ,Project Number:19NRM05

Participating Euramet NMIs and DIs

CMI (Czechia)

INRIM (Italy)

LNE (France)

PTB (Germany)

UME (Türkiye)

VSL (Netherlands)

Other participants

Alma mater studiorum Università di Bologna (Italy)
Ricerca sul Sistema Energetico – RSE S.p.A. (Italy)
Technische Universität Dresden (Germany)
Università degli studi della Campania Luigi Vanvitelli (Italy)

Project type
Joint Research Project