Instrument Transformers for Power Quality Measurements: a Review of Literature and Standards

Abstract

Measurements of Power Quality (PQ) are gaining more importance due to increasing presence of switching power converters that deform the waveform of the distributed voltage further and further away from a sine wave. Especially at medium and high voltage levels, PQ measurements are carried out by means of Instrument Transformers (ITs). A recently started European metrology project, EMPIR 19NRM05 IT4PQ, aims at establishing the methods and procedures for assessing the accuracy of ITs used for PQ measurements. This paper, that is written in the framework of the IT4PQ project, presents a thorough review of the current state-of-the-art of literature and international standards about ITs and PQ. The main results from several papers and the main information from IT and PQ related international standards are summarized.

Current Status and Future Trends of Power Quality Analysis

“…In other words, the necessity to research more complex events has incrementally grown to reach a better understanding of the operation of the current network and, therefore, the signals obtained synthetically are being adapted to this phenomenon. In addition, although the most common network faults are still mostly single events, there is a clear trend towards the combination of sag (usually considered the most common disturbance [32,64,65]) with harmonics or transients. Furthermore, by carefully analyzing the data, the number of papers in which harmonics are located as signal disturbances ( 73) is slightly higher than the number of papers that include sags (71), displacing the last one to second place in most common disturbances.…”

“…In addition, although the most common network faults are still mostly single events, there is a clear trend towards the combination of sag (usually considered the most common disturbance [32,64,65]) with harmonics or transients. Furthermore, by carefully analyzing the data, the number of papers in which harmonics are located as signal disturbances ( 73) is slightly higher than the number of papers that include sags (71), displacing the last one to second place in most common disturbances.…”

How Instrument Transformers Influence Power Quality Measurements: A Proposal of Accuracy Verification Tests

“…This section aims to provide a brief overview of the literature and international standards related to ITs and PQ and to identify the PQ phenomena that are relevant for ITs testing. More details on this review can be found in [ 14 ].…”

“…As a starting point, based on a thorough review of the scientific literature and existing standards, the PQ phenomena to be included in this study and their relevant characteristics in terms of voltage or current behavior, in the frequency domain or the time domain, have been defined [ 14 ].…”

“…Starting from the review activity presented in [ 14 ], this paper provides possible ranges of variations of the relevant PQ phenomena for IT testing.…”