The harmonic and interharmonic analysis recommendations contained in the latest International Electrotechnical Commission (IEC) standards on power quality are considered. The spectral leakage problems due to synchronization errors of the analyzed waveforms with the window widths adopted are analyzed. Improvements of the signal processing recommended by the IEC, based on the utilization of the classical Hanning window in place of the rectangular window, are proposed and made compatible with the grouping technique introduced in the standards. Sensitivity analyses on simple case studies together with experimental results show the sensitivity of the signal processing recommended by the IEC to synchronization errors and the usefulness of the improvements proposed.

Nowadays, the interest in low-cost and increasingly accurate phasor measurement units (PMUs) for active distribution systems is steadily growing. In this paper, an algorithm for synchrophasor, fundamental frequency, and rate of change of frequency estimation tailored for processing platforms with limited computational resources is described and characterized extensively in terms of both accuracy and processing time. The proposed solution harnesses the main advantages of two state-of-the-art algorithms, i.e., the interpolated discrete Fourier transform and the Taylor-Fourier transform. Such algorithms are combined and implemented in a computationally efficient manner to reduce processing time as much as possible, while ensuring good accuracy in the main testing conditions specified in the IEEE Standard C37.118.1-2011 and its Amendment C37.118.1a-2014. Estimation accuracy has been evaluated not only through simulations but also experimentally. The good consistency between simulation-based and experimental results provides clear evidence that the uncertainty contributions due to transducers, acquisition, and synchronization systems can be reasonably kept under control. The processing times of the algorithm, implemented on an embedded platform suitable for PMU prototyping, are compliant with the mandatory reporting rates of Class M PMUs.

The assessment of the power quality could be a valuable tool to foster the efficiency of the railway systems. Power quality is a well-addressed topic in conventional AC 50/60 Hz power systems and many procedures, algorithms and measurement systems were presented in the international standards and widely discussed in the scientific literature. A less explored research field is the assessment of the power quality in the railway traction supply systems, in particular with reference to the DC and 16.7 Hz systems. The paper explores this theme, proposing an extension of the definitions and of the standard measurement procedures for some of main power quality indexes, well defined and widely used for conventional power systems, in order to be used also in all railway traction supply systems. The limits or difficulties of applicability are discussed with reference to measurements performed both on-board and in substation. The proposed procedures are applied to an experimental case of a real DC railway system with a large measurement campaign.

A setup for the measurement of the frequency response of voltage measurement transformers under actual waveform conditions is presented. It is based on a two-step procedure that makes use of high voltage gas insulated capacitors and a digital bridge. It allows calibrations using distorted waveforms, with a fundamental tone at medium voltage level and superimposed harmonics up to 20% and 15 kHz. Combined standard uncertainty in the measurement of the voltage transformer (VT) error is estimated at 200 μV/V for the ratio error and 300 μrad for the phase displacement up to 10 kHz. First applications to the measurement of the frequency response of VTs with different rated primary voltages up to 50 kV are presented.

In this paper, the authors propose a methodology to guide the verification of single-phase energy meters under sinusoidal and nonsinusoidal conditions. At first, a brief review is presented about definitions of the quantities that should be measured or monitored for revenue purposes and their relationship with electrical quantities that are recognized to be important in terms of metering accuracy. Then, a design of an experiment that allows the testing meters under a combination of disturbances showing positive and negative correlations are described. Finally, a hardware and software system to perform verification procedures in complex situations is presented with some preliminary analyses.