The IEEE Std C37.118.1(a) describes synchrophasor measurement by Phasor Measurement Unit (PMU) for the system fundamental frequency. Harmonic synchrophasor, i.e. synchrophasor measured for harmonic frequencies, is not considered in the Standard. Harmonic synchrophasor is useful for harmonic state estimation, Power Quality (PQ) monitoring, and harmonic power flow analysis. In this paper we investigate usability of the Standard basic synchrophasor estimation model for estimation of harmonic phasor up to the 50th harmonic as advised by the IEC Std 61000-4-7. For estimation of harmonic phasors an application of the flat-top FIR filter is proposed. Results for the maximally flat differentiator and the interpolated DFT are also presented, confirming the superior performance of the proposed flat-top filter approach. Harmonic phasor estimation is verified with extended tests of the IEEE Std C37.118.1(a) including steady-state and dynamic conditions with additive 60 dB noise.

This paper presents a method for contactless measurement of instantaneous voltage and waveform reconstruction for use in a medium voltage (MV) indoor substation. Voltage waveforms are reconstructed by artificial neural network (ANN) using the signals originating from electric field sensors located under MV bus. The method is validated by the experiment in a typical indoor MV substation. Depending on the selection of ANN architecture and data used for training the root mean squared error of waveforms, reconstruction as low as 0.3% to 2.1% can be achieved in a steady state. The practical advice on the application of the proposed measurement method in a production environment is also given.

The coherent resampling (CR) algorithm, which improves the accuracy of discrete Fourier transform (DFT)-based power system frequency analysis, is described in the paper. The algorithm uses extended Kalman filter for instantaneous frequency tracking and fractional B-spline resampler for signal approximation. The CR algorithm is a software counterpart of synchronous sampling, i.e., sampling, synchronized with fundamental frequency of the signal. CR may either be applied to previously noncoherently sampled signals or to work in realtime. Frequency estimation, amplitude spectrum estimation and THD factor estimation results obtained by presented algorithm are compared to those obtained by other methods. Both simulated and real signals were used for tests. Brief summary of realtime DSP implementation of CR algorithm is also given.

The new, noninvasive method of measurement for power system harmonic impedance is presented in the paper. The method is based on the observation of variations of voltage and current harmonics caused by natural load variability. The novelty of the method lays in a way the method rejects segments of data containing insufficient or false information about the identified power system. Segment selection/rejection uses logical conditions applied to RMS values of measured voltage and current. Harmonic impedance of the power grid is then calculated using modified power spectral method. The method was validated in a field test conducted at 30 kV feeder bus of HV/MV substation. Details of the experiment and the results are discussed the paper. Obtained results confirm that the method copes with temporal, band-limited excitation as well as with deep, sudden changes of utility background voltage.

Voltage distortions and disturbances in power network are an important power quality factor. Usually in literature phase disturbances are neglected and only amplitude distortions are discussed. Amplitude disturbances are interpreted as amplitude modulation (AM) of main 50 Hz frequency and considered to be the only reason of light flicker. Standard flicker measurement method is based under two not fulfilled assumptions: 1) AM with modulating frequency lower then 50 Hz carrier frequency and 2) constant carrier frequency. In the article detailed analysis of possible disturbances and it sources is presented. It is shown that AM and narrow band PM (phase modulation) take place in power network simultaneously and those two modulations interact with each other. Theoretical results are verified by field experiment.