Paul Clarkson

A wavelet-based method of measuring fluctuating harmonics for determining the filter time constant of IEC standard harmonic analyzers

Harmonic analyzers are used to test the fluctuating harmonic emissions of electrical appliances to international regulations. This paper describes a wavelet-based method of measuring level-changing harmonics (bursts) for use in the calibration of these analyzers. The method is shown to be reliable for measuring various mixtures of harmonics. The importance of calibrating harmonic analyzers under conditions of fluctuating harmonics is discussed.

Measurement Infrastructure to Support the Reliable Operation of Smart Electrical Grids

Grid operators are facing a significant challenge in ensuring continuity and quality of electricity supply, while more and more renewable energy sources are connected to the grid. The resulting evolvement of so-called smart grids strongly relies on the availability of reliable measurement data for monitoring and control of these grids. This paper presents an overview of the results achieved in recent smart grid metrology research in Europe, aiming to realize the required metrology infrastructure for ensuring security and quality of supply in future smart electrical grids. A consortium of 22 metrology and research institutes has made significant steps in modeling of smart grids, enhancement of the revenue metering infrastructure, performance and evaluation of onsite power quality campaigns, and the development of a metrological framework for traceability of smart grid phasor measurements.

Development of an Ethernet-Enabled Digitizer for On-Site AC Measurements

This paper describes the development of an Ethernet-enabled digitizer system with a digital signal processor suitable for isolated measurements in the field environment. An implementation using a commercial 24-bit analog-to-digital converter is described, giving a six-channel instrument capable of sampling with real-time data transfer and processing at up to 32 kS/s. Implementation of real-time power quality algorithms is described. Performance results are presented, which show accuracy within 10 μV/V.

The calibration of IEC standard flickermeters using complex modulated signals

Flickermeter calibrations currently rely on the predicted response of a standard flickermeter to basic waveforms. A description is given of an interpretation and implementation of the IEC standard flickermeter, developed at the national physical laboratory (NPL), to assess the response of commercial flickermeters to more complex waveforms, which are representative of signals that occur in practice. A description of the incorporation of the resulting model into a calibration system for flickermeters under complex-waveform conditions is given.

The role of accurate measurements within smartgrids

The necessity of developing alternatives to fossil combustibles as energy sources is increasingly leading towards non-conventional, renewable and distributed generation systems. To manage the transition from the present centralized grid to the future active systems consisting of multiple bi-directional energy clients it is necessary to extend the measurement systems to LV grids. The overall objective of this work is to install real-time measuring devices at a few grid locations, and use distribution state estimation techniques to implement active network management techniques on an experimental 100-kVA micro-grid.

Comparison of Asynchronous Sampling Correction Algorithms for Frequency Estimation of Signals of Poor Power Quality

The measurement of many signal parameters using digital sampling relies on synchronization between the sampling clock and the signal under analysis. Deviations in the frequency of the measured signal from that expected can lead to significant measurement errors. Many techniques for overcoming these problems have been developed. Appraisals of the performance of these algorithms usually involve relatively benign steady-state signals, and the treatment is often heavily mathematical. This paper describes the testing of several algorithms for accurately recovering frequency and harmonic amplitude and phase information from mains-borne waveforms. This paper focuses on their practical use while avoiding abstract mathematical concepts.

The Influence of the Network Impedance on the Nonsinusoidal (Harmonic) Network Current and Flicker Measurements

The influence that small variations of the network impedance may have on the nonsinusoidal (harmonic) network current at the point of connection of a harmonic distortion measurement system, as well as on flicker measurements, has been studied. In this respect, an equivalent circuit was devised as a possible low-voltage urban network model. Harmonic disturbances, using three different disturbance sources, and voltage variations that induce the flicker sensation, using square modulation waveforms, were simulated on a computer. The variation with ±10% of the magnitude of the network impedance at 50 Hz was also simulated, and the influence it may have on the spectral distribution of current and power, as well as on the modulation depth generating the flicker sensation, was analyzed.

Smart grid metrology to support reliable electricity supply

An overview is presented of the results achieved in recent smart grid metrology research in Europe. The research focused on metrological challenges related to ensuring security and quality of supply in future smart electrical grids. A consortium of 22 metrology and research institutes has made significant achievements in smart grid sensoring and security, enhanced revenue metering, on-site power quality campaigns, and traceability of synchrophasor measurements.

Power source impedance measurement system for testing compliance to IEC 61000-3-3

Flicker compliance tests for mains connected appliances rely on a power source and reference impedance network which simulates the mains supply. Assessment of an appliance is achieved by measuring the flicker induced on the power source output by the appliance, which is dependent on the output impedance of the power source and reference impedance network. The value of this output impedance and its associated accuracy are specified in international standard IEC 61000-3-3 [1]. A description is given here of a method for measuring this impedance so that compliance with [1] can be verified.

Evaluation of Flicker Measurement Uncertainties by a Monte Carlo Method

The measurement of the severity of electric light flicker is achieved using a complex model of the human response embodied in a flickermeter. The complex nature of the model leads to variations in flicker readings with voltage input that can be hard to predict. Uncertainty evaluation is therefore difficult to achieve by conventional methods, and a Monte Carlo approach is required. This paper describes the implementation of such an approach to evaluate the uncertainty for flicker measurements based on a model of the measurement.