A. Lazkano

Flicker Measurement System for Wind Turbine Certification

There is currently a shortage of equipment specifically designed to measure and assess power quality in wind turbines in accordance with the IEC standard. This deficiency negatively affects the work of wind park installation companies facing the certification process. We have designed a system to measure and assess flicker in wind turbines in accordance with the standard. The system consists of two modules. The first is a signal register to store the established voltage and current series as a function of the wind speed; the second module processes these stored series in accordance with the standard specification to precisely obtain the required flicker parameters of the wind turbine. Our system facilitates the certification process and is sufficiently flexible to cope with changing standards.

A Review of Flicker Severity Assessment by the IEC Flickermeter

This paper presents an analysis of the flicker assessment by block 5 of the International Electrotechnical Commission (IEC) flickermeter. We compare the values provided by the IEC flickermeter from field measurements and the complaints from the customers. We also analyze the behavior of the IEC flickermeter when subject to signals containing nonuniform rectangular fluctuations. Finally, as it is not easy to find a consistent relationship between the true annoyance and the flicker severity, we describe some laboratory subjective tests with a small group of people, carried out to assign a true quantitative value of annoyance to a nonuniform light fluctuation from real situations. Block 5 of the IEC flickermeter derives its estimate of the annoyance accurately only for uniform fluctuations. In realistic conditions, when the voltage fluctuations are not uniform but have varying frequencies and amplitudes, the IEC flickermeter does not assess the true flicker annoyance precisely.

A new approach to high impedance fault detection using wavelet packet analysis

The paper presents a new approach to high impedance fault detection based on wavelet packet analysis. The nature and dynamics of the arc phenomenon related to high impedance faults are analyzed. A background is reported about wavelet transform and wavelet packet decomposition. Then, detecting criteria are proposed and assessing parameters calculated. Finally, in order to evaluate the procedure, the approach is applied to power system signals in normal conditions.

Distinction of ventricular fibrillation and ventricular tachycardia using cross correlation

The accurate discrimination of ventricular tachycardia (VT) from ventricular fibrillation (VF) is an important issue in automated external defibrillator (AED) and other cardiac monitoring systems. The correlation function of the ECG signal is an adequate tool for detecting irregularities or noise in signals. Therefore, methods for VF/VT discrimination based on the autocorrelation of the ECG signal and on the cross correlation of the ECG signal with different templates have been proposed. Our work is focused on the use of the cross correlation of the ECG signal with a segment of the same ECG signal, instead of using a given template. The developed algorithm has been tested on a database consisting of 179 human VF and 74 human VT records. The new algorithm classifies accurately 313 VF windows (90.2% sensitivity) and 179 VT windows (96.75% sensitivity). These results improve those obtained from other techniques, considered as a reference, for the same records database.

Study of high impedance fault detection in Levante area in Spain

This paper presents a study of high impedance fault detection in a particular case of the Spanish power distribution network. It aims to carry out an analysis of high impedance fault riskiness in three-wire distribution systems. A study of the presumed fault is performed considering 64N protection device alarm. Data from staged faults are presented in which downed conductors in different surfaces and conditions were recorded. Measurement system and electric conditions of the test location are described. Then, a fault riskiness diagnosis is proposed based on an arc existence confidence together with presumed fault context conditions. A new analysis methodology for electric arc detection is presented and assessed taking into account low order harmonic current.

Influence of the Carrier Phase on Flicker Measurement for Rectangular Voltage Fluctuations

This paper presents an analysis of the influence of the phase relationship between the fundamental frequency and the rectangular voltage fluctuation on flicker measurements made by the International Electrotechnical Commission (IEC) flickermeter. We analytically studied the origin of the deviations for a set of significant fluctuation frequencies. We found that the nonlinear behavior of the squaring multiplier of the IEC flickermeter produces an additional dc component in instantaneous flicker sensation Pinst for several rectangular fluctuation frequencies. The value of this dc component depends on the phase relationship between the fundamental and the fluctuation frequency. The analysis of this paper has contributed to clarify the definition of some performance tests of the IEC flickermeter standard IEC 61000-4-15 ed.2. This will help develop calibration and verification methods for the flickermeters.

A Precise Analysis of the IEC Flickermeter When Subject to Rectangular Voltage Fluctuations

The Pst measured using the International Electrotechnical Commission (IEC) flickermeter for a rectangular fluctuation is discontinuous for certain values of the frequency of fluctuation. These discontinuities do not represent a real physiological perception of flicker, but they are a consequence of the nonlinear behavior of blocks 1, 4, and 5 of the IEC flickermeter. We have theoretically proved the origin of these discontinuities, and we have experimentally identified and quantified them. Although these discontinuities do not influence the Pst values recorded in the field, they are an intrinsic characteristic of the flickermeter model proposed in the IEC 61000-4-15 standard. This paper contributes to a better understanding of how the IEC flickermeter works when subject to rectangular fluctuations. Furthermore, the identification and quantification of these discontinuities can help to improve the design of the performance tests of the flickermeter.

Effect of the Sampling Rate on the Assessment of Flicker Severity Due to Phase Jumps

This paper presents an analysis of the effect of the sampling rate on the calculation by a digital flickermeter of the flicker severity caused by phase jumps. The new edition of the IEC 61000-4-15 standard includes an innovative test aimed at verifying that a flickermeter works properly during a phase jump event. Since phase jumps are rapid angle changes, it seems that a high sampling rate should be used by a digital instrument. This requirement could be too demanding, so we have studied this hypothesis by defining three analytical signal models. One is based on the characterization of ideal phase jump sequences and the other two are based on the definition of realistic band-limited signals containing phase jumps. We found that the minimum sampling rate necessary to pass that test is not as demanding as expected. Practical experiments made by an actual generation and acquisition system confirm this conclusion. A typical sampling rate of 3200 S/s, usually used in commercial flickermeters, becomes clearly sufficient to pass the test. However, we give notice that passing this test could not guarantee accurate results when the phase jumps are different from those specified by the standard.

Rapid Voltage Changes in Power System Networks and Their Effect on Flicker

A rapid voltage change (RVC) is a type of power-quality (PQ) disturbance that has not received sufficient attention in the international PQ standards. Presently, EC 61000-4-30, Ed. 3, defines a precise method for RVC detection and analysis. RVCs can cause or contribute to flicker. However, the existing studies on the subject have not found a correlation between the short-term flicker severity index Pst and the parameters of an RVC event. This paper provides an interpretation of this lack of correlation and shows that instead there is a correlation of RVC events with the instantaneous flicker sensation Pinst. This work is based on the analysis of both simulated waveforms containing RVCs and waveforms recorded in low-voltage and medium-voltage locations.

Type testing of a highly accurate illuminance flickermeter

The standard IEC 61000-4-15 establishes the design specifications to measure the annoyance produced by flicker. This instrument is based on the working principles and the response to input voltage variations of an incandescent lamp, which was taken as the reference lamp for the design. However, nowadays new lighting technologies are being adopted worldwide and the incandescent lamp has fallen into disuse. With the purpose of characterizing the sensitivity to voltage fluctuations of new modern lamps an adapted flickermeter has been designed. This tool uses as input the illuminance signals registered from the different lighting technologies. This paper describes the implementation of an illuminance flickermeter as well as its functional verification according to the type tests described in the new edition of the IEC 61000-4-15 standard.