Roberto Tinarelli

Investigation on Multipoint Measurement Techniques for PQ Monitoring

The problem of locating the sources of harmonic distortion in power networks is still a critical task. Several methods based on multipoint measurement techniques have been recently proposed in the literature for harmonic-pollution monitoring. The main goal of this paper is to compare the two most powerful tools designed for this purpose. In this paper, the results of both computer simulations on an IEEE test network and experimental tests performed by means of simultaneous measurements on an ad hoc benchmark power system are presented along with a discussion on the practical usability of such monitoring techniques

On the use of data from distributed measurement systems for correlating voltage transients to lightning

Voltage transients are the main causes of complaints from medium-voltage customers. For this reason, utilities and independent authorities are focusing their attention on investigation techniques capable of providing information useful for classifying voltage transients depending on their origin. Distributed measurement systems for power quality monitoring able to detect, measure, and classify impulsive transients can be used in coordination with lightning location systems to assess whether there is a relation between a given transient and a lightning event. In this paper, a criterion for evaluating the above correlation is proposed and a numerical example, which is based on real accuracy specifications, is presented. The results show that attempting a correlation between lightning events and induced transients is quite reasonable.

A Distributed Measurement System for Locating Transient-Voltage Sources

The use of a distributed measurement system to locate the source of transient voltages is discussed in this paper. The system implements a method based on the measurement of the starting instants of a transient in the nodes of the monitored network. The method performance is investigated by simulating the system operation. Results in the case of both faults and insertion of capacitors in an IEEE test network are presented and discussed

Design and Performance Analysis of a Differential Current Sensor for Power System Applications

Current measurement is required to ensure the correct operation of power systems. Conventional current transformers are still widely employed in such networks, but their well-known limits make them not suitable for the incoming smart meters. In this paper, a current sensor based on proper measurements of the magnetic field produced by the primary current is proposed. Its main feature is the capability, owing to its particular geometry, of neglecting the effect of external fields without using traditional coil structure. An experimental analysis of its performance in both time and frequency domains is presented and discussed.

Investigation on the Response of the Human Eye to the Light Flicker Produced by Different Lamps

The response of the human eye to flicker depends on the type of lamp used. The standard flickermeter is based on the measurement of voltage and assumes the light source to be a 60 W incandescent lamp. When a different lamp is the source of light flicker, the standard flickermeter gives erroneous results. This paper presents a dynamic model of the eye-brain response to flicker. The model is based on the analysis of the light emitted by the lamp. A suitable measurement system has been developed and three different kinds of lamps have been considered. Experimental results show how the emitted light spectra and the human eye response to different colors determine the level of annoyance

Measurement of the pupil diameter under different light stimula

The subjectivity and the limitation of the standard method for the flicker evaluation have suggested the research of different approaches. The intent is to achieve objective information on the state of annoyance of a human being subjected to light flicker. Recently, a technique based on the analysis of the pupil size variation has been proposed. This paper studies the effects of different light stimula on pupil diameter and highlight some interesting results.

Fault location in underground power networks: A case study

The present paper addresses the topic of fault location in power networks with cable lines. In the era of smart-grid the demand of intelligent measurement systems capable of providing quickly and with high accuracy the right location of faults in power networks is growing fast. Many proposals can be found in literature relevant to different approaches. Some commercial instrumentation is also available on the market for this purpose. Protection relays implementing this feature can either be found. This paper presents the experimental results of a measurement campaign carried out in the MV power network in the city of Milan (Italy). For this purpose the local Utility (A2A SpA) is using a commercial distributed measurement system (the ALTEA FLS) for locating both faults and also fast transients due to customers loads operation. Preliminary experimental results have shown good performance. They have been better analyzed in order to investigate over the reliability and the accuracy of such measurement system.

Analysis of the Effects of Flicker on the Blood-Flow Variation in the Human Eye

Flicker annoyance measurement, regardless if it is performed by processing the supplying voltage or by evaluating the light emitted by the lamp, relies on the assumption of a proper model of the behavior of the complex eye-brain system in the presence of fluctuating light. The only experimental data available are the ones obtained, for a certain incandescent lamp, by asking several people to report their perception about the flicker to which they were subjected. In this paper, the possibility of achieving an ldquoobjectiverdquo evaluation of the flicker effects on a human subject is investigated. In particular, the increment of the blood flow in a vessel at the optic nerve is considered and taken as a possible index of annoyance due to flicker.

Traceability of Low-Power Voltage Transformer for Medium Voltage Application

In this paper, the measuring and calibration techniques useful for ensuring the traceability of nonconventional voltage transformer (VT), used in ac power plant up to 52 kV, are described and discussed. In particular, a setup made by commercially available devices is presented and an in-depth accuracy analysis is performed by considering all the uncertainty sources located in the measurement chain. The obtained results prove that it can be used for the calibration of 0.5 accuracy class low-power VTs. In addition, the sources that contribute more to the uncertainties on the ratio and phase errors are highlighted and suggestions on where to act to further improve the accuracy of the presented setup are given.

Study of the Accuracy Requirements of the Instrumentation for Efficiency Measurements in Power Conversion Systems

Efficiency of power conversion apparatus must usually be measured with very low uncertainty, and depending on the kind of apparatus under test and on the measurement method applied, more or less accurate instrumentation is required. The main issues to be faced, once the target uncertainty is fixed, concern the choice of the measurement method as well as the instruments to be used for fulfilling such requirement. This paper investigates by means of both theoretical analysis and experimental results on the relationship between target uncertainty and instrumentation accuracy in the measurement of uninterruptible power supply efficiency. The results show, amongst other things, that the measurement method allows obtaining very low uncertainty values by means of low accuracy instrumentation.