This paper aims at characterizing and improving the metrological performances of Current (CT) and Voltage Instrument Transformers (VT) in harmonic measurements in power system. A theoretical analysis is carried out to demonstrate that, due to the iron core non linearity, CT and VT output signal is distorted even when the input signal is a pure sinusoidal. Starting from this analysis, a new method for CT and VT characterization and compensation is proposed. In a first step, they are characterized in sinusoidal conditions and the harmonic phasors of the distorted output are measured; in the second step, these phasors are used to compensate the harmonic phasors measured in normal operating conditions, which are typically distorted. The proposed characterization and compensation techniques are called SINDICOMP (SINusoidal characterization for DIstortion COMPensation). Several experimental tests, using high accuracy calibration setups, have been performed to verify the proposed methods. The experimental results showed that the SINDICOMP technique assures a significant improvement of CT and VT metrological performances in harmonic measurements.

The electrical arc occurring in the sliding con-1 tact between the supply contact line and the current collector 2 (pantograph) of an electrical locomotive is a fast transient 3 phenomenon able to degrade progressively the line-to-pantograph 4 contact quality and, consequently, the continuity of operation.

RIASSUNTOScopo - Descrizione del carico, degli atteggiamenti e degli interventi ricevuti da un campione di familiari di pazienti con schizofrenia reclutati in otto DSM stratificati per area geografica e per densità di popolazione. Disegno - Studio trasversale di familiari-chiave di pazienti con diagnosi DSM-IV di schizofrenia in fase di compenso clinico. Valutazione delle: a) relazioni tra carico e caratteristiche cliniche del paziente, socio-demografiche del nucleo familiare, atteggiamenti del familiare nei confronti del paziente, sostegno professionale e sociale ricevuto dalla famiglia; b) differenze nei carico, negli atteggiamenti e nell'aiuto professionale in relazione all'area geografica e alia densità di popolazione. Setting - 8 DSM stratificati per area geografica (Nord, Centro, Sud) e densità di popolazione (urbana vs. rurale).Principali misure - a) dello stato clinico e del funzionamento sociale del paziente: BPRS e ADC; b) del carico, degli atteggiamenti e del sostegno ricevuto: QPF.Risultati - Sono stati raccolti dati relativi a 144 pazienti con schizofrenia e altrettanti familiari. Il carico è risultato correlato positivamente con i livelli di disabilita e di sintomi BPRS positivi e di mania/ostilita, e con il numero di ore trascorse dal familiare a contatto quotidiano col paziente, e negativamente con il livello di aiuto professionale ricevuto dalla famiglia. Il carico è risultato maggiore tra i familiari reclutati nei due centri meridionaii. Gli interventi offerti ai familiari dei pazienti sono piu frequenti e differenziati al Nord e al Centro rispetto al Sud. Solo una minima parte dei familiari ha ricevuto interventi psicoeducativi.Conclusioni - 1 risultati di questo studio sottolineano la necessita di assicurare un'assistenza psichiatrica integrata per i pazienti con schizofrenia che comprenda sia programmi riabilitativi per gli utenti sia interventi informativi e psicoeducativi per le loro famiglie.

With the proliferation of harmonic sources in power systems, current transformers (CTs), which are the most widely used current transducers in power systems, will have to measure and monitor signals with increasing levels of distortion. The accuracy of the measurement can be affected by the nonlinear response of the CT, which is dependent on the distortion in the measured signal, but nonlinear mathematical models can be used to compensate the measured value. In this paper, the complex ratio of the CT is modeled using a frequency domain model based on tensor linearization, obtaining a real-valued compensation matrix. An accurate measurement setup has been built to characterize the CTs performance in distorted conditions. Experimental results using the proposed compensation technique are presented and discussed for two commercial CTs of accuracy class 0.5 and 1. It is demonstrated that the proposed technique can accurately reconstruct the harmonic components (up to several kilohertz) of the CT primary current from the measured CT distorted secondary current.

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This paper proposes a method for the measure-1 ment of digitizer absolute phase errors, defined as the phase 2 displacement between the digitized output and the input analog 3 waveform. The measurement procedure is based on the use of a 4 phase reference signal (PRS), which is theoretically synchronous 5 with the input analog waveform and that triggers the digitizer 6 sampling clock. From the characterization of the waveform 7 generator phase response and the measurement of the time 8 delay of the digitizer sampling clock with respect to the PRS, 9 an accurate evaluation of the digitizer absolute phase error is 10 obtained. The method has been applied to a high-performance 11 digitizer, measuring the absolute phase errors of two different 12 channels. The expanded uncertainty of the method has been 13 quantified as a few microradians at 50 Hz and 150 µrad 14 at 20 kHz.

The assessment of the power quality (PQ) could be a valuable tool to foster the efficiency of the railway systems. PQ 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 PQ in the railway traction supply systems, in particular with reference to the dc and 16.7 Hz systems. The article explores this theme, proposing an extension of the definitions and of the standard measurement procedures for some of the main PQ 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.

This paper proposes a method for the measure-1 ment of digitizer absolute phase errors, defined as the phase 2 displacement between the digitized output and the input analog 3 waveform. The measurement procedure is based on the use of a 4 phase reference signal (PRS), which is theoretically synchronous 5 with the input analog waveform and that triggers the digitizer 6 sampling clock. From the characterization of the waveform 7 generator phase response and the measurement of the time 8 delay of the digitizer sampling clock with respect to the PRS, 9 an accurate evaluation of the digitizer absolute phase error is 10 obtained. The method has been applied to a high-performance 11 digitizer, measuring the absolute phase errors of two different 12 channels. The expanded uncertainty of the method has been 13 quantified as a few microradians at 50 Hz and 150 µrad 14 at 20 kHz.