Dario Di Cara

Oil-Filled MV/LV Power-Transformer Behavior in Narrow-Band Power-Line Communication Systems

The aim of this paper is to characterize oil-filled power transformers in the narrow-band power-line communication (PLC) frequency range of 50-150 kHz. A new model is proposed for such type of a transformer, in the aforementioned frequency range of interest, in order to study its influence on the signal transmission and to investigate the possibility that the PLC signal can cross the power transformer itself. The new model is simpler than those previously proposed in literature, and it can be used in the whole frequency range available for NB PLC according to the CENELEC EN 50065-1 A-band. In order to validate the model, simulation and measurement results are compared for four oil-filled power transformers with different rated power values. A complete PLC system in the case of a medium-voltage (MV) power network is also simulated, in order to perform a preliminary evaluation of the influence of power transformers on the communication system. The MV overhead power line, the oil-filled power transformers, the MV signal coupling network, and two ST7540 frequency shift keying (FSK) power-line transceivers are included in the simulated system. The performances of the complete PLC communication system are evaluated in the case of both MV to low voltage (LV) and LV to MV transmissions. The analysis is carried out by evaluating the signal attenuation, which is computed as the ratio between the received and transmitted voltage signals, in the case of different line lengths and carrier frequency values.

Current Transformers Effects on the Measurement of Harmonic Active Power in LV and MV Networks

The harmonic active power is used to determine the location of polluting loads, the direction of harmonic power flow and to estimate how consequential a certain current harmonic source is. The highest uncertainties, when measuring harmonic active power, are introduced by the current and voltage transducers. This paper presents experimental results which show the impact of current transformers (CTs) on the accuracy of the harmonic power measurements. An expression for the evaluation of the power error in distorted conditions was developed which can be easily utilized in the case of linear current transducers. It is shown how CTs cannot be considered linear transducers and how the higher the absolute value of the CT phase angle error is, the higher becomes the harmonic power error. The harmonic power error reaches maximum value when the phase shift between the voltage and current harmonic nears . Even high accuracy class CTs may not be adequate enough to assist on harmonic power measurement, while linear current transducers will perform satisfactorily.

On the use of narrow band power line as communication technology for medium and low voltage smart grids

The aim of this work is to perform a feasibility study on the power line communication for the development of a new generation of interface devices (IDs) for smart grid applications. More in detail, this paper deals with one of the most important issues on this topic which is the communication system. Among the existing communication technologies, the study is focused on power line communications (PLCs). After a analysis of the state of the art in the field, the main aspects are analyzed, concerning the open issues on the use of PLCs, especially for medium voltage (MV) and low voltage (LV) systems. In this work the use of PLC in MV-LV networks is investigated, by means of simulations and experimental tests. These tests are performed in a test power network, which includes a MV overhead power line and a MV/LV transformer. The two ways communication channel is characterized, by transmitting a signal from the MV bus-bars and receiving it from the LV network and vice-versa. In this way the possibility to cross the power transformer is investigated.

A PC-based wattmeter for high accuracy power measurements

This paper proposes the use of a commercial data acquisition board (DAQ) connected to a common personal computer for high accuracy power measurements. In the paper the set up of the PC-based wattmeter is described and an experimental evaluation of its metrological performances is made by means of the comparison with a simultaneous coherent digital sampling wattmeter realized with two high-precision DMMs Hewlett Packard Model 3458 A. In both cases the power source is a Fluke 6100A/E electrical power standard.

Secondary substation power line communications for medium voltage smart grids

In this paper a performance analysis is carried out, in order to evaluate the possibility to employ power line communication (PLC) between secondary substations of a medium voltage (MV) distribution networks in a smart grid. The study is focused on the analysis of PLC technologies and the evaluation of the influence quantities on the communication performance in the most common case of by-pass connection at MV bus-bars of secondary substations. Different quantities have been analyzed as modulation techniques, requested bandwidth and bitrate, coupling device and system attenuation versus frequency in order to find the best solution for a reliable communication system. A complete model of a real case study, the distribution network of Ustica Island, have been carried out. Simulation results are presented and discussed.