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Investigating Lightning Induced Currents in Photovoltaic Modules
Kurt Michael Coetzer, Pieter Gideon Wiid, Arnold Johan Rix
Stellenbosch University, South Africa
Bypass diode failures have been observed within solar photovoltaic (PV) plants after thunderstorm activity, with no evidence of direct lightning strikes to the PV plant. This paper examines the mechanisms by which currents may be induced within PV installations. Firstly by means of computational electromagnetic simulations, and secondly by means of real-world testing in a high-voltage laboratory. These investigations were conducted with the objective of minimizing the magnitudes of induced currents within a PV installation. It was found that poor inter-module wiring in a PV installation, and not the internal layout of the PV modules themselves, resulted in the largest magnitudes of the induced currents, and that better wiring practice would significantly reduce these magnitudes. The presence of the conductive frame of a PV module was shown to reduce the magnitudes of the currents induced within the installation.
Characteristics of Radiated Emission by PLC Signal from Three-wire Power Cable
1Kyushu Institute of Technology, Japan; 2Panasonic Corporation, Japan
Characteristics of radiated emission from the three-wire power cable where the power line communication signal was transmitting was studied by using circuit theory. The simple model whose length was 14.4m was used for the investigation, and the radiated emission was calculated and measured. The average deviation between the calculated data and the measured data was -3.6dB and the standard deviation was 3.3dB. The calculation results indicated that the maximum magnetic field strength could be estimated from the maximum common-mode current. The analysis also suggested that the maximum common-mode current of a three-wire cable was less than that of a two-wire cable in many cases.
Detection Methods for Current Signals Causing Errors in Static Electricity Meters
Fani Barakou1, Paul Wright1, Helko van den Brom2, Gertjan Kok2, Gert Rietveld2
1National Physical Laboratory, United Kingdom; 2VSL, The Netherlands
In recent years, the shift to Distributed Generation (DG) and the use of smarter domestic appliances has led to an increasing integration of power electronics (active infeed converters, power drive systems etc.) at the household level. However, the use of more power electronics results in the generation of highly distorted currents entering the distribution grid. Previous research shows that such current waveforms can cause large errors in static electricity meters. Thus, there is an imperative need to study the characteristics of these current waveforms and their impact on meter readings by performing extended measurements in households. Since it is not practical to store all the high granularity waveform data of such measurements, suitable detection methods and trigger levels need to be defined to only capture the potentially problematic current waveforms. In this paper, signal processing techniques (differentiation, Short Time Fourier Transform and Wavelet Transform) are applied to
current signals in order to extract features suitable for use as a trigger. Results show that the Discrete Wavelet Transform and the filter with derivative method give the most promising results and work reliably even for very noisy signals.