WSEAS Transactions on Circuits and Systems
Print ISSN: 1109-2734, E-ISSN: 2224-266X
Volume 13, 2014
Time-Scale Analysis of Magnetic Field Intensity Produced by High Voltage Powerlines
Authors: , , ,
Abstract: High voltage powerlines represent one of the most important source of exposition to ELF electrical and magnetic fields for population and environment. The time and frequency analysis of fields produced by such sources is fundamental in order to properly characterize them and correctly evaluate the relative exposition. This is particularly important for fields characterized by different spectral components, for which the exposure limits are specified in function of frequency as stated by the ICNIRP guidelines for limiting exposure to time – varying electric, magnetic, and electromagnetic fields. If the frequency composition of such fields is non – stationary during the measurement time interval, the “traditional” frequency analysis techniques based on simple Fourier transform cannot be applied, but time -frequency and /or time –scale analysis techniques, assuming the signal stationary during a sufficiently small time interval, must be performed. Among these, a great importance have those based on different versions of multiresolution algorithms. The aim of this work is to analyse, by means of such techniques, the time – frequency features of magnetic ELF fields produced by typical high voltage (150 and 220kV) powerlines in their neighbourhood. To such purpose, a set of magnetic broadband field measurements has been performed at specific points placed at difference distances from high voltage wires during a “typical” day (that’s to say during normal operative conditions). Discrete wavelet transform and Daubechies multiresolution algorithms has been applied to the measured fields time history, showing the results obtained respectively using various base atoms system (Gabor, Gauss, Morlet and Franklin atoms in particular) and different Daubechies parameters number. It will be shown how a properly use of these transforms can help us to characterise sources emission especially in order to evaluate human and environmental exposition to ELF magnetic fields.
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Keywords: Magnetic Field, ELF, Time – Frequency Analysis, Multiresolution, Wavelet, High – Voltage Powerlines, Human Exposition
Pages: 233-240
WSEAS Transactions on Circuits and Systems, ISSN / E-ISSN: 1109-2734 / 2224-266X, Volume 13, 2014, Art. #24