POWER LINE MAGNETIC FIELD DEVIATIONS FOR THREE DIFFERENT DEFINITIONS OF CURRENT UNBALANCE
Abstract
An estimation procedure of the public’s exposure to the low-frequency magnetic field generated by overhead power lines, according to the international standards, implies measurement and an extrapolation. It is necessary to measure both the magnetic field around the lines and the current in the lines simultaneously. The extrapolation procedure implies the calculation of the maximum magnetic
field that will occur when the line current achieves its maximum. The calculation relies on a proportion between the current in the power line and the magnetic field around the power line, which is valid only when the currents are balanced. Unfortunately, the standards do not cover the unbalanced cases. The relation between the current unbalance and magnetic field could improve the estimation
procedure. In the literature, several different definitions of the current unbalance could be found. In this paper, a comparison of three different definitions of current unbalance and their relation to the
deviation of a magnetic field are considered. The magnetic field is calculated in the vicinity of the bus bar. The same procedure could also be applied around overhead power lines. The definitions for the current unbalance used in this paper are derived from the existing definitions of the voltage unbalance. Only one of these three definitions considers phase unbalance. The relationships between current unbalance and the maximum deviation of the magnetic field are found to be proportional.
Downloads
References
BioInitiative Report: A rationale for a biologically‐based public exposure standard for electromagnetic fields (ELF and RF), http://www.bioinitiative.org
ICNIRP, Guidelines for limiting exposure to time‐varying electric and magnetic fields (1 Hz – 100 kHz), Health Physics, vol. 99(6), pp. 818‐836, June 2010.
Pravilnik o granicama izlaganja nejonizujućim zračenjima, “Službeni glasnik RS“, broj 104, 2009.
IEEE Std 644‐1994, Standard procedures for measurement of power frequency electric and magnetic fields from AC power lines.
IEC 62110:2009, Electric and magnetic field levels generated by AC power systems – Measurement procedures with regard to public exposure.
M. Milutinov, A. Juhas, N. Pekarić‐Nađ, Analysis of effects of current unbalance on magnetic field, 17th Int. Symp. Power Electronics – Ee 2013, Paper No. T.3.7, pp. 1‐4, Novi Sad, Serbia, 30 Oct.‐1. Nov., 2013.
M. Milutinov, A. Juhas, N. Pekarić‐Nađ, Magnetic field in vicinity of busbars with unbalanced currents, 8th Int. PhD Seminar on Computational Electromagnetics and Electromag‐netic Compatibility – CEMEMC 2014, Sep. 02‐04, 2014, Timisoara, Romania.
M. Milutinov, A. Juhas, N. Pekarić‐Nađ, Relative deviation of magnetic flux density as a function of current unbalance, 9th Int. PhD Seminar on Computational Electromagnetics and Bioeffects of Electromagnetic Fields ‐ CEMBEF 2015, Niš, Serbia, Aug. 31, 2015, Proceedings of full papers, pp. 19‐22.
M. Milutinov, A. Juhas., N. Pekarić‐Nađ, A study on exposure to magnetic field generated by unbalanced currents, Trans. on Mathematics & Physics, Scientific Bulletin of Polytehnica, University of Timisoara, vol. 60(74), no.1, pp. 59‐69, 2015.
D. Antić, M. Milutinov, A. Juhas, Polarization of magnetic field in vicinity of busbars with unbalanced currents, 10th Int. PhD Seminar on Computational Electromagnetics and Bioeffects of Electromagnetic Fields ‐ CEMBEF 2017, Osijek, Croatia, Oct. 18, 2017, Proceedings of full papers, pp. 49‐52
J. Driesen, T. Van Craenenbroeck, Power Quality Applica‐tion Guide: Voltage Disturbances ‐ Introduction to Unbal‐ance, Copper Development Association, IEE Endorsed Pro‐vide, May 2002
T. H. Chen, C. H. Yang, N. C. Yang, Examination of the definitions of voltage unbalance, Electrical Power and Energy Systems, vol. 49, 2013, pp. 380‐385
