Download PDFAbstract:
The aim of this paper is to present the results of the
performance study of medium voltage overhead distribution
lines against lightning discharges, in the way to define
methodologies to reduce the system failures.
The results are obtained within the partnership among the
High Voltage Laboratory of the Federal University of
Itajubá, AES Sul Utility Company and the University of
Bologna.
Direct discharges and induced surges were simulated into
real networks to identify the major factor of influence for
network failures. Then commentaries on the relative
performance and comparisons of different construction
configurations of overhead lines are presented.
Introduction:
The standard medium voltage distribution network are
subjected to incidence of direct lightning discharges and
induced surges, that are one of the main causes of
interruptions and failures of the lines.
The majority of the damages to the distribution network are
caused by direct discharges, its destructive effects
frequently extends to equipments and connected
installations, with the possibility to cause personal injuries
and material damages, beyond economic losses, due to out
of income and the possibility of indemnities, penalties and
fines.
However, they can be deviated by tall structures, such as
towers, buildings, high constructions, and trees. Even when
the lightning does not intercept the network, they induce
surges that travel throughout the lines. These surges are able
to cause many damages and interruptions to the distribution
network.
Some actions were been taken by the utilities for the
prevention and minimization of the damages associated to
the lightning discharges.
However, as the lightning discharges are random events,
consequently, difficult to predict, the majority of these
actions does not follow a study or a detailed analysis of the
problem.
By this way, in the majority of the cases the actions were
taken based on the knowledge of the engineer in charge, or
based in rules defined without any effective evidence, by
means of studies or by laboratory tests. As a result, many of
them besides of presenting high cost are not effective.
Among others, the distribution network reliability depends
directly on its exposition to the lightning discharges. The
topology of the distribution network is the major factor of
influence for analysis [1], and its density and distribution
results in a greater or minor probability of incidence of
direct lightning discharges.
Once that the atmospheric discharges phenomena are
random, this work considers that the parameter generation
of the discharges follows the statistical data proposed by
Anderson and Eriksson.
The Monte Carlo Method is used for the incidence
distribution of the discharges and the Electro Geometrical
Model for the interception point of the discharge.
References:
[1] M. A. M. Saran, M. L. B. Martinez, H. R. P. M. de Oliveira, 2006, “Performance of Medium Voltage Urban and Rural Distribution Lines Front Lightning Discharges and Induced Surges”, GROUND’2006 & 2nd LPE, Maceió, Brazil;
[2] M. A. M. Saran, R. R. Bonon, M. L. B. Martinez, H. R. P. M. de Oliveira, C. A. Nucci, M. Paolone, 2006, “Performance of Medium Voltage Overhead Distribution Lines Against Lightnitning-Induced Voltages: A Comparative Analysis”, GROUND’2006 & 2nd LPE, Maceió, Brazil;
[3] IEEE working group on the lightning performance of distribution lines, 2004, “Guide for improving the lightning performance of electric power overhead distribution lines”, IEEE Std 1410;
[4] IEEE Fast Front Transients Task Force, 1996, “Modelling guidelines for fast front transients”, IEEE Trans. on PWRD, Vol. 11, No. 1, pgs. 493 – 506;
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[8] Rachidi F., Nucci C.A., Ianoz M., 1999, “Transient analysis of multiconductor lines above a lossy ground”, IEEE Trans. on PWDR, Vol.14, No.1, pgs. 294-302;
[9] Paolone M., Nucci C.A., Rachidi F., 2001, “A New Finite Difference Time Domain Scheme for the Evaluation of Lightning Induced Overvoltage on Multiconductor Overhead Lines”, Proc. 5th Int. Conf. on Power System Transient, vol. 2, Rio de Janeiro, Brazil, pgs. 596-602;
[10] Anderson R.B., Eriksson A.J., 1980, “Lightning parameters for engineering application”, Electra, No. 69;
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[12] Borghetti A., Nucci C.A., 1998, “Estimation of the frequency distribution of lightning induced voltages on an overhead line above a lossy ground: a sensitivity analysis”, in Proc. International Conference on Lightning Protection, Birmingham, United Kingdom;
[13] Borghetti A., Nucci C.A., Paolone M., 2001, “Statistical Evaluation of Lightning Performances of Distribution Lines”, Proc. of the International Conference on Power System Transient, Rio de Janeiro, Brazil;
[14] Borghetti A., Nucci C.A., Paolone, “An Improved Procedure for the Assessment of Overhead Line Indirect Lightning Performance and its Comparison with the IEEE Std. 1410 Method”, in press on IEEE Trans. on PWRD;
[15] De Salles, C., Figueira, A. D., Violin, A., Martinez, M. L. B., Oliveira, H. R. P. M., Oling, R., 2003, “Insulation Coordination for a 23 kV Medium Voltage Distribution”, Powertech, Bologna, Italy.
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