Download PDFAbstract:
This paper has as objective to present
preliminary results of a study of lightning performance
for medium voltage distribution networks, submitted to
direct and induced lightning overvoltages. In order to
define actions to reduce the network rate of failure the
main parameters responsible for the increase of the
network failure rate are investigate.
In this stage of the study, some simplifications had been
considered. However, the result show that is possible to
direct the actions for an economic solution of a series of
problems, which represents the great majority of the
occurrences involving lightning discharges.
Introduction:
Nowadays many actions for the protection of overhead
distribution lines are not well defined and normally
without any transient performance study. As a result,
many of them besides of presenting high costs are not
effective. This study has the purpose of leading to an
efficient method for the reduction and mitigation of the
effects of the lightning discharges in medium voltage
overhead distribution lines.
The lightning discharges are one the main causes of
interruptions of medium voltage overhead distribution
lines, being the reason of great concern for the utility
companies. 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
applied by ANEEL (National Agency of Electric
Energy).
With the beginning of the deregulation of the electric
energy supply, 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 most 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 even by laboratory tests.
Therefore, the results are not the most satisfactory and
do not achieve a suitable rate of cost by benefit.
Among others, the distribution network reliability
depends directly on its exposition to the lightning
discharges. To determine the exposition level of the
line, the designer should know the number of discharges
to the ground per unit of area per unit of time.
Once that the atmospheric discharges phenomena are
random, this paper considers that the parameter
generation of the discharges follows the statistical data
proposed by Anderson and Eriksson [3]. The Monte
Carlo Method is used to generate the incidence
distribution of the discharges and the Electro
Geometrical Model for determining the interception
point of the discharge.
References:
[1] Nucci, Carlo Alberto; Paolone, Mario; Borghetti, Alberto. “Effect of tall-instrumented towers on the statistical distributions of lightning current parameters and its influence on the power system lightning performance assessment.”, VII SIPDA, Curitiba, November, 2003;
[2] IEEE Guide for Improving the lightning performance of electric power overhead distribution lines, IEEE Standard 1410-1997, June 1997;
[3] Anderson R.B., Eriksson A.J., “Lightning parameters for engineering application”, Electra, No. 69, 1980;
[4] Martinez, Manuel L. B.; Mendonça dos Santos, Pedro H. “Induced Voltages in Distribution Networks Study, Guide for Improvement of the Performance of Overhead Distribution Networks Against Lightning Discharges.” High Voltage Laboratory of the Federal University of Itajubá, MG, Brazil, March 2004;
[5] Metwally, I. A.; Heidler, F. H.; Nickel, R. “Computation of collection area and probability of lightning strikes to structures using the Electro geometric model.”, VIII SIPDA, São Paulo, November 2005;
[6] Grzybowski, S.; Rodriguez-Medina, B. “Striking distance dependence on rod height and impulse polarity: A system identification approach.” VIII SIPDA, São Paulo, November 2005;
[7] Torres, Horacio. “Statistical evaluation of lightning induced overvoltages in distribution lines in the presence of transformers and surge arresters.” VII SIPDA, Curitiba, November 2003.
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