1 Prevention of Flashover on a Double-circuit 220 kV Line Ivo Uglešić*, A. Xemard**, V. Milardić*, B. Filipović-Grčić* *Faculty of Electrical Engineering and Computing University of Zagreb, Croatia **EDF R&D, Paris, France EMTP-RV USER GROUP MEETING, DUBROVNIK, 30 APRIL 2009
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1
Prevention of Flashover on a Double-circuit 220 kV
Line
Ivo Uglešić*, A. Xemard**, V. Milardić*, B. Filipović-Grčić*
*Faculty of Electrical Engineering and Computing
University of Zagreb, Croatia
**EDF R&D, Paris, France
EMTP-RV USER GROUP MEETING, DUBROVNIK, 30 APRIL 2009
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OUTLINE OF PRESENTATION
INTRODUCTION
SIMULATION OF LIGHTNING STROKES TO
TRANSMISSION LINE
MODELING PROCEDURE FOR TRANSIENT
SIMULATIONS
SIMULATION RESULTS
CONCLUSIONS
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INTRODUCTION
- The case study is related to the improvement of the lightning
performance of a 220 kV double-circuit overhead line, which connects
the thermo power plant to the rest of the power system.
- Several double-circuit outages provoked by lightning caused the
interruption of power supply of the power plant.
- To avoid back-flashovers due to lightning strokes to tower or
overhead shielding wires, the tower footing resistance should be as
low as possible.
- Installation of unbalanced insulation on a double-circuit line is one of
possible solution for suppression of double-circuit simultaneous
faults.
- Installation of line surge arresters (LSA).
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The goal of the simulation is to determine the distribution of lightning
current amplitudes which strike HV transmission line towers and shield
wires or the phase conductors directly.
The Monte Carlo method is used – reproducing numerically a
stochastic problem.
The log–normal distribution of lightning current amplitude:
SIMULATION OF LIGHTNING STROKES TO TRANSMISSION LINE
P - probability of occurrence of lightning current amplitude
higher than I.
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The general expression for the striking distance:
SIMULATION OF LIGHTNING STROKES TO TRANSMISSION LINE
R - striking distance,
I - lightning current amplitude,
a - constant [3.3 – 10.6],
b - constant [0.5 – 0.85].
In calculations is used a=7.2, b=0.65.
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SIMULATION OF LIGHTNING STROKES TO TRANSMISSION LINE
4,5 m
6,5 m
5,0 m
6,7
m6,0
m6
,0 m
A
B
C
30,00m
27,30m
24,60m
22,00m
19,50m
17,10m
4,5 m
6,5 m
5,0 m
6,7
m6
,0 m
6,0
m
3D model of the part of the studied transmission line
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SIMULATION OF LIGHTNING STROKES TO TRANSMISSION LINE
-Total number of simulations 37932,
-1000 simulations finished with phase conductor strikes,
-25635 ground strikes,
-11297 with shielding wire and tower strikes,
-shielding failure occurs in 8.85% cases.
According to statistical calculation, the following characteristics of
the crest values of the current for lightning striking phase conductors
are calculated:
- average value: 15.40 kA,
- variance: 98.36 kA,
- standard deviation: 9.92 kA,
- maximal phase conductor strike current: 42.80 kA,
- critical current: 47.30 kA.
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SIMULATION OF LIGHTNING STROKES TO TRANSMISSION LINE
Distribution of lightning currents striking phase conductors