This document discusses modeling lightning performance of transmission lines using EMTP-RV. It presents methods for computing the annual back flashover rate and critical current for back flashover. Automatic simulations are developed using EMTP-RV to calculate the critical current by running simulations in a loop until flashover occurs. Future work proposed includes developing a 3D EGM interface for EMTP-RV and performing Monte Carlo statistical studies of lightning performance.

1. EMTP-RV
USER GROUP MEETING
EMTP_RV MODELLING FOR THE TRANSMISSION LINE
LIGHNTING PERFORMANCE COMPUTATION
T. Sadovic, S. Sadovic
Dubrovnik 30.04.2009

2. LINE LIGHTNING PERFORMANCE
THE ANNUAL NUMBER OF LIGHTNING
OUTAGES PER 100 KM OF LINE LENGTH
I0, tf
BACK FLASHOVERS
I0, tf I 0, t f
INDUCED
SHIELDING FAILURES

3. LINE BACK FLASHOVER RATE
THE ANNUAL OUTAGE RATE CAUSED BY A I0, tf
FLASHOVER OF LINE INSULATION
RESULTING FROM THE STROKES TO THE
TOWERS AND TO THE GROUND WIRES
Back
flashover

4. LINE SHIELDING FAILURES
THE ANNUAL NUMBER OF LIGHTNING EVENTS THE ANNUAL NUMBER OF
THAT BYPASS THE OVERHEAD GROUND WIRES FLASHOVERS CAUSED BY
AND TERMINATE ON THE PHASE CONDUCTORS SHIELDING FAILURES
I0, tf
Shielding failure
flashover
Shielding failure

5. HOW TO IMPROVE LINE LIGHTNING PERFORMANCE?
Additional Shield Wires
Underbuilt Ground Wire
Increasing Insulation
Line Surge Arrester
Guy Wires
Foot_resistance
improvement

6. LINE SURGE ARRESTER APPLICATION
123 kV Line Dubrovnik - Ston
2 LSA
per tower
1 LSA
per tower

7. ELECTROMAGNETIC TRANSIENTS SIMULATION
MODEL OF THE LINE INSULATION FLASHOVER
(s2)
Flashover models:
U(t) (s1)
(U - t) Insulation characteristic Constant voltage
U2 Equal area
U1
Leader propagation
U0
Leader propagation model:
t2 t1 t u (t )
u (t ) 0 , 0015
d
vl 170 d E0 e
d ll
d l vl - Leader speed (m/s)
u(t)
d - Arcing distance (m)
ll - Leader length (m)
u(t) - Applied voltage (kV)
E0 = 520 (kV/m)

8. EQUAL AREA FLASHOVER MODEL d Ugap(t)
U(t)
t 710
( U gap (t ) U 0 ) k
D U (400 ) d (kV) [IEEE]
U2 s t0
t 0, 75
k 1
U50% D 710
U0 U8 s U 50% (400 ) d 550 d
80, 75
2 8 t ( s) U0 0,9 U 50% 495 d
EMTP_RV Model data:
710
U2 s (400 ) d 822 d
[d - arcing distance in meters] 2 0, 75
U0 495 d
D 0,2045 d
k 1
D 0,2045 d

9. ELECTROMAGNETIC TRANSIENTS SIMULATION
SOIL IONIZATION TOWER FOOTING RESISTANCE MODEL
I
Rlc
Ri U (kA) Linear Resistance
I
1
Ig
Non-Linear Resistance
Eg
Ig 2 I (kA)
2 Rlc
Ig
Rlc – low current tower footing resistance ( )
Ri – tower footing impulse resistance ( )
I – impulse current (kA)
Ig – soil ionisation limit current (kA)
Eg – soil ionisation critical electric field (kV/m) – [Eg = 400 (kV/m)]

10. QUICK BACK FLASHOVER RATE COMPUTATIONS
Stroke current is changed until
flashover [IC obtained]
W - Line shadow width
A - Line attraction area
IC
hav - Tower average height
IC - Back flashover critical current
100 km
A = 100 x W (km2) W
Back
hav Flashover
Ra 14 hav, 6
0
W 2 Ra b
A 100 W
N L NG A
W

11. QUICK BACK FLASHOVER RATE COMPUTATIONS
100 km
IC
A = 100 x W (km2) W
1 Ra 14 hav, 6
0
PI C
I
Back 1 ( C ) 2,6 W 2 Ra b
hav Flashover 31
A 100 W
BFR 0,6 N L PI C
N L NG A
W - Line shadow width
b - Ground wire separation distance
W
NL - Number of strokes collected [str/100km/year]
NG – Ground flash density [str/km2/year]
BFR - Back flashover rate
0,6 > Takes into account strokes hitting shield wire

12. IEEE DISTRIBUTION
1 i0 (t) S (kA/ s)
CURRENT PEAK
PI
I
1 ( ) 2,6 I0
31
I0/2
1 t ( s)
STEEPNESS PS
S 4 tf tt
1 ( )
24
Equal Probability PS PI
I0
S
tf
Equivalent Front Time

13. 123 kV TRANSMISSION LINE DUBROVNIK STON
No DC Resistance Outside diameter x [m] y [m] y [m]
[Ohm/km] [cm] at midspan
1 0.1444 1.708 2.5 22.7 14.1
2 0.1444 1.708 -3 20.5 11.9
3 0.1444 1.708 3.5 18.3 9.7
4 0.4555 0.9 0 28.9 21.3
4
L1 = 2,8 H
L2 = 1,37 H
Un= 123 kV
Length = 46 km L3 = 1,37 H
1 Span = 200 m
L = ZT/v
2 v - velocity of light hT = 28,9 m Propagation
3 element
lprop = 20 m
ZT = 184

14. LINE SURGE ARRESTER
Rated voltage: 123 kV
IEC Class II
Polymer housed
Current (A) Voltage (V)
1000 239000
2500 252000
5000 275000
10000 291000
20000 324000
40000 357000

15. 123 kV TRANSMISSION LINE DUBROVNIK STON
Ground flash density: 5 strokes/km2/year
Length = 46 km
Ra 14 hav, 6
0
14 28,90, 6 105 (m)
W 2 Ra b 2 105 0 210 (m)
A 100 W 100 0,210 21 (km2)
N L N G A 5 21 105 (strokes/100km/year)
Using EMTP_RV find IC (Critical current)
1
PI C
I
1 ( C ) 2,6
31
BFR 0,6 105 PI C

16. AUTOMATIC BACKFLASHOVER COMPUTATIONS
EMTP_RV Line section model created
Netlist file obtained

17. AUTOMATIC BACKFLASHOVER SIMULATIONS
Tower Model> Sub circuits
Air gap model
Signal = 0: No flashover
Signal =1: Flashover

18. AUTOMATIC BACKFLASHOVER SIMULATIONS
Tool developed to run EMTP_RV in a loop
Initial stroke current Current step

19. AUTOMATIC BACKFLASHOVER SIMULATIONS
EMTP_RV is running in the loop until gap signal > 0
Stroke Sub circuit
Flashover Tower 2
Phase conductor C

20. AUTOMATIC BACKFLASHOVER SIMULATIONS
EMTP_RV is running in the loop until gap signal > 0
Critical current
Back flashover rate

21. FUTURE WORK > 3D EGM
I0, tf
WS - SIMULATED WIDTH
STRIKING DISTANCES
DOWNWARD
LEADER 1. TO PHC & GW:
rT1 rS = A I B
rT2
[A=10, B=0,65]
span 2. TO TOWERS:
rTT = k rS
rE
[k= 1 – 1,1]
3. TO EARTH:
x0 WS
y0 IEEE : rE 3,6 1,7 ln(43 yv ) I0,65

22. FUTURE WORK > 3D EGM
DOWNWARD
I0, tf
LEADER APPROACHES
UNDER ANGLE
2
f cos2
rGW rGW = rPHC = rNO = rS
rPHC GW
rNO
NEARBY PHC
OBJECT
hl
dl
x0
WS/2 WS/2

23. FUTURE WORK > sigma slp like interface
EMTP_RV modeling and transients computation
Monte Carlo Statistical Study and 3D EGM