IEEE St 1410 Revision Lightning Induced Voltages A. Borghetti C.A. Nucci M. Paolone
description
Transcript of IEEE St 1410 Revision Lightning Induced Voltages A. Borghetti C.A. Nucci M. Paolone
ALMA MATER STUDIORUM – UNIVERSITA’ DI BOLOGNA
IEEE St 1410
Revision
Lightning Induced Voltages
A. Borghetti C.A. Nucci M. Paolone
2009 IEEE JTCMeetingAtlanta, GA
Lightning Performance of Distribution Lines
To get the ___ we need:
1. Statistical distribution of lightning current parameters (peak, rise time, …)
2. Incidence model
3. Induced-voltage model
4. Statistical approach
1.00 10.00 100.00 1000.00
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0.501.002.00
5.00
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20.0030.004 0.0050.0060.0070.0080.00
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95.00
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1. Statistical Distribution of Lightning Current Amplitude
6.2*
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1)(
P
PPI
IIP
[kA]
IEEE:
Ip 20kAIp = 61.1 kAln Ip = 1.33
Ip > 20 kAIp = 33.3 kAln Ip = 0.605
Cigré:
For our purposesthe two approaches are equivalent
Lightning Performance of Distribution Lines
To get the ___ we need:
1. Statistical distribution of lightning current parameters (peak, rise time, …)
2. Incidence model
3. Induced-voltage model
4. Statistical approach
Lightning Performance of Distribution Lines
To get the ___ we need:
1. Statistical distribution of lightning current parameters (peak, rise time, …)
2. Incidence model
3. Induced-voltage model
4. Statistical approach
0.65s I10r sg rr 0,9
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sl hrrd
IEEE WG lateral attractive distance
2. Incidence model
It is just worth mentioning that other expressions exist: - Eriksson- Rizk- Dellera and Garbagnati (LPM)
rs
rg
Nearby stroke
hdl
Direct stroke
Lightning Performance of Distribution Lines
To get the ___ we need:
1. Statistical distribution of lightning current parameters (peak, rise time, …)
2. Incidence model
3. Induced-voltage model
4. Statistical approach
2
00
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1
12
11
cvc
vyhIZ
Umax
2
00
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1
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11
cvc
vyhIZ
Umax
Rusck simplified formula
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Assumptions: a. single-conductor b. infinitely long lines above ac. perfectly cond. groundd. step current waveshape
v return stroke velocity
3. Induced voltage calculation model (present)
'1
2sw sw c
sw g
h ZU
U h Z R
'1
2sw sw c
sw g
h ZU
U h Z R
h=0,75h=0,75
Too simple: not adequate in many cases!
Return stroke model: Modified Transmission Line Exponential Decay (MTLE) or any other typeLEMP: Uman and McLain and Cooray-RubinsteinCoupling model: Agrawal extended to the case of lossy ground
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z
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3. Induced voltage calculation model (revised)
Note: the shield wire is simply one of the conductors of the n-conductor system
Lightning Performance of Distribution Lines
To get the ___ we need:
1. Statistical distribution of lightning current parameters (peak, rise time, …)
2. Incidence model
3. Induced-voltage model
4. Statistical approach
4. Statistical approach (present)a) The assumed range of peak values of lightning current Ip at the
channel base, from 1 kA to 200 kA, is divided in 200 intervals of 1 kA.
b) For each interval i, the probability pi of current peak value Ii to be within interval i is found as the difference between the p for current to be than the lower limit and the p for current to reach or exceed the higher limit. These ps are obtained by using the formula seen before
c) For each interval i, also two distances form the line (in m) are calculated: 1) the minimum distance ymin,i (using the IEEE incidence
model) for which lightning of peak current Ii (in kA) will not divert to
the line, and 2) the maximum distance ymax,i at which lightning may
produce an insulation flashover (using the Rusck formula), i.e. an induced voltage equal to the line critical flashover voltage CFO (in kV), multiplied by a factor equal to 1.5 (to take into account the turn-up in the insulation volt-time curve for short front-time surges).
d)
200
max min1
0,2 i ip g i
i
F y y N p
4. Statistical approach (present)a) The assumed range of peak values of lightning current Ip at the
channel base, from 1 kA to 200 kA, is divided in 200 intervals of 1 kA.
b) For each interval i, the probability pi of current peak value Ii to be within interval i is found as the difference between the p for current to be than the lower limit and the p for current to reach or exceed the higher limit. These ps are obtained by using the formula seen before
c) For each interval i, also two distances form the line (in m) are calculated: 1) the minimum distance ymin,i (using the IEEE incidence
model) for which lightning of peak current Ii (in kA) will not divert to
the line, and 2) the maximum distance ymax,i at which lightning may
produce an insulation flashover (using the Rusck formula), i.e. an induced voltage equal to the line critical flashover voltage CFO (in kV), multiplied by a factor equal to 1.5 (to take into account the turn-up in the insulation volt-time curve for short front-time surges).
d)
4. Statistical approach (revised)1. Inputs: lightning current parameters, return stroke velocity, line
and ground data2. Random generation of events ( Ip tf x y) (e.g. > 10 000)
3. Selection of indirect lightning events by using a lightning incidence model
4. Induced overvoltage calculation using advanced models (and relevant tools)
5. Counting of the n events generating overvoltages greater than the insulation level (e.g. 1.5·CFO)
6. Plot the graph: No. of flashovers/100 km/year vs CFO where No. of flashovers/100 km/year = (n/ntot)·ng·S·100/L(with ng = annual ground flash density, S = striking area, L=line length)
correlated
4. Statistical approach (revised)1. Inputs: lightning current parameters, return stroke velocity, line
and ground data2. Random generation of events ( Ip tf x y) (e.g. > 10 000)
3. Selection of indirect lightning events by using a lightning incidence model
4. Induced overvoltage calculation using advanced models (and relevant tools)
5. Counting of the n events generating overvoltages greater than the insulation level (e.g. 1.5·CFO)
6. Plot the graph: No. of flashovers/100 km/year vs CFO where No. of flashovers/100 km/year = (n/ntot)·ng·S·100/L(with ng = annual ground flash density, S = striking area, L=line length)
correlated
The revised method and the new Statistical approach
equivalent as far as an ‘infinitely long line’ is concerned
improved in the new version when distribution systems having realistic configurations are analyzed.
4. Statistical approach (revised)
0.001
0.010
0.100
1.000
10.000
100.000
50 100 150 200 250 300
CFO (kV)
Fla
shov
ers/
100k
m/y
r
ideal ground
ground conductivity = 10 mS/m
ground conductivity = 1 mS/m
Fig. 5 of rev. 1410 (Modelling details in Appendix B)
From De La Rosa et al, IEEE Trans. on PWDR, 1988 From Ishii et al. CIGRE Colloquium SC33, Toronto, 1997
Validation – Scale Model, Univ. of Tokyo and Real Lines, IIE, Cuernavaca
0.001
0.010
0.100
1.000
10.000
50 100 150 200 250 300
Fla
shov
ers/
100k
m/y
r
CFO (kV)
(A) IEEE Std. 1410 2004 - Rusck (B.2)
(B) ideal ground
(C) ideal ground, tf =1 μs
Fig. B.3 in Appendix B of rev. 1410 – “Check”
0.001
0.010
0.100
1.000
10.000
50 100 150 200 250
Fla
shov
ers/
100k
m/y
r
CFO (kV)
(A) IEEE Std. 1410 2004 - Rusck (B.2) and (B.3)
(B) tf =1 μs (groundings each 30 m)
(C) tf =1 μs (groundings each 500 m)
Fig. B.4 in Appendix B of rev. 1410 – Effect of shield wire
Fig. B.5 a, b in Appendix B of rev. 1410 – Effect of SA
σg = 1 mS/m
Ideal ground
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