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LightningLightning&&
insulationinsulationcoordinationcoordination
S. R. LAMBERTS. R. LAMBERTSHAWNEE POWER Consulting, SHAWNEE POWER Consulting, llcllc
LIGHTNINGLIGHTNINGFLASHFLASH
CHARACTERISTICSCHARACTERISTICS
FLASH STATISTICSFLASH STATISTICS55% OF FLASHES HAVE MORE THAN ONE STROKE
90% OF FLASHES HAVE LESS THAN NINE STROKES
MEAN NUMBER OF STROKES/FLASH -THREE
80-90% OF STROKES ARE NEGATIVE
+++++++++ ++++++++++++++++ +++++++
++---------------------- -------------------- ++
-- ++-- ++
Neg Flash Pos Flash
LIGHTNINGLIGHTNING
CHARACTERIZED BY
CURRENT MAGNITUDE
STROKE RISE TIME
KERAUNIC LEVEL OR FLASHES/km2
STROKE MAGNITUDESSTROKE MAGNITUDES
0.01
0.1
1
10
100
0 50 100 150 200 250
Stroke Current kA
Prob
. of E
xcee
ding
Abs
ciss
a First Stroke
STROKE MAGNITUDESSTROKE MAGNITUDES
0.01
0.1
1
10
100
0 50 100 150 200 250
Stroke Current kA
Prob
. of E
xcee
ding
Abs
ciss
a
First StrokeSubsequent Strokes
STROKE MAGNITUDESSTROKE MAGNITUDES
6.2I6.2I
1211
1 P
3111
1 P
+
=
+
=
FIRST STROKE SUBSEQUENTSTROKES
TYPICAL FIRST STROKETYPICAL FIRST STROKE
-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0 5 10 15 20 25 30 35 40
µs
pu c
urre
nt
First Stroke
SUBSEQUENT STROKESSUBSEQUENT STROKES
-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0 5 10 15 20 25 30 35 40
µs
pu c
urre
nt
First Stroke
Subsequent Strokes
1.2 x 50 IMPULSE SHAPE1.2 x 50 IMPULSE SHAPE
-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0 5 10 15 20 25 30 35 40
µs
pu c
urre
nt
First Stroke
Subsequent Strokes
1.2 x 50 wave
GROUND FLASH DENSITYGROUND FLASH DENSITY
GROUND FLASH DENSITYGROUND FLASH DENSITY
HOW DOES LIGHTNING GET HOW DOES LIGHTNING GET INTO THE SYSTEM?INTO THE SYSTEM?
Shielding Failures
Back Flashovers
Induced Surges
SHIELDING FAILURESHIELDING FAILUREZph 400 Ω
Is = 5 kA
Vph =5 kA/2*400 =1 MV
`
Zsw
Zsw
Is
Ztwr
Vph
Vtwr
`
Zph
`
Zph
BACK FLASHOVERBACK FLASHOVER
`Zsw
Ztwr
Ztfr
Vph
Vtwr
Zsw
Is
EXAMPLEEXAMPLE
TLine TLine
10 kA SURGE10 kA SURGESWITLIGHTB
15000
10000
5000
0
-5000
# 7:LIGHT SURGEC (A)
2.000E6
1.500E6
1.000E6
500000
0
# 5:SURGEC (V)
4.000E6
3.000E6
2.000E6
1.000E6
0
# 1:XFRMC (V)
0Time in Seconds C:\ATPDraw\Atp\SWITLIGHTB.mdb
5.000E-6 1.000E-5 1.500E-5 2.000E-5 2.500E-5 3.000E-5 3.500E-5 4.000E-5 4.500E-5 5.000E-5
XFRM W/WO CAPACITORXFRM W/WO CAPACITOR
0
500000
1e+006
1.5e+006
2e+006
2.5e+006
3e+006
3.5e+006
0.000025 0.000030 0.000035 0.000040 0.000045 0.000050
Time in Seconds
# 1:XFRMC (V) XFRMC w/10000pF Cap
C:\ATPDraw\Atp\SWITLIGHTB.mdb
SWITLIGHTB
SURGE ARRESTERSURGE ARRESTERAPPLICATIONAPPLICATION
WITH CAP AND SAWITH CAP AND SA
0
500000
1e+006
1.5e+006
2e+006
2.5e+006
0.000025 0.000030 0.000035 0.000040 0.000045 0.000050
Time in Seconds
# 1:XFRMC (V) XFRMC w/SA
C:\ATPDraw\Atp\SWITLIGHTB.mdb
SWITLIGHTB
XFRM VOLTAGEXFRM VOLTAGE--SA AMPSSA AMPSSWITLIGHTB
300000
250000
200000
150000
100000
50000
0
XFRMC w/SA
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
SA Current
3.300E-5Time in Seconds C:\ATPDraw\Atp\SWITLIGHTB.mdb
3.400E-5 3.500E-5 3.600E-5 3.700E-5 3.800E-5 3.900E-5
SURGE ARRESTERSURGE ARRESTERAPPLICATION APPLICATION -- ZnO TYPEZnO TYPE
FOR THE ARRESTER TO SURVIVE:MCOV - maximum continuous operating voltageTOV - temporary overvoltage capabilityENERGY - Absorption Capability
PROTECTIVE LEVEL - function of surge magnitude and rise time
PROTECTIVE LEVELPROTECTIVE LEVEL
0
10
20
30
40
50
60
70
80
0 5000 10000 15000 20000 25000
8x20 Impulse Current
Dis
char
ge V
olta
ge ZnO Arrester
27 kV Rating
PL as f(rise time, current)PL as f(rise time, current)
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
0.1 1 10
Time to Crest of Current Wave µs
PL in
pu
of 1
0 kA
, 8x2
0
40 kA20 kA10 kA 5 kA
WHERE DID BIL’SWHERE DID BIL’SCOME FROMCOME FROM
LOW FREQUENCY TEST
BIL - (from transformers)
2.2 X LOW FREQUENCY TEST + 40 kV
38 kV - 70 x 2.2 + 40 = 194 kV ::: 200 kV BIL
TEST LEVELSTEST LEVELS
SA PROTECTIVE MARGINSSA PROTECTIVE MARGINSAFTER SELECTING ARRESTER FOR MCOV AND TOVCALCULATE MARGIN - BIL DIVIDED BY PROTECTIVE LEVEL - at 10 kA, 8x20µs27 kV - 10 kA PL is 66.3 kV
150 kV BIL/ 66.3 kV PL = 2.26 or 126% MARGIN SEPARATION DISTANCE, ALTITUDE, LEAD LENGTH, CURRENT MAGNITUDE, RISE TIMEI THINK A MARGIN OF 40% IS THE MINIMUM ACCEPTABLE FOR NSR
ARRESTER SEPARATION DIST.ARRESTER SEPARATION DIST.
ARRESTER SEPARATION DIST.ARRESTER SEPARATION DIST.
950
1000
1050
1100
1150
1200
1250
0 5 10 15 20 25 30 35 40
Separation Distance (ft.)
Prot
ectiv
e Le
vel (
kV)