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)