INSULATIONINSULATIONCOORDINATIONCOORDINATION
AC HIGH VOLTAGEAC HIGH VOLTAGECIRCUIT BREAKERSCIRCUIT BREAKERS
STEPHEN R. LAMBERTSTEPHEN R. LAMBERTSHAWNEE POWER CONSULTING, LLCSHAWNEE POWER CONSULTING, LLC
1. Preinsertion Resistor
2. Grading Capacitor
3. Interrupter
4. Support Column
INSULATION PATHSINSULATION PATHS
PHASE TO GROUND
ACROSS THE OPEN BREAKER
PHASE TO PHASE
1. Preinsertion Resistor
2. Grading Capacitor
3. Interrupter
4. Support Column
VOLTAGE STRESSESVOLTAGE STRESSES
60 Hz
SWITCHING SURGES
LIGHTNING SURGES
60 Hz Overvoltages60 Hz Overvoltages
UNGROUNDED SYSTEMS – 1.73 PUWITH FAULTS
ACROSS OPEN BREAKER – 2.2 PU
SWITCHING SURGE SWITCHING SURGE OVERVOLTAGESOVERVOLTAGES
NO SURGE CONTROLENERGIZING – 3.0 PURECLOSING (trapped charge) – 4.0 PU
WITH PREINSERTION RESISTORS – 2.2 PU
SURGE ARRESTERS LIMITING – 1.9 PU
2.90 PU Phase to Ground Switching Surge345 kV System
-1000
-800
-600
-400
-200
0
200
400
600
800
20 30 40 50 60 70 80 90 100 110 120
Time (ms)
kV
Application of 276 kV Surge Arrester1.83 PU
-600
-400
-200
0
200
400
600
20 30 40 50 60 70 80 90 100 110 120
Time (ms)
kV
-1000
-800
-600
-400
-200
0
200
400
600
800
20 30 40 50 60 70 80 90 100 110 120
Time (ms)
kV
Application of 276 kV Surge Arrester1.83 PU
LIGHTNINGLIGHTNINGFLASHFLASH
CHARACTERISTICSCHARACTERISTICS
+++++++++ ++++++++++++++++ +++++++
++---------------------- -------------------- ++
-- ++-- ++
Neg Flash Pos Flash
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
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
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
BACKFLASHOVERS
INDUCED
BACK FLASHOVERBACK FLASHOVER
`
Zsw
Zsw
Is
Ztwr
Ztfr
Vph
Vtwr
SHIELDING FAILURESHIELDING FAILUREZph 400 Ω
Is = 10 kA
Vph = ? `
Zsw
Zsw
Is
Ztwr
Vph
Vtwr
`
Zph
`
Zph
SHIELDING FAILURESHIELDING FAILUREZph 400 Ω
Is = 10 kA
Vph = 2 MV`
Zsw
Zsw
Is
Ztwr
Vph
Vtwr
`
Zph
`
Zph
EXAMPLEEXAMPLE
TLine TLine
SHIELDING FAILURESHIELDING FAILUREPHASE TO GROUND SURGEPHASE TO GROUND SURGE
@ OPEN BREAKER@ OPEN BREAKER
-1000
-500
0
500
1000
1500
2000
2500
3000
3500
5 7 9 11 13 15 17 19
Time (μs)
kV
INSULATION CAPABILITYINSULATION CAPABILITY& TESTING& TESTING
EARLY 1900’s
60 Hz TESTING ONLY
TEST LEVEL:2.25 x RATED VOLTAGE + 2000 V
1 MINUTE DRY – 10 SECONDS WET
POWER FREQUENCY TEST POWER FREQUENCY TEST LEVELSLEVELS
-960800
-860550
-555362
350425245
315365170
275310145
230260123
14016072.5
758038
506025.8
455015.5
10 Second Wet(kV, rms)
1 Minute Dry(kV, rms)
Rated MaximumVoltage (kV, rms)
Power Frequency Test
CONTACTS OPENCONTACTS OPEN
CONTACTS CLOSEDCONTACTS CLOSED
RATIO TEST VOLTGE TO RATEDRATIO TEST VOLTGE TO RATEDMAXIMUM VOLTAGEMAXIMUM VOLTAGE
2.08960800
2.71860550
2.66555362
3.00425245
3.72365170
3.70310145
3.66260123
3.8216072.5
3.658038
4.036025.8
5.595015.5
In pu of Rated L-G Voltage
1 Minute Dry
(kV, rms)
Rated Maximum
Voltage (kV, rms)
Power Frequency Test
MINIMUM CREEPAGE DIST.MINIMUM CREEPAGE DIST.CONTAMINATION ISSUES
LIGHT CONTAMINATION
MINIMUM CREEP AT 27.7 mm/kVrms, p-g
SALT FOG, INDUSTRIAL CONTAMINATION MAY NEED MORE CREEP
CREEPAGE REQUIREMENTSCREEPAGE REQUIREMENTS
12900800
8890550
5850362
3960245
2750170
2340145
1990123
117072.5
61038
42025.8
25015.5
Minimum Creepage to Ground,(mm)
Rated Maximum Voltage (kV, rms)
LIGHTNING IMPULSE TESTLIGHTNING IMPULSE TESTINTRODUCED IN 1930’s
TEST LEVEL – 2 x LF TEST + 40 kV
1.5 x 40 μs WAVE SHAPE
NOW – 1.2 x 50 μs
FULL WAVE & 2 μs CHOPPED WAVE
10 % PROB. OF FLASHOVER OR LESS
LIGHTNING IMPUSE LIGHTNING IMPUSE WAVESHAPEWAVESHAPE
0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60
Time μs
V
LIGHTNING IMPUSE TEST LEVELSLIGHTNING IMPUSE TEST LEVELS
26402050800
23201800550
16801300362
1160900245
968750170
838650145
710550123
45235072.5
25820038
19415025.8
14211015.5
Chopped Wave (2μs)Full WaveRated MaximumVoltage (kV, rms)
Lightning Impulse
TEST PROCEEDURETEST PROCEEDURECONTACTS OPEN – ALL OTHER TERMINALS GROUNDED
CONTACTS CLOSED – ALL OTHER PHASES GROUNDED
APPLY THREE IMPULSES (NEG AND POS)
IF ZERO FLASHOVERS – PASS
IF ONE FLASHOVER IN FIRST THREE, THEN 9 MORE TESTS WITH NO FLASHOVERS
RATIO OF FULL WAVE IMPULSE RATIO OF FULL WAVE IMPULSE TO RATED MAXIMUM VOLTAGETO RATED MAXIMUM VOLTAGE
3.1420508004.0118005504.4013003624.509002455.407501705.496501455.485501235.9135072.56.45200387.1215025.88.6911015.5
In pu of Rated L-G Crest Voltage
Full WaveRated MaximumVoltage (kV, rms)
Lightning Impulse
SWITCHING IMPULSE TESTINGSWITCHING IMPULSE TESTING
INCREASE IN SYSTEM VOLTAGE TO EHV LEVELS - 345 AND 500 kV
BEGUN IN EARLY 1960’S
TEST WAVESHAPE - 250 x 2500 μs
TEST PROCEDURETEST PROCEDUREPOSITIVE AND NEGATIVE POLARITIES
SAME 3 – 9 TEST SERIES
WET AND DRY TESTS REQUIRED
OPEN AND CLOSED TEST VALUES DIFFERENT
10 % PFO OR LESS
TEST LEVELSTEST LEVELS
15001425800
13001175550
900825362--245--170--145--123--72.5--38--25.8--15.5
Breaker Open(kV, cr)
Breaker Closed(kV, cr)
Rated MaximumVoltage (kV, rms)
Switching Impulse Terminal toTerminal
RATIO OF TEST LEVELS TO RATIO OF TEST LEVELS TO RATED MAXIMUM VOLTAGERATED MAXIMUM VOLTAGE
2.181425800
2.621175550
2.79825362
In pu of Rated L-G Crest Voltage
Breaker Closed(kV, cr)
Rated MaximumVoltage (kV, rms)
Switching Impulse Terminal toTerminal
2.90 PU Phase to Ground Switching Surge345 kV System
-1000
-800
-600
-400
-200
0
200
400
600
800
20 30 40 50 60 70 80 90 100 110 120
Time (ms)
kV
Application of 276 kV Surge Arrester1.83 PU
-600
-400
-200
0
200
400
600
20 30 40 50 60 70 80 90 100 110 120
Time (ms)
kV
LIGHTNING SURGE PROTECTIONLIGHTNING SURGE PROTECTIONUSE OF GAPUSE OF GAP
TLine TLine
LIGNTINING SURGE LIGNTINING SURGE PROTECTION PROTECTION -- GAPSGAPS
-4000
-3000
-2000
-1000
0
1000
2000
5 7 9 11 13 15 17 19
Time (μs)
kV
2 m Rod Gap
No Protection
APPLICATION OF ARRESTERAPPLICATION OF ARRESTERSEPARATION DISTANCESEPARATION DISTANCE
TLine TLine
APPLICATION OF ARRESTERAPPLICATION OF ARRESTERPHASE TO GROUND AT OPEN BREAKERPHASE TO GROUND AT OPEN BREAKER
-500
0
500
1000
1500
2000
5 7 9 11 13 15 17 19
Time μs
kV
80 m separation40 m0 m
APPLICATION OF ARRESTERAPPLICATION OF ARRESTERACROSS OPEN BREAKERACROSS OPEN BREAKER
0
500
1000
1500
2000
2500
5 7 9 11 13 15 17 19
Time μs
kV
80 m separation40 m0 m
EFFECT OF ALTITUDEEFFECT OF ALTITUDE
TESTED AT NTP (normal temperature and pressure)
REDUCTION IN EXTERNAL INSULATION WITH INCREASING ALTITUDE
ALTITUDE CORRECTION ALTITUDE CORRECTION FACTORFACTOR
H – ALTITUDE IN METERS
m – GAP FACTOR1 FOR POWER FREQUENCY, LIGHTNING AND PHASE TO PHASE SWITCHING SURGES0.9 FOR INSULATION ACROSS OPEN GAP0.75 FOR PHASE TO GROUND SWITCHING SURGES
)8150
( Hm
d ek−
=
ALTITUDE CORRECTIONALTITUDE CORRECTION
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
0 500 1000 1500 2000 2500 3000 3500 4000
Alltitude Above Sea Level, m
Alti
tude
Den
sity
Cor
rect
ion
Fact
or
Switching Surge to GroundLightning
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1
Deviation in Strength in Number of Sigmas
Prob
abili
ty o
f Pas
sing
Tes
t
3+33+915x2
