Post on 06-Sep-2021
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 1
High-Power Testing ofCircuit Breakers
Prof. Dr. Rene Smeets
KEMA T&D Testing
The Netherlandsrene.smeets@kema.com
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 2
categories of tests
development teststype-tests (for certification)acceptance tests
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 3
1 development tests
ordered by: manufacturer
standard: according clients instructionslaboratory: mostly at manufacturer's site
product development
testing of prototypes
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 4
2 type tests
provide confidence that a duly indentifiedproduct conforms with requirements of a specific standard
ordered by: manufacturer
standard: (Inter)national standard
aim: certification
laboratory: independent testing instituterecognised group of manuf. labs
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 5
3 acceptance tests
ordered by: user of the equipmentstandard: agreement manufacturer - user
laboratory: independent testing institute
recognised group of manuf. labs
verify that a certain product complies with a specific application specified by the user
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test methods
direct testing- on the grid- generator fed- capacitor bank fed
synthetic testing
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direct testing
pros
simple
cheap
representative
high-power available
cons
poor flexibility
difficult to adjust
laboratory supplied by power grid
EDF
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 8
pros
adjustable
flexible
no influence on local grid
con
huge investment
generator supplied laboratory
direct testing
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generator master breaker
current limiting coils
TRV generating circuit
voltage measurement
current measurement
test objecttransformersmaking switch
slamecka 1966
direct test lay-out
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 10
increase of capacity per break
electra 2003
highest lab-power
available
GVA / break
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synthetic testing
example: short-circuit test of a CB (three-phase)420 kV - 63 kA - 50 Hz
⇒ necessary power: 420 x 63 x √3 = 45830 MVA
this exceeds any laboratory's direct power (Max: 8400 MVA)other methods must be sought:
- single phase test: necessary power 45830/3 = 15277 MVA- half-pole testing (if possible): 15277/2 = 7638 MVAthis still does not match the power-voltage characteristics of the most powerful labs.
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solution
short-circuit current
reignition
interruption
contact separation
arcing time
transient recovery voltage
after interruption there is only the need for a sufficiently high voltage- from precharged capacitor
special circuit needed to reignite the arc
⇒ synthetic test
before interruption a sufficiently large power must be available to maintain the full (arc) current at moderate voltage (< 60 kV)- from generators
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 13
generator circuit capacitor circuitaux
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synthetic testing
Synthetic circuit (parallel current injection)
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current through test-CB
delayed current zeroinjected
current
generator current
synthetic testing
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 16
three-phase synthetic testing
first pole to clear
last poleto clear
last poleto clear
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synthetic testing in practice
2 x cap. bank720 kV - 1.7 MJ
test methods:current injectionvoltage injection
ratings to be tested synthetically:1100 kV - 63 kA - 60 Hz - 1Ø (experimentally)550 kV - 63 kA - 60 Hz - 1Ø (routine)245 kV - 63 kA - 60 Hz - 3Ø
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 18
high-power test of 1100 kV CB
test-breaker
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 19
switchyard (245 kV)
generator building
(8400 MVA)
on-board trans-former testing
new MV test lab (38 kV)
synthetic installation (720 kV)high-power labsopen-air test site
test station lay-out
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grey zones in testing
Test-circuit should represent the service conditions of equipment as much as possibleStandards prescribe inherent behaviour of test-circuits.Inherent means 'naked' circuit only, without test-object.This can be different when a real test-objects interacts with the test-circuitThen, the representation must still be realistic.
But: test are possible with test-circuits that show inherently adequate behaviour in accordance with standards, but do not reflect realistic service conditions
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circuit breaker testing
Many arcs in series: high total arc voltage counteracts source voltage (in 800 kV testing: 8 arcs in series)Especially with- synthetic testing (auxiliary breakers)- when testing breakers with multiple arcing chambersCurrent supply sources must have terminal voltage as high as possible to guarantee sufficient arcing stressesRisk is to apply too little energy into the fault current arc. Testing is too light in that case
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 225 10 15 20 25 30 35 40 45 50
ampl
itude
time [ms ]
arc energy with14 kV s ource
arc energy in s ervice s ituation
current in s ynthetic tes t
arc voltage
current in service s ituation
influence of manyseries arcs on current
Source voltagetoo low
Source voltagehigh enough
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 23
Immediately after interruption
Immediately after interruption hot gases are still in the gap and feel fast rising voltage:thermal stresses
A little later very high voltage is reached across the open gap:dielectric stresses
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transient recovery voltage (TRV)Voltage immediately after current interruption (TRV) is of crucial importance for success or failure
circuit breaker arc strongly interacts with TRV circuittest-circuit topology very importantmicrosecond scale
time (us )
current,voltage
time 5 us /divvoltage 5 kV/divcurrent 50 A/div
terminal fault TRV
s hort-line fault TRV
s hort-line fault currentterminal fault current
interaction interval
current zero
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 25
high-frequency effects of circuits
Seldomly specified in standardsWill affect result of tests in which high-frequency behaviour is important
Example: interruption tests with vacuum circuit breakerSuch a breaker is very good in interruption of current of high-frequency
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effect of TRV circuit
0.0
0.4
0.8
1.2
1.6
2.0
0 50 100 150 200
-50
50
150
250
-5 0 5 10 15 20 25 30
series damped + pow er freq.
parallel damped + power freq.
series damped TRV
parallel damped TRV
current at re-ignition (A)
TRV (pu)
re-ignition
time (us)
time (us)
Research:cable systems have oscillatory TRV, so
test should be performed with oscillatory TRV
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half-pole tests for (U)HVtest voltage application across full-polehalf-pole testingquarter-pole testing
non-full pole ("unit"-) testing should consider uneven voltage
distribution across circuit breaker,
especially when there are no grading capacitors
full-pole testing eliminates doubts
800 kV breaker
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half-pole testing of GIS
2U
2 U
2U
hot exhaust gas from breaker
Full-pole test:interrupter stress OK
internal stress OK
Half-pole test:interrupter stress OKinternal stress NOK
2 U
U
2 U
U
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 29
ultra high voltage testing
For metal enclosed breakers, half-pole testing does not represent the conditions in service:
dielectric stresses of half-pole tests equivalent to full-pole conditions- between phases- between phases and enclosureeffects of exhaust gases equivalent
mechanical stresses equivalent
forces (electrodynamical stresses) equivalent
IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 30
single phase testing of three-phase circuit breaker
Often practiced when power of test laboratory is insufficientIn principle possible, but with care
Not realistic when common mechanism is controlling contact movement (circuit breaker, earthing switch)Beware of three-phase interactions, that single phase circuits fail to represent
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three-phase testingof three-phase devices
current
recovery voltage
no-load contact movement
three-phas e tes t contact movement
s ingle-phas e tes t contact movement
contact s eparation
voltage: 80 kV/divcurrent: 111kA/divtime: 10 ms /div
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conclusions
Standards do not cover everythingGrey zone exists between allowable but different stresses that make life easier/worse for a breakerTest-engineers knowledge and test-lab policies must ensure that realistic testing will prevail:- supply sufficient arc energy even for highest
voltages- have knowledge of arc-circuit interactions- being aware of high-frequency pitfalls- test three-phase when necessary