High-Power Testing of Circuit Breakers Prof. Dr. Rene Smeets KEMA T&D Testing The Netherlands rene.smeets@kema.com IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 1 categories of tests development tests type-tests (for certification) acceptance tests IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 2
1 development tests product development testing of prototypes ordered by: standard: laboratory: manufacturer according clients instructions mostly at manufacturer's site IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 3 2 type tests provide confidence that a duly indentified product conforms with requirements of a specific standard ordered by: standard: aim: laboratory: manufacturer (Inter)national standard certification independent testing institute recognised group of manuf. labs IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 4
3 acceptance tests verify that a certain product complies with a specific application specified by the user ordered by: standard: laboratory: user of the equipment agreement manufacturer - user independent testing institute recognised group of manuf. labs IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 5 test methods direct testing - on the grid - generator fed - capacitor bank fed synthetic testing IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 6
direct testing pros laboratory supplied by power grid simple cheap representative high-power available cons poor flexibility difficult to adjust IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 7 EDF direct testing generator supplied laboratory pros adjustable flexible no influence on local grid con huge investment IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 8
direct test lay-out slamecka 1966 making switch transformers test object generator master breaker current limiting coils TRV generating circuit current measurement voltage measurement IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 9 increase of capacity per break GVA / break highest labpower available electra 2003 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 10
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 MVA this still does not match the power-voltage characteristics of the most powerful labs. IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 11 solution before interruption a sufficiently large power must be available to maintain the full (arc) current at moderate voltage (< 60 kv) - from generators contact separation reignition arcing time interruption after interruption there is only the need for a sufficiently high voltage - from precharged capacitor short-circuit current transient recovery voltage special circuit needed to reignite the arc IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 12 synthetic test
synthetic tests generator circuit capacitor circuit Lv aux Ls G G Ug Ig TO U TRV TO R C Ii Uh0 + - Ch Ig Ug Ii Ui UTRV IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 13 synthetic testing Synthetic circuit (parallel current injection) Lv aux Ls G G Ug Ig U TRV TO R C Ii + - Ch Ig+Ii Ui UTRV IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 14
synthetic testing generator current current through test-cb injected current delayed current zero IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 15 three-phase synthetic testing first pole to clear last pole to clear last pole to clear IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 16
synthetic testing in practice test methods: current injection voltage 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 2 x cap. bank 720 kv - 1.7 MJ 17 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 high-power test of 1100 kv CB test-breaker IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 18
test station lay-out open-air test site high-power labs synthetic installation (720 kv) switchyard (245 kv) generator building (8400 MVA) new MV test lab (38 kv) on-board transformer testing IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 19 grey zones in testing Test-circuit should represent the service conditions of equipment as much as possible Standards 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-circuit Then, 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 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 20
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 chambers Current supply sources must have terminal voltage as high as possible to guarantee sufficient arcing stresses Risk 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 21 influence of many series arcs on current arc energy in service situation Source voltage high enough arc energy with 14 kv s ource Source voltage too low amplitude arc voltage current in service situation current in synthetic test 5 10 15 20 25 30 35 40 45 50 IEEE Tutorial on Design and Application of High-Voltage time [ms Circuit ] Breakers July 2008 22
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 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 23 transient recovery voltage (TRV) Voltage immediately after current interruption (TRV) is of crucial importance for success or failure g e o l ta v t, u ren c short-line fault current terminal fault current interaction interval short-line fault TRV current zero terminal fault TRV circuit breaker arc strongly interacts with TRV circuit test-circuit topology very important microsecond scale time 5 us/div voltage 5 kv/div current 50 A/div time (us) IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 24
high-frequency effects of circuits Seldomly specified in standards Will affect result of tests in which high-frequency behaviour is important Example: interruption tests with vacuum circuit breaker Such a breaker is very good in interruption of current of high-frequency IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 25 2.0 1.6 1.2 TRV (pu) re-ignition series damped TRV effect of TRV circuit 0.8 0.4 parallel damped TRV 0.0 0 50 100 time (us) 150 200 current at re-ignition (A) 250 series damped + power freq. 150 parallel damped + pow er freq. 50 Research: cable systems have oscillatory TRV, so test should be performed with oscillatory TRV -5 0 5 10 15 time 20 (us) 25 30-50 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 26
half-pole tests for (U)HV test voltage application across full-pole half-pole testing quarter-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 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 27 half-pole testing of GIS 2U U 2U U 2 U hot exhaust gas from breaker 2 U 2 U Half-pole test: interrupter stress OK internal stress NOK Full-pole test: interrupter stress OK internal stress OK IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 28
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 enclosure effects of exhaust gases equivalent mechanical stresses equivalent forces (electrodynamical stresses) equivalent IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 29 single phase testing of threephase circuit breaker Often practiced when power of test laboratory is insufficient In 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 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 30
three-phase testing of three-phase devices contact separation recovery voltage current three-phase test contact movement single-phase test contact movement voltage: 80 kv/div current: 111kA/div time: 10 ms/div no-load contact movement IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 31 conclusions Standards do not cover everything Grey zone exists between allowable but different stresses that make life easier/worse for a breaker Test-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 IEEE Tutorial on Design and Application of High-Voltage Circuit Breakers July 2008 32