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2003-04 FLORIDA WORKSHOP.PPT CONDITIONS FOR SUCCESSFUL INTERRUPTION: Current Contact parting 1)After contact parting there must be current zeros present.

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Presentation on theme: "2003-04 FLORIDA WORKSHOP.PPT CONDITIONS FOR SUCCESSFUL INTERRUPTION: Current Contact parting 1)After contact parting there must be current zeros present."— Presentation transcript:

1 FLORIDA WORKSHOP.PPT CONDITIONS FOR SUCCESSFUL INTERRUPTION: Current Contact parting 1)After contact parting there must be current zeros present Current 2)The circuit-breaker must pass the thermal interrupting mode 1)After contact parting there must be current zeros present Contact parting Current Recovery voltage 3)The circuit-breaker must pass the dielectric interrupting mode T arc Interruption 2)The circuit-breaker must pass the thermal interrupting mode 1)After contact parting there must be current zeros present Contact parting Current Recovery voltage

2 FLORIDA WORKSHOP.PPT THERMAL INTERRUPTION Post arc current Rising voltage after clearing thermal interruption Electric conductivity at successful thermal interruption Current Voltage time Current at failed thermal interruption Arc voltage after failed thermal interruption Electric conductivity after failed thermal interruption

3 FLORIDA WORKSHOP.PPT DIELECTRIC INTERRUPTION Current Voltage time Current at failed dielectric interruption Insufficient voltage withstand capability for successful interruption. Dielectric failure Rising voltage after clearing thermal interruption Insufficient voltage withstand capability for successful interruption. Dielectric failure Rising voltage after clearing thermal interruption Voltage withstand capability for successful interruption

4 FLORIDA WORKSHOP.PPT CONDITIONS FOR INTERRUPTION Conditions for successful interruption: 1)After contact parting there must be current zeros present 2)The circuit-breaker must pass the thermal interrupting mode 3)The circuit-breaker must pass the dielectric interrupting mode Conclusion: The interrupting performance is strongly related to the arcing time

5 FLORIDA WORKSHOP.PPT Additional performance by controlled interruption ??? LIMITATIONS FOR SUCCESSFUL INTERRUPTION Random interruption Voltage Current Dielectric limit Thermal limit ? ? ? ? ? ?

6 FLORIDA WORKSHOP.PPT Possible upgrading area by means of controlled switching LIMITATIONS FOR SUCCESSFUL INTERRUPTION Random interruption Voltage Current No thermal interrupting stress

7 FLORIDA WORKSHOP.PPT INCREASED DIELECTRIC PERFORMANCE Approach: Controlled reactor switching has become an accepted method for making circuit-breakers reignition free

8 FLORIDA WORKSHOP.PPT SOLVING AN INHERENT PROBLEM Recovery voltage phase R Recovery voltage phase Y Recovery voltage phase B Voltage withstand capability RRDS

9 FLORIDA WORKSHOP.PPT DE-ENERGISING A GROUNDED REACTOR BANK Controlled contact partings

10 FLORIDA WORKSHOP.PPT SOLVING AN INHERENT PROBLEM Reignition Supply side voltage Load side voltage Voltage across CB Current Contact travel Trip coil current 4 ms

11 FLORIDA WORKSHOP.PPT SOLVING AN INHERENT PROBLEM Supply side voltage Load side voltage Voltage across CB Current Contact travel Trip coil current 9 ms

12 FLORIDA WORKSHOP.PPT RRDS Rate of Rise of Dielectric Strength at opening T arcmin Typical: T ARCMIN 4 ms (Shorter arcing times will result in re-ignition) Window allowing Reignition-free operation SAFE contact parting area U Source Current RRDS at min. arcing time U across CB Voltage withstand characteristic of the circuit-breaker contact gap at opening, RRDS REACTOR CURRENT INTERRUPTION U across CB Contact separation Instant 1 Contact separation Instant 2

13 FLORIDA WORKSHOP.PPT DE-ENERGISING OF CAPACITIVE LOAD + + _ _ ~ I USUS UCUC U S = U C I time + U B - Interruption UCUC USUS Bus voltage Load side voltage

14 FLORIDA WORKSHOP.PPT T/2 = 10 ms at 50 Hz Capacitive current case Recovery voltages Inductive current case 200 s COMPARISON OF RECOVERY VOLTAGES Inductive and capacitive case Voltage across contacts Time 0

15 FLORIDA WORKSHOP.PPT Recovery voltages COMPARISON OF RECOVERY VOLTAGES Voltage across contacts Time 0 Typical RRDS starting several ms prior to current zero resulting in proper interruption Inductive current case 200 s Inductive case Typical RRDS starting at minimum arcing time (0 ms) T/2 = 10 ms at 50 Hz Capacitive current case Inductive and capacitive case Typical RRDS starting at minimum arcing time (0 ms)

16 FLORIDA WORKSHOP.PPT Typical RRDS starting at minimum arcing time (0 ms) T/2 = 8,33 ms at 60 Hz T/2 = 10 ms at 50 Hz Time 0 Voltage across contacts RECOVERY VOLTAGE VERSUS TYPICAL RRDS, capacitive case Typical RRDS starting some ms before current zero T/2 = 7,58 ms at 66 Hz Upgrading potential at 60 Hz

17 FLORIDA WORKSHOP.PPT Test circuit for determination of RRDS (Cold characteristic) 0 kV

18 FLORIDA WORKSHOP.PPT Test circuit for determination of RRDS (Cold characteristic) 0 kV

19 FLORIDA WORKSHOP.PPT Test circuit for determination of RRDS (Cold characteristic) 0 kV

20 FLORIDA WORKSHOP.PPT Test circuit for determination of RRDS (Cold characteristic) 0 kV

21 FLORIDA WORKSHOP.PPT Test record from Cold characteristic test Supply side voltage Load side voltage Voltage across CB (160 Hz) Current Contact travel Contact parting Limit of voltage withstand vs. time or distance

22 FLORIDA WORKSHOP.PPT Test record from Cold characteristic test Limit of voltage withstand vs. time or distance

23 FLORIDA WORKSHOP.PPT Plot of RRDS vs. time for a certain condition

24 FLORIDA WORKSHOP.PPT Plot of RRDS compared to a 50 Hz recovery voltage starting at minimum arcing time

25 FLORIDA WORKSHOP.PPT Plot of RRDS compared to recovery voltages of 50 and 60 Hz and at minimum arcing times

26 FLORIDA WORKSHOP.PPT Plot of RRDS compared to recovery voltages of different frequencies and at minimum arcing times

27 FLORIDA WORKSHOP.PPT Plot of RRDS compared to recovery voltages of different frequencies and at minimum and prolonged arcing times

28 FLORIDA WORKSHOP.PPT Plot of RRDS compared to recovery voltages of different frequencies and at minimum and prolonged arcing times

29 FLORIDA WORKSHOP.PPT Plot of RRDS compared to recovery voltages of different frequencies and at minimum and prolonged arcing times About 15 % increased performance can be reached by pre-setting the arcing time by some ms.

30 FLORIDA WORKSHOP.PPT Impact of missing arcing How to compare Cold characterisic with cap. Switching performance?

31 FLORIDA WORKSHOP.PPT Impact of missing arcing How to compare Cold characterisic with cap. Switching performance? Cold characteristic determined RRDS fits well to reactor switching performance

32 FLORIDA WORKSHOP.PPT Impact of missing arcing How to compare Cold characterisic with cap. Switching performance? Cold characteristic determined RRDS fits well to reactor switching performance Full-scale capacitive current switching tests show equal performance

33 FLORIDA WORKSHOP.PPT IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS Controlling the contact parting instant at interruption of capacitive loads can: -compensate for a lower gas density.

34 FLORIDA WORKSHOP.PPT IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS Controlling the contact parting instant at interruption of capacitive loads can: -compensate for a lower gas density. -compensate for lower contact speed.

35 FLORIDA WORKSHOP.PPT IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS Controlling the contact parting instant at interruption of capacitive loads can: -compensate for a lower gas density. -compensate for lower contact speed. -improve the "safety" against restrikes by increasing the voltage withstand margin and taking care of scatter in the early stage.

36 FLORIDA WORKSHOP.PPT IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS Controlling the contact parting instant at interruption of capacitive loads can: -compensate for a lower gas density. -compensate for lower contact speed. -improve the "safety" against restrikes by increasing the voltage withstand margin and taking care of scatter in the early stage. -can make a circuit-breaker capable to operate in networks with higher frequencies if the performance at random switching is not good.

37 FLORIDA WORKSHOP.PPT IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS Controlling the contact parting instant at interruption of capacitive loads can: -compensate for a lower gas density. -compensate for lower contact speed. -improve the "safety" against restrikes by increasing the voltage withstand margin and taking care of scatter in the early stage. -can make a circuit-breaker capable to operate in networks with higher frequencies if the performance at random switching is not good. -compensate for ageing represented by contact burn-off.

38 FLORIDA WORKSHOP.PPT IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS Controlling the contact parting instant at interruption of capacitive loads can: -compensate for a lower gas density. -compensate for lower contact speed. -improve the "safety" against restrikes by increasing the voltage withstand margin and taking care of scatter in the early stage. -can make a circuit-breaker capable to operate in networks with higher frequencies if the performance at random switching is not good. -compensate for ageing represented by contact burn-off. If restrike-free perfomance at capacitive current switching is a limiting factor, controlled interruption is a useful tool for uprating.

39 FLORIDA WORKSHOP.PPT IMPACT OF CONTROLLED INTERRUPTION OF CAPACITIVE CURRENTS Controlling the contact parting instant at interruption of capacitive loads can: -compensate for a lower gas density. -compensate for lower contact speed. -improve the "safety" against restrikes by increasing the voltage withstand margin and taking care of scatter in the early stage. -can make a circuit-breaker capable to operate in networks with higher frequencies if the performance at random switching is not good. -compensate for ageing represented by contact burn-off. If restrike-free perfomance at capacitive current switching is a limiting factor, controlled interruption is a useful tool for uprating. Pre-set arcing time will not be longer than average: reduction of contact wear

40 FLORIDA WORKSHOP.PPT IDEAL CASES FOR ADAPTING CONTROLLED OPENING OF CAPACITIVE LOADS FREQUENT OPERATIONS REINSERTION OF LINE SERIES CAPACITORS voltage steepness may be high due to power swing SWITCHING OFF HARMONIC FILTER BANKS initial slope of the recovery voltage is steeper and the peak is higher due to the harmonic content. When beeing used in combination with thyristor controlled equipment commutation transients may also be added to the recovery voltage across the circuit-breaker, thus increasing the risk.

41 FLORIDA WORKSHOP.PPT APPLICATION WITH CONTROLLED DE-ENERGISING OF GROUNDED CAPACITOR BANK

42 FLORIDA WORKSHOP.PPT Possible upgrading area by means of controlled switching LIMITATIONS FOR SUCCESSFUL INTERRUPTION Random interruption Voltage Current Thermal interrupting stress

43 FLORIDA WORKSHOP.PPT FUTURE? Controlled fault interruption? Increased electrical life and improved performance compared to random fault interruption? Reduced pressure build-up at current zero in worn CB Pressure at current zero, new CB Normal "arc extinguishing window >1/2 cycle Tarc Blast pressure Pressure required for interruption Narrow window with increased interrupting capability

44 FLORIDA WORKSHOP.PPT WHAT CAN BE REACHED? Increased electrical life compared to random interruption Increased interrupting margins Slightly increased performance

45 FLORIDA WORKSHOP.PPT FUTURE? Controlled fault interruption? Infoga tabellen


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