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

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

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

4. 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. LIMITATIONS FOR SUCCESSFUL INTERRUPTION
Random interruption
Voltage
Current
Dielectric
limit
Additional performance
by controlled interruption ??? ?
Thermal
limit

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

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

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

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

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

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

12. RRDS Rate of Rise of Dielectric Strength at opening
Voltage withstand characteristic of the
circuit-breaker contact gap at opening,
RRDS
Contact separation
Instant 2
RRDS at min. arcing time
Uacross CB
Tarcmin
Typical: TARCMIN  4 ms
(Shorter arcing times will result in re-ignition)
Window allowing
Reignition-free operation
SAFE contact parting area
Uacross CB
Contact separation
Instant 1
Uacross CB
Uacross CB
Current
REACTOR CURRENT INTERRUPTION
SESWGBTA SWITCHSYNC.PPT
USource

13. DE-ENERGISING OF CAPACITIVE LOAD
+ UB -
Interruption + _ ~ I US UC UC US
Bus voltage
Load side voltage
US = UC I
time
A discharged capacitor is similar to a momentary short-circuit when connected to a power source. If made when the source voltage is high, the connection results in voltage and current transients that may cause serious problems. Depending on the network configuration, the voltage surge
may cause breakdown somewhere in the high voltage network, and low voltage equipment may suffer insulation damage or malfunction. With back-to-back capacitor banks, the inrush current may be steep and high enough to threaten the mechanical integrity of both capacitors and breaker.
Synchronising the breaker to energise a capacitive load at source voltage zero will eliminate harmful transients.
It is possible to use a three-pole operated circuit-breaker with staggered poles, together with a simple Switchsync model.
The voltage measurement shown are from a commissioning test of a 72.5 kV capacitor bank by NESA in Denmark.

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

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

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

17. Test circuit for determination of RRDS (“Cold characteristic”)
0 kV

18. Test circuit for determination of RRDS (“Cold characteristic”)
0 kV
0 kV

19. Test circuit for determination of RRDS (“Cold characteristic”)
0 kV
0 kV

20. Test circuit for determination of RRDS (“Cold characteristic”)
0 kV
0 kV

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

22. Test record from “Cold characteristic test”
Limit of voltage withstand
vs. time or distance

23. Plot of RRDS vs. time for a certain condition

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

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

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

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

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

29. 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. Impact of missing arcing
How to compare “Cold characterisic” with cap. Switching performance?

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

32. 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. 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. 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. 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. 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. 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. 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. 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. 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. APPLICATION WITH CONTROLLED DE-ENERGISING OF GROUNDED CAPACITOR BANK

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

43. FUTURE? Controlled fault interruption?
Increased electrical life and improved performance compared to random fault interruption?
Tarc
Blast
pressure
Pressure required for interruption
Pressure at current zero,
new CB
Normal "arc extinguishing window” >1/2 cycle
Narrow window with increased interrupting capability
Reduced pressure build-up
at current zero in worn CB
A discharged capacitor is similar to a momentary short-circuit when connected to a power source. If made when the source voltage is high, the connection results in voltage and current transients that may cause serious problems. Depending on the network configuration, the voltage surge
may cause breakdown somewhere in the high voltage network, and low voltage equipment may suffer insulation damage or malfunction. With back-to-back capacitor banks, the inrush current may be steep and high enough to threaten the mechanical integrity of both capacitors and breaker.
Synchronising the breaker to energise a capacitive load at source voltage zero will eliminate harmful transients.
It is possible to use a three-pole operated circuit-breaker with staggered poles, together with a simple Switchsync model.
The voltage measurement shown are from a commissioning test of a 72.5 kV capacitor bank by NESA in Denmark.

44. WHAT CAN BE REACHED?
Increased electrical life compared to random interruption
Increased interrupting margins
Slightly increased performance
A discharged capacitor is similar to a momentary short-circuit when connected to a power source. If made when the source voltage is high, the connection results in voltage and current transients that may cause serious problems. Depending on the network configuration, the voltage surge
may cause breakdown somewhere in the high voltage network, and low voltage equipment may suffer insulation damage or malfunction. With back-to-back capacitor banks, the inrush current may be steep and high enough to threaten the mechanical integrity of both capacitors and breaker.
Synchronising the breaker to energise a capacitive load at source voltage zero will eliminate harmful transients.
It is possible to use a three-pole operated circuit-breaker with staggered poles, together with a simple Switchsync model.
The voltage measurement shown are from a commissioning test of a 72.5 kV capacitor bank by NESA in Denmark.

45. FUTURE? Controlled fault interruption?
Infoga tabellen
A discharged capacitor is similar to a momentary short-circuit when connected to a power source. If made when the source voltage is high, the connection results in voltage and current transients that may cause serious problems. Depending on the network configuration, the voltage surge
may cause breakdown somewhere in the high voltage network, and low voltage equipment may suffer insulation damage or malfunction. With back-to-back capacitor banks, the inrush current may be steep and high enough to threaten the mechanical integrity of both capacitors and breaker.
Synchronising the breaker to energise a capacitive load at source voltage zero will eliminate harmful transients.
It is possible to use a three-pole operated circuit-breaker with staggered poles, together with a simple Switchsync model.
The voltage measurement shown are from a commissioning test of a 72.5 kV capacitor bank by NESA in Denmark.