1. A Unified Approach to Controlled Switching of Power Equipment
Gabriel Benmouyal, Normann Fischer, Douglas Taylor, Mark Talbott-Williams, and Ritwik Chowdhury
Schweitzer Engineering Laboratories, Inc.

2. Overview
Comprehensive methods for controlled closing and opening of breakers
Transformer configuration considerations
Controlled switching devices (CSDs)

3. What Is Controlled Switching?
Methods to reduce or eliminate voltage and current transients from breaker operation

4. Four Closing Settings Per Phase
Definition
Units
TClose
Compensated breaker pole closing time ms
TCarc
Difference between electrical arcing and mechanical contact
Degrees
TCpow
Voltage point-on-wave closing angle
TCdel
Additional closing delay
Cycles

5. Controlled Closing Timing

6. Single-Phase Closing

7. Optimal TCpow Settings
Equipment
Configuration
TCpow.a
TCpow.b
TCpow.c
TCdel.a
TCdel.b
TCdel.c
Shunt capacitors Yg 0°
180°
Y, D
30°
150°
Reactors
90°
270°
60°
300°
0.5 • N

8. Example of Closing on Three Independent Power Inductors (Single Phase)

9. Closing on Three Independent Power Inductors

10. Relation Between Voltage and Prospective Flux

11. TCpow for Single-Phase Transformer With Residual

12. How Do We Measure Residual Flux?

13. Closing on a Wye-Delta-Connected Transformer With Residual Flux

14. Simulated Magnetizing Curve

15. Delayed Closing Strategy
Calculate residual fluxes in all three phases
Close phase with the highest flux
Close other two phases (0.5 • N cycles later) when
Corresponding fluxes are equal
First closed phase is at zero voltage

16. TCpow With Wye-Grounded Transformers Magnetically Dependent Cores
Maximum Flux
TCpow.a
TCpow.b
TCpow.c
TCdel.a
TCdel.b
TCdel.c A
60°
300°
0.5 • N B C
240°
120°

17. Controlled Closing Fluxes

18. Final Settings Supplied to Closing Algorithm

19. Controlled Closing Magnetizing Currents

20. Random Closing Magnetizing Current

21. Breaker Opening Reignition Constraints

22. Breaker Pole Opening Settings
Units
TOpen ms
TOarc
Degrees

23. Breaker Pole Opening Timing

24. Conclusion Controlled closing Controlled opening
Eliminates voltage or current transients
Improves power quality
Protects equipment
Makes protective relays more reliable
Controlled opening
Eliminates breaker restrike or reignition
Protects equipment

25. Conclusion Breaker closing settings Breaker opening settings TClose
TCarc
TCpow
TCdel
Breaker opening settings
TOpen
TOarc

26. Questions?