1. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 1 VACUUM INTERRUPTERS FOR GENERATOR CIRCUIT BREAKERS, THEY'RE NOT JUST FOR DISTRIBUTION CIRCUITS BREAKERS ANYMORE Presented by:R. Kirkland Smith, Ph.D. Eaton / Cutler-Hammer, Horseheads, NY, USA Co-authors: R. William Long & Dale L. Burmingham

2. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 2 A new, compact generator circuit breaker with TMF Vacuum Interrupters Vacuum interruption –compact breaker –contained arc –sealed for life interrupter –long, low maintenance life Replaces old, large breakers Tested to new revised standard for Generator Circuit Breakers C37.013a

3. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 3 Transverse Magnetic Field Contacts Great for Generator Circuit Breakers Spreads arc energy over contact surfaces Tolerates long arcing times Produces significant arc voltage I I Current Loop Drives the Arc

4. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 4 TMF VIs Now Interrupt High Currents First VIs - 1966 for C-H –low interrupt ratings for distribution circuits –15 kV - 12 kA Present VIs - 2003 –High interrupt ratings –15 kV - 63 kA Heading to 80 kA –Long arcing time tolerance –Fast TRV RRRV Ability

5. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 5 Generator Circuit Fault Interruption Severe conditions for a circuit breaker –High short circuit currents –Long DC time constants and high DC components –Fast Transient Recovery Voltages (TRVs) –Delayed current zeroes Transverse Magnetic Field (TMF) Vacuum interrupters are now well suited for this duty

6. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 6 A Typical Generator Circuit A - System-Source Fault B - Generator-Source Fault

7. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 7 System-source faults Highest fault current magnitude Short, low resistance connections –High ratio of L / R, inductance to resistance Asymmetrical current for fault interruption –Long DC time constant –High DC component at contact part –Low added circuit capacitance plus high natural frequency of transformer Fast Transient Recovery Voltages

8. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 8 System-source fault - High DC Component Generator Circuit System- source Fault - DC component of 75% or more Distribution Circuit faults - DC component of 30% to 50% Contact Part

9. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 9 System-source fault - Fast TRV TRV for Generator Breaker about 10 times faster than TRV for Distribution Breaker Fast TRV - high transformer natural frequency - low added capacitance from connected circuit Fast Generator Breaker TRV Slow Distribution Breaker TRV

10. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 10 A Typical Generator Circuit A - System-Source Fault B - Generator-Source Fault

11. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 11 Generator-source faults Lower fault current level –50% of System-Source Fault Fast Transient Recovery Voltages –high generator natural frequency –low added capacitance from connected circuit Extremely high DC component > 100% causing Delayed current zeros

12. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 12 Delayed Current Zero High DC Component >100% Long DC Time Constant Arcing time nearly 3 cycles

13. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 13 Arc Voltage in a Transverse Magnetic Field (TMF) Vacuum Interrupter VI Arc Voltage –TMF VI 150 volts –AMF VI 50 volts

14. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 14 Arc Voltage Advances 1st Current Zero 150 Volts Doubles Circuit Resistance Cuts Time Constant in Half Arcing time reduced to < 2 cycles

15. SMITH_USA_Author_ALPHA1_BLOCK1_Paper No 5-ECH_Smith_A1 Barcelona 12-15 May 2003 15 Tests on New, Compact Generator CB with TMF Vacuum Interrupter 15 kV, 63 kA, 60 Hz, 3000 Amp, STC of 3s. System-source fault –63 kA79 % DC3.7 kV /  sec to 28 kV Generator-source fault –31.5 kA 135% DC1.6 kV/  sec to 28 kV Out-of-Phase Switching –31.5 kA 3.7 kV /  sec to 45 kV Robust performance for generator protection