Title: VACUUM INTERRUPTERS FOR GENERATOR CIRCUIT BREAKERS, THEY'RE NOT JUST FOR DISTRIBUTION CIRCUITS BREAK
1VACUUM 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
2A 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
3Transverse Magnetic Field Contacts Great for
Generator Circuit Breakers
- Spreads arc energy over contact surfaces
- Tolerates long arcing times
- Produces significant arc voltage
Current Loop Drives the Arc
4TMF 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
5Generator 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
6A Typical Generator Circuit
- A - System-Source Fault B -
Generator-Source Fault
7System-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
8System-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
9System-source fault - Fast TRV
Fast Generator Breaker 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
Slow Distribution Breaker TRV
10A Typical Generator Circuit
- A - System-Source Fault B -
Generator-Source Fault
11Generator-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 gt 100
- causing
- Delayed current zeros
12Delayed Current Zero
- High DC Component
- gt100
- Long DC Time Constant
Arcing time nearly 3 cycles
13Arc Voltage in a Transverse Magnetic Field (TMF)
Vacuum Interrupter
- VI Arc Voltage
- TMF VI
- 150 volts
- AMF VI
- 50 volts
14Arc Voltage Advances 1st Current Zero
- 150 Volts
- Doubles Circuit Resistance
- Cuts Time Constant in Half
Arcing time reduced to lt 2 cycles
15Tests on New, Compact Generator CB with TMF
Vacuum Interrupter
- 15 kV, 63 kA, 60 Hz, 3000 Amp, STC of 3s.
- System-source fault
- 63 kA 79 DC 3.7 kV / msec to 28 kV
- Generator-source fault
- 31.5 kA 135 DC 1.6 kV/ msec to 28 kV
- Out-of-Phase Switching
- 31.5 kA 3.7 kV / msec to 45 kV
- Robust performance for generator protection