Development of mixed gas GCB applied to
low-temperature environment
Daisuke Yoshida, Yuji Yoshitomo, Daisuke Fujita
Mitsubishi Electric Corporation
Japan
1
Introduction
 Development of mixed gas GCBs
• A gas mixture of SF6 and CF4 enables the application of GCBs to
extremely low ambient temperatures (lower than -40 deg C)
• Two mixed gas GCB developments are introduced using the
same hardware as pure SF6 GCB
– 800kV GCB
– 245kV GCB
 Advantage of spring operating mechanism
• Maintenance work
• Reliability during operation
• Application of torsion bar spring
2
800 kV mixed gas circuit breaker
2-break Interrupter
Main
Grading contacts
capacitor
Mixed gas
Arcing contacts
Closing
resistor
Tank
Puffer cylinder
Support insulator
Insulating rod
Closing resistor
contacts
Linkage connection
Linkage guide
Pneumatic Operating Mechanism
Closing coil
Moving drive rod
Trip coil
Control Valve
Air cylinder
800 kV gas circuit breaker
during installation
Closing spring
Shock absorber
3
Feature of 800 kV GCB
 550 kV 1-break GCB interrupter is used for each break
 Interrupters and closing resistors are arranged so that all the moving contacts
are driven simultaneously by one mechanism through an insulating rod
 Simple pneumatic operating mechanism is used to obtain large operating
energy
Arc contacts
Main contacts
SF6 and CF4 mixed
gas
Closing resistor
Grading capacitor
Tank
Puffer cylinder
Closing resistor contacts
Support insulator
Linkage connection
Insulating rod
Linkage guide
4
Rating of 800 kV GCB
 Same hardware is used for SF6 and mixed gas
 Lower specification is applied on dielectric capability and interrupting capability
while application at -50 deg C is achieved
Medium
Pure SF6 gas
SF6 and CF4 mixed gas
Rated voltage
800 kV
Rated lightning impulse
withstand voltage (phase to earth)
2050 kV
2100 kV
2 μs chopped wave
2640 kV
-
Rated normal current
Rated breaking current
4000 A
63 kA
50 kA
Rated interruption time
Operation sequence
Operation mechanism
Rated gas pressure
Ambient air temperature
2 cycles
O-0.3sec.-CO-1min.-CO
Pneumatic (Open), Spring (Close)
0.59 MPa-g
-30 to +50 deg C
-50 to +40 deg C
5
Type tests
800 kV GCB
during interruption test
800 kV GCB
during high and low temperature test
6
245 kV mixed gas GCB
1-break Interrupter
Insulating drive rod
Tank
Main
contacts
Support insulator
Puffer cylinder
Nozzle
Arcing
contacts
Mixed
gas
Support
insulator
Spring Operating Mechanism
245 kV mixed gas GCB
during short-circuit tests
Helical coil
spring for IPO
Torsion bar spring for
3GO
7
Feature of 245 kV GCB



Same interrupter is used for pure SF6 and mixed gas, IPO and 3GO
Spring operating mechanism is applied to achieve low lifetime cost and high
reliability of circuit breaker
Common hardware is used between pure SF6 and mixed gas


IPO GCB: Helical spring operating mechanism
3GO GCB: Torsion bar spring operation mechanism
Independent pole operation
(IPO)
Closing coil
Three pole gang operation
(3GO)
Trip coil
Torsion bar spring
Charging motor
Trip coil
for opening
Closing coil
Output lever
Shock
absorber
torsion bar spring
Helical spring for Charging Closing linkage Shock
connection
absorber for closing
closing
gear
Charging
motor
Output
lever
Ratings of 245 kV GCB
 Same hardware is used for SF6 and mixed gas
 Lower specification is applied on dielectric capability and interrupting capability
while application at -50 deg C is achieved
Medium
Pure SF6 gas
Rated voltage
SF6 and CF4 mixed gas
245 kV
Rated lightning impulse
withstand voltage
(phase to earth)
900 kV
950 kV
2 μs chopped wave
1160 kV
-
Rated normal current
4000 A
Rated breaking current 50 kA without TRV capacitor
Rated interruption time
Operation sequence
Operation mechanism
Rated gas pressure
Ambient air
temperature
50 kA with TRV capacitor
40 kA without TRV capacitor
2 cycles
3 cycles
O-0.3sec.-CO-1min.-CO
Spring (Open, Close)
0.59 MPa-g
-30 to +50℃ deg C
-50 to +40 deg C
9
Advantage in maintenance work
Number of parts and maintenance items
Item
Spring GCB
Hydraulic GCB
Number of Parts
60%
100%
Number of parts for replacement
40%
100%
Number of oil seals
>1%
100%
Inspection item
60%
100%
Test item
40%
100%
maintenance fee（％）
Maintenance
Hydraulic
operated GCB
550kV
ｈｙｄraulic
GCB
Spring operated
GCB
550kV
spring GCB
100%
80%
100%
60%
40%
40%
20%
0%
0
6
12
18
24
Field aging (year)
30
36
Comparison of Maintenance Fee
10
Advantage in reliability
 Less failure is expected in spring operated GCB than in hydraulic operated GCB
 Many of the failures experienced are related to hydraulic system
Failure rate of GCBs
Failure rate of each functional element
11
Feature of torsion bar spring
Torsion bar spring
Helical spring
F
Ｔ
Shape
Torsion bar spring
configuration
10%
100%
Mass per charged
energy
65%
100%
Equivalent spring
mass
1%
100%
Kinetic energy
consumed by spring
0%
25%
100%
75%
Driving energy for
interrupter
Fixed end
Rotating end
Volume
joint end
 Torsion bar spring gives higher
spring energy for operation because
kinetic energy loss is ignorable
550kV spring operated GCB
 A torsion bar spring operating
mechanism containing higher
operating energy and lightweight
interrupter
 Sufficient opening speed for
capacitive current switching can be
achieved at rated voltage of 550kV
550 kV 2-break GCB
Torsion bar spring
operating mechanism
13
Conclusion
 A gas mixture of SF6 and CF4 enables the application of GCBs to
extremely low ambient temperatures (less than -40 deg C).
 Development of 800kV mixed gas GCB and 245kV GCB is
introduced. Same hardware as SF6 GCB is used and lower
specification on dielectric capability and interrupting capability is
applied while application at -50 deg C is achieved.
 Advantages of spring operating mechanism is presented. Low
maintenance work and high reliability can be achieved.
 Torsion bar spring can achieve higher operating energy than
helical coil spring. Torsion bar spring operating mechanisms have
applied to 550kV spring operated GCB with lightweight
interrupter.
14