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The impact of the application of vacuum switchgear at transmission voltages
CIGRE WG A3.27Motivation
• SF6 has been identified as a greenhouse gas
• Efforts are being made to reduce utilization and emission
of SF6
• Users of HV switchgear are looking at alternative
switching and insulation media
• Vacuum has established itself as the technology of choice
in the medium voltage domain
• Vacuum circuit breakers could be an alternative
Increase in breaking capacity of HV VCB‘s
Application of HV VCB‘s in Japan
The MV experience of VCB‘s
• ams
Study Committee A3HIGH VOLTAGE EQUIPMENT
• No SF6
• Less maintenance work
• No gas condensation at very low temperatures
• Non-flammability
• Low operating energy
• Frequent switching capability
Utilities Industrial system
Advantages of VCB
Vacuum circuit breakers are relatively simple with the interrupter having only one moving component which moves linearly over a very short stroke 6-8 mm for 12 kV for example
ceramic enclosure
arc control devices
bellows
metal vapour shield
contacts
0
100
200
300
400
500
600
700
93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10FY
CB u
nit
0%
10%
20%
30%
40%
50%
60%
70%
VCB u
nit ratio
72/84kV C B unit
VC B ratio
Medium voltage vacuum
interrupter
SF6 world record:550 kV 63 kA: 20 GVA/break
Vacuum arc in interrupter
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The utility perception of HV VCB‘s Products on the market and in development
Study Committee A3High Voltage Equipment
Comparison of HV VCB‘s and SF6 CB‘s
Comparison of HV VCB’s with HV SF6 CB’s (Same rating of one manufacturer)
Attribute SF6 CB VCB
• Mechanical life 10,000 operations 10,000 operations
• Electrical life @ rated current 6,000 operations 10,000 operations
• Nr. of short circuit interrupt. 10 - 20 30 - 100
Comparison of 145kV VCB’s with 145kV SF6 CB’s (same manufacturer)
SF6 CB VCB
• General inspection 3 - 6 years 3 - 6 years
• Gas monitoring or refilling required not required
• Maintenance (wearing parts) 12 years 12 years
• Overhaul of CB chamber required not required
• SF6 emission data report possibly required not required
• Electrical cost for tank heater (sometimes) not required
Issues raised as appreciation/hesitation towards application of HV VCB, as percentage of all issues raised
Conclusions:
• Some 8000 HV VCB’s are already in service in Japan (sometimes
for 20 years) with very good service record.
New products appear on the market frequently, up to 145 kV.
• There is no reason to assume that the excellent reliability
performance of MV VCB’s cannot be extrapolated to high
voltage
• Main driver for utilities to be interested in HV VCB’s is absence
of greenhouse gas SF6 and advantages regarding lifetime
management (reduced maintenance and long electrical life)
• Potential users see issues regarding the (capacitive) switching
and dielectric performance (late breakdown) of HV VCB’s
• Current chopping and Xray generation are not an issue
The impact of the application of vacuum switchgear at transmission voltages
CIGRE WG A3.27
126 kV 40 kA(China)
72.5 kV 31.5 kA(Germany)
170 kV 50 kA(S. Korea)
Up to 242 kV cap bank load break switch (USA)
84 kV 31.5 kAC-GIS (Japan)
145 kV 40 kA (Japan)
72.5 kV 31.5 kA(China)
Comparison of closing and opening energy of motor-charged spring operators for 72.5/84 kV SF6-CB and VCB from the same manufacturer. E, F, G interrupters have different insulation gas pressure
