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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