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50kV-4kVA TR
Start manufacturing in 1894
Worlds first by Ganz 1050kV-3000/3MVAUHV TR
330kV-400MVA GIT(Worlds largest)
66kV-3000kVA GIT
(Japans first)
275kV-99MVA TR(Japans first)
220kV-80MVA TR(Asias first)Almost sameyear as Europes
first operation
525kV-1450MVA TR(Worlds largest) Fig.1
Toshiba TransformersHistory & Background
Only 9 years after the worlds first transformer was manufactured, Toshiba started supplying transformers
to the market in 1894. Since then, Toshiba has been one of the most innovative transformer manufacturersin the world. In 1967, Toshiba delivered the first GIT, 66kV, 3MVA transformer to the market, which features
excellent characteristics for safety and environmental friendliness.
As power consumption in urban areas increases, a large number of substations have been constructed
underground, beneath commercial buildings, parks and public spaces. Safety and the avoidance of fireincidents is the most important consideration for substations in urban areas. Compact and cost effective
solutions are required for substations installed in areas where space is limited. Gas insulated transformers(GITs) instead of Oil immersed transformers (OITs) offer the best solution for overcoming the sharp increase
in electric power demand in large cities.
History of Toshiba Power Transformers
GIT World wide application Underground Substation within a business complex
1
Application: GITs excel in explosion-proof safety and are
widely used in underground and indoor substations in urban
areas. GITs are also installed in environmentally critical
areas where oil leakage is prohibited.
Toshiba has supplied a large number of GITs all over
the world and there are many GIT projects planned for
the future.
As of 2008
Supplied
Under discussionFig.2 Fig.3
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Pressure rise during fault is small
SF6 Insulation Non-flammable
Non-explosive
0
20
40
60
80
100
0 0.2 0.4 0.6 0.8 1 1.2
OIT
GIT
Fault Time(sec)
PressureRise(%) Tank Strength
Pressure rise of GIT is very small
TRANSFORMER ROOM
GIT
GIB
GISROOM
CONSERVATOR
OIL TRANSFORMEROILCABLEBOX
PRESSURERELIEFDEVICE
> Close Arrangement of
Transformers and GISWithout Partitions> Low Ceiling Substation Room
* No Conservator andPressure Relief Device
150MVA-275kV Shunt Reactor
300MVA-275kV GIT GIS
Advantages of GIT Technology
Excellent features of GIT
GITs employ SF6 gas as the insulation & cooling medium, which avoids the need for fire
fighting equipment, oil collection tanks and pits outside the transformer room.
Since the rise in tank pressure for an internal fault is very small compared with the GIT
tank withstand strength, the GIT tank will not explode on internal fault ensuring the safety
of equipment within the substation.
Since neither a conservator nor pressure relief arrangement is required, the height of the
transformer room can be reduced. For the case of a 275kV 300MVA class application,
approximately 2 to 2.5 meter reduction in height can be achieved.
The application of GIT together with GIS offers a very compact substation design as the
equipment is installed in the same room. A significant cost reduction for civil construction
can thus be achieved.
Features Advantages with GIT
Non-flammability
Non-explosive feature
Compactness
Excellent interface withGas Insulated Switchgear(GIS)
Pressure rise on internal fault
Compact substation design throughapplication of GIT
2
As oil is not used in a GIT, a fire wall between the GIT and
GIS or separate rooms are not required. Therefore GITand GIS can be instal led in the same room. This
arrangement enables a compact substation to beachieved.
Significant tank pressure increases do not occur during
internal failures due to the Gas characteristics. The risk of
a tank explosion or fire incident can be completelyeliminated.
Fig.4
Fig.5
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Insulation / Cooling
Insulating Oil SF6Pressure 0.14 or 0.43MPa-g(20)
Solid Insulation Material
Oil Impregnated Paper, Pressboard PET Film,PPS Film, Aramide Paper,Pressboard
Conservator
Necessary Unnecessary
On-Load Tap Changer
Diverter Switch
Arcing Switching in Oil Vacuum Interrupter
Tap Selector
Slide Contact Roller Contact
Construction
The construction of a GIT is basically the same
as an OIT, with the exception of insulatingmaterial and cooling medium. Therefore, broad
experience of OIT technology can be applied toGIT design, manufacturing and maintenance.
Features of GIT
3
Oil Immersed Transformer(OIT)
Gas Insulated Transformer(GIT)
Fig.6
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Air Outlet
Air Inlet
Cooling Fan
Air Cooler
Commercial building
Cooling system
The concept of the external cooling design for a GIT is nearly the same as that for an OIT; for this reason
various types of cooling method can be applied.
4
Cooling design for GIT
Since the head pressure of SF6 gas is negligiblylow, cooling equipment can be located above the
GIT level as indicated in the figure. The GIT offersexcellent flexibility when locating components
such as radiators or coolers.
A water cooling system is widely used in large-capacity
underground and/or indoor substations. The heat
generated from a GIT is efficiently transferred towater-air heat exchangers by water flow. The coolingsystem is usually located on the top floor of the
substation building.
Flexibility in substation design Water cooling system forurban substations
GDAN/GDAF-20/63MVA - 110kV GIT
1. GNAN Type 2. GDAN Type 3. GDAF Type 4. GDWF Type
RadiatorGas Blower
Radiator
Gas Blower Gas - WaterHeat-Exchanger
Cooler
Water
Gas to Water
Circulating water pumpUnderground
Gas Watercooler
Gas Blower
Silencer
Water to Air
Gas to Water
P
Fig.7
Fig.8 Fig.9
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Fig.10
Fig.11
Computer AidedEngineering (CAE)
Radiator coolingWinding cooling
Transformer room cooling
5
Temperature analysis for GIT design and GIT room considerations
In the cooling design for the GIT winding or substation buildings, Computer Aided Engineering (CAE)
methods can be applied. The calculation using CAE for the airflow inside the building and/or outside isvery useful during the planning stage of the substation building.
The calculation result used in the figure shows that the top cooler arrangement is suitable in terms of
efficient substation cooling for this case. Positions of coolers can be decided by carrying out the CAE
analysis taking into consideration the arrangement of the substation.
Air Temperature distribution Air velocity vector and distribution
Exhaust Flow Late = 760m3/min, No-Duct
Coil
HorizontalCooling Duct
Gas Stopper
Gas Stopper
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Fig.12
Interface with other substationequipment
Cable connection
6
There are various types of terminal construction for GIT applications. In order to reduce the space required
for the terminal construction, cable connection or GIB direct connection is widely applied instead of airbushing connection especially for underground or indoor substations.
The cable interface construction is well defined and termination
work can be done in a secure manner in accordance with theinternational standard (IEC or others).
Plug-in connector interface
Gas treatment work at the cable compartment is not required
during installation work in the case of the plug-in connector. Aplug-in connector is usually only applied for small capacity, low
voltage GITs due to availability of the connector.
Gas Insulated Busbar (GIB) direct connection
GITs can be installed together with GIB or GIS in the same
room by applying either GIB or GIS direct connection as shownin Fig. 5 on Page 2.
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Type GVT-D100AL GVT-M100CL GVT-100DH
Photo
Step Voltage
Rated Current
1200V 1500V 2500V
380A 600A 870A
On-Load Tap Changers (OLTC)& Accessories
Temperature indicationSudden gas pressure relay
Line-up of OLTC for GIT
7
Comparison between accessories for GIT and OIT
Item GIT OIT
ProtectiveDevice &
Accessory
Air ventilation
Temperature
Leak
Protection
Others
Gas Temperature IndicatorWinding Temperature Indicator
Oil Temperature IndicatorWinding Temperature Indicator
Oil Preservation SystemDehydrating Breather
Ventilation with fireproof dampers tooutdoors
Buchholtz relay, Gas detection relay,Pressure relief device,
Gas density relayCompound gauge
Sudden gas pressure relay (OLTC)
Oil Level gauge
Ventilation to outdoors
SENSING UNIT
DIAL TYPE THERMOMETER
RESISTANCEBULB
GAS WTI
Fig.14 Fig.15
Fig.13
Table.1
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Diagnostics & Maintenance
GIT Diagnostics
GIT Maintenance Program (Example)
8
NO. Maintenance Item
1
2
3
4
5
6
7
8
9
10
11
12
Gas analysis
Replenish the bearing grease of gas blower
Gas blower bearings
Exchange Gas blower
Indication and protection devices
Exchange Gas pressure sensor
Exchange Bushing
Exchange control cable Wiring
Inspection of OLTC
Exchange a Cooler
Exchange O-ring, Gasket
Running repairs of small gas leakage
when failureoccur
30 yearsEvery
15 years
Every
10 years
Every
5 years
Every
3 years
Every
2 years
Required maintenance period
Maintenance cycle & items for GITs
Fig.16
Table.2
The integrity of GITs can be checked and a failure cause analysis can be made using gas chromatography.Using a simple gas detective tube device, GIT integrity can be confirmed at site.
Gas sampling bag
Gas detective tube
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Typical application
400MVA GIT in underground substation15/50MVA - 110kV GIT in underground substation
OIT and GIS application GIT and GIS application
9
As oil is not used in both GIT and GIS equipment,neither a fire wall nor separate rooms are required. Byinstalling both GIT and GIS in the same room, acompact substation can be realized.
Toshiba supplies a wide range of GITswith low pressure gas and high pressuregas technology.
OIT and GIS must be separated by a fire wall orinstalled in separate rooms dependent upon the firerisk.
Low pressure design:
0.14MPa-g
High pressure design:0.43MPa-g
Applied Voltage, Capacity & Gas pressure
Voltage
(kV)
Capacity (MVA)
275
154
500
66
22
10 200 30010068
Low PressureSmall Capacity
High PressureLarge Capacity
Water cooling system is applied
Fire extinguisher
Gravel fillingoil catch pit
Long GISinterface
High ceiling
Fire wall
GIT substation is simple & small
Lower ceiling
Substation size is half
Fig.17 Fig.18
Fig.19
Fig.20
Fig.21
0.43Mpa-g
0.14Mpa-g
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Environmentally friendly feature
39MVA-132kV GIT near Australian national park
SF6 gas emission from gas-insulated equipment in Japan Gas leak test at the factory
10
In order to confirm no gas leakagefrom the GIT tank, gas leak testsare performed at the factory for allGIT tanks. At site the gas leaktest is performed on re-assembledparts to ensure no leakage.
Electric power companies and Electric equipment manufacturers in Japan have made tremendous efforts to reduce
SF6 gas emissions based on an agreed voluntary target. With careful gas treatment and complete SF6 gas recoverysystems, the amount of SF6 gas emission from gas insulated equipment has been dramatically reduced as indicatedby the green bars.If no action had been taken, the amount of SF6 gas emissions would still be increasing as indicated by the orangebars.
The Hydro Power station shown in this photograph is located in the wet tropical area within a worldheritage site. A GIT was provided at the power station to remove the risk of oil leakage.
With Action Without Action700
600
500
400
300
200
100
0
1990
1992
1994
1996
1998
2000
2002
2004
2006
2010
SF6Emissions(t)
Control for SF6 gas emission
28.729405065
86117
209
378449
491
Fig.22
Fig.23
Fig.24
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