Mr. Sudipto Basak.pdf

Gas Insulated Substations (GIS) Pathway for future Expansion

BY SUDIPTO BASAK Senior operations of f icer Hindustan petroleum corporation l imited

Flow of the Presentation

Conclusion

Advancement in GIS Technology

Life Cycle cost analysis of GIS & AIS

Major Suppliers in India for GIS

Advantages over conventional Substations

Design of Gas Insulated Substations

Concept and overview of Gas Insulated Substations

SF6 The gas that revolutionized the switchgear technology

Overview on Conventional substation

Gas insulated Switchgears - Pathway for future expansions, By Sudipto Basak

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Overview on Conventional

Switchgears Gas insulated Switchgears - Pathway for future expansions, By Sudipto Basak

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A:Primary power lines' side B:Secondary power lines' side

1.Primary power lines 2.Ground wire 3.Overhead lines 4.Lightning arrester

5.Disconnect switch 6.Circuit breaker 7.Current transformer 8.Voltage

Transformer 9.Main transformer 10.Control building 11.Security fence

12.Secondary power lines


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SF6 The gas that revolutionised Switchgear Technology Gas insulated Switchgears - Pathway for future expansions, By Sudipto Basak

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SF6 Properties Inert

Non Toxic

Colourless

Odourless

Non Flammable

The Edge SF6 has 2-3 times the insulating ability of air at the same pressure. SF6 is about 100 times better than air for interrupting arcs.

Minimum Clearance

Levels reduced

Sulphur

Hexaflouride

Minimum Clearance Level

Comparison AIS Vs GIS Gas insulated Switchgears - Pathway for future expansions, By Sudipto Basak

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132 KV 220 KV 400 KV 765 KV

AIS GIS (145KV)

AIS GIS (245KV)

AIS GIS (420 KV)

AIS GIS (800KV)

Mini.

Clearance

B/W Ph-Ph

1.22

0.37 2.06 0.46 4.0 0.66 7.6 0.81

Diff. in

clearance

with Next

Voltage

Level

0.84 0.09 1.94 0.20 3.6 0.15 - -

All in meters


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Concept & Overview -GIS

A gas-insulated substation (GIS) is a substation in which the insulating medium between the phases and between the phase and earth is SF6

Gas insulated substations originated in various countries between 1968 and 1972 where there is a major need to develop technology that would allow substations to be made as compact as possible. After about 5 years of experience, the use rate increased to about 20% of new substations in these countries.

Different dielectric mediums are used in electrical equipment like Air , oil, Vacuum and SF6. In GIS, all the bus bars, breakers, isolating switches earth switches, CT, PT are immersed in SF6.

Gas insulated Switchgears - Pathway for future expansions, By Sudipto

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All Bay Functions in 1 Module Gas insulated Switchgears - Pathway for future expansions, By Sudipto

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GIS MODULE Combined disconnector &

earthing switch

Current Transformers

Potential Transformers

Circuit Breakers


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Design of Components

o Circuit Breakers

GIS uses essentially the same dead tank SF6 puffer circuit

breakers used in AIS. Instead of SF6-to-air as connections

into the substation as a whole, the nozzles on the circuit

breaker enclosure are directly connected to the adjacent GIS

module.

o Bus Bar

To connect GIS modules that are not directly connected to

each other, an SF6 bus consisting of an inner conductor and

outer enclosure is used. Support insulators, sliding electrical

contacts, and flanged enclosure joints are usually the same

as for the GIS modules.


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Design of Components Gas insulated Switchgears - Pathway for future expansions, By Sudipto

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CTs are inductive ring types installed either inside the GIS enclosure or outside the GIS enclosure.

The GIS conductor is the single turn primary for the CT. CTs inside the enclosure must be shielded from the electric field produced by the high voltage conductor or high transient voltages can appear on the secondary through capacitive coupling.

For CTs outside the enclosure, the enclosure itself must be provided with an insulating joint, and enclosure currents shunted around the CT. Both types of construction are in wide use.

Current Transformer

CURRENT TRANSFORMERS


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VTs are inductive types with an iron core.

The primary winding is supported on an insulating plastic film immersed in SF6.

The VT should have an electric field shield between the primary and secondary windings to prevent capacitive coupling of transient voltages.

The VT is usually a sealed unit with a gas barrier insulator.

The VT is either easily removable so the GIS can be high voltage tested without damaging the VT, or the VT is provided with a disconnect switch or removable link

VOLTAGE TRANSFORMERS


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Disconnect switches have a moving contact that opens or closes a gap

between stationary contacts when

activated by an insulating operating rod

that is itself moved by a sealed shaft

coming through the enclosure wall.

The stationary contacts have shields that provide the appropriate electric field

distribution to avoid too high a surface

stress.

The moving contact velocity is relatively low (compared to a circuit breaker

moving contact) and the disconnect

switch can interrupt only low levels of

capacitive current (for example,

disconnecting a section of GIS bus) or

small inductive currents (for example,

transformer magnetizing current).

DISCONNECT SWITCHES


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Ground switches have a moving contact that opens or closes a gap between the high voltage conductor and the enclosure.

Sliding contacts with appropriate electric field shields are provided at the enclosure and the conductor.

A maintenance ground switch is operated either manually or by motor Ground switches for GIS.

A fast-acting ground switch has a high speed drive, usually a spring, and contact materials that withstand arcing so it can be closed twice onto an

energized conductor without significant damage to itself or adjacent parts.

Fast-acting ground switches are frequently used at the connection point of the

GIS to the rest of the electric power network, not only in case the connected

line is energized, but also because the fast-acting ground switch is better able

to handle discharge of trapped charge and breaking of capacitive or inductive

coupled currents on the connected line.

GROUND SWITCHES


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SF6-to-air bushings are made by attaching a hollow insulating cylinder to a flange on the

end of a GIS enclosure. The insulating

cylinder contains pressurized SF6 on the

inside and is suitable for exposure to

atmospheric air on the outside.

The conductor continues up through the center of the insulating cylinder to a metal

end plate. The outside of the end plate has

provisions for bolting to an air insulated

conductor.

The insulating cylinder has a smooth interior. Sheds on the outside improve the

performance in air under wet and/or

contaminated conditions. Electric field

distribution is controlled by internal metal

shields. Higher voltage SF6-to-air bushings

also use external shields. The SF6 gas inside

the bushing is usually the same pressure as

the rest of the GIS.

AIR CONNECTION


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To connect a GIS directly to a transformer, a special SF6-to-oil bushing

that mounts on the transformer is used.

The bushing is connected under oil on one end to the transformers high voltage

leads.

The other end is SF6 and has a removable link or sliding contact for connection to

the GIS conductor.

The bushing may be an oil-paper condenser type or more commonly today,

a solid insulation type. Because leakage

of SF6 into the transformer oil must be

prevented, most SF6-to-oil bushings have

a centre. section that allows any SF6

leakage to go to the atmosphere rather

than into the transformer

DIRECT TRANSFORMER CONNECTIONS


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LCC local control cabinet The control and power wires of all operating mechanisms, auxillary switches,

alarms, heaters, CTs and VTs are brought from the GIS equipment modules to the LCC using shielded multiconductor control cables.

LCC has a mimic diagram of the part of the GIS being controlled. Associated with the mimic diagram are control switches and position indicators for the circuit breaker and switches.

Annunciations and Electrical interlockings are also incorporated in the LCC

Gas Monitoring System The pressure of the SF6 gas varies with temperature, so a mechanical

temperature-compensated pressure switch is used to monitor the equivalent of gas density.

GIS is filled with SF6 to a density far enough above the minimum density for full dielectric and interrupting capability so that from 10 to 20% of the SF6 can be lost before the performance of the GIS detieorates. The density alarm provide a warning of gas being lost, and can be used to operate the circuit breakers and switches to put a GIS that is losing gas into a condition selected by the user

Microprocessor based measurement systems are available that provide pressure, transmitter, density and even percentage of proper SF6 content.

LCC & GAS MONITORING SYSTEM


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Advantages over AIS Gas insulated Switchgears - Pathway for future expansions, By Sudipto

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LOW SPACE REQUIREMENT


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LOW SPACE REQUIREMENT

Usage of SF6 Gas brings down the minimum clearance level and makes GIS more compact

The weight and size of the GIS equipment do not change appreciably with the voltage class as bulk of the current carrying components and enclosures have identical dimensions for similar thermal and short time current

The additional insulation required for the next voltage class is achieved by increased gas density

Owing to these flexibilities, a few manufacturers offer the same equipment for two voltage classes.

Even when the GIS equipment is designed for an individual voltage class, the dimensions and weights of the equipment differ marginally.

Rated Voltage 145 KV 170 KV 245 KV

Bay Width, m 1.5 2.0 2.0

Bay Depth, m 3.3 3.35 3.4

Bay Height, m 3.2 3.4 3.4

Floor Area, Sq. m 4.95 6.7 6.8

Volume, m3 15.84 22.78 23.12

Weight, Kg 3800 5000 5700

Floor Landing, Kg/Sq. m 765 750 840

Advantages over AIS

Experience has shown that the internal parts of GIS are so well protected inside the metal enclosure that they do not

age and as a result of proper material selection and

lubricants, there is negligible wear of the switch contacts.

GIS will not need to be opened for maintenance.

The external operating mechanisms and gas monitor systems should be visually inspected, with the frequency

of inspection determined by experience.


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LOW MAINTENANCE


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LOW TRANSPORT & INSTALLATION COST

A large number of versions are small enough to be

transported in containers or on trucks with phases open

spread open for quick installation, thus saving on transport

cost and installation times.


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Operation at Low temperatures

GIS performs perfectly in harsh climates, even under snow and ice loads, or at temperatures down to -60C with pure SF6. This is due to the well covered movable parts that are mechanically protected against the influence of heavy snow and ice-loads. Additionally these can be provided with a thermostat driven heating mechanism.

Operation in Hazardous areas

GIS performs perfectly in environments filled with corrosive and harmful chemicals as the movable parts are enclosed under sealed containers. It is ideal for use in the presence of highly inflammable gases because of the perfect sealing of sparks and arcs. This makes it ideal of petrochemical installations


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Major Suppliers

SrNo. Name of the

company

Product Range Product

Name

1 GE 72.5 800 KV XD

2 SIEMENS 72.5 800 KV 8D RANGE

3 HYOSUNG 25.8 800 KV HICO

4 ABB 72.5 1200 KV ENK-ELK

5 ALSTOM 72.5 800 KV F35-T155

6 CG 72.5 145 KV GT01

7 SEL ELECTRIC 7.2 40.5 KV TPR6


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Conclusion










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Life Cycle cost analysis of

GIS & AIS

Life Cycle cost of HV Substation

Cost of Acquisition

Cost of Operation

Renewal Cost


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Composition of Cost Gas insulated Switchgears - Pathway for future expansions, By Sudipto Basak

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

AIS GIS

Composition of Cost 145 KV H-Arrangement

System Cost Ground Acquisition Costs Scheduled Maint Cost

Unscheduled Maint Cost Replacement of Equipment

Cost of

Acquisition

Cost of

Operation

Renewal

Cost

Cost of

Acquisition

Cost of Operation

Renewal Cost

Life Cycle cost analysis of

GIS & AIS Gas insulated Switchgears - Pathway for future expansions, By Sudipto Basak

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LIFE CYCLE COST AIS GIS

Planning and Engineering 100% 80%

Real Estate 100% 40%

Primary Equipment 100% 120%

Secondary Equipment 100% 100%

Earthwork, civil work, Structures 100% 60%

Electrical Assembly and Erection 100% 70%

Maintenance 100% 50%

Outage 100% 50%

Life Cycle costs after 10 Years 100% 71%


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Further Advancement in

GIS Technology

Gas Insulated Transformers

SMART GIS Integrated Electronic CTs and PTs

Combined earthing switch and disconnector


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FOR FURTHER SPACE REDUCTION


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Conclusion

Even though the equipment cost of GIS is higher than that of AIS due to the grounded metal enclosure, the low space requirement, the high degree of factory assembly, the lower erection, commissioning and maintenance cost makes it more cost effective in the long run.

Also with increase in system voltage AIS take very large areas because of the long insulating distances in atmospheric air. Cost comparisons of GIS projected that, on a total installed cost basis, GIS costs would equal AIS costs at 345 kV. For higher voltages, GIS was expected to cost less than AIS.

Due to its superior operational advantages like error free control by

LCC, insulation from corrosive and inflammable environment and higher seismic qualification due to lower centre of gravity and high compactness it becomes a better product over AIS in sensitive and hazardous location like those of petrochemical and oil & gas industries.


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Bibliography

IEEE Guide for Gas-Insulated Substations, IEEE Std. C37.122.1-1993. IEEE Standard for Gas-Insulated Substations, IEEE Std. C37.122-1993. IEC 517: 1990, Gas-insulated metal-enclosed switchgear for rated voltages of 72.5 kV and

above (3rd ed.).

IEEE Guide for Moisture Measurement and Control in SF6 Gas-Insulated Equipment, IEEE Std. 1125-1993

IEC 1634: 1995, IEC technical report: High-voltage switchgear and controlgear use and handling of sulphur hexafluoride (SF6) in high-voltage switchgear and controlgear.

User guide for the application of gas-insulated switchgear (GIS) for rated voltages of 72.5 kV and above, CIGRE Report 125, Paris, April 1998.

Operating experience of gas-insulated switchgear (GIS) and its influence on the future substation design, Paper 23-04 of CIGRE General Meeting, Paris, 1982.

Paper on Modern Subterranean Substations in GIS Technology by Bert Strassburger (Siemens)

Paper on Gas Insulated Substations by R.Rajmohan (East Coast Energy Ltd) Article on Substations that embellish not blemish the streetscape from November 2009

issue of Living Energy Journal

High Voltage GIS by M/s ABB Substation life cycle cost management supported by Stochastic optimization algorithm, by

Martin Hinow - ETH-Zurich (Switzerland), Mark Waldron National Grid (UK), Dr. Lorenz Muller-ABB(Switzerland), Heinz Aeschbach, Karsten Pohlink, Areva T&D AG (Switzerland)


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THANK YOU QUESTIONS PLEASE..


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