11-03-2011, 04:21 PM
presented By :
Arupananda Pattanaik
gis.ppt (Size: 2.08 MB / Downloads: 451)
gis.ppt (Size: 2.08 MB / Downloads: 451)
GAS INSULATED SUBSTATION
Introduction
It is a one type of switchgear.
The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects.
There are 3 types of switchgear.i.e
1. AIS
2. HYBRIT GIS
GIS
Gas Insulated Substations (GIS) is a compact,multicomponent assembly enclosed in a ground metallic housing in which the primary insulating medium is compressedSulphur hexafluoride (SF6)gas.
SF6acts as an insulation between live parts & the earthed metal closure.
Gas insulated switchgear is used in industrial areas to fulfil high-energy demands by space saving design with a minimum of cost
SF6 switchgear installed in Canada in a 550 kV substation with 100 kA
Comparison between AIS &GIS
AIS
Air-insulated substation:- An electric power substation that has the busbars and equipment terminations generally open to air.
It utilizes insulation properties of ambient air for insulation to ground.
Very fast electromagnetic transients (VFT) in air insulated substations (AIS)
Air Insulated Substation (AIS) makes it possible to install High Voltage substations that take-up less space
These are more cost-efficient than conventionally designed outdoor infrastructures.
Image of AIS
Hybrid Gas Insulated Switchgear
Small equipment cost.
It takes less area.
High reliability similar to GIS substation.
Easy extension.
It is a combination of AIS and GIS.
GIS
Gas Insulated Substations (GIS) is a compact,multicomponent assembly enclosed in a ground metallic housing in which the primary insulating medium is compressedSulphur hexafluoride (SF6)gas.
SF6acts as an insulation between live parts & the earthed metal closure.
Gas insulated substations are particularly suitable for underground construction beneath public buildings.
Gas insulated substation mainly used for a power transmission system or a sub-station system, of which outgoing bus bar is shortened to reduce consumption of the outgoing bus bar
Sulfur Hexafluoride
A colorless, odorless, non-toxic, liquified gas. Shipped as a liquid under its own vapor pressure.
Sulfur Hexafluoride gas, which is itself inert.
It disassociates in the presence of an RF field to form reactive fluorine ions.
SF6acts as an insulation between live parts & the earthed metal closure.
The dielectric strength of SF6 gas at atmospheric pressure is approximately three times that of air.
pace requirement is only 10 to 25 percent of what is required is a conventional substation.
SF6 can be prepared from the elements through exposure of S8 to F2. This is also the method used by the discoverers Henri Moissan and Paul Lebeau in 1901
It does not react with molten sodium, but reacts exothermically with lithium.
Of the 8,000 tons of SF6 produced per year, most (6,000 tons) is used as a gaseous dielectric medium in the electrical industry,
it has a much higher dielectric strength than air or dry nitrogen.
This property makes it possible to significantly reduce the size of electrical gear.
Properties
Molecular formula SF6
Molar mass 146.06 g/mol,
Density 6.164 g/L (gas, 1 bar)
1.329 g/ml (liquid, 25 °C)
2.510 g/cm3 (solid, −50.8 °C)
Melting point- 50.7 °C (triple point)
Boiling point− 64 °C (209 K) (subl.)
decomp. at ca. 500 °C (773 K)
Solubility in waterslightly soluble
Solubility in ethanolsoluble
Specification of GIS
The weight and size of the GIS equipment do not change appreciably with the voltage class.
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 (like 170/145 kV).
Even when the GIS equipment is designed for an individual voltage class, the dimensions and weights of the equipment differ marginally.
Component of GIS
Bus bars.
Circuit Breakers.
Disconnecting switches.
Earthing switches.
Current transformer.
Voltage transformers.
Cable and boxes.
Gas supply and gas monitoring equipment.
Circuit Breakers
A circuit breaker is an automatically-operated electrical switch designed to protect from damage caused by overload or short circuit.
Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.
Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
Current interruption in a high-voltage circuit-breaker is obtained by separating two contacts in a medium, such as SF6, having excellent dielectric and arc quenching properties.
After contact separation, current is carried through an arc and the arc is interrupted & cooled by a gas blast of sufficient intensity.
Current transformer
Current transformer (CT) is used for measurement of electric currents.
Current transformers are also known as instrument transformers.
Current transformers are commonly used in metering and protective relays in the electrical power industry.
Voltage transformers
Voltage transformers (VTs), also referred to as “Potential transformers" (PTs), are used in high-voltage circuits.
They are designed to present a negligible load to the supply being measured, to allow protective relay equipment to be operated at lower voltages, and to have a precise winding ratio for accurate metering
Disconnecting switches
Disconnector switches are safety devices used to open or to close a circuit when there is no current through them.
These are used to isolate a part of a circuit, a machine, a part of an overhead line or an underground line so that maintenance can be safely conducted.
The opening of the line isolator or busbar section isolator is necessary for safety, but not sufficient.
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 100% 60%
Electrical assembly 100% 70%
Maintenance 100% 50%
Outage 100% 50%
Life cycle costs after 10 years 100% 70%
Arupananda Pattanaik
gis.ppt (Size: 2.08 MB / Downloads: 451)
gis.ppt (Size: 2.08 MB / Downloads: 451)
GAS INSULATED SUBSTATION
Introduction
It is a one type of switchgear.
The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects.
There are 3 types of switchgear.i.e
1. AIS
2. HYBRIT GIS
GIS
Gas Insulated Substations (GIS) is a compact,multicomponent assembly enclosed in a ground metallic housing in which the primary insulating medium is compressedSulphur hexafluoride (SF6)gas.
SF6acts as an insulation between live parts & the earthed metal closure.
Gas insulated switchgear is used in industrial areas to fulfil high-energy demands by space saving design with a minimum of cost
SF6 switchgear installed in Canada in a 550 kV substation with 100 kA
Comparison between AIS &GIS
AIS
Air-insulated substation:- An electric power substation that has the busbars and equipment terminations generally open to air.
It utilizes insulation properties of ambient air for insulation to ground.
Very fast electromagnetic transients (VFT) in air insulated substations (AIS)
Air Insulated Substation (AIS) makes it possible to install High Voltage substations that take-up less space
These are more cost-efficient than conventionally designed outdoor infrastructures.
Image of AIS
Hybrid Gas Insulated Switchgear
Small equipment cost.
It takes less area.
High reliability similar to GIS substation.
Easy extension.
It is a combination of AIS and GIS.
GIS
Gas Insulated Substations (GIS) is a compact,multicomponent assembly enclosed in a ground metallic housing in which the primary insulating medium is compressedSulphur hexafluoride (SF6)gas.
SF6acts as an insulation between live parts & the earthed metal closure.
Gas insulated substations are particularly suitable for underground construction beneath public buildings.
Gas insulated substation mainly used for a power transmission system or a sub-station system, of which outgoing bus bar is shortened to reduce consumption of the outgoing bus bar
Sulfur Hexafluoride
A colorless, odorless, non-toxic, liquified gas. Shipped as a liquid under its own vapor pressure.
Sulfur Hexafluoride gas, which is itself inert.
It disassociates in the presence of an RF field to form reactive fluorine ions.
SF6acts as an insulation between live parts & the earthed metal closure.
The dielectric strength of SF6 gas at atmospheric pressure is approximately three times that of air.
pace requirement is only 10 to 25 percent of what is required is a conventional substation.
SF6 can be prepared from the elements through exposure of S8 to F2. This is also the method used by the discoverers Henri Moissan and Paul Lebeau in 1901
It does not react with molten sodium, but reacts exothermically with lithium.
Of the 8,000 tons of SF6 produced per year, most (6,000 tons) is used as a gaseous dielectric medium in the electrical industry,
it has a much higher dielectric strength than air or dry nitrogen.
This property makes it possible to significantly reduce the size of electrical gear.
Properties
Molecular formula SF6
Molar mass 146.06 g/mol,
Density 6.164 g/L (gas, 1 bar)
1.329 g/ml (liquid, 25 °C)
2.510 g/cm3 (solid, −50.8 °C)
Melting point- 50.7 °C (triple point)
Boiling point− 64 °C (209 K) (subl.)
decomp. at ca. 500 °C (773 K)
Solubility in waterslightly soluble
Solubility in ethanolsoluble
Specification of GIS
The weight and size of the GIS equipment do not change appreciably with the voltage class.
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 (like 170/145 kV).
Even when the GIS equipment is designed for an individual voltage class, the dimensions and weights of the equipment differ marginally.
Component of GIS
Bus bars.
Circuit Breakers.
Disconnecting switches.
Earthing switches.
Current transformer.
Voltage transformers.
Cable and boxes.
Gas supply and gas monitoring equipment.
Circuit Breakers
A circuit breaker is an automatically-operated electrical switch designed to protect from damage caused by overload or short circuit.
Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.
Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
Current interruption in a high-voltage circuit-breaker is obtained by separating two contacts in a medium, such as SF6, having excellent dielectric and arc quenching properties.
After contact separation, current is carried through an arc and the arc is interrupted & cooled by a gas blast of sufficient intensity.
Current transformer
Current transformer (CT) is used for measurement of electric currents.
Current transformers are also known as instrument transformers.
Current transformers are commonly used in metering and protective relays in the electrical power industry.
Voltage transformers
Voltage transformers (VTs), also referred to as “Potential transformers" (PTs), are used in high-voltage circuits.
They are designed to present a negligible load to the supply being measured, to allow protective relay equipment to be operated at lower voltages, and to have a precise winding ratio for accurate metering
Disconnecting switches
Disconnector switches are safety devices used to open or to close a circuit when there is no current through them.
These are used to isolate a part of a circuit, a machine, a part of an overhead line or an underground line so that maintenance can be safely conducted.
The opening of the line isolator or busbar section isolator is necessary for safety, but not sufficient.
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 100% 60%
Electrical assembly 100% 70%
Maintenance 100% 50%
Outage 100% 50%
Life cycle costs after 10 years 100% 70%