GAS INSULATED SUB-STATION

RONAL PARMAR140080707003

CONTENTS Typical bay overview Enclosures Conductor SF6 sealing Insulators SF6 accessories Circuit Breaker Disconnector ( Isolator ) Earthing ( grounding) switch Current transformer Voltage transformer Surge arrester GAS-insulated line / bus

TYPICAL BAY OVERVIEW

ENCLOSURES

Aluminium alloy◦ No corrosion◦ Low resistance to

return current◦ No eddy current

losses◦ Lower weight◦ Industrial casting ,

except straight extruded / welded tubes

CONDUCTORS Aluminium alloy material ,most often

For light weightFor mechanical propertiesSilver-plating for sliding contact

SF6 SEALINGSealing design recruitments

Tightness (<0.5% per year)Lifetime ( 50 year)Avoid under-gasket corrosion

Gasket material is essentialNo electronic corrosionLifetimeTight across the temperature rangeTight dynamic sealing

Sealing manufacture requires utmost carePrevent leakages

INSULATORS Insulators

Gas barriersSupports insulators

3-ph gas barrier

Support insulatorGas barrier

SF6 ACCESSORIES Each GIS compartment shall be

associated with one set of accessoriesDensity sensor

oPresser switch oAnalogue / digital sensor oSensors should be same temp as

enclosures temp. SF6 valve

oValve can be no return /tapoSection shall be high enough to

enables appropriate vacuum (< 1 mbar) within a reasonable time

o Moisture absorber = molecular sieveAbsorption surface: 20 to 800 sq.m/gAbsorption ratio: 10~20%, by mass

o Pressure reliefPressure does not go beyond the enclosureheat-resistant deflector shall protect person in

case of internal flashover

SF6 ACCESSORIES

CIRCUIT-BREAKER

Main sub-station itemgrading capacitors in case of several breaks per

poleTested at 10,000 close/open cycles

CIRCUIT-BREAKER DRIVEDifferent types

Spring drive with no driving fluid

Hydraulic drivegas storageSpring storage

Pneumatic drivesOut-datedNeed of water draining

No move when CB is not operated, while hydraulic and pneumatic mechanisms daily require several pump starts for pressure topping up

Stable timing, insensitiveness to temperature and pressure, ideal for POW(point of wave) switching.

CIRCUIT-BREAKER DRIVE

DISCONNECTOR ( ISOLATOR ) Does not break any other current than

capacitive current of short length of GIS: <0.1~0.5ATransfer current of double BB substation: 1600A @ 10-40V

Can be associated with a grounding switch

EARTHING (GROUNDING) SWITCH

Insulation Grounding switch is normally

connected the ground Can be insulated to tests

o Contact resistanceo CB timingo CT primary injection

Safety issueo Never disconnect a GS

from ground when 0 voltage is not ascertained

Current transformer

Rating Power Accuracy Safety factor Saturation

Low ratios Difficult to achieve with a single primary turn

Overvoltage protection Specific design to implement inside GIS

VOLTAGE TRANSFORMER

Ratings Powero Quite often over-specified

AccuracyFerro-resonance

Mainly in case of CB grading capacitors

Can be avoided using a special inductance

SURGE ARRESTEROverhead line connections

Generally air-insulated Sometimes gas-insulated

Cable connection / direct transformer connection

GAS-INSULATED LINE/BUS

FURTHER PRESENTATION WORK

Construction of low & medium voltage GIS sub-stationConstruction of high voltage GIS sub-stationMaintenance of GIS sub-stationGIS approach in the GRID Visit of 400/220KV GIS substation located at DASTAN

, bardoli .

REFERENCES

Jean-Louis Habert , ” GIS substation design and execution for HV and EHV application “ , IEEE , 04/2014

Thank you