Gas insulated sub station 2

GAS INSULATED SUB-STATION
RONAL PARMAR
140080707003

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

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 weight
 For mechanical properties
 Silver-plating for sliding contact

SF6 SEALING
 Sealing design recruitments
 Tightness (<0.5% per year)
 Lifetime ( 50 year)
 Avoid under-gasket corrosion
 Gasket material is essential
 No electronic corrosion
 Lifetime
 Tight across the temperature range
 Tight dynamic sealing
 Sealing manufacture requires utmost
care
 Prevent leakages

INSULATORS
 Insulators
 Gas barriers
 Supports insulators
3-ph gas barrier
Support insulatorGas barrier

SF6 ACCESSORIES
 Each GIS compartment shall be
associated with one set of accessories
 Density sensor
o Presser switch
o Analogue / digital sensor
o Sensors should be same temp as
enclosures temp.
 SF6 valve
o Valve can be no return /tap
o Section shall be high enough to
enables appropriate vacuum (< 1
mbar) within a reasonable time

o Moisture absorber = molecular sieve
 Absorption surface: 20 to 800 sq.m/g
 Absorption ratio: 10~20%, by mass
o Pressure relief
 Pressure does not go beyond the enclosure
 heat-resistant deflector shall protect person in
case of internal flashover
SF6 ACCESSORIES

CIRCUIT-BREAKER
 Main sub-station item
 grading capacitors in case of several breaks per
pole
 Tested at 10,000 close/open cycles

CIRCUIT-BREAKER DRIVE
 Different types
 Spring drive with no
driving fluid
 Hydraulic drive
 gas storage
 Spring storage
 Pneumatic drives
 Out-dated
 Need 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: <0.1~0.5A
Transfer 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 resistance
o CB timing
o CT primary injection
 Safety issue
o 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
 Power
o Quite often over-specified
 Accuracy
 Ferro-resonance
 Mainly in case of CB
grading capacitors
 Can be avoided using a
special inductance

SURGE ARRESTER
 Overhead line connections
 Generally air-insulated
 Sometimes gas-insulated
 Cable connection / direct
transformer connection

FURTHER PRESENTATION WORK
 Construction of low & medium voltage GIS sub-station
 Construction of high voltage GIS sub-station
 Maintenance of GIS sub-station
 GIS 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

Gas insulated sub station 2

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