29-03-2014, 11:38 AM
GAS INSULATED SUBSTATION
INTRODUCTION
A gas insulated substation is an electrical substation in which the major structures are contained in a sealed environment with sulfur hexafluoride gas as the insulating medium.
Originated in Japan where there is a major need to develop technology that would allow substations to be made as compact as possible.
SWITCHGEAR
Combination of electrical disconnect switches, fuses or circuit breakers.
Used to control, protect and isolate electrical equipment.
Used both to de-energize equipment to allow work to be done and to clear faults downstream.
[b]Need for GIS[/b]
Less cost
Conventional substations require huge spaces whereas GIS requires very minimum space
Flexible design.
Less sensitivity to pollution, as well as salt or even large amount of snow.
Less field construction work resulting in quicker installation time.
MAIN COMPONENTS
BUS BARS
CIRCUIT BREAKERS
DISCONNECTING SWITCHES
HIGH SPEED EARTHING SWITCHES
CURRENT TRANSFORMERS
POTENTIAL TRANSFORMERS
CABLES AND BOXES
GAS SUPPLY AND GAS MONITORING EQUIPMENT
LOCAL CONTROL CUBICLE
LOCAL CONTROL CUBICLES
LCC is the interface cubicles to
all secondary systems of a
substation which represent a
station control and protection.
LCC includes control and alarm functions as well as the correct distribution of auxiliary power supply for the relevant GIS bay.
PROPERTIES OF SF6
Pure SF6 is non-toxic and chemically inert.
Excellent dielectric properties.
Captures free electrons.
The dielectric strength of SF6 is about 2.5 times higher than that of air under the same conditions.
It is poorly soluble in water but soluble in nonpolar organic solvents and is non-flammable.
Results in efficient utilization of resources.
CONCLUSIONS
The adoption of SF6 in switchgear for all operating conditions has brought advantages in performance, size, weight, global cost and reliability.