Gas Insulated Substations Advantages Disadvantages

Gas Insulated Substations (GIS):

Gas Insulated Substations (GIS) are differ from Air Insulated Substations (substations we usually see) such that all the substation equipment such as busbars, circuit breakers, current transformer, potential transformers and other substation equipment are placed inside SF6 modules filled with SF6 gas. SF6 gas which has high dielectric property acts as insulating medium to the High Voltage or Extra High Voltage substation equipment. Generally Gas Insulted Substations (GIS) are indoor type as it requires 1/10th of the space required for conventional substations. Some of the advantages and disadvantages of Gas Insulated Substations (GIS) are:

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Advantages of GIS Substation:

• It occupies very less space (1/10th) compared to ordinary substations. Hence these Gas Insulated Substations (GIS) are most preferred where area for substation is small (eg: Cities)
• Most reliable compared to Air Insulated Substations, number of outages due to the fault is less
• Maintenance Free
• Can be assembled at the shop and modules can be commissioned in the plant easily

Disadvantages of GIS Substation:

• Cost is higher compared to Ordinary Conventional Substations
• Care should be taken that no dust particles enter into the live compartments which results in flash overs
• When fault occurs internally,diagnosis of the fault and rectifying this takes very long time (outage time is high)
• SF6 gas pressure must be monitored in each compartment, reduction in the pressure of the SF6 gas in any module results in flash overs and faults