Air Insulated Switchgear Substation (AIS)

Air Insulated Switchgear Substation (AIS)

In this type of switchgear substation, atmospheric air is used as the phase to ground insulation for the switchgear of an electrical substation. The installations of AIS are generally outdoor. These type of substions are popular in 400 kV substations.

All equipments in air insulated switchgear substations are exposed to weather conditions. The busbars and equipment terminations normally open to air. The insulation properties of ambient air are used for insulation to ground.

The advantages of AIS substations are as given below :

1. This arrangement is best suited for low voltage rating substations and where plenty of space is available for installation.

2. The expansion for future is easier.

3. Time required for erection is less.

4. The propogation of fault from one point to another is less likely as the equipments are spaced away from each other sufficiently.

5. Location of fault is easier and all the equipments in AIS switchyard are within view.

6. The construction work to be carried out is comparatively less. 

The limitations of AIS substations are as given below :

1. Space requirement for erection is large.

2. As the equipments are exposed to atmosphere, outdoor switch yards are more vulnerable to faults.

3. Lesser reliablity as it is exposed to lightning strokes and other external conditions such as winds, rains and cyclones.

4. Periodic maintainance is required due to exposure of this type of installation to outside environment.