Substation Components and SAS
Large substations usually have four standard physical environments: The main control house, one or more local control rooms, the switchyard and the voltage transformation area. The switchyard may have different appearances, mainly depending on the substation insulation media (air‐insulated or gas‐insulated) and its design for environmental exposition (outdoor or indoor).
In case of air‐insulated substations, the primary equipment are svelte structures made of porcelain or polymeric material that provide electrical insulation between the energized upper part and the substation earth plane. Some of this apparatus is filled with gas, such as puffer type circuit breakers, which contain sulfur hexafluoride (SF6).
Others are filled with dielectric oil, such as instrument transformers and power transformers.
This chapter covers SAS related details of substation components installed in the switchyard.
In the lexicon of power systems, operating voltages applicable to equipment and devices have been classified as follows:
- Low voltage: When the 3-phase system voltage is less than 1kV.
- Medium voltage: When the 3-phase system voltage is above 1kV and less than 52kV.
- High voltage: When the 3-phase system voltage is from 52kV to less than 300kV.
- Extra high voltage: When the 3-phase system voltage is from 300kV to 765kV.
- Ultra high voltage: When the 3-phase system voltage is above 765kV.
The primary equipment of a transmission substation operates at standardized rated voltages, such as 72.5, 123, 145, 245, 420, 525 and 765 kV, whilst in most distribution substations, primary equipment works at lower standardized voltages, such as 7.2, 12, 24 or 36 kV.