Substation
transformer station
A substation is a site with equipment that raises or lowers the voltage of electricity and passes it on to the next part of the grid.
Substations next to power plants step voltage up for transmission; substations near cities step 345 kV or 154 kV down for the distribution network. Korea's grid special act groups substations with towers and lines as 'transmission and transformation facilities'.
Each substation can take only so much generation. Government figures put a new 154 kV substation at about six years, so once a substation is full, new plants cannot connect even if the distribution line below it has room.