Electrical power on the National Grid

Electrical power on the National Grid
● Electricity is generated in large modern power stations at 25 kV.
● It is then transformed up to 132 or 270 kV for transmission to other parts of the country on the National
Grid network.
● Raising the voltage to these very high values reduces the losses.
● 66 or 33 kV is used for secondary transmission lines.
● These high voltages are reduced to 11 kV at local sub-stations for distribution to end users such as fac-
tories, shops and houses at 400 and 230 V.
● The ease and effi ciency of changing the voltage levels is only possible because we generate an a.c. sup-
ply. Transformers are then used to change the voltage levels to that which is appropriate. Very high volt-
ages are for transmission, lower voltages are for safe end use. This would not be possible if a d.c. supply
was generated.
● Fig. 2.9 below shows a simplifi ed diagram of electricity distribution.