Electrical power for the railway grid — and for traction sub-stations that feed the OHE — originates at generating stations (thermal, hydro, nuclear, or renewable) and reaches consumers through a chain of transmission and distribution stages, each stepping voltage up or down for efficiency and safety.
The Power System Chain
- Generation — typically 11–25 kV at the generator terminals.
- Step-up transformation for transmission — 132 kV, 220 kV, 400 kV, or 765 kV depending on distance/load.
- Step-down at grid substations to sub-transmission levels (e.g. 132 kV → 33 kV).
- Primary distribution (33 kV/11 kV) feeds distribution transformers and railway traction sub-stations.
- Secondary distribution (415 V/230 V) supplies low-voltage loads such as station lighting.
Why Transmit at High Voltage?
- For a given power, higher voltage means lower current — and I²R losses fall with the square of current.
- Lower current also permits thinner (cheaper) conductors for the same power transfer.
Exam Focus
Expect questions distinguishing transmission voltage levels (132/220/400 kV) from distribution levels (33/11/0.4 kV), and questions applying P = VI cos φ to compare current at different voltages for the same power.
Content Status
Draft note, self-authored for the platform skeleton. Not yet cross-verified against the official RBE 14/2014 syllabus PDF — treat as study-aid only until verified.