Power Systems (Electrical)

Generation:

Sources:

• Thermal (coal): ~50% of India. Boilers + steam turbines.
• Hydro: ~12%. Dams + Pelton / Francis / Kaplan turbines.
• Nuclear: ~3%. Uranium / Thorium.
• Solar: ~10% and growing.
• Wind: ~10%.
• Gas: ~6%.
• Biomass, others.

Plant terminology:

• Connected load: max possible.
• Maximum demand: highest actual load.
• Load factor: avg load / max demand.
• Capacity factor: actual energy / installed × time.
• Demand factor: max demand / connected load.

Transmission:

• EHV (Extra-High Voltage): 220, 400, 765 kV.
• HVDC: for long distance, no skin effect, lower losses.
• Choice of voltage: higher = less I²R loss but more insulation cost.

Distribution:

• Primary distribution: 11 kV / 33 kV.
• Secondary: 415/230 V (3-phase 4-wire).

Substations:

• Transformer + switchgear + protection.
• Step-down voltage for distribution.

Protection:

• Fuses: for low voltage.
• Circuit breakers: MCCB, ACB, SF6.
• Relays: sense faults, trip breaker.
• Earthing: for safety.

Tariff:

• Flat rate.
• Two-part tariff: fixed + variable (per kWh).
• Maximum demand tariff.
• Time of day (TOD).

Indian transmission:

• National Grid: synchronously interconnected.
• POWERGRID (PGCIL): central transmission utility.
• State Electricity Boards / Discoms: distribution.

RRB JE focus: voltage levels, transmission losses, basic substation, India's power mix.