Understanding AC Power Supply Systems

Aug 22, 2024

Working of AC Power Supply System

Introduction

  • Overview of the AC power supply system.
  • Focus on transmission from generating end to load end.

Generating End

  • Example: Thermal Power Plant (using coal).
  • Power is generated and transmitted to load end (e.g., society/locality).

Types of Loads

  • Various types of loads: industries, colleges, hospitals, markets, etc.
  • Hypothetical case: Society as load.

Need for Long-Distance Transmission

  • Historical context: Earlier power stations were built near loads or raw materials.
  • Current scenario:
    • Example: Thermal plant near coal mines (generating 2000 MW, 200 MW consumed locally, 1800 MW needs transmission).
    • Transmission to cities with high demand (e.g., Delhi).

Reasons Against Building Near Load

  • High transportation costs of coal if power plants are near load.
  • Coal transportation via Indian Railways.
  • Cost of coal vs. cost of power transmission.
  • Nuclear power plants must be located away from populated areas due to safety concerns.
  • Hydro power plants require specific geographical conditions (hilly regions).

Voltage Levels in Transmission

  • Generators produce power at lower voltages (e.g., 11 kV).
  • Voltage is stepped up to higher levels (e.g., 400 kV) using transformers.
    • Purpose: To reduce current and minimize I²R losses in transmission lines.

Generator Transformers

  • Generating transformers always step up voltage.
  • Power transformers can step up or step down voltages.

Substations

  • Function: Reduce voltage for distribution.
  • Example: Voltage stepped down from 400 kV to 220 kV, then to 132 kV, 33 kV, and finally to 11 kV.

Standard Transmission Voltages

  • Importance of standard voltage levels.
  • Three-phase three-wire and three-phase four-wire systems.

Voltage Relationships

  • Line voltage vs. Phase voltage:
    • Line voltage (V_L): Voltage between two lines (e.g., 400 V).
    • Phase voltage (V_PH): Voltage between a line and neutral (e.g., 230 V).
  • Relationship: V_PH = V_L / √3.

Household Connections

  • Common household appliances operate on single-phase loads (e.g., AC, TV, fridge).

Distribution

  • Transmission and distribution parts of the power system:
    • Generation part: Before the transmission line.
    • Transmission part: Between generation and load.
    • Distribution part: From transmission to load.
  • Can be divided into primary and secondary transmission/distribution.

Conclusion

  • Summary of the AC power supply system.
  • Open floor for questions and future topics in power systems.