Power Systems Basic concepts of electrical power generation

1. Introduction to Power System

A Power System is a network that generates, transmits, and distributes electrical energy to consumers.

Main Parts:

1. Generation

2. Transmission

3. Distribution

4. Load (Consumer)

Flow:

Power Plant → Transmission Line → Substation → Distribution Line → Consumer

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PART 1: GENERATION OF ELECTRICAL POWER

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2. Basic Principle of Power Generation

Based on Electromagnetic Induction.

When a conductor rotates in a magnetic field, EMF is produced.

Formula:

$$E = \frac{d\Phi}{dt}$$

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3. Main Components of Power Plant

(1) Prime Mover

Converts energy into mechanical energy.

Examples:

• Steam turbine
• Water turbine
• Gas turbine
• Wind turbine

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(2) Generator (Alternator)

Converts mechanical energy into electrical energy.

Output: AC voltage

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(3) Exciter

Provides magnetic field to generator.

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(4) Transformer

Used to increase voltage for transmission.

Example:
11 kV → 220 kV

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4. Types of Power Plants

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(A) Thermal Power Plant

Fuel: Coal

Process:

Coal → Boiler → Steam → Turbine → Generator

Efficiency:
30–40%

Advantages:
• Low initial cost
• Easy installation

Disadvantages:
• Pollution
• Fuel required

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(B) Hydroelectric Power Plant

Fuel: Water

Process:

Water → Turbine → Generator

Efficiency:
80–90%

Advantages:
• No fuel required
• No pollution

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(C) Nuclear Power Plant

Fuel: Uranium

Process:

Nuclear → Heat → Steam → Turbine → Generator

Advantages:
• Large power generation

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(D) Diesel Power Plant

Fuel: Diesel

Used for:

• Standby power
• Emergency supply

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(E) Solar Power Plant

Fuel: Sunlight

Renewable energy source

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5. Frequency of Generated Power

Formula:

$$f = \frac{PN}{120}$$

Where:

P = number of poles
N = speed in RPM

In India:

Frequency = 50 Hz

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6. Generation Voltage

Typical values:

11 kV
15 kV
22 kV

Not generated at very high voltage due to insulation problems.

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PART 2: TRANSMISSION OF ELECTRICAL POWER

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7. Definition

Transmission is the process of transferring electrical power from power plant to substation over long distance.

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8. Need for High Voltage Transmission

Power formula:

$$P = VI$$

For same power:

If voltage increases → current decreases

Loss formula:

$$Loss = I^2R$$

Therefore:

High voltage → Low current → Low loss

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9. Transmission Voltage Levels

Common values:

132 kV
220 kV
400 kV
765 kV

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10. Transmission System Components

(1) Transmission Lines

Carry power from plant to substation

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(2) Substation

Functions:

• Voltage increase
• Voltage decrease
• Switching
• Protection

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(3) Transformer

Step-up transformer increases voltage

Example:

11 kV → 220 kV

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11. Types of Transmission

(A) Overhead Transmission

Uses poles and towers

Advantages:

• Low cost
• Easy maintenance

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(B) Underground Transmission

Uses underground cables

Advantages:

• Safe
• No weather effect

Disadvantages:

• High cost

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PART 3: DISTRIBUTION OF ELECTRICAL POWER

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12. Definition

Distribution is the process of supplying power from substation to consumers.

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13. Distribution System Parts

(1) Distribution Substation

Voltage reduced:

220 kV → 11 kV

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(2) Feeder

Carries power from substation to distribution area

No tapping

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(3) Distributor

Supplies power to consumers

Tapping allowed

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(4) Service Line

Connects distributor to consumer

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14. Distribution Voltage Levels

Primary distribution:

11 kV

Secondary distribution:

415 V (3 phase)
230 V (single phase)

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15. Types of Distribution System

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(A) Radial System

Simple system

Power flows in one direction

Disadvantage:
If fault occurs, supply stops

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(B) Ring Main System

Power flows in ring

More reliable

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(C) Interconnected System

Most reliable

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PART 4: IMPORTANT LOAD TERMS (SSC JE IMPORTANT)

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16. Connected Load

Total load connected to system

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17. Maximum Demand

Maximum load on system

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18. Demand Factor

$$Demand\ Factor = \frac{Maximum\ Demand}{Connected\ Load}$$

Value < 1

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19. Load Factor (VERY IMPORTANT)

$$Load\ Factor = \frac{Average\ Load}{Maximum\ Load}$$

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20. Diversity Factor

$$Diversity\ Factor = \frac{Sum\ of\ Individual\ Max\ Demand}{Max\ Demand\ of\ System}$$

Value > 1

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21. Capacity Factor

$$Capacity\ Factor = \frac{Actual\ Energy}{Rated\ Capacity × Time}$$

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PART 5: LOSSES IN POWER SYSTEM

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22. Types of Losses

(1) Transmission Loss

$$Loss = I^2R$$

(2) Distribution Loss

Due to:

• Resistance
• Leakage

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PART 6: ADVANTAGES OF POWER SYSTEM

• Large power generation
• Reliable supply
• Efficient system

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PART 7: COMPLETE FLOW SUMMARY

Step 1: Generation
Voltage = 11 kV

Step 2: Step-up transformer
Voltage = 220 kV

Step 3: Transmission
Voltage = 220 kV

Step 4: Step-down transformer
Voltage = 11 kV

Step 5: Distribution
Voltage = 415 V / 230 V

Step 6: Consumer
Voltage = 230 V

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PART 8: MOST IMPORTANT SSC JE EXAM POINTS (REVISION)

Remember these:

• Frequency in India = 50 Hz
• Generation voltage = 11 kV
• Transmission voltage = 132–765 kV
• Distribution voltage = 11 kV
• Domestic voltage = 230 V
• Diversity factor > 1
• Demand factor < 1
• Loss = I²R
• Hydro plant efficiency highest
• Thermal plant most common