BEEE-UNIT 5

Unit 5–Power Engineering

Electrical Supply System

• The electrical power system consists of generation, transmission, and distribution.

• Simple layout includes:

  • Generation (power stations)

  • Transmission (high voltage transportation)

  • Distribution (normal voltage delivery to consumers)

• Importance of substations in the supply system, particularly the 11kV/400V indoor substation.

• Introduction to smart grid technology.

Safety Measures in Electrical Systems

• Basic principles and importance of earthing to prevent electric shock.

• Safety precautions when handling electrical systems, including devices like circuit breakers and fuses for protection.

Renewable Energy Resources

• Overview of renewable energy sources (e.g., solar photovoltaic, battery storage technologies, fuel cells).

• Electric vehicle technologies, including HEVs (Hybrid Electric Vehicles), PHEVs (Plug-in Hybrid Electric Vehicles), and EVs (Electric Vehicles).

• Importance of charging stations for EVs and their role in renewable energy integration.

Electrical Supply System

Power Generation

• Power generation typically occurs at voltages such as 11 kV or 6.6 kV in parallel generators.

• Power is stepped up using transformers to voltages like 110 kV, 230 kV, or 400 kV for transmission.

Transmission System - AC

Primary Transmission

• Power is transmitted at high voltages (765 kV, 400 kV, 220 kV) to main load centers.

• Advantages of high voltage transmission:

  1. Reduced volume of conductor material.

  2. Lower current reduces line losses and improves efficiency.

  3. Improved line regulation.

• Secondary transmission occurs at voltages like 33 kV or 66 kV to sub-load centers using overhead or underground systems depending on location.

Distribution System

• Power received at the 33 kV, 66 kV, or 110 kV is stepped down to 11 kV for primary distribution.

• 11 kV lines distribute power through streets using 3-phase, 4-wire configurations.

• Components:

  • Feeders: Link distribution transformers to mains.

  • Distributors: Supply to consumers (residential and industrial).

• Radial versus ring distribution configurations.

Main Components of Transmission and Distribution Systems

• Conductors: Carry electrical power.

• Supports: Maintain height of conductors (RCC poles, MS poles, towers).

• Cross arms: Support conductors on poles/towers.

• Insulators: Prevent current leakage.

• Miscellaneous items: Lighting arresters, ground wires, etc.

Overhead (OH) vs Underground (UG) Systems

Comparison Factors

• Safety: UG preferred for less public hazard.

• Cost: UG systems are ~10 times costlier than OH systems.

• Flexibility: OH systems are easier to modify.

• Faults: UG systems have fewer fault occurrences.

• Maintenance: UG systems have lower maintenance costs and better aesthetics.

Key Diagram of 11 kV/400 V Indoor Sub-Station

• G.O. Switch: Connects 11 kV line to indoor sub-station.

• Transformers: Steps down voltage from 11 kV to 400 V.

• Bus-bars: Distributes 400 V supply to consumers.

• CTs (Current Transformers): Used for metering.

Introduction to Smart Grid

Traditional Power Grid

• One-way flow of electricity from centralized generation to consumers.

• Limited data and automation limit consumer energy management.

Smart Grid Features

• Two-way flow of electricity and information.

• Improved communications and situational monitoring.

Safety Precautions when Working with Electricity

1. Avoid working with wet hands.

2. Do not use damaged equipment.

3. Turn off mains when working on sockets.

4. Use insulated tools.

5. Wear protective rubber gloves and goggles.

6. Ensure circuits are de-energized before repairs.

7. Know local wiring codes and use appropriate circuit protection devices.

Electrical Safety Devices

Fuses

• Protect circuits from excess current by breaking the circuit when overcurrent occurs.

Circuit Breakers

• Protect circuits similarly to fuses but are resettable.

Earthing

• Connecting electrical equipment to the ground to ensure safe current discharge.

• Importance of earthing to prevent electric shock in various faulty conditions.

Types of Earthing

1. Plate Earthing: Uses a G.I. or copper plate for grounding.

2. Pipe Earthing: Installation of G.I. pipe as ground electrode.

Renewable Energy

Overview

• Renewable energy is sourced from naturally replenishing processes: solar, wind, geothermal, hydro, tidal, and biomass.

Advantages

• Low maintenance costs and minimal environmental impact.

• Sustainable and non-depleting resources.

Solar Photovoltaic System

Basics

• Solar cells convert light energy into electrical energy through the photovoltaic effect.

• Solar cell construction and functioning as a p-n junction diode.

Solar Cell Operation

1. Absorption of photons knocks electrons loose.

2. Interconnected solar cells form modules and panels to produce higher output.

Energy Storage Systems

• Applications include portable electronics, UPS, and renewable energy offset.

• Key for balancing demand and supply in energy systems.

Types of Energy Storage

1. Chemical: e.g., vanadium redox batteries.

2. Electrochemical: Rechargeable batteries.

3. Electrical: Capacitors and super-capacitors.

4. Thermal: Storage of heat energy.

Fuel Cell Technologies

Working Principle

• Converts chemical energy (hydrogen and oxygen) into electricity and heat efficiently with water as the only byproduct.

Advantages

• High efficiency (60%) with low environmental impact.

Disadvantages

• High costs and specific storage conditions.

Applications

• Used in transportation, backup power systems, and electronic devices.

Electric Vehicles (EVs)

Types

1. BEV: Electricity only.

2. HEV: Combines electric and combustion engines with regenerative braking.

3. PHEV: Greater battery storage for improved fuel efficiency.

Market Growth

• Increasing public interest and government incentives post-2000s.

EV Charging Stations

• Defined by power output (kW) and charging speed.

• Types of chargers range from slow to fast based on usage and technology.