Electrical Applications 2

Electrical Applications 2 covers the BTEC NII level objectives in Electrical Applications U86/330. To understand the applications, a knowledge of the underlying principles is needed and these are covered briefly in the text. Key topics discussed are: the transmission and distribution of electrical energy; safety and regulations; tariffs and power factor correction; materials and their applications in the electrical industry; transformers; DC machines; illumination; and fuse protection. Included in each chapter are worked examples which should be carefully worked through before progressing to the next section. At the ends of chapters, further problems are provided for consolidation and self-testing; where these have numerical answers, they may be found at the end of the book. In a subject such as this, many problems ask for explanations and descriptions and here the answers must be sought in the text. When dealing with a descriptive question, a good diagram almost always helps to give a clear answer and saves many words of explanation. The book aims to promote this approach by the use of over 170 figures throughout the eight chapters.

Preface

1 Transmission and Distribution of Electrical Energy

Synchronous Generators

Economics of Generation and Transmission

Overhead Lines

Comparison between Overhead Lines and Underground Cables

Cost

Environment

Reliability

Fault Finding

Switchgear, Definitions and Uses

Substation Layout and Equipment

The Three-Phase System

Load Balancing

Industrial Installations

General Arrangement

Distribution Systems

Radial System

Ring System

Distributor Calculations

Radial

Distributor Fed at Both Ends

Problems for Section 1

2 Regulations

Safety and Regulations

The Electricity Supply Regulations

Electricity (Factories Act) Special Regulations

Fixed Apparatus

Substations and Transformers

The Institution of Electrical Engineers' Regulations for Electrical Installations

The Health and Safety at Work Act

Outline of the Requirements of the HASAWA

The Health and Safety Inspectorate

Comparison between the Scopes of the Regulations

Problems for Section 2

3 Tariffs and Power Factor Correction

Generation and Transmission Costs

Capital Charges

Running Charges

Power Factor

Maximum Demand

Diversity Factor

Load Factor

Cost of Electrical Energy

Domestic

Industrial

Problems for Section 3

4 Materials and Their Applications in the Electrical Industry

Conductor Materials for Overhead Lines and Underground Cables

Performance of Insulating Materials

Loss Angle Δ

Breakdown Voltage

Insulating Materials for Cables

Cable Construction

Materials Used in Electronic Circuits

Conductor Screening and Coaxial Cable

Printed Circuits

Circuit Damage due to Overcurrents

Heating of Cables

Permitted Volt-Drops in Cables

Effect of Ambient Temperature on Rating

Cables in Ducts or in Close Proximity

Heat Sinks

The Insulation of Overhead Lines

Eddy Current and Hysteresis Losses

Magnetic Materials

Minimization of Losses

Permanent Magnets

Magnetic Screening

Problems for Section 4

5 Transformers

Principle of Action of the Transformer

EMF Equation

The Single-Phase Transformer

The Three-Phase Transformer

Transformer Cooling

The Auto-Transformer

Advantages of the Auto-Transformer over the Double-Wound Transformer

Disadvantages of the Auto-Transformer

Current Transformers

Voltage or Potential Transformers

Measurement of Power and Power

Problems for Section 5

6 DC Machines

Principle of Action

Power, Force and Torque

Fleming's Rules

For Motors

For Generators

The Action of the Commutator

The Ring-Wound Armature

The Lap Winding

The Wave Winding

The EMF and Speed Equations

DC Machine Connections

Shunt

Series

Compound

The DC Motor

Speed/Armature Current Characteristics

The Torque Equation

Torque/Armature Current Characteristics

Motor Applications

Speed Control

DC Motor Starters

The Addition of Resistance to the Armature Circuit

The Manually-Operated Face-Plate Starter

The Automatic Contactor-Type Starter

Electronic Means

The DC Generator

Shunt-Wound

Series-Wound

Compound-Wound

Armature Reaction

Further Work on Commutation

Armature Reaction

Compensating Windings and Interpoles

Changes in Characteristics due to Armature Reaction

Losses in DC Machines

Field Loss

Armature Loss

Commutator Losses

Bearing Friction

Windage

The Power Flow Diagram

For a Motor

For a Generator

Problems for Section 6

7 Illumination

Lighting Standards

Luminance and Luminous Intensity

The Lumen and the Steradian

The Inverse Square Law

The Cosine Law

The Polar Diagram

Reflection and Refraction of Light

Use of the Polar Diagram

Indirect Illumination of a Surface

Types of Lamp

The Incandescent Lamp

The High-Pressure Discharge Lamp

The Low-Pressure Mercury (Fluorescent) Tube

The Low-Pressure Sodium Discharge Lamp

The Halogen Lamp

The Mercury-Metal Halide Lamp

The High-Pressure Sodium Lamp

Types of Luminaire

Daylighting

Problems for Section 7

8 Fuse Protection

Fault Level

Earthing

Fuse Protection

Operation of Fuses

The Semi-Enclosed Rewireable Fuse

The High Rupturing Capacity (HRC) Fuse

Fuse Characteristics

Problems for Section 8

Solutions to Problems

Index