FIRST AND SECOND EDITIONS
This book covers the major topics likely to be encountered by the transmission
and distribution power systems engineer engaged upon international project
works. Each chapter is self-contained and gives a useful practical introduction
to each topic covered. The book is intended for graduate or technician level
engineers and bridges the gap between learned university theoretical textbooks
and detailed single topic references. It therefore provides a practical grounding
in a wide range of transmission and distribution subjects. The aim of the book is
to assist the project engineer in correctly specifying equipment and systems for
his particular application. In this way manufacturers and contractors should
receive clear and unambiguous transmission and distribution equipment or project enquiries for work and enable competitive and comparative tenders to be received. Of particular interest are the chapters on project, system and software management since these subjects are of increasing importance to power systems engineers. In particular the book should help the reader to understand the reasoning behind the different specifications and methods used by different electrical supply utilities and organizations throughout the world to achieve their specific transmission and distribution power system requirements. The second edition includes updates and corrections, together with the addition of two extra major chapters covering distribution planning and power system harmonics
THIRD EDITION
As this book is particularly designed to help those running projects to correctly
specify, the approach has been to make frequent reference to applicable national
and international standards. This is because basing specifications on such standards will ensure consistency of bids, and generally will enable bidders to offer the most economic prices for technically compliant offers. The skill of the project engineer and manager comes in applying the standards most effectively to the particular requirements of the project.In the period between the publication of the second and third editions the work of updating electrical standards by the committees of the International Electrotechnical Commission (IEC) has proceeded apace. Moreover, within
Europe the development of European Norms (ENs) has resulted in the revision and alignment of many national standards – often to result in complete consistency with the corresponding IEC standard. This has meant that every chapter in Transmission and Distribution Electrical Engineering has had to be carefully checked to ensure that the frequent references to standards are correct and the relevant content updated where appropriate. Developments in the recognized
approach to earthing and bonding have resulted in a complete re-write of the relevant chapter, and legislation changes have necessitated updates to the chapter
on electromagnetic compatibility. Recent trends in protection equipment and
SCADA have needed to be mentioned and developments in the requirements of
both users and public utilities in the area of power system quality have justified
the expansion of the coverage of this increasingly important area of supply system engineering
1 System Studies
1.1 Introduction
1.2 Load flow
1.2.1 Purpose
1.2.2 Sample study
1.3 System stability
1.3.1 Introduction
1.3.2 Analytical aspects
1.3.3 Steady state stability
1.3.4 Transient stability
1.3.5 Dynamic stability
1.3.6 Effect of induction motors
1.3.7 Data requirements and interpretation of transient 30
stability studies
1.3.8 Case studies
1.4 Short circuit analysis
1.4.1 Purpose
1.4.2 Sample study
2 Drawings and Diagrams
2.1 Introduction
2.2 Block diagrams
2.3 Schematic diagrams
2.3.1 Method of representation
2.3.2 Main circuits
2.3.3 Control, signalling and monitoring circuits
Manufacturers’ drawings
2.4.1 Combined wiring/cabling diagrams
2.4.2 British practice
2.4.3 European practice
2.4.4 Other systems
2.5 Computer aided design (CAD)
2.6 Case study
2.7 Graphical symbols
Appendix A: Relay identification – numerical codes
Appendix B: Comparison between German, British,
US/Canadian and international symbols
B1 General circuit elements
B2 Operating mechanisms
B3 Switchgear
3 Substation Layouts
3.1 Introduction
3.2 Substation design considerations
3.2.1 Security of supply
3.2.2 Extendibility
3.2.3 Maintainability
3.2.4 Operational flexibility
3.2.5 Protection arrangements
3.2.6 Short circuit limitations
3.2.7 Land area
3.2.8 Cost
3.3 Alternative layouts
3.3.1 Single busbar
3.3.2 Transformer feeder
3.3.3 Mesh
3.3.4 Ring
3.3.5 Double busbar
3.3.6 11⁄2 Circuit breaker
3.4 Space requirements
3.4.1 Introduction
3.4.2 Safety clearances
3.4.3 Phase–phase and phase–earth clearances
4 Substation Auxiliary Power Supplies
4.1 Introduction
4.2 DC supplies
4.2.1 Battery and charger configurations
4.2.2 Battery charger components
4.2.3 Installation requirements
4.2.4 Typical enquiry data – DC switchboard
Batteries
4.3.1 Introduction
4.3.2 Battery capacity
4.3.3 Characteristics of batteries
4.3.4 Battery sizing calculations
4.3.5 Typical enquiry data
4.4 AC supplies
4.4.1 Power sources
4.4.2 LVAC switchboard fault level
4.4.3 Auxiliary transformer LV connections
4.4.4 Allowance for future extension
4.4.5 Typical enquiry data
4.4.6 Earthing transformer selection
4.4.7 Uninterruptible power supplies
Transmission and Distribution in Electrical Engineering
Transmission and distribution (T&D) are critical processes in electrical engineering, ensuring the efficient delivery of electrical energy from power generation plants to end users. These systems form the backbone of the power supply infrastructure, supporting residential, commercial, and industrial applications.
1. Overview of Transmission and Distribution
Transmission
Transmission systems are designed to carry electricity over long distances from generation stations to substations. High-voltage levels (typically above 110 kV) are used to minimize energy losses during transmission.Distribution
Distribution systems step down the high-voltage electricity to lower voltage levels suitable for end users. This occurs through a network of substations, transformers, and distribution lines.
2. Components of T&D Systems
A. Transmission System Components
Transmission Lines
- Types: Overhead lines (most common) and underground cables.
- Voltage Levels: Typically 110 kV, 220 kV, 400 kV, or even higher for long-distance transmission.
- Materials: Conductors like aluminum or copper, often reinforced with steel.
Substations
- Convert voltage levels using transformers.
- Facilitate switching operations and fault isolation.
Transformers
- Step-up transformers: Increase voltage for transmission.
- Step-down transformers: Decrease voltage for distribution.
Protection Systems
- Circuit breakers, relays, and surge arresters ensure system safety.
B. Distribution System Components
- Primary Distribution
- Medium voltage (11 kV to 33 kV) lines deliver power to local substations.
- Secondary Distribution
- Low voltage (230 V to 415 V) lines supply power to consumers.
- Distribution Transformers
- Reduce medium voltage to usable levels for homes and businesses.
- Service Lines
- Connect distribution transformers to individual consumers.
3. Key Considerations in T&D Engineering
A. Efficiency and Losses
- Transmission Losses: Include resistive (I²R) losses and corona losses.
- Distribution Losses: Result from lower voltage lines and higher current.
- Mitigation: Use higher voltage levels, better conductors, and optimized load management.
B. Reliability
- Redundancy in the network and robust protection systems reduce downtime.
- Automation and smart grid technologies improve fault detection and restoration.
C. Safety
- Grounding systems, insulation, and protection devices prevent accidents.
- Compliance with standards like IEC and IEEE ensures safe operations.
D. Environmental Impact
- Overhead lines impact landscapes and ecosystems.
- Underground cabling is less intrusive but more expensive.
4. Emerging Trends in T&D Engineering
A. Smart Grids
- Integration of digital technologies for real-time monitoring and control.
- Improves efficiency, reliability, and energy management.
B. Renewable Energy Integration
- Transmission systems now accommodate decentralized power generation from solar, wind, and other renewable sources.
- Requires flexible and dynamic grid operation.
C. High Voltage Direct Current (HVDC)
- HVDC systems are increasingly used for long-distance power transmission due to lower losses compared to AC systems.
D. Energy Storage Solutions
- Battery storage systems improve grid stability and manage demand-supply fluctuations.
E. Decentralized Distribution
- Microgrids and distributed energy resources (DERs) enable localized power generation and consumption.
5. Challenges in T&D Systems
- Aging Infrastructure: Many existing systems require upgrades to handle modern energy demands.
- Load Balancing: Increasing demand for electricity requires smarter load distribution strategies.
- Cybersecurity Threats: Digitalization of grids introduces vulnerabilities to cyberattacks.
- Regulatory Compliance: T&D systems must adhere to evolving standards and regulations.
6. Conclusion
Transmission and distribution engineering is a dynamic and essential field in ensuring the delivery of reliable and efficient electrical power. With advances in technology, T&D systems are becoming more intelligent, sustainable, and capable of meeting the growing energy needs of the future. However, continuous investment in infrastructure, research, and skilled personnel is crucial to overcoming challenges and maximizing the potential of modern T&D networks.
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