The document provides information about transmission and distribution of electric power. It discusses key topics like:
- The historical development of AC and DC transmission systems.
- The basic structure of an electric power system including generation, transmission, and distribution.
- Different types of transmission lines like overhead lines and underground cables, and their characteristics.
- Components of transmission and distribution systems like towers, conductors, transformers and substations.
- High voltage direct current transmission including different technologies and applications.
- Mechanical design aspects of transmission lines including line supports, sag and tension calculations, and effects of wind and ice loading.
The document discusses the evolution of electric power systems from the late 19th century to the present. Key developments include the shift from DC to AC systems in the late 1880s, increasing transmission voltages from the early 1900s to the 1990s, and the development of HVDC transmission in the 1950s to overcome limitations of HVAC systems. It also summarizes the present state of the Indian power system and projected scenarios by 2012 with increasing installed capacity, demand, and the need for stronger inter-regional transmission networks. Emerging transmission technologies discussed include UHVAC, gas insulated lines, HVDC-Light, and FACTS devices.
Chaper 4 Unit 1 Basics of HVDC Transmission.pptonlystu007
Introduction in High voltage dc you are
HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end. HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end.
This document discusses the distribution of a transmission line project among group members and provides background information on electricity distribution in Pakistan. It outlines the members of the group working on the transmission line distribution project and their registration numbers. It then provides an introduction to transmission and distribution lines. The document continues by describing the basic concepts of energy transmission and providing historical context of electricity in Pakistan. It outlines the various organizations involved in electricity production and distribution in Pakistan. Finally, it describes the layout of Pakistan's power system and classifications of transmission lines.
HVDC transmission systems were developed as an alternative to AC transmission for long distance or underwater power transmission. HVDC uses voltage source converters to convert AC to DC for transmission and back to AC at the receiving end. Some key advantages of HVDC include being able to transmit power over longer distances than AC systems and enabling asynchronous connections between separate AC networks. The first commercial HVDC system was installed in 1954 between Sweden and Gotland island. Important applications of HVDC systems include bulk power transmission over long distances, underwater cables longer than 30 km, and asynchronous links between AC systems.
1) HVDC transmission was first developed in the late 19th century by Rene Thury. Early systems used DC series generators and mechanical converters.
2) HVDC became more viable with the development of mercury arc valves in the 1950s and thyristor valves in the 1960s, allowing more efficient conversion between AC and DC.
3) HVDC is preferable to HVAC for long distance bulk power transmission, asynchronous connections, offshore wind connections, and other applications where HVDC has technical advantages over HVAC. Key components of HVDC systems include converters, smoothing reactors, filters, and the DC transmission line.
1. The document discusses the status of HVDC links in India and abroad. It provides a history of HVDC technology and describes several existing and upcoming HVDC projects in India such as the 800kV multi-terminal system and India-Bangladesh interconnector project.
2. Major HVDC projects discussed overseas include the Itaipu project in Brazil, which holds the world record voltage of ±600kV, and underwater HVDC links like the Gotland wind power project in Sweden and the Leyte-Luzon link in the Philippines.
3. HVDC transmission is concluded to be an economical and environmentally-friendly technology that is becoming viable for lower power levels and shorter distances due to new
This document discusses various methods for generating high direct current (DC) voltages, including:
1. Rectifier circuits that convert alternating current (AC) to DC such as half-wave and full-wave rectifiers.
2. Voltage multiplier circuits like the Cockroft-Walton circuit that use cascaded rectifiers to generate higher voltages.
3. Electrostatic generators like the Van de Graaff generator that use a mechanically driven belt to generate very high voltages at low currents.
Bulk transmission of electricity over long distances at high voltages helps transfer power from surplus to deficit regions in India. The transmission network in India has expanded significantly from 3,708 circuit km in 1950 to over 280,000 circuit km today. A national grid connecting regional grids was established in stages, achieving a single national grid with one frequency in 2013. High voltage transmission above 132kV is preferred for reduced transmission losses. The Power Grid Corporation of India manages the national transmission system and ensures integrated operation.
The document discusses the evolution of electric power systems from the late 19th century to the present. Key developments include the shift from DC to AC systems in the late 1880s, increasing transmission voltages from the early 1900s to the 1990s, and the development of HVDC transmission in the 1950s to overcome limitations of HVAC systems. It also summarizes the present state of the Indian power system and projected scenarios by 2012 with increasing installed capacity, demand, and the need for stronger inter-regional transmission networks. Emerging transmission technologies discussed include UHVAC, gas insulated lines, HVDC-Light, and FACTS devices.
Chaper 4 Unit 1 Basics of HVDC Transmission.pptonlystu007
Introduction in High voltage dc you are
HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end. HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end.
This document discusses the distribution of a transmission line project among group members and provides background information on electricity distribution in Pakistan. It outlines the members of the group working on the transmission line distribution project and their registration numbers. It then provides an introduction to transmission and distribution lines. The document continues by describing the basic concepts of energy transmission and providing historical context of electricity in Pakistan. It outlines the various organizations involved in electricity production and distribution in Pakistan. Finally, it describes the layout of Pakistan's power system and classifications of transmission lines.
HVDC transmission systems were developed as an alternative to AC transmission for long distance or underwater power transmission. HVDC uses voltage source converters to convert AC to DC for transmission and back to AC at the receiving end. Some key advantages of HVDC include being able to transmit power over longer distances than AC systems and enabling asynchronous connections between separate AC networks. The first commercial HVDC system was installed in 1954 between Sweden and Gotland island. Important applications of HVDC systems include bulk power transmission over long distances, underwater cables longer than 30 km, and asynchronous links between AC systems.
1) HVDC transmission was first developed in the late 19th century by Rene Thury. Early systems used DC series generators and mechanical converters.
2) HVDC became more viable with the development of mercury arc valves in the 1950s and thyristor valves in the 1960s, allowing more efficient conversion between AC and DC.
3) HVDC is preferable to HVAC for long distance bulk power transmission, asynchronous connections, offshore wind connections, and other applications where HVDC has technical advantages over HVAC. Key components of HVDC systems include converters, smoothing reactors, filters, and the DC transmission line.
1. The document discusses the status of HVDC links in India and abroad. It provides a history of HVDC technology and describes several existing and upcoming HVDC projects in India such as the 800kV multi-terminal system and India-Bangladesh interconnector project.
2. Major HVDC projects discussed overseas include the Itaipu project in Brazil, which holds the world record voltage of ±600kV, and underwater HVDC links like the Gotland wind power project in Sweden and the Leyte-Luzon link in the Philippines.
3. HVDC transmission is concluded to be an economical and environmentally-friendly technology that is becoming viable for lower power levels and shorter distances due to new
This document discusses various methods for generating high direct current (DC) voltages, including:
1. Rectifier circuits that convert alternating current (AC) to DC such as half-wave and full-wave rectifiers.
2. Voltage multiplier circuits like the Cockroft-Walton circuit that use cascaded rectifiers to generate higher voltages.
3. Electrostatic generators like the Van de Graaff generator that use a mechanically driven belt to generate very high voltages at low currents.
Bulk transmission of electricity over long distances at high voltages helps transfer power from surplus to deficit regions in India. The transmission network in India has expanded significantly from 3,708 circuit km in 1950 to over 280,000 circuit km today. A national grid connecting regional grids was established in stages, achieving a single national grid with one frequency in 2013. High voltage transmission above 132kV is preferred for reduced transmission losses. The Power Grid Corporation of India manages the national transmission system and ensures integrated operation.
The document discusses the components of electric power grids including power generation plants, transmission lines, transformers, and distribution systems. It describes different types of power generation such as fossil fuel, nuclear, hydroelectric, and renewable sources. Key components of the transmission and distribution system are described including step-up and step-down substations, overhead and underground transmission lines, and distribution lines. Diagrams illustrate one-line diagrams of power systems and characteristics of transmission lines.
System Studies on interaction of HTS cables with power gridsDutch Power
This document discusses the potential for using superconducting cables in power grids. It notes several challenges with current systems, including limited capacity and space. Superconducting cables could help address these issues by allowing higher power transmission at lower voltage levels with less infrastructure. The document outlines a study comparing the performance of superconducting cables to traditional copper cables. The results found that superconducting cables reduced losses, voltage fluctuations, and fault currents. They also decreased loading on parallel lines. The document concludes that superconducting cables have advantages like increased capacity and power transmission efficiency. They could help upgrade grids in a way that reduces costs, losses, and environmental impacts.
This document discusses fault analysis in HVDC and HVAC transmission lines. It begins with a brief history of HVDC systems and then covers the basics of HVDC transmission including components and types. The main sections compare HVAC and HVDC systems, discuss fault analysis in both, and describe various protection methods. HVDC transmission is described as advantageous for long distance bulk power transmission, underground/underwater cables, and asynchronous grid interconnection. Protection of AC and DC lines includes overcurrent, overvoltage, and DC reactor methods.
This document discusses high voltage direct current (HVDC) transmission and compares it to high voltage alternating current (HVAC) transmission. It notes that HVDC is more efficient for long distance power transmission as losses are lower. The history and evolution of HVDC are presented, including early projects in Europe and growth globally. India's adoption and expansion of HVDC are covered. Technical advantages of HVDC include better voltage regulation and controllability while economic advantages include lower costs for lines and cables. Disadvantages include costly converter stations and inability to transmit reactive power. The document concludes that HVDC is more reliable than HVAC for long distance bulk power transmission including between unsynchronized grids.
The document discusses high-voltage direct current (HVDC) transmission. It provides examples of HVDC projects around the world, including connections between countries in Europe and South America. It also discusses technical aspects of HVDC transmission such as converter stations needed to connect to AC grids. While HVDC transmission has higher upfront costs than AC transmission, it has lower transmission losses over long distances and provides more flexibility in transmission capacity.
- American Electric Power owns the largest electricity transmission system in the US, totaling 39,059 miles of transmission lines ranging from 765kV to below 100kV voltage levels.
- AEP developed its 765kV transmission system in the 1960s to provide a robust backbone infrastructure to efficiently meet growing electricity demand.
- Typical installation costs per mile are $2.6-4 million for 765kV, $2.3-3.5 million for 500kV, and $1.1-2.5 million for 345kV lines, depending on terrain and other factors.
WIRELESS TRANSMISSION METHODS DEVLOPEMENT AND POSSIBILITYIESSamiullah m shai...SAMIULLAH SHAIKH
The document discusses the development and possibility of wireless transmission of electricity. It describes how wireless transmission can reduce transmission and distribution losses by transmitting power as microwaves without using wires. It summarizes different proposed methods for wireless transmission including Tesla's atmospheric conduction method and electrodynamic induction methods using microwaves or lasers. It discusses the history of wireless power transmission research and experiments. It also outlines the components, advantages, disadvantages and applications of wireless power transmission systems.
The document summarizes HVDC (High Voltage Direct Current) transmission. It discusses why DC transmission is used over long distances, the key components of an HVDC system including converters and transmission lines, and different HVDC system configurations like monopolar, bipolar, and homopolar links. It also provides examples of HVDC applications in India and notes that while HVDC transmission has high costs, it offers benefits like reduced losses over long distances and increased power transmission stability and flexibility.
introduction to high voltage engineering.pdfHASNAINNAZIR1
This document provides an introduction to high voltage engineering. It discusses key topics including:
- The importance of high voltage insulation design and testing for electric power systems.
- How higher transmission voltages are needed to reduce line losses and increase efficiency.
- Common voltage levels used in power generation, transmission, distribution and consumption.
- The advantages of interconnected high voltage power grids and why higher voltages are needed on power systems.
- Key factors in electrical insulation and the various dielectric materials that are used.
The document traces the evolution of electric power systems from Thomas Edison's first system in 1882 to modern systems. Key developments include the introduction of AC power which allowed transmission over longer distances, standardization of frequencies and voltages, increasing use of higher voltages for transmission, and integration of different energy sources like fossil fuels, nuclear, and renewables. Modern power systems have generation, transmission, sub-transmission and distribution components to supply, transfer and deliver electricity reliably.
This document provides an overview of electrical power transmission in India. It discusses the components of transmission lines including conductors, spacers, and supports. It also covers transmission line design considerations such as voltage levels, ground clearances, conductor spacing, and tower heights. The document outlines India's existing transmission system and some issues in further developing the system such as right of way, regulation of power flows, and integration of new technologies like HVDC transmission and gas insulated substations.
1. The document discusses electrical transmission systems, which convey electric power from power stations to consumers. It describes the key components of a typical electric supply system, including power stations, transmission lines, and distribution networks.
2. Transmission lines are conductors that transmit electric power over long distances from power stations to substations. Different types of transmission lines are discussed, including overhead lines, underground cables, and various conductor configurations.
3. The document covers the classification of transmission lines based on voltage level, structure, and length. It also discusses the typical elements that make up a power transmission system and the electrical design of transmission lines, focusing on the resistance, inductance, and capacitance properties that determine their performance
Generation and transmission of electric energy – voltage stress –
testing voltages-AC to DC conversion – rectifier circuits – cascaded
circuits – voltage multiplier circuits – Cockroft-Walton circuits –
voltage regulation – ripple factor – Van de-Graaff generator.
The document is a report on high voltage direct current (HVDC) transmission systems submitted for a Bachelor of Technology degree. It discusses the history and development of HVDC transmission, the basic principles of AC/DC conversion using converter stations, harmonic filtering, HVDC control methods, different types of HVDC links, economic considerations, applications of HVDC systems, and advantages of HVDC over AC transmission for long distance bulk power transmission.
Power System electrical and electronics .pptxMUKULKUMAR210
The document discusses transmission lines, including their objectives, classification, key terms, and components. It aims to minimize energy costs, maintain reliable power supply to consumers, and allow flexible power transfer. Transmission lines are classified based on voltage level, distance, and whether AC or DC. Common conductor types include ACSR, AAAR, and bundled conductors. Insulators provide electrical insulation from supporting structures. Skin effect causes current to flow near the surface of conductors. An equivalent circuit models the parameters of an actual transmission line.
This document provides an overview of electrical power supply systems. It discusses how power stations have moved away from consumers as demand has increased. It then summarizes the efficiencies of different power plant types, with hydroelectric being the most efficient at 85%. The key components of an electric supply system are described as the power station, transmission lines, and distribution network. Common voltage levels for generation, transmission, and distribution are also outlined. Block diagrams of steam and hydroelectric power stations are included.
This document provides an overview of wireless power transmission (WPT), including its history, types, advantages, and applications. It discusses how Nikola Tesla first proposed WPT in the late 1890s using atmospheric conduction methods. Two main electrodynamic induction methods are microwave and laser transmission. WPT could be used for electric vehicle charging, consumer electronics, and transmitting power from solar satellites. While more efficient than wired systems, WPT also faces challenges like interference, conversion inefficiencies, and safety concerns around high frequencies.
POWER SYSTEMS – II chapter 1 transmission line modelling.pptxMaipaliJyoshnaDevi
- Power systems involve the generation, transmission, and distribution of electric power. Most transmission lines are high-voltage alternating current (AC).
- Electricity is transmitted at high voltages like 115kV or above to reduce energy losses over long distances.
- Transmission systems can be AC or DC. AC is more common and can generate power at high voltages easily using transformers, while DC is used for longer distances.
- Key components of transmission lines include conductors, insulators, and supports to carry the lines overhead or underground. The document discusses different types of conductors, insulators, and overhead line configurations.
This document discusses different methods for collecting primary data, including observation, interviews, questionnaires, and schedules. It provides details on each method such as the steps involved, types or classifications, advantages, and disadvantages. The key methods covered are observation, where a researcher directly observes participants; interviews, which involve asking participants questions; questionnaires, which are forms mailed to participants to complete; and schedules, where an enumerator asks participants questions and records responses, similar to interviews.
The document discusses the components of electric power grids including power generation plants, transmission lines, transformers, and distribution systems. It describes different types of power generation such as fossil fuel, nuclear, hydroelectric, and renewable sources. Key components of the transmission and distribution system are described including step-up and step-down substations, overhead and underground transmission lines, and distribution lines. Diagrams illustrate one-line diagrams of power systems and characteristics of transmission lines.
System Studies on interaction of HTS cables with power gridsDutch Power
This document discusses the potential for using superconducting cables in power grids. It notes several challenges with current systems, including limited capacity and space. Superconducting cables could help address these issues by allowing higher power transmission at lower voltage levels with less infrastructure. The document outlines a study comparing the performance of superconducting cables to traditional copper cables. The results found that superconducting cables reduced losses, voltage fluctuations, and fault currents. They also decreased loading on parallel lines. The document concludes that superconducting cables have advantages like increased capacity and power transmission efficiency. They could help upgrade grids in a way that reduces costs, losses, and environmental impacts.
This document discusses fault analysis in HVDC and HVAC transmission lines. It begins with a brief history of HVDC systems and then covers the basics of HVDC transmission including components and types. The main sections compare HVAC and HVDC systems, discuss fault analysis in both, and describe various protection methods. HVDC transmission is described as advantageous for long distance bulk power transmission, underground/underwater cables, and asynchronous grid interconnection. Protection of AC and DC lines includes overcurrent, overvoltage, and DC reactor methods.
This document discusses high voltage direct current (HVDC) transmission and compares it to high voltage alternating current (HVAC) transmission. It notes that HVDC is more efficient for long distance power transmission as losses are lower. The history and evolution of HVDC are presented, including early projects in Europe and growth globally. India's adoption and expansion of HVDC are covered. Technical advantages of HVDC include better voltage regulation and controllability while economic advantages include lower costs for lines and cables. Disadvantages include costly converter stations and inability to transmit reactive power. The document concludes that HVDC is more reliable than HVAC for long distance bulk power transmission including between unsynchronized grids.
The document discusses high-voltage direct current (HVDC) transmission. It provides examples of HVDC projects around the world, including connections between countries in Europe and South America. It also discusses technical aspects of HVDC transmission such as converter stations needed to connect to AC grids. While HVDC transmission has higher upfront costs than AC transmission, it has lower transmission losses over long distances and provides more flexibility in transmission capacity.
- American Electric Power owns the largest electricity transmission system in the US, totaling 39,059 miles of transmission lines ranging from 765kV to below 100kV voltage levels.
- AEP developed its 765kV transmission system in the 1960s to provide a robust backbone infrastructure to efficiently meet growing electricity demand.
- Typical installation costs per mile are $2.6-4 million for 765kV, $2.3-3.5 million for 500kV, and $1.1-2.5 million for 345kV lines, depending on terrain and other factors.
WIRELESS TRANSMISSION METHODS DEVLOPEMENT AND POSSIBILITYIESSamiullah m shai...SAMIULLAH SHAIKH
The document discusses the development and possibility of wireless transmission of electricity. It describes how wireless transmission can reduce transmission and distribution losses by transmitting power as microwaves without using wires. It summarizes different proposed methods for wireless transmission including Tesla's atmospheric conduction method and electrodynamic induction methods using microwaves or lasers. It discusses the history of wireless power transmission research and experiments. It also outlines the components, advantages, disadvantages and applications of wireless power transmission systems.
The document summarizes HVDC (High Voltage Direct Current) transmission. It discusses why DC transmission is used over long distances, the key components of an HVDC system including converters and transmission lines, and different HVDC system configurations like monopolar, bipolar, and homopolar links. It also provides examples of HVDC applications in India and notes that while HVDC transmission has high costs, it offers benefits like reduced losses over long distances and increased power transmission stability and flexibility.
introduction to high voltage engineering.pdfHASNAINNAZIR1
This document provides an introduction to high voltage engineering. It discusses key topics including:
- The importance of high voltage insulation design and testing for electric power systems.
- How higher transmission voltages are needed to reduce line losses and increase efficiency.
- Common voltage levels used in power generation, transmission, distribution and consumption.
- The advantages of interconnected high voltage power grids and why higher voltages are needed on power systems.
- Key factors in electrical insulation and the various dielectric materials that are used.
The document traces the evolution of electric power systems from Thomas Edison's first system in 1882 to modern systems. Key developments include the introduction of AC power which allowed transmission over longer distances, standardization of frequencies and voltages, increasing use of higher voltages for transmission, and integration of different energy sources like fossil fuels, nuclear, and renewables. Modern power systems have generation, transmission, sub-transmission and distribution components to supply, transfer and deliver electricity reliably.
This document provides an overview of electrical power transmission in India. It discusses the components of transmission lines including conductors, spacers, and supports. It also covers transmission line design considerations such as voltage levels, ground clearances, conductor spacing, and tower heights. The document outlines India's existing transmission system and some issues in further developing the system such as right of way, regulation of power flows, and integration of new technologies like HVDC transmission and gas insulated substations.
1. The document discusses electrical transmission systems, which convey electric power from power stations to consumers. It describes the key components of a typical electric supply system, including power stations, transmission lines, and distribution networks.
2. Transmission lines are conductors that transmit electric power over long distances from power stations to substations. Different types of transmission lines are discussed, including overhead lines, underground cables, and various conductor configurations.
3. The document covers the classification of transmission lines based on voltage level, structure, and length. It also discusses the typical elements that make up a power transmission system and the electrical design of transmission lines, focusing on the resistance, inductance, and capacitance properties that determine their performance
Generation and transmission of electric energy – voltage stress –
testing voltages-AC to DC conversion – rectifier circuits – cascaded
circuits – voltage multiplier circuits – Cockroft-Walton circuits –
voltage regulation – ripple factor – Van de-Graaff generator.
The document is a report on high voltage direct current (HVDC) transmission systems submitted for a Bachelor of Technology degree. It discusses the history and development of HVDC transmission, the basic principles of AC/DC conversion using converter stations, harmonic filtering, HVDC control methods, different types of HVDC links, economic considerations, applications of HVDC systems, and advantages of HVDC over AC transmission for long distance bulk power transmission.
Power System electrical and electronics .pptxMUKULKUMAR210
The document discusses transmission lines, including their objectives, classification, key terms, and components. It aims to minimize energy costs, maintain reliable power supply to consumers, and allow flexible power transfer. Transmission lines are classified based on voltage level, distance, and whether AC or DC. Common conductor types include ACSR, AAAR, and bundled conductors. Insulators provide electrical insulation from supporting structures. Skin effect causes current to flow near the surface of conductors. An equivalent circuit models the parameters of an actual transmission line.
This document provides an overview of electrical power supply systems. It discusses how power stations have moved away from consumers as demand has increased. It then summarizes the efficiencies of different power plant types, with hydroelectric being the most efficient at 85%. The key components of an electric supply system are described as the power station, transmission lines, and distribution network. Common voltage levels for generation, transmission, and distribution are also outlined. Block diagrams of steam and hydroelectric power stations are included.
This document provides an overview of wireless power transmission (WPT), including its history, types, advantages, and applications. It discusses how Nikola Tesla first proposed WPT in the late 1890s using atmospheric conduction methods. Two main electrodynamic induction methods are microwave and laser transmission. WPT could be used for electric vehicle charging, consumer electronics, and transmitting power from solar satellites. While more efficient than wired systems, WPT also faces challenges like interference, conversion inefficiencies, and safety concerns around high frequencies.
POWER SYSTEMS – II chapter 1 transmission line modelling.pptxMaipaliJyoshnaDevi
- Power systems involve the generation, transmission, and distribution of electric power. Most transmission lines are high-voltage alternating current (AC).
- Electricity is transmitted at high voltages like 115kV or above to reduce energy losses over long distances.
- Transmission systems can be AC or DC. AC is more common and can generate power at high voltages easily using transformers, while DC is used for longer distances.
- Key components of transmission lines include conductors, insulators, and supports to carry the lines overhead or underground. The document discusses different types of conductors, insulators, and overhead line configurations.
This document discusses different methods for collecting primary data, including observation, interviews, questionnaires, and schedules. It provides details on each method such as the steps involved, types or classifications, advantages, and disadvantages. The key methods covered are observation, where a researcher directly observes participants; interviews, which involve asking participants questions; questionnaires, which are forms mailed to participants to complete; and schedules, where an enumerator asks participants questions and records responses, similar to interviews.
This document discusses voltage sag mitigation using a static synchronous compensator (STATCOM). It begins with an introduction to power quality issues such as voltage sags and describes how STATCOM can improve power quality through shunt compensation. Various voltage sag mitigation techniques are reviewed, including ferroresonant transformers, dynamic voltage regulators, static VAR compensators, sag-proofing transformers, static transfer switches, and energy storage options. The document proposes implementing a STATCOM in an induction generator-driven wind farm to mitigate voltage sags caused by load conditions. Diagrams show the load voltage with and without sags, as well as models of the wind farm system both with and without the STATCOM.
Working capital refers to funds used for day-to-day operations of a business. It includes current assets like inventory, receivables, cash, and prepaid expenses. Effective working capital management involves determining the appropriate level of current assets and arranging sources of short-term financing. Key aspects of working capital management include accounts receivable management through techniques like factoring, inventory management using methods such as determining economic order quantity and reorder levels, and evaluating sources of working capital.
The document discusses fundamental analysis for evaluating investment opportunities. It covers analyzing the economy, industries, and individual companies. For economic analysis, it examines factors like GDP, inflation, and interest rates. Industry analysis focuses on growth stage, competition level, and government policies. Company analysis evaluates management, financial statements, earnings forecasts, and financial/non-financial indicators. The goal is to identify sound investments with a reasonable expected return by studying the fundamentals.
This document provides information on technical analysis and its key concepts. It defines technical analysis as using past and current price and volume movements to predict future market direction. It discusses the assumptions of technical analysis and compares it to fundamental analysis. It then describes various charting methods used in technical analysis like bar charts, line charts, point and figure charts, and Japanese candlestick charts. It also covers chart patterns, efficient market theory, Dow theory, and random walk theory as related concepts in technical analysis.
This document defines key concepts related to portfolio management including portfolio, portfolio analysis, construction, and evaluation. A portfolio is a combination of different financial securities like stocks, bonds, and cash held by investors. Portfolio management involves identifying objectives, developing strategies, monitoring performance, and evaluating results. Portfolio analysis assesses the risks of an entity's business areas. Construction requires determining objectives and formulating investment strategies. Evaluation models like Sharpe ratio, Treynor ratio, and Jensen measure are used to assess risk-adjusted performance.
The document discusses capital budgeting, which refers to the planning process used to determine whether long-term investments are worth funding with cash. It defines capital budgeting, outlines its key characteristics and process, and describes various techniques used, including payback period, accounting rate of return, net present value, internal rate of return, and profitability index. It also discusses determining relevant cash flows, the cost of capital, and calculating the weighted average cost of capital.
Working capital refers to the capital required to meet the day-to-day operational expenses of a business like wages, raw materials, utilities etc. It consists of current assets like inventory, receivables, cash etc. Proper management of working capital involves determining the optimal level of current assets and liabilities and arranging sources to finance them. The key components of working capital to be managed are inventory, receivables and cash. Firms use various short-term financing options like bank finance, trade credit, commercial paper etc. to manage their working capital requirements.
The document discusses various concepts related to leverage, dividends, and dividend policy. It defines leverage as using assets and funds with fixed costs to increase shareholder returns. It also defines different types of leverage including operating, financial, and combined leverage and provides formulas to calculate them. The document also defines dividends and lists various sources and forms of dividends. Finally, it discusses dividend policy, factors affecting policy, and theories related to dividends proposed by Modigliani-Miller, Walter, and Gordon.
The document provides information on various aspects of the Indian capital market, including definitions of key terms like capital market, primary market, secondary market, and sources of long-term financing. It also discusses various capital market instruments like shares, debentures, term loans, leasing, hire purchase, venture capital, and private equity - outlining their meaning, types, advantages and disadvantages. The primary and secondary segments of the Indian capital market are described along with new issue market and stock market.
The document discusses key concepts in investment analysis including:
1) The various steps involved in the investment process such as setting objectives, establishing policy, selecting strategies and assets, and measuring performance.
2) Definitions of return, risk, systematic and unsystematic risk, beta which measures sensitivity to market returns, and alpha which measures performance independent of market returns.
3) The meanings of speculation which involves taking business risks for short term gains, and gambling which involves wagering without understanding the risks.
1. Substations receive power transmitted at high voltages from generating stations and transform the voltage to appropriate levels for local use while providing facilities for switching.
2. Typical components of a power plant substation include busbars, disconnectors, circuit breakers, current transformers, voltage transformers, earthing switches, and surge arrestors.
3. Substations are classified based on their function and location as generating, grid, secondary, distribution, and special purpose substations and based on physical features as indoor, outdoor, pole mounted, and underground substations.
The document presents a STATCOM control scheme for improving power quality in a grid-connected wind energy generation system. A battery energy storage system is integrated with the STATCOM to help stabilize the grid during fluctuations in wind power. The control scheme is simulated in MATLAB/Simulink. Results show the STATCOM is able to maintain unity power factor at the point of common coupling, reducing harmonics to below 0.01% and frequency oscillations to less than 1%. This allows the system to meet power quality standards while supporting the wind generator and loads on the grid.
This document discusses different types of substation bus schemes, including single bus, double bus with double or single breakers, main and transfer bus, ring bus, breaker-and-a-half with two main buses, and double bus-bar with bypass isolators. The choice of bus scheme depends on factors like safety, reliability, voltage level, simplicity of relaying, flexibility of operation, cost, maintenance needs, available land, and the location and provision of connecting lines and expansion. Seven common bus scheme types are described but not explained in detail.
1) Sub-stations are facilities that change characteristics of electric power such as voltage, frequency, and power factor. They receive power at one voltage and deliver it at another.
2) Sub-stations are classified based on their function (e.g. transformer, switching) and construction (e.g. indoor, outdoor). Transformer sub-stations change voltage levels while switching sub-stations perform switching without changing voltage.
3) Key equipment in sub-stations include transformers, circuit breakers, buses, insulators, and instrumentation transformers which step voltages/currents down for metering and protection. Proper layout and equipment are needed for safe and reliable power distribution.
1) Sub-stations are facilities that change characteristics of electric power supply like voltage, frequency, and current. They receive power at one voltage and deliver at another.
2) Sub-stations are classified by their service (e.g. transformer, switching) and construction (e.g. indoor, outdoor). Transformer sub-stations are the most common and change the voltage level.
3) Key equipment in sub-stations includes transformers, busbars, insulators, circuit breakers, and protection devices that allow safe transmission of power from high voltage lines to distribution networks.
The document presents a wind-solar hybrid power generation system that aims to harness both wind and solar power, store the generated power in batteries, and design a charger for the batteries. The major advantage of the hybrid system is its enhanced reliability from combining solar and wind sources. It has low operating costs and high power quality. The block diagram shows the system design and it has applications for powering cell towers, rural areas, homes, and street lighting.
This document describes the design of a micro solar inverter. It begins with an abstract that outlines how the micro inverter converts DC power from a solar panel to AC power and is mounted directly behind the panel for simplified installation. It then provides details on solar power generation, characteristics of solar panels, and compares centralized string inverters to the proposed micro inverter system. The document concludes that micro inverters have been successful for residential use where space is limited, as they can produce AC power directly at the back of each panel.
Perception is how individuals interpret and organize their sensory impressions to make sense of their environment, but what we perceive can differ from objective reality. Managers need to understand how perception affects various aspects of managing employees. Perception influences motivation, as employees who are experiencing money troubles may perceive compensation issues differently. It also impacts hiring, as contrasts between job applicants can affect hiring decisions based on perceptions. Performance appraisals are highly dependent on the accuracy of a manager's perceptions of a subordinate's work.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
1. EE2303
TRANSMISSION & DISTRIBUTION
V Sem, BE (EEE)
Regulation 2008
Dr.P.Valsalal
Associate Professor
DEEE, Anna University
Chennai 600 025
1
Transmission & Distribution
13. - Tappings can be made at desired
points, so cost of providing service
mains is also reduced
- OHL has considerable inductance
which causes voltage drop.
13
Transmission & Distribution
17. • Grid: The transmission system of an
area (or state)
• Regional Grid: Different grids are
interconnected through tie lines
• National Grid: Different regional grids
are further inter-connected
• Each grid operates independently
17
Transmission & Distribution
19. Transmission Voltage Level
Tamil Nadu
110kV, 230kV, 400kV
Other states
132kV, 220kV, 400kV, and
765kV
19
Transmission & Distribution
20. Typical Construction – O/H
• Towers / Poles – to increase
phase to ground distance and
limit exposure to the public
• Cross arms – separate phases
from each other and from ground
potential
20
Transmission & Distribution
21. • Insulators – to separate phase
voltage from ground potential
• Ground/Static Wire - for
lightning protection
21
Transmission & Distribution
27. Underground cable
-Less prone to natural hazards
-More costly and so limited to
only densely populated places
-Dielectric loss and sheath loss
are also significant
27
Transmission & Distribution
28. -Lower series impedance and
higher shunt capacitance
-Cables have low inductance ,
so lower voltage drop
-Fault detection and rectification
is very difficult
-Limited distance due to Ferranti
effect
28
Transmission & Distribution
39. Potential Transformer
Step down the
Voltage to the
required Level
Used for both
metering and
Protection
Purposes
39
Transmission & Distribution
40. A 69 kV Substation
Circuit
breaker
Disconnect Disconnect
Current CT
Bus bar
Circuit
breaker
Disconnect Disconnect
Current CT
Bus bar
Circuit
breaker
Disconnect Disconnect
Current CT
Bus bar
40
Transmission & Distribution
45. High Voltage DC
Transmission
• High-voltage dc lines are used to
transport large amounts of energy
over a long distance.
• A representative application is
the Pacific DC Intertie, which
interconnects the Los Angeles
area with Oregon.
Cont…
45
Transmission & Distribution
46. • The voltage of the DC Intertie is
±500 kV and the maximum
energy transport is 3100 MW.
• More than one hundred dc
transmission systems operate
around the world, one of the
oldest and most famous is the
cable interconnection between
England and France.
Cont…
46
Transmission & Distribution
47. HVDC –world’s first HVDC –
Gotland scheme in Sweden
in1954(20MW, 96km cable
sea return), -100kV
In 1965 – Japan – 50 & 60 Hz
system – zero length (Back to
Back), 300MW, 250kV in
either direction
Cont…
47
Transmission & Distribution
48. First converter station using
exclusively Thyristors – Eel River
Scheme in Canada-60Hz, 1972,
320MW,80kV, zero length
48
Transmission & Distribution
49. Few in - India
- 1500MW +/-500kV 814km long
bipole between Rihand-dadri in
Northern region
- 2X250MW,70kV Vindhyachal
back- to-back connecting
Northern and Western regions
Cont…
49
Transmission & Distribution
50. - 2X500MW, 140kV Chandrapur
back-to-back link connecting
Southern and Western regions
50
Transmission & Distribution
53. A Schematic of a Bipolar HVDC
System identifying main
Components
53
Transmission & Distribution
54. Merits
- More power can be
transmitted per conductor per
circuit.
- Use of Ground Return Possible
- Smaller Tower Size
Cont…
54
Transmission & Distribution
55. - Higher Capacity available for
cables
- No skin effect
- Less corona and radio
interference
- No Stability Problem
- Asynchronous interconnection
possible
Cont…
55
Transmission & Distribution
56. - Lower short circuit fault levels
- Tie line power is easily
controlled
56
Transmission & Distribution
57. Demerits
- Difficulty of breaking DC
currents (high cost of DC
breakers)
- Inability to use transformers
- High cost of conversion
equipment
Cont…
57
Transmission & Distribution
58. - Generation of harmonics,
requires AC & DC filters / costly
- Complexity of control
- Difficulty of high power
generation
- Reactive power requirement
- Absence of overload capacity
58
Transmission & Distribution
61. In South America and Japan
(50 and 60 Hz )networks
It would be impossible to
exchange power between them
with an AC line or cable. HVDC
is then the only solution.
61
Transmission & Distribution
62. Comparison of costs of
AC and DC Transmission
62
Transmission & Distribution
63. Break- even Distance
OHL – 800km
Submarine cables – 25km
UGC – 50km
Cont…
63
Transmission & Distribution
64. -HVAC needs only transformers
-HVDC needs very expensive
converters and inverters (capital
cost is very high)
-Below 800km, HVAC is
cheaper
-Above 800km, greater the
distance, the more money
saved.
64
Transmission & Distribution
69. Comparison
Monopolar – cost-wise good
(cable tr)
Bipolar – If one pole is isolated
due to fault,pole can operate
with ground withhalf the rated
load
Cont…
69
Transmission & Distribution
70. - Equal to double circuit
transmission line
- Less harmonics interference
than monopolar
- Power reversal is possible
Homopolar – reconnection is
done
70
Transmission & Distribution
71. FACTS devices
Flexible AC transmission systems (FACTS)
controllers have been mainly used for solving
various power system steady state control
problems. However, recent studies reveal that
FACTS controllers could be employed to
enhance power system stability in addition to
their main function of power flow control.
71
Transmission & Distribution
73. Performance- Electrical
Design
Power Flow Analysis
Short Circuit Analysis
Power System Stability
Overvoltage Protection
73
Transmission & Distribution
76. Line Supports
Loads due to
Conductors and insulators
(including ice and wind loads
on the conductors) together
with wind load on the support
itself.
76
Transmission & Distribution
77. Types of Line supports
-Wooden poles
-RCC poles
-Steel tubular poles
-Steel towers
77
Transmission & Distribution
78. Wooden Poles
-Made up of chemically treated
wood
-Used for distribution purpose
-Very economical
-Susceptible to decay
78
Transmission & Distribution
80. Reinforced Cement
Concrete Poles
-Stronger and costlier than
wooden poles
-They have long life and little
maintenance
-Used up to 33kV lines
80
Transmission & Distribution
86. Supports at same level
(Parabolic form)
86
Transmission & Distribution
87. Let
l = length of span, i.e., horizontal
distance between supports, m
S = sag at mid span, m
T = conductor tension (assumed
constant over the whole span)N
w = Conductor weight, N/m
87
Transmission & Distribution
88. Parabolic form
when
S
y 2
l
x
2
)
2
(l
a
S
2
ax
y
2
4 l
S
a (5.2a)
2
4
l
x
S
y (5.2b)
88
Transmission & Distribution
89. Load is uniformly distributed : N/m
Total weight =
Total weight is taken by two supports at two
ends
Total Force in A :
Total Force in B :
Bending Moment (BM) = Force X distance
BM at O = 0
2
wl
2
wl
wl
w
89
Transmission & Distribution
90. Consider the equilibrium of half
line OB. Assuming that the
conductor is almost horizontal and
taking moments about B.
90
Transmission & Distribution
98. Consider 1m length of conductor
d = diameter of conductor, m
t= radial thickness of ice, m
Overall diameter of ice covered
conductor is D=d + 2t
Volume of ice per metre length of
conductor 3
2
2
)
(
4
m
d
D
98
Transmission & Distribution
99. Density of Ice = 915
Area of Ice = C/S area of conductor along
with Ice - C/S of conductor
3
/ m
kg
2
2
2
2
4
4
4
d
D
d
D
Ai
d
t
t
d
t
d
Ai
2
2
2
4
99
Transmission & Distribution
100. Weight of Ice = kg/m
N/m
N/m
N/m
d
t
t
Ai
i
915
d
t
t
81
.
9
915
d
t
t
14
.
3
15
.
8976
d
t
t
4
10
82
.
2
100
Transmission & Distribution
101. -The wind pressure is assumed to
act horizontally on the projected
area of the ice covered conductor.
-The projected area is D sq.m/
metre length of conductor
- For a wind pressure of p N/sq.m
of projected area, the wind load
is
w
F
m
N
pD
Fw /
(5.6)
101
Transmission & Distribution
108. s is curve distance from o to Point
P(x,y). Let the length of line be z.
Substitute and
We get length of half line z/2
2
l
x 2
4
l
S
a
l
S
l
l
l
S
l
z 2
3
4
2
3
4
2
3
8
16
2
2
2
l
S
l
z
2
3
8
108
Transmission & Distribution
109. Substituting the value of S:
T
l
F
S t
8
2
2
2
4
2
8
3
8
T
l
F
l
l
z t
2
2
2
24
1
T
l
F
l
z t
109
Transmission & Distribution
111. Substituting the co-ordinates of point C in
eqn
2
1
c
l
l
x
(5.14)
T
wl
S c
8
2
(5.15)
2
2
4
l
x
S
y
h
S
y
1
2
2
1
1
4
c
l
Sx
y
111
Transmission & Distribution
112. Substituting the value of S and
2
2
1
4
c
l
Sx
h
S
S
l
h
S
x c
4
2
2
1
1
x
T
wl
l
h
T
wl
l
l
c
c
c
c
8
4
8
2
2
2
2
2
112
Transmission & Distribution
114. Problem 1
An overhead line, over a river
crossing, is supported by two
towers 50m and 80m above
water level. The horizontal span
is 300m.
114
Transmission & Distribution
115. If the weight of the conductor
is 8.28N/m and the tension in
the conductor is 19620 N, find
the height of the mid-point of
the line above water level.
115
Transmission & Distribution
116. Given Data
Height of towers = 50m and 80m
Horizontal span, l= 300m
Weight of conductor = 8.28N/m
Tension = 19620N
Height of mid point of line above
water level??
116
Transmission & Distribution
117. Length of conductor
Since both the supports are
on the same side of point O
wl
Th
l
lc
2
300
28
.
8
50
80
19620
2
300
c
l
m
lc 9
.
773
l
lc 2
117
Transmission & Distribution
119. Horizontal distance between O and C
Height of point C above O
Horizontal distance between O and P
m
96
.
86
300
2
9
.
773
m
T
wx
595
.
1
19620
2
96
.
86
28
.
8
2
2
2
m
96
.
236
150
96
.
86
119
Transmission & Distribution
120. Height of P above O
Height of mid point P above point C
Height of mid point P above water level
m
847
.
11
19620
2
96
.
236
28
.
8 2
m
252
.
10
595
.
1
847
.
11
m
252
.
60
50
252
.
10
120
Transmission & Distribution
122. Problem 2
An overhead line has ACSR conductor of
1.95cm diameter and a span of 244m.
The allowable tension is . Find
sag in still air condition with no ice
covering, vertical sag when there is an ice
covering of 0.96cm thickness and a
horizontal wind pressure of 382 N/sq.m of
projected area. Ice weighs 8920 .
N
4
10
56
.
3
3
/ m
N
122
Transmission & Distribution
123. Cond….
The line is carried by insulator
strings 1.43m long. What should
be the height of lowest cross-
arm to give a minimum ground
clearance of 7.62m under bad
weather conditions? The
conductor weight is 0.847 kg/m.
123
Transmission & Distribution
124. Given Data
Diameter of conductor = 1.95cm
Span = 244m
Allowable tension =
Thickness of ice covering = 0.96cm
Horizontal wind pressure, p = 382 N/sq.m
Weight of Ice = 8920
Weight of conductor = 0.847 kg/m
= 0.847×9.81=8.31N/m
N
4
10
56
.
3
3
/ m
N
124
Transmission & Distribution
125. To be calculated
-Sag in still air condition??
-Vertical sag with ice??
-Height of lowest arm??
125
Transmission & Distribution
129. Height of lowest cross arm
= minimum ground clearance +
vertical sag + length of insulator
string
= 7.62+3.37+1.43= 12.42m
129
Transmission & Distribution
130. Weight of conductor
Sag is directly proportional to
weight per unit length of the
conductor. Ice and wind loads
also increase the sag.
Factors affecting sag
130
Transmission & Distribution
131. Span
A longer span causes more sag.
Sag is proportional to square of
span.
T
l
F
S t
8
2
2
l
S
Cond….
131
Transmission & Distribution
132. Conductor Tension
Sag is inversely proportional to
conductor tension
An increase in conductor tension
causes more stresses in the
conductor and more load on
insulators and towers.
Cond….
132
Transmission & Distribution
133. Temperature
A decrease in temperature reduces
the sag. If accompanied by snow
and wind, the sag may increase.
Heavy snow and high wind
pressure create worst conditions
for the line.
Cond….
133
Transmission & Distribution
135. Clearanc
e to
ground
400V 11kV 33kV 66kV 132kV 220kV 400kV
Across
Street
(m)
5.8 5.8 6.1 6.1 6.1 7.0 8.4
Along
Street
(m)
5.5 5.5 5.8 6.1 6.1 7.0 8.4
Other
areas
(m)
4.6 4.6 5.2 5.5 6.1 7.0 8.4
135
Transmission & Distribution
136. Stringing Chart
-The curves of sag and tension
with temperature variation are
called stringing charts.
-These are useful in erecting the
transmission line conductors at
specified temperatures and
loading conditions.
136
Transmission & Distribution
140. Discussions
140
Transmission & Distribution
1.The power is not generated at very high
voltage level. Why?
2.Why is power transmitted at very high
voltage?
3.Why is negative polarity conductor used
in HVDC applications?
4.HVDC is preferred over HVAC, other than
economic point of view - discuss?
141. Selected References
1. B.R.Gupta, ‘Power system analysis and
design’, S. Chand & Company Ltd, New
Delhi, 3rd Edition.
2. R.K.Rajput, ‘Power system Engineering’,
Laxmi Publications (P) Ltd. New Delhi, 1st
Edition.
3. S.M.Singh, ‘Electric Power, Generation,
Transmission and Distribution’, PHI
Learning Private Limited, New Delhi, 2nd
Ed. 141
Transmission & Distribution
Editor's Notes
Structure of electric power system - different operating voltages of generation, transmission and distribution – advantage of higher operating voltage for AC transmission. An introduction to EHV AC transmission, HVDC transmission and FACTs. Mechanical design of transmission line between towers – sag and tension calculations using approximate equations taking into account the effect of ice and wind.
The initial application of electricity started with the use of direct current. The invention of transformer and induction motor and the concept of three phase system initiated the use of AC. The main problems of long distance power transmission using AC are: voltage regulation associated with reactive power balance, steady state, transient state and dynamic stability of the system under different load conditions and also under outage conditions. In view of these problems with AC, the DC transmission has staged a comeback, in the form of High Voltage DC (HVDC) Transmission to supplement the High Voltage AC (HVDC) transmission system.
Power system network may be divided into three parts, viz., Generation, Transmission and Distribution. The power is generated at voltage between 6.6 kV and 11kV. The maximum generation voltage in India is 11kV. Transmission lines transmit this bulk generated power from sending end to receiving ends without supplying any consumers ; by contrast, a distribution system supplies consumers directly at short intervals along the line.
Electric energy is obtained, conventionally, by conversion from fossil fuel (coal, oil, natural gas), the nuclear and hydro sources. Heat energy released by burning fossil fuels or by fusion of nuclear material is converted to electricity by first converting heat energy to mechanical form and then converting mechanical energy to electrical energy through generators.
These generating stations are generally situated far away from the load centres.
Few advantages are :
Thermal: Coal can be found in lots of places in the world . It can be easily transported to the power stations.Coal is a relatively cheap energy source.
Hydro: When the electricity is generated, no greenhouse gases are made.The water used is free.
Nuclear: Nuclear fuel does not make harmful greenhouse gases.It is only enough a very small amount of nuclear fuel to make a lot of energy.
Thermal power plants are major sources of air pollutants. On the basis of particle size, there are different categories of air pollutants : gaseous pollutants, particulates pollutants and aerosols.
Energy generated by using wind, tides, solar, geothermal heat and biomass including farm and animal waste is known as non-conventional energy. All these sources are renewable or inexhaustible and do not cause environmental problems. They are pollution free and eco-friendly.
The power is generated at voltage between 6.6 kV and 11kV. Due to technical problems like need of higher size of generator and requirement of more insulation, this is stepped up with the help of transformers and transmitted at high voltage (110 kV / 230 kV / 400 kV). For the given power, the voltage is increased and current is decreased thereby the losses are reduced and efficiency of the system is improved. At the receiving end, the power is stepped down to required voltage level with the help of transformers. Sub-transmission system is used to transmit power for large consumers. Primary distribution (33 kV, 22 kV and 11 kV) is used for medium large consumers and secondary distribution is for small consumers, 400 V/ 230 V (three phase / single phase). Every power system need not necessarily have all the parts as in the above figure.
All transmission and distribution systems are three phase systems since it is more economical than a single phase in terms of initial cost and losses. The three phase transmission and distribution systems may consist of overhead lines or underground cables or combination of these two.
Because of the cost consideration , the transmission and sub-transmission system in India are generally overhead. In overhead lines, the power loss is due to the loss in the conductor.
When the distribution system is through overhead lines, tappings can be made at desired points on the distributors to provide connections to the consumers. The cost of providing service mains is also reduced. Voltage regulation is also important factor. The lines have considerable inductance which causes voltage drop.
The conductor should have low resistivity to reduce the loss and voltage drop. The cost of its installation and maintenance should be low and it should have a long life. The final choice of material is often a compromise.
Aluminium has the advantage of much lower cost and less weight as compared to copper.
Hard drawn copper has the advantage of very high conductivity, good tensile strength and weather resisting properties.
Overhead conductors are invariably stranded to make them more flexible during erection and while in service. A stranded conductor has a central wire and one or more layers of conductors over the central wire.
ACSR (Aluminium Conductor Steel Reinforced) conductor comprises hard drawn aluminium wires stranded around a core of single or multiple strand galvanized steel wire.
The material for the conductor should have a high tensile strength so that the spans between the towers can be as long as possible and the sag as small as possible, thus reducing the number and height of towers and number of insulators.
For different voltage levels, various types of conductors are used.
AAC – All Aluminium Conductors (7/3.35:total no. of strands / diameter in mm)
ACSR – All Aluminium Conductor Steel Reinforced
(ACSR 30/7/3.35 : ACSR total no. of strands / no. of steel strands /diameter in mm)
The transmission system of an area (state) is known as grid. The different grids are interconnected through tie lines to form a regional grid and the different regional grids are further interconnected to form a national grid. Each grid operates independently. However, power can be transmitted from one grid to another, over the tie lines, under conditions of sudden loss of generation or increase in load.
There are five regional grids in India.
A distributor is subject to the legal requirement that power must be supplied at a voltage within ±6% of the rated voltage whereas a transmission line is not subject to any such restriction and its voltage can vary as much as 10% or even 15% due to variation in loads. Any restriction on transmission voltage is technical and not legal.
Classification based on voltages are tabulated.
This is single circuit horizontal configuration
This is double circuit vertical configuration
The dielectric loss and loss in the metallic sheath are also significant in case of underground cables. The charging current, in cables, is more and also contributes to power loss
Cables have small spacing between conductors. So cables have lower inductance and lower voltage drop as compared to overhead lines.
One advantage of the cable is to beautify the city, especially in densely populated areas.
XLPE – Cross Linked Polythene Cables
There are four cores, one is for grounding
Single core cable used above 33 kV is arranged in horizontal configuration.
A view of 400 kV cable.
Surge arrester is a protective device, used for protecting the power system equipment.
Bare copper conductor is usually used for the substation earthing grid.
The earthing grid must be supplemented by earthing rods to assist in the dissipation of earth fault currents and further reduce the overall substation earthing resistance. These rods are usually made of solid copper, or copper clad steel
One transformer must be in star-star connection and other should be in star-delta connection.
A view of HVDC substation
It uses only one conductor, usually of negative polarity. The return path is provided by ground or water. This is cost-wise good and mainly used for cable transmission.
It has two conductors one positive and other negative. Each terminal has two converters of equal rated voltage, connected in series on the DC side. The junction between the converters is grounded and carries no current under normal operating conditions. The two poles can operate independently. If any one pole is isolated due to a fault on its conductor, the other pole can operate with ground and thus carry half the rated load or more by using the overload capabilities of its converters and line.
It has two or more conductors, all having the same polarity. The return path for such a system is through ground.
Alternating current transmission systems incorporating power-electronic based and other static controllers to enhance controllability and increase power transfer capability. The need for more efficient and fast responding electrical systems has given rise to innovative technologies in transmission using solid-state devices. These are called FACTS devices which enhance stability and increase line loadings closer to thermal limits. The development of power semiconductor devices with turn-off capability(GTO) opens up new perspectives in the development of FACTS devices. FACTS devices are the key to produce electrical energy economically and environmental friendly in future
The design of transmission line has to be satisfactory from electrical as well as mechanical considerations. The line should have sufficient current carrying capacity so that the required power transfer can take place without excessive voltage drop or overheating.
The line conductors, supports and cross-arms should have sufficient mechanical strength to cope with the worst possible (but not worst possible) weather conditions. These are essential and must be strong enough to give satisfactory service over a long period of time without the necessity of too much maintenance. The tension in the conductor should be well below the breaking load and a reasonable factor of safety should be used. To achieve this, an appreciable amount of sag has to be allowed. Adequate clearance between the lowest point on the line and ground must be maintained.
Insulators, which support and electrically isolate the conductors;
Tower, which holds the insulators and conductors;
Foundation and grounding; and
Optional shield conductors, which protect against lightning
To cope with an ever increasing demand, it is necessary to transmit large blocks of power over long distances. An increase in line voltage increases transmission efficiency. At voltage above 300 kV, corona causes a significant power loss and interference with communication circuits, if the circuit has one conductor per phase. The use of multiple conductors per phase decreases the voltage gradient in the vicinity of the line and thus reduces the possibilities of the corona discharge. Such an arrangement is known as Bundled conductors. Lines of 400 kV and higher voltages invariably use bundled conductor.
The different types of line supports are: Wooden poles, RCC poles, Steel tubular poles and steel towers.
The exact shape of the line is that of a catenary. Except for lines with very long span and large sag, it is sufficiently accurate to assume that the shape of the line is of parabola.
The line is assumed to be flexible and sags below the level AB due to its weight
In addition to its own weight, a transmission line is also subject to wind pressure. A coating of ice may also be formed on the conductors of the lines in hilly areas during severe winter season.
Total force is due to wind pressure and effect of ice coating.
In hilly areas, the two supports of a span may be at different levels