Repair and maintenance of power distribution lines ncert. Maintenance plan for transmission and distribution overhead and. Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. This is distinct from the local wiring between highvoltage substations and customers, which is typically referred to as electric power. Two parallel wires coaxial cable microstrip line optical fiber waveguide very high frequencies, very low loss, expensive etc. An introduction to electric power transmission presentation. Engineers need an overview of the important aspects contemporary applications of transmission lines. Maintenance of overhead transmission lines electric power.
An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. Now let us discuss the about overhead lines and their design. An ad hoc committee was formed and charged with addressing the following issues. Comparison of overhead and underground transmission lines. Our analysis of transmission lines will include the derivation of transmission line. Westerns substations and transmission lines are under the jurisdiction of westerns power operation and maintenance staff and are subject to their standard operating procedures and regulations. The guy strain insulators are used in overhead electrical line.
The interconnected lines which facilitate this movement are known as a transmission network. Transmission line problems are usually solved using em field theory and electric theory, the two major theories on which electrical engineering is based, we use circuit theory because it is easier to deal with mathematics. Volume ii contains a comprehensive list of federal and state permits required. The transmission line is made up of a conductor having a uniform crosssection along the line. There are three main types of overhead transmission lines. Aluminum is preferred over copper for its lower cost and lighter weight, however, this comes at the price of some energy loss that doesnt occur with copper. Ergon energy corporation limited abn 50 087 646 062. Line availability line reliability capacityload transfer capability. Therefore, additional transmission power capacities are required for transfer of electrical power over the transmission line. The pjm overhead transmission oht ratings spreadsheet was expanded to include. Cowritten by experts in power engineering, this detailed guide addresses component selection and design, current ieee standards, loadflow analysis, power. Epris overhead transmission inspection and assessment guidelines 1012310 provides a stateoftheart resource on the latest inspection and assessment methods to help utilities increase reliability and reduce maintenance costs. Overhead transmission lines research papers academia. While burying transmission lines is an intuitively desirable approach, many people dont recognize the technical difficulties.
Since most of the insulation is provided by air, overhead power lines are generally the lowestcost method of power. Calculation of overhead transmission line impedances a finiteelement approach article pdf available in ieee transactions on power delivery 141. Managing overhead lines 1 overhead lines form an integral part of the utility asset base and must be managed as such. Bundled conductors are mainly used in high voltage overhead transmission lines to a increase mechanical strength. High voltage or transmission overhead lines, medium. Because overhead transmission lines are constructed over open areas where it is not possible to. Since most of the insulation is provided by air, overhead power lines are generally the lowestcost method of transmission for large quantities of electric energy. Transmission and distribution mcq how enginering works. An overhead power line is an electric power transmission line suspended by towers or utility poles. Overhead power lines presents not only the scientific and engineering basis for the electric and mechanical design, but also comprehensively describes all aspects of most recent technology, including the selection and design of components such as conductors, insulators, fittings, supports and foundations. Planning and amenity aspects of high voltage electricity. The following rules apply to electric transmission lines operating at alternating current voltages over 50,000 volts phase to phase in overhead and underground construction operated in connection with public utilities, privately or municipally owned. Provisions will be made to deenergize only those buses and circuits necessary to accomplish the work.
Overhead transmission inspection and assessment guidelines. Maintenance of transmission linesthe transmission lines play a very important role in transmitting the huge quantum of electrical power generated at various generating stations to the whole area of the country from one end to other end over a distance of several hundreds of kilometers. Full detail design of hvac lines up to 765kv and hvdc up to 800kv providing support to over 31 000 km of transmission lines 220kv,275kv,400kv, 533kvhvdc, 765kv 340 000 km of distribution lines 11kv, 22kv,66kv, 88kv,2kv, busy with designs for over 8 000km of new transmission lines to be built in next 10 years. Over head transmission lines live line maintenance techniques based on condition monitoring in indian power. Electrical design of overhead power transmission lines discusses everything electrical engineering students and practicing engineers need to know to effectively design overhead power lines. If the value of the thi is 100%, the health of the asset is in good condition, hence no maintenance is. Possible visions for the inspection of transmission lines in a multidecade time. The purpose of this article is to give a general overview of the steps that are necessary in the planning and construction of a typical overhead transmission line, to give newcomers to the trade a general format to follow, and assist transmission design engineers in understanding how such lines are built.
Pdf maintenance of a highvoltage overhead transmission. Regular monkey thorough line patrolling with digital photography of the line components is carried out. For uninterrupted power supply it is essential to maintain the transmission lines in trim and healthy condition. For preventive and predictive maintenance of transmission lines following methods are applied. The overhead distribution line clearance program consists of a split fouryear and eightyear cycle for planned tree trimming. You can also follow us in other social medias to gain. In overhead transmission lines, the bare conductors are suspended. Future inspection of overhead transmission lines electric power. Guidelines for the construction and maintenance of transmission. Guidelines for the construction and maintenance of. Overhead power lines are structures that are used in electric power transmission and distribution over long distance.
Dispersionless transmission lines because lo and co do not depend on frequency for a superconductor, the phase velocity is independent of frequency. Maintenance technique llmt for overhead lines based on condition monitoring to maintain system reliability. Pdf design criteria of overhead transmission lines. It will cost more to place lines underground than overhead. This study focuses in particular on the structural health monitoring of overhead transmission lines. The underground cables are rarely used for power transmission due to two main reasons. Hello everyone, in this video i will discuss about 10 difference between overhead transmission system and underground transmission system. Complete coverage of power line design and implementation.
Pdf calculation of overhead transmission line impedances. Although proximity to other energized lines may be limited on the rightofway, extra care must be exercised to protect the conductor so that when energized, power loss and corona are not a problem. Also, the amount of attenuation is extremely small, since this is due to ro. Transmission lines a transmission line connects a generator to a load a two port network transmission lines include physical construction. Electrical design of overhead power transmission lines. Construction is set to occur from spring 2021 to late summer 2022 on the western.
Calculation of the two high voltage transmission line. The examples presented in this paper show that the rearranged line con. This transmission system which operates at 400,000 and 275,000 volts 400kv and 275kv is known as the national grid and covers some 4,500 route miles of overhead line, 420 route miles of underground cable and more than 335 substations. Overhead transmission lines shorter than 80 km 50 miles can be modeled as a series resistance and inductance, since the shunt capacitance can be neglected over short distances. It consists of one or more conductors commonly multiples of three suspended by towers or poles. Transmission line design manual bureau of reclamation. Overview of different overhead transmission line conductors. Replacing all the overhead lines in a state transmission and distribution with underground lines is probably not possible or distribution with underground lines is probably not possible or desirable. Epri, and others, have in the past, and are currently developing inspection technologies for implementation using traditional manned inspection methods. Owing to rising global electricity consumption, population growth. Anatomy of a transmission line overhead transmission line components conductor alternatives typically aluminum or copper conductors are used. These are the structures towerspoles that support the transmission. Maintenance of overhead transmission lines view presentation slides online. Principles of mechanical design in overhead transmission lines.
Monitoring the integrity of these cables becomes increasingly important as the cable ages. The purpose of this article is to give a general overview. Overhead transmission lines mea is often asked why it doesnt simply bury its transmission lines. The strain insulator is inserted between stay wire to isolate the lower portion from. Underground lines are protected from some, but not all, types of storm damage. Limitations on allowable spans of the same circuit to mitigate midspan conductor clashing are as per the provisions of asnzs 7000 section 3. It transmits the wave of voltage and current from one end to another. What are the main components of overhead transmission of. Visualbased positioning of aerial maintenance platforms on.
Introduction when the high voltage transmission lines are designed, it is inevitably needed to intersect across, change the arrangement modes of wires, and etc. To ensure high reliability and availability of the overhead lines for bulk electricity transmission. Masters thesis submitted in partial fulfillment of. Pdf maintenance of a highvoltage overhead transmission line. Overhead transmission lines, distance of two lines, equation of wire balance, wire sag 1. Overhead conductors, made of naked metal and suspended on insulators, are preferred over underground conductors because of the lower cost and easy maintenance. Ptec 500 fundamentals of overhead transmission line design. Principles of mechanical design in overhead transmission. Ensure adequate transmission from resources to serve loads in a reliable and economical manner.
Manual for transmission lines and substation construction. Subcommittee provide an update to the bare overhead transmission conductor ratings guide. There are two types of transmission line conductors. Inspectionthe inspection of a overhead line orl is performed by taking. Overhead lines have more advantages than underground lines. Overhead telephone and cable tv lines are common in north america. Overhead highvoltage lines are a common choice for power transmission, but their planning, installation and management are often challenging tasks because of the surrounding public interest and. The most common methods for transfer of electric power are. Maintenance practices for transmission overhead lines. The clearances listed in the tables take into account the fact that the transmission line. View overhead transmission lines research papers on academia. Full detail design of hvac lines up to 765kv and hvdc up to 800kv providing support to over 31 000 km of transmission lines 220kv,275kv,400kv, 533kvhvdc. The inductive reactance at 60 hz for overhead lines is typically much larger than the resistance of the line.
An overhead cable is a cable for the transmission of information, laid on utility poles. Procurement errors, ineffective line design and bad construction cannot be corrected through maintenance. Medium transmission line the line length is between 60 km to 160 km and the line voltage is between 20kv to 100kv. Over head transmission lines live line maintenance. First of all, the lines are operating as an element of transmission of. Since the spacing between lines in buried cables is very small, series inductance of cables is much smaller than the inductance of overhead lines. Firstly, power is generally transmitted over long distances to load centres. Typically 69 kv all the way up to 1200 kv, these lines transfer power in bulk from generation stations to city centers. Overhead lines ohl operating at 400kv, form the backbone of clp powers transmission network. The transmission of electric energy can be done in alternate current or continuous current and can also be done by using underground cables or overhead lines. Overhead lines design main components of overhead lines. Depending on the level of voltage of the transmission of electric energy there can be three kinds of overhead lines.
Comparison of overhead and underground transmission lines 1. Pdf overhead highvoltage lines are a common choice for power transmission, but their planning, installation and management are often. Cowritten by experts in power engineering, this detailed guide addresses component selection and design. There are four methods that can be used to install overhead transmission conductors. Nondestructive testing of overhead transmission lines. Since the phases of a highvoltage overhead transmission line must be spaced further apart to ensure proper insulation, a highvoltage line will have a higher inductance than a lowvoltage line. Physical characteristics overhead lines an overhead transmission line usually consists of three conductors or bundles of conductors containing the three phases of the power system. So that a pulse will propagate down a superconducting transmission line without dispersing. Transmission lines a transmission line is used for the transmission of electrical power from generating substation to the various distribution units. Efficient electrical power transmission and distribution is cut down due to overloaded rashmi materials today. Standard for distribution line design overhead page 9 of 206 standard stnw3361 ver 2. Short transmission line the line length is up to 60 km and the line voltage is comparatively low less than 20kv. They are also seeking ways to increase transmission capacity without making large capital investments. Unlike underground cables, overhead lines are vulnerable to external environmental attacks, such as adverse weather, high humidity, pollution, ground stability, vegetation, and flying objects etc.