Most commonly used material for overhead line insulators is porcelain. Various types of insulators used for overhead transmission and distribution lines are described below. These insulators provide necessary insulation between the line conductors and supports and hence. Pin type insulators are used for supporting line conductors. Transmission line insulator distribution line insulator.
Find details of companies offering overhead line insulator at best price. Ppt overhead line insulators powerpoint presentation free. Composite based ehv ac overhead transmission lines core. In order to prevent the flow of current to earth through supports, the line conductors must be properly insulated from supports. Both computations are taken over a length of 30cm from the energized end.
Cables typically consist of multiple conductors, colorcoded for identification. As a result, an improved flashover performance is achieved by the shape and by the nonwettability of the surface. Dynamics characteristic of vstring composite insulators for. Chapter 4 overhead line insulators notes, power system.
Although the two above materials are brittle and inelastic but it are the best materials that used to insulate the conductors. Another objective was to calculate material and installation costs for the chosen components and lines. Oct 21, 2017 there are some important terms related to insulators that we discussed before going to the topic on types of insulator. Current carrying capacity strength weight diameter corrosion resistance creep rate thermal coefficient of expansion fatigue strength operating temperature short circuit currenttemperature thermal stability cost categories of overhead conductors. Standard strength classes and end fittings for string insulator units, standards australia, 1999 11. The british standard specification gives particulars of porcelain.
The overhead line conductors are supported on the poles turns with the help of insulator to prevent the flow of current to earth. The chapter deals with the different types of ageing mechanisms. Dynamics characteristic of composite insulators under horizontal load caused by wind load is studied in this paper. The pin type insulator is screwed onto a galvanized steel bolt which in turn is installed on the crossarm of the. For low voltage lines insulators are used as strain insulators. This requires large stocks of different units which is uneconomical and impractical. Jumpers for easy handling of the jumper set by rubber gloves or hot line tools 21. The chapter deals with the different types of ageing mechanisms that composite. Chapter 4 overhead line insulators notes, power system, electrical engineering electrical engineering ee notes edurev notes for electrical engineering ee is made by best teachers who have written some of the best books of electrical engineering ee.
Insulators transmission and distribution system leak overhead line of theby chance current can not flow, so that the line from the earth, theinsulator is used for the line. It is refreshing to see a book on high voltage insulators that addresses so many. General concept for 800 kv dc ohl in china are composite insulators composite insulators considered for 765 kv ac ohl in south africa station insulators. Insulation coordination of overhead transmission lines. The new ecmei long rod insulators type 45spi marked with elsewedy polymer insulators combine the. Overhead line insulators it is obvious that if overhead power lines are not properly insulated from their support polestowers, the current will flow towards the ground through the polestowers which also become hazardous.
Proceedings of the 14 parameters affecting the back. Construction of transmission and distribution lines. The magnitude of the overvoltage is approximately the same in all phases and may rise to several hundred kilovolts between the phase and earth. It consists of one or more conductors commonly multiples of three suspended by towers or poles. Proper operation of a transmission or distribution line is highly dependent upon the proper working of insulators. Development of composite insulators for overhead lines by satoshi kobayashi, yutaka matsuzaki, hiroshi masuya 2, yoshihiro arashitani 3 and ryuzo kimata the united states is leading a worldwide trend toward replacing ceramic and glass insulators with composite insulators that are lighter in weight, as well as. Technical specification for overhead line porcelain and. Pin, suspension, and strain insulators are used in medium to high voltage. Pollutionareas special designs of towers in all areas of contamination. Ppt overhead line insulators powerpoint presentation. Mar 09, 20 insulators transmission and distribution system leak overhead line of theby chance current can not flow, so that the line from the earth, theinsulator is used for the line. September 1, 2016 by admin cleaning of overhead transmission line is not required because any dust and dirt that falls out of the sky onto them will be limited thickness and will not affect the electricity flow in any way nor will it decrease clearance which is the insulation in any meaningful way. How many type of insulator use in electrical transmission and. Constant spacing between two conductors through the entire length of the cable provides a transmission line.
A lead sheath is commonly applied over the insulation to prevent water or moisture ingress into. Since most of the insulation is provided by air, overhead power lines are generally the lowestcost method of power transmission for large quantities of. Germanys existing grid infrastructure and transport of energy from north to south requires insulators that withstand the most varied weather conditions along the long route from the sea to the mountains. Typically, composite line insulators have smaller average diameters than porcelain or glass insulators. Overvoltage is induced on the line when lightning strikes an overhead line or its vicinity. In 1999, in japan the first power line designed for kv with 2 circuits were built, the kitaiwaki power line. Electrical insulators and accessories elsewedy electric. Overhead insulators inspected from the ground against a uniform temperature sky are also clear from interference.
Flashover tests of insulators three types of flashover tests are conducted before the insulator is said to have passed the flashover test. Some of the best insulators, in order of higher resistivity, are. There are 5 types of insulators used as electrical overhead insulation pin insulator, suspension insulator, strain insulator, stay insulator, and. Insulators, also called dielectrics, have a high resistance and do not pass an electric current. Media in category overhead line section insulators the following 42 files are in this category, out of 42 total. Technical specification for overhead line porcelain and glass insulators. When there is a dead end of the line or there is corner or sharp curve, the line is subjected to greater tension. This is achieved by securing line conductors to supports with the help of overhead line insulators. Copper aac all aluminum conductor aaac all aluminum. No failure in service through all our experiences excellent longterm performance normal type. Resin insulators indoor and outdoor insulators in aromatic indoor or cykloaliphatic outdoor epoxy resin. They combine the functions of a fuse, a switch and. To furnish the diverse requirements of our customers, we are involved in supplying a wide range of overhead line insulators in gum.
The electric field distribution is obtained along the center of the rod and from the sheath. Double shed antipollution insulators ceramic porcelain line post insulator. Development of composite insulators for overhead lines by satoshi kobayashi, yutaka matsuzaki, hiroshi masuya 2, yoshihiro arashitani 3 and ryuzo kimata the united states is leading a worldwide trend toward replacing ceramic and glass insulators with composite insulators that are. Types of overhead line insulators the most commonly used overhead transmission line insulators are. Kothari, centre for energy studies, iit delhi for more details visit htt. Pin type insulators pin type insulators or pin insulators are popularly used in electric distribution systems up to 33 kv voltage level. The insulators for overhead lines provide insulation to the power conductor from ground. Mar 20, 2011 types of overhead conductors properties of overhead bare conductors.
Breaking load of insulators with the shed of the insulating part cracked or completely broken off. Testing of insulators following are the different types of tests that are carried out on overhead line insulators. Potential distribution over a string of suspension insulators p. The objective of this thesis was to create a model of the overhead transmission line. Ssen 60372 locking devices for ball and socket couplings of string insulator units dimensions and tests. As the name suggests, the pintype insulator is secured to the crossarm on the pole.
The most common methods for transfer of electric power are. An overhead line is designed on the principle of one or more overhead wires or rails, particularly in tunnels situated over rail tracks, raised to a high electrical potential by. There are several types of overhead line insulators. Insulators are generally classified in following types. Types of insulators, string efficiency and methods for improvement. Components were defined for each voltage ratings which are 72.
There are some important terms related to insulators that we discussed before going to the topic on types of insulator. In 1999, in japan the first power line designed for. Overhead line systems realized with ensto fittings. In general, the insulator should have the following properties. Development of composite insulators for overhead lines. Overhead line insulators are mostly made of the following materials unsw, 2006a. Composite based ehv ac overhead transmission lines print. Overhead line insulators are essential components in power transmission and failure of them due to pollution flashover results in unplanned outage and huge cost to the power transmission network. However, for high voltage transmission lines, strain insulator consists of an assembly of suspension. The part section of a pintype insulator is shown in figure 1. Insulators transmission and distribution system leak overhead line of the by chance current can not flow, so that the line from the earth, the insulator is used. Especially the transition to alternative energy in germany can be taken as a good example. Insulation feature transmission line insulator condition. Condition monitoring of overhead line insulator by.
An overhead line is designed on the principle of one or more overhead wires or rails, particularly in tunnels situated over rail tracks, raised to a high electrical potential by connection to feeder stations at regular intervals. An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. Insulators transmission and distribution system leak overhead line of the by chance current can not flow, so that the line from the earth, the insulator is used for the line. In this example an insulator from a threephase power line is examined. Feeder stations at regular intervals along the overhead line supply power from the highvoltage grid. Widely applied for 11001200 kv ac the only alternative for 8001200 kv dc. Repair and maintenance of power distribution lines ncert. The overhead line conductors are supported on the poles or towers. These capacitances could be made negligibly small by increasing the distance between the insulators and the tower structure which.
Transmission line design manual bureau of reclamation. How many type of insulator use in electrical transmission. A good insulator should have a good mechanical strength to withstand the mechanical load and stresses. Purpose and scope this specification sets out the requirements for the manufacture, testing and delivery of. Overhead transmission line insulators your electrical guide. Types of insulators in transmission lines electrical4u. In 1982 overhead power lines were built in russia between elektrostal and the power station at ekibastusz, this was a threephase alternating current line at 1200 kv power line ekibastuzkokshetau.
Glass plastics, ceramics, rubber, wood, and paper are all good insulators. For the successful operation of power lines, proper selection of insulators is very essential. Dynamics characteristic of vstring composite insulators. Post insulators 172,5kv and bushing insulators 1236kv. This type of insulator is used up to 33kv level due to increase in size, weight, and cost. Their design varies to suit different types of polluted zones and. As a result, an improved flashover performance is achieved by. For low voltages up to and including 11 kv one piece insulators can be used and two piece insulators are commonly used for 25 kv and for 44 kv up to and including 66 kv three and four piece insulators can be employed. It should have a high dielectric strength to withstand operating and flashover voltages. Jumpers for easy handling of the jumper set by rubber gloves or hotline tools 21. Types of overhead conductors properties of overhead bare conductors. It is expected that corona and infrared will be effective inspection tools for polymeric insulators but we do not have survey results at this time. This analysis will firstly focus on the dielectric stresses, then.
Proceedings of the 14th international middle east power systems conference mepcon10, cairo university, egypt, december 1921, 2010, paper id 111. Insulators types of electrical insulators in overhead lines. The insulators are connected to the cross arm of the tower and the power conductor passes through the clamp of the insulator. Single piece type pin insulator used for lower voltage. Page 3 of 43 specification ets100101 ver 5 ergon energy corporation limited abn 50 087 646 062 1. The inductance of a transmission line is defined as the number of flux linkages wbturns produced per ampere of current flowing through the line. The materials that used for made the insulators of overhead line are 1 porcelain 2tougheneed glass.
Mechanical design of transmission lines overhead line insulators. Request pdf condition monitoring of overhead line insulator by measuring. Power line insulators at walthamstow, london, england. Usage insulators in overhead power lines it is obvious that if overhead power lines are not properly insulated from their support polestowers, the current will flow towards the ground through the polestowers which also become hazardous. In coastal areas, insulator pollution is produced by salt particles, which forms a. Overhead lines requirements for the resistance to forces and climate our insulators are exposed daily to enormous tensile stress in the construction of transmission lines, because the towers used in energy transmission utilize 0 ft to 1700 ft spans with a weight of approx. Sep 01, 2016 how are overhead line insulators cleaned.
In overhead line poles, where are isolators and insulators. Typical application areas for different types of insulators. This is because of the capacitances formed between the metal parts of the insulators and tower structure. Hence, overhead power lines are always supported on insulators mounted on their support polestowers. Also, an insulator must be free from pores or voids, which may damage it.
Of course, the power line wont even work in that case. In order to relieve the line of excessive tension, strain insulators are used. Silcosil silicone insulators thorne and derrick uk. No deterioration in electrical and mechanical performance actual result. For the advantages, vstring insulators are widely used in overhead transmission. Two or three single piece type pin insulator are joined together by cement to form 2 or 3 piece type pin insulator respectively. Interpretation of the long line equations surge impedance and surge impedance loading wavelengths and velocity of propagation ferranti effect, charging currentnumerical problems. The insulators used in connection with overhead systems employing bare conductors are composed almost invariably of glazed porcelain, although some moulded materials are used for low voltages, and glass has been used on the european continent and in america for medium voltages. Pdf a detailed investigation of overhead line insulators. Overvoltage travels along the line to the nearest pole where it discharges by igniting an arc between the cros. Used for the termination of insulated messenger wires insulation shall be peeled of before. Types of wire conductors two or more conductors in a common covering form a cable. Condition monitoring of overhead line insulator by measuring. But glass, steatite and some other special composite material may also be used sometimes.
Ssen 603831 insulators for overhead lines with a nominal voltage above 1 000 v part 1. In this article, the generic term overhead line is used, as used by the international union of railways. The series inductance of a transmission line consists of two components. They are secured on the cross arms of the pole to carry power lines. Lecture series on power system generation, transmission and distribution by prof. With this objective in mind, another two standards will be compared and analyzed. It is the phenomenon in which an arc passes through the body of the insulator due to lightning or line surge. Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains. Overhead line is designed on the principle of one or more overhead wires situated over rail tracks. Thus the insulator plays an important part in the successful operation of the lines. Chapter 8 lists the iec documents relating to the different insulator types. There are 5 types of insulators used in transmission lines as overhead insulation.
701 355 111 1215 267 985 871 1264 480 396 570 1545 1306 1243 322 1499 194 128 280 1269 132 1337 291 837 1332 1051 960 383 261 17 976 464 1136 1366 1329 1370 1151 214