Sep 01, 2016 how are overhead line insulators cleaned. In this article, the generic term overhead line is used, as used by the international union of railways. 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. Constant spacing between two conductors through the entire length of the cable provides a transmission line. However, for high voltage transmission lines, strain insulator consists of an assembly of suspension. With this objective in mind, another two standards will be compared and analyzed. Limited olf supply porcelain insulators suitable for all overhead line applications ranging from low voltage, using one piece service insulators, to pin insulators and cap and pin type disc insulators for medium and high voltage usages. The insulators for overhead lines provide insulation to the power conductor from ground. Especially the transition to alternative energy in germany can be taken as a good example. Long rod insulators have high strength in compression and tension, it mainly used at suspension and very high tension area of a transmission line. Power system 2 pdf notes ps 2 pdf notes smartzworld. Strain and shackle type insulator mcqs with answers q1. In a paper read to the students section of the institution of electrical engineers on november 30, mr. They have the advantage of reduced weight, high creepage offset and resistance to the effects of vandalism since the sheds do not shatter on impact.
Overhead line conductor an overview sciencedirect topics. Transmission line design manual bureau of reclamation. Click download or read online button to get overhead and underground transmission lines book now. In order to relieve the line of excessive tension, strain insulators are used. 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. Jun 30, 20 types of insulators there are several types of insulators but the most commonly used are pin type, suspension type, strain insulator and shackle insulator. As the name suggests, the pin type insulator is secured to the crossarm on the pole. The increases in safe currentcarrying capability over the summer ratings can be clearly seen. 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. Insulators mcqs with answers solaimathi v 072819 can u explain 6th question. Widely applied for 11001200 kv ac the only alternative for 8001200 kv dc. For the successful operation of power lines, proper selection of insulators is very essential. Power system 2 notes pdf ps notes pdf book starts with the topics sag and tension calculations with equal and unequal heights of towers,types of conductors calculation of resistance for solid conductors.
Testing of insulators following are the different types of tests that are carried out on overhead line insulators. Transmission line post insulators are used on overhead transmission lines operating from 11 kv to 66kv. We manufacture all types of polymer insulator in india, delhi. Types of insulators there are several types of insulators but the most commonly used are pin type, suspension type, strain insulator and shackle insulator. The overhead line conductors are supported on the poles turns with the help of insulator to prevent the flow of current to earth. This is achieved by securing line conductors to supports with the help of overhead line insulators.
No failure in service through all our experiences excellent longterm performance normal type. A pin insulator is a device that isolates a wire from a physical support such as a pin a wooden or metal dowel of about 3 cm diameter with screw threads on a telegraph or utility pole. Breaking load of insulators with the shed of the insulating part cracked or completely broken off. Mechanical design of overhead lines cedengineering. Aug 24, 2011 there are several types of insulators but the most commonly used are pin type, suspension type, strain insulator and shackle insulator. It is the phenomenon in which an arc passes through the body of the insulator due to lightning or line surge. Overhead line insulators are used for transmission, distribution lines and electrical traction lines.
The proper overhead line operation depends to a big extent upon its mechanical design. Overhead transmission line insulators your electrical guide. Also, an insulator must be free from pores or voids, which may damage it. Pollutionareas special designs of towers in all areas of contamination. Most commonly used material for overhead line insulators is porcelain. Transmission insulators come in various shapes and types, including. Innovative solutions for distribution and transmission lines. Electrical pylon with disc and pin type overhead line insulators source. As technology developed insulators were needed for telephone lines, electric power lines, and other applications. Types of insulators complete knowledge database of. The insulators are connected to the cross arm of the tower and the power conductor passes through the clamp of the insulator. The insulators used for overhead transmission lines are. D insulators product types vertical clamp top line post insulators ppc insulators offer vertical clamp top line post assemblies for ratings 15 kv through 45 kv.
These capacitances could be made negligibly small by increasing the distance between the insulators and the tower structure which. 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. The most common methods for transfer of electric power are. An ideal insulator should not allow leakage of current from the line conductor to the earthed crossarm besides providing adequate clearance between the line conductors and metal work. The part section of a pin type insulator is shown in figure 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. Pdf a detailed investigation of overhead line insulators.
But glass, steatite and some other special composite material may also be used sometimes. Two types of the insulators of the overhead transmission line ohtl are studied in this paper. 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. Here you can download the free lecture notes of power system 2 pdf notes ps pdf notes materials with multiple file links to download. Types of wire conductors two or more conductors in a common covering form a cable. No deterioration in electrical and mechanical performance actual result. Hence, overhead power lines are always supported on insulators mounted on their support polestowers. Types of insulators, string efficiency and methods for improvement.
Typical application areas for different types of insulators. Interpretation of the long line equations surge impedance and surge impedance loading wavelengths and velocity of propagation ferranti effect, charging currentnumerical problems. Insulation coordination of overhead transmission lines. Potential distribution over a string of suspension insulators p. Overhead insulators free download as powerpoint presentation. Clark discussed the design, manufacture and testing of overhead line insulators. Power line insulators at walthamstow, london, england. This will be greater when the temperature of the air around an overhead line conductor or the soil around an underground cable is low.
Various types of insulators used for overhead transmission and distribution lines are described below. Ppc vertical clamp top line post insulators are mounted upright on crossarms and structures. Insulators types of electrical insulators in overhead lines. 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. Pin type insulator can be one part, two parts or three parts type, depending upon application voltage in a 11 kv system we generally use one part type insulator where whole pin insulator is one piece of properly shaped porcelain or glass. Mechanical design of overhead lines ced engineering. Media in category overhead line section insulators the following 42 files are in this category, out of 42 total. While constructing an overhead line, it has to be verified that line mechanical strength is such so as to provideagainst the most probable weather conditions. We are an approved vendor in most discoms in india also supplied material in different part of africa. The overhead line conductors are supported on the poles or towers. There are nonshielding methods, such as use of lightning arresters and spark gaps. A good insulator should have a good mechanical strength to withstand the mechanical load and stresses.
Ppt overhead line insulators powerpoint presentation free. An overhead line may be used to or distribute electrictransfer power. Ppt overhead line insulators powerpoint presentation. For low voltage lines download overhead and underground transmission lines or read online books in pdf, epub, tuebl, and mobi format. The series inductance of a transmission line consists of two components. This analysis will firstly focus on the dielectric stresses, then. Oct 21, 2017 there are some important terms related to insulators that we discussed before going to the topic on types of insulator.
These standards ensure meeting of ergon energys requirements. Insulator in overhead line and types of insulators. Of course, the power line wont even work in that case. In order to prevent the flow of current to earth through supports, the line conductors must be properly insulated from supports. This is because of the capacitances formed between the metal parts of the insulators and tower structure. Standard for distribution line design overhead these standards created and made available are for the construction of ergon energy infrastructure. The following figure shows a suspension type for above 33 kv. Proper operation of a transmission or distribution line is highly dependent upon the proper working of insulators. The pin type insulator is screwed onto a galvanized steel bolt which in turn is installed on the crossarm of the. Ssen 60305 insulators for overhead lines with a nominal voltage above 1 kv ceramic or glass insulator units for a. There is a groove on the upper end of the insulator for housing the conductor. There are some important terms related to insulators that we discussed before going to the topic on types of insulator. Glass insulators were first produced in the 1850s for use with telegraph lines. The number of discs in a string of insulators for 400 kv ac over head transmission line lies in the range of a.
Cables typically consist of multiple conductors, colorcoded for identification. In the mid 1960s a few people began collecting these glass and porcelain insulators. Overhead insulators electrical conductor electrical. Orienttypes of overhead line insulators composite insulator. These insulators provide necessary insulation between the line conductors and supports and hence. Mechanical design of transmission lines overhead line insulators. For low voltage lines insulators are used as strain insulators. The materials that used for made the insulators of overhead line are 1 porcelain 2tougheneed glass. Overhead line polymeric insulators sometimes called silicone insulators are a development dating from the 1960s.
Types of insulators in transmission lines electrical4u. Ssen 100451 metallic materials charpy impact test part 1. It should have a high dielectric strength to withstand operating and flashover voltages. Today there are over 2,000 collectors, and insulator clubs, national shows, and good reference books are available.
When there is a dead end of the line or there is corner or sharp curve, the line is subjected to greater tension. It is thought to be the earliest developed overhead insulator and is still popularly used in power. With over 50 years of manufacturing experience and performance testing, you can confidently specify newell. 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. This requires large stocks of different units which is uneconomical and impractical. The overhead line insulators provide insulation between the overhead line conductors and the earthed crossarm to which they are connected and also provide support to the conductors. In general, the insulator should have the following properties. Flashover tests of insulators three types of flashover tests are conducted before the insulator is said to have passed the flashover test. Overhead and underground transmission lines download ebook. Overhead transmission lines insulators svenska kraftnat. Which type of insulator is used on 2 kv transmission lines.
The design may be different for each application and the product range is wide depending on the dimensional, mechanical and electrical requirements. Pin type insulators as the name suggests, the pin type insulator is secured to the cross arm on the pole. Download insulators catalogue pdf overhead line fittings. External companies should not use these standards to construct nonergon energy assets. Overhead lines and substation equipment can be protected against direct strokes to a considerable extent by using earth or ground wires, which shield the equipment. Pin insulators are the earliest developed overhead insulator, but are still commonly used in power networks up to 33 kv system. Types of overhead line insulators the most commonly used overhead transmission line insulators are. Pdf simulation of overhead transmission line insulators.
It is a formed, single layer shape that is made out of a nonconducting material, usually porcelain or glass. The proper overhead line operation depends to a significant extent upon the adequate selection of insulators. The standard, seasonal static ratings are shown as dashed lines for a particular overhead line conductor type along with the dynamically calculated realtime rating for two weeks at the beginning of june in one particular year. This site is like a library, use search box in the widget to get ebook that you want. Although the two above materials are brittle and inelastic but it are the best materials that used to insulate the conductors. Thus the insulator plays an important part in the successful operation of the lines.