7. FUSES AND ISOLATING SWITCHESThey are different parts of the overhead system, the network can be isolated if necessary. Disconnecting Switch (Isolator) High-voltage fuse cutout applied to alternating current system
8. CONTINOUS EARTH WIRETower or the poll is over the top of the line along the entire Earth trait. The unusualcircumstances created by the additional voltage Discharge line to protect the soil easily. Protective grounding jumper installation for two-pole and three-pole structures (grounded structures). OGW denotes overhead ground wire. OGWs must be bonded to the worksite grounding system if within reach of linemen. OGWs may be bonded to the cluster bars or to the grounded phase conductors with protective grounds.
8. CONTINOUS EARTH WIRE The most effective method of providing protection to transmission lines against directlightning strokes is by use of overhead ground wires as shown in Fig 6. For simplicity, oneground wire and one line conductor are shown. The ground wires are placed above the lineconductors at such positions that practically all lightning strokes are intercepted by them (i.e. ground wires). The ground wires are grounded at each tower or pole through a lowresistance as possible. Due to their proper location, the ground wires will take up all thelightning strokes instead of allowing them to line conductors. The degree of protectionprovided by the ground wires depends upon the footing resistance of the tower. A lightning stroke hits an earth wire
9. GUARD WIREWhen a power line, telephone or telegraph line crossing, and then find theline that connects the top and bottom of the Earth Wire is used to guard.
10. BIRD GUARDS It is created on the side of the saw teeth as longebonite basest plate, which is a cross - is prevented inthe presence of arm insulator. The birds of hokiercross - in the arm and conductor Flash - Over inthe out .
11. VIBRATION DAMPER vibration damper dimple shape in the presence of these lines connect to the poll, that tremble down the line. The air flow through the conductor is conductor vibration, the vibration is. The pressure on the conductor in the conductor can be read off tear. The best way to protect against damage from vibration induced arms rod is used. Bates is one of the Stock Bridge damper .The shaking intensity is used to prevent damper betas.
12. JUMPERS jumpers connection is connected via thetwo conductor. Nevertheless, as part of thephase plate, Danger plate, Barbed wire,Cradle guard. Etc.
12. JUMPERSfor easy handling of the jumper set by rubber gloves or hot-line tools
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. Insulator important role in systemoperation. Transmission line insulators are devices used to contain,separate or support electrical conductors on high voltage electricitysupply networks. Transmission insulators come in various shapesand types, including individual or strings of disks, line posts or longrods. They are made of polymers, glass and porcelain--each withdifferent densities, tensile strengths and performing properties inadverse conditions
TYPES OF INSULATORSThere are several types of insulators but the most commonly usedare pin type, suspension type, strain insulator and shackle insulator.
PIN TYPE INSULATORS As the name suggests, the pin type insulator is secured to the cross- arm on the pole. There is a groove on the upper end of the insulator for housing the conductor. The conductor passes through this groove and is bound by the annealed wire of the same material as the conductor.
PIN TYPE INSULATORSPin type insulators are used for transmission and distribution ofelectric power at voltages upto 33 kV. Beyond operating voltage of33 kV, the pin type insulators become too bulky and henceuneconomical.
PIN TYPE INSULATORS Pin type insulators are used for the transmission of lowervoltages. A single pin type insulator is used to transmit voltages up to11 kV (kilovolts) and higher voltages require two-, three- or four-piece pin insulators. They are not economically feasible for 33 kV andhigher transmission lines. Pin type insulators are secured with steel or lead bolts ontotransmission poles. These are typically used for straight-runningtransmission lines
SUSPENSION TYPE INSULATORSFor high voltages (>33 kV), it is a usual practice to use suspensiontype insulators shown in Figure. consist of a number of porcelaindiscs connected in series by metal links in the form of a string.
SUSPENSION TYPE INSULATORS The conductor is suspended at the bottomend of this string while the other end of thestring is secured to the cross-arm of thetower. Each unit or disc is designed for lowvoltage, say 11 kV. The number of discs inseries would obviously depend upon theworking voltage. For instance, if the workingvoltage is 66 kV, then six discs in series will beprovided on the string. Suspension type transmission line insulators suspend andsupport high voltage transmission lines. They are cost effective forhigher voltage transmission, typically replacing multiple pin typeinsulators. Suspension type insulators have a number ofinterconnected porcelain discs, with each individual unit designed tosupport a particular voltage.
SUSPENSION TYPE INSULATORSTogether, a system of these discs is capable of effectively supportinghigh voltages. There are three types of suspension insulators:cemented cap suspension insulators; interlinking or Hewlettsuspension insulators; and link or core suspension insulators.
ADVANTAGES OF SUSPENSION TYPE INSULATORS1. Suspension type insulators are cheaper than pin type insulators for voltages beyond 33 Kv.2. Each unit or disc of suspension type insulator is designed for low voltage, usually 11 kV. Depending upon the working voltage, the desired number of discs can be connected in series.3. If any one disc is damaged, the whole string does not become useless because the damaged disc can be replaced by the sound one.4. The suspension arrangement provides greater flexibility to the line. The connection at the cross arm is such that insulator string is free to swing in any direction and can take up the position where mechanical stresses are minimum.5. In case of increased demand on the transmission line, it is found more satisfactory to supply the greater demand by raising the line voltage than to provide another set of conductors. The additional insulation required for the raised voltage can be easily obtained in the suspension arrangement by adding the desired number of discs.6. The suspension type insulators are generally used with steel towers. As the conductors run below the earthed cross-arm of the tower, therefore, this arrangement provides partial protection from lightning.
STRAIN TYPE INSULATORS When there is a dead end of the line or there is corner or sharp curve, the line is subjected to greater tension. In order to relieve the line of excessive tension, strain insulators are used. For low voltage lines (< 11 kV), shackle insulators are used as strain insulators.
STRAIN TYPE INSULATORS However, for the high voltagetransmission lines, strain insulator consists ofan assembly of suspension insulators asshown in Figure. The discs of strain insulatorsare used in the vertical plane. When thetension in lines is exceedingly high, at longriver spans, two or more strings are used inparallel.
STRAIN TYPE INSULATORSStrain type insulators are horizontally suspended suspensioninsulators. They are used to handle mechanical stresses and take thepressure off a conductor at the end of a transmission line, at a sharpcorner or curve or over long river crossings. Strain insulators aretypically used for higher voltage transmissions
SHACKLE TYPE INSULATORSShackle type insulators, similar to strain type insulators, are used onsharp curves, end poles and in section poles.
SHACKLE TYPE INSULATORS However, unlike strain insulators,shackle insulators are designed tosupport lower voltages. These insulatorsare single, round porcelain parts that aremounted horizontally or vertically. Inearly days, the shackle insulators wereused as strain insulators. But now a days, they are frequently used for low voltage distribution lines. Such insulators can be used either in a horizontal position or in a vertical position. They can be directly fixed to the pole with a bolt or to the cross arm
STAY TYPE INSULATORS STAY, GUY, AND EGG INSULATORS
STAY TYPE INSULATORS Stay insulators, also called egg insulators, are primarily used toprevent stay wires from becoming energized from accidentallybroken live wires. They, therefore, function to provide insulationbetween stay clamps and transmission poles. Stay insulators aremounted at a height of at least 3 meters (118 inches) from groundlevel.