INSULATORS BY: Raviteja Damerla
[email protected] EEE. Department, B V C ENGG COLLEGE Main component parts of the overhead line MAIN COMPONENTS Support Cross - arm and clamp Insulator Guys and stays Conductor Lighting arrestors Fuses and Isolating switches Continuous earth wire Guard wire Bird guards Vibration damper Jumpers 1. SUPPORT Support : Pole, Tower, etc., which depends on the size and height of the processing voltage. SUPPORT – WOODEN, STEEL POLES WOODEN POLES STEEL POLES SUPPORT – RCC POLES SUPPORT – TOWERS 2. CROSS ARM AND CLAMP 3. INSULATORS Let we talk about this section in detail in upcoming slides 4. GUYS AND STAYS Stays poll over his use of the guys and the Insulator. guy wire clamp power transmission line fittings 5. CONDUCTOR copper, Aluminium, or A.C.S.R Through a line of electric coductor power one place to another must be in place. ACSR Aluminum conductor Steel Reinforced conductor 6. LIGHTENING ARRESTORS 7. FUSES AND ISOLATING SWITCHES They 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 WIRE Tower or the poll is over the top of the line along the entire Earth trait. The unusual circumstances 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 direct lightning strokes is by use of overhead ground wires as shown in Fig 6. For simplicity, one ground wire and one line conductor are shown. The ground wires are placed above the line conductors 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 low resistance as possible. Due to their proper location, the ground wires will take up all the lightning strokes instead of allowing them to line conductors. The degree of protection provided by the ground wires depends upon the footing resistance of the tower. A lightning stroke hits an earth wire 9. GUARD WIRE When a power line, telephone or telegraph line crossing, and then find the line 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 long ebonite basest plate, which is a cross - is prevented in the presence of arm insulator. The birds of hokier cross - in the arm and conductor Flash - Over in the 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 the two conductor. Nevertheless, as part of the phase plate, Danger plate, Barbed wire, Cradle guard. Etc. 12. JUMPERS for easy handling of the jumper set by rubber gloves or hot-line tools 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. Insulator important role in system operation. Transmission line insulators are devices used to contain, separate or support electrical conductors on high voltage electricity supply networks. Transmission insulators come in various shapes and types, including individual or strings of disks, line posts or long rods. They are made of polymers, glass and porcelain--each with different densities, tensile strengths and performing properties in adverse conditions TYPES OF INSULATORS There are several types of insulators but the most commonly used are 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 INSULATORS Pin type insulators are used for transmission and distribution of electric power at voltages upto 33 kV. Beyond operating voltage of 33 kV, the pin type insulators become too bulky and hence uneconomical. PIN TYPE INSULATORS Pin type insulators are used for the transmission of lower voltages. A single pin type insulator is used to transmit voltages up to 11 kV (kilovolts) and higher voltages require two-, three- or four- piece pin insulators. They are not economically feasible for 33 kV and higher transmission lines. Pin type insulators are secured with steel or lead bolts onto transmission poles. These are typically used for straight-running transmission lines SUSPENSION TYPE INSULATORS For high voltages (>33 kV), it is a usual practice to use suspension type insulators shown in Figure. consist of a number of porcelain discs connected in series by metal links in the form of a string. SUSPENSION TYPE INSULATORS The conductor is suspended at the bottom end of this string while the other end of the string is secured to the cross-arm of the tower. Each unit or disc is designed for low voltage, say 11 kV. The number of discs in series would obviously depend upon the working voltage. For instance, if the working voltage is 66 kV, then six discs in series will be provided on the string. Suspension type transmission line insulators suspend and support high voltage transmission lines. They are cost effective for higher voltage transmission, typically replacing multiple pin type insulators. Suspension type insulators have a number of interconnected porcelain discs, with each individual unit designed to support a particular voltage. Together, a system of these discs is capable of effectively supporting high voltages. There are three types of suspension insulators: cemented cap suspension insulators; interlinking or Hewlett suspension insulators; and link or core suspension insulators. SUSPENSION TYPE INSULATORS ADVANTAGES OF SUSPENSION TYPE INSULATORS 1. 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 voltage transmission lines, strain insulator consists of an assembly of suspension insulators as shown in Figure. The discs of strain insulators are used in the vertical plane. When the tension in lines is exceedingly high, at long river spans, two or more strings are used in parallel. Strain type insulators are horizontally suspended suspension insulators. They are used to handle mechanical stresses and take the pressure off a conductor at the end of a transmission line, at a sharp corner or curve or over long river crossings. Strain insulators are typically used for higher voltage transmissions STRAIN TYPE INSULATORS SHACKLE TYPE INSULATORS Shackle type insulators, similar to strain type insulators, are used on sharp curves, end poles and in section poles. SHACKLE TYPE INSULATORS However, unlike strain insulators, shackle insulators are designed to support lower voltages. These insulators are single, round porcelain parts that are mounted horizontally or vertically. In early days, the shackle insulators were used 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 SHACKLE TYPE INSULATORS OTHER MODELS STAY TYPE INSULATORS STAY, GUY, AND EGG INSULATORS Stay insulators, also called egg insulators, are primarily used to prevent stay wires from becoming energized from accidentally broken live wires. They, therefore, function to provide insulation between stay clamps and transmission poles. Stay insulators are mounted at a height of at least 3 meters (118 inches) from ground level. STAY TYPE INSULATORS