130110109005_2150908

G H Patel College of Engineering & Technology

Prepared By : Jash Bhatt (130110109005) Yagnik Patel (130110109039)

Topic Name: INSULATORS

Electrical Power System-1 (2150908)

ELECTRICAL POWER SYSTEM-1 (2150908)

Main component parts of the overhead line


• 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

MAIN COMPONENTSENTS


• 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

INSULATORS


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 crossarm 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 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 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 fourpiece 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.


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 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 ofinterconnected 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.


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.


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 lowvoltage lines (< 11 kV), shackleinsulators are used as strain 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.


SHACKLE TYPE INSULATORS

Shackle type insulators, similar to strain type insulators, are used on sharp curves, end poles and in section poles.


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 usedfor low voltage distribution lines. Suchinsulators can be used either in ahorizontal position or in a vertical position.They can be directly fixed to the pole with a bolt or to the cross arm.


OTHER MODELS OF SHACKLE TYPE INSULATORS


STAY TYPE 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 aremounted at a height of at least 3 meters (118 inches) from ground level.


Thank You


130110109005_2150908

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