A material that does not let electricity and heat travel through it is known as an insulator. The electrical insulator is a protector or protective device that finds a use for connecting many electrical components. It plays a notable role in the making of various electrical and electronic circuits and overhead power systems.
The overhead line conductors on the poles are supported by an Insulator, which prevents current flow toward the ground. The transmission lines must function properly. Different materials, such as rubber, wood, plastic, mica, and others, can be used to create an insulator. insulators are available from a variety of Suppliers and Companies, as well as manufacturers and distributors, and there are many Insulators for Sale on Linquip.
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Here, we are describing one of the most significant overhead system’s components and its different types. Read this new blog in Linquip to find out more about types of insulator.
What is an insulator?
Insulators are materials that inhibit the flow of electrical current. They are implemented in household items and electrical circuits as protection and provide the required insulation between the line conductor and earth. Insulators possess high resistivity and low conductivity. In addition to protecting the loss of current, insulators make an electrical current more efficient by concentrating the flow.
Insulator properties
Insulators have some specific properties that make them different from other electrical devices. These are some features of insulators:
High resistivity
Good mechanical strength for the conductor load
The high relative permittivity of insulator material
Good dielectric strength
Waterproof or non-porous
Types of insulator materials
Insulators consist of different types of insulator materials like plastic, rubber, mica, wood, glass, etc. In the electrical system, specific insulating materials are used like porcelain, glass, steatite, polymer, ceramic, PVC.
The importance of insulators
Help to protect from heat, noise, and electricity
Support the overhead conductor
Insulate the live parts of equipment or conductor from the earth
Help to save switchgear, transformer, and other systems in a substation
Types of insulator
4 Main Types of Insulator are:
Pin insulator
Post insulator
Suspension insulator
Shackle insulator
Insulators are classified into different types based on their voltage rating. There are several types of insulators, but the most commonly used are:
Let’s dive in each one-by-one.
An insulator that isolates a wire from physical support, such as a pin on a utility pole or tower, is known as pin type insulator. It is the first developed insulators and being used for overhead lines. As the name suggests, the pin insulator is secured to the cross-arm on the pole. A pin insulator consists of nonconducting material such as porcelain, glass, plastic, polymer, or wood. Pin type insulators find a use for transmission and distribution of electric power at voltages up to 33 kV. Beyond operating voltage of 33 kV, the pin type insulators become too bulky and hence uneconomical.
Pin insulator specifications
It has high mechanical strength.
It requires less maintenance as compared to other insulator types.
Pin insulator pros
Good creepage distance
Simple in construction and cheap in cost
Easy maintenance
Can be used both vertically & horizontally
Applicable to a high voltage transmission line.
The mechanical strength of this insulator is high.
Pin insulator cons
It applies only to transmission lines.
It must be used by the spindle.
The insulator pin can damage the thread of an insulator.
Post insulators are similar to pin-type insulators, but they are more suitable for higher voltage applications. Post insulators are commonly used in the substation or generating substation. They are made in ceramic and also composite material for special applications.
Post Insulator specifications
In a substation, it is suitable from a higher to a lower voltage.
It helps to protect switchgear, transformers, and other connecting devices.
Strong mechanical strength
Can be mounted both horizontally and vertically
A suspension type insulator protects an over headed transmission line like a conductor. It operates at above 33KV and overcomes the limitation of pin type insulator. Mostly, suspension insulator is made of glass or porcelain discs connected in series by metal links in the form of a string.
Suspension insulator specifications
The voltage operating capacity of the insulator is from 11 kV to 765 kV.
Mostly used in the overhead transmission system or line.
It provides more flexibility to the overhead lines.
The multiple discs find usage based on voltage level (low to high).
Generally placed with the steel tower.
Suspension insulator pros
If anyone of the disc insulators in a suspension string is damaged, it can be replaced easily.
Mechanical stresses on the suspension insulator are less since the line hanged on a flexible suspension string.
By using different numbers of discs, a suspension string can be made suitable for any voltage level.
Suspension insulator cons
Suspension insulator string costlier than pin and post type insulator.
It requires more height of supporting structure than that for pin or post insulator to maintain the same ground clearance of the current conductor.
The amplitude of the free swing of conductors is vaster in the suspension insulator system, so it should provide more spacing between conductors.
Shackle type insulator
An insulator that finds use in distribution networks that works with low voltage is known as a shackle insulator. This insulator, that is also known as a spool insulator, is used on sharp curves, end poles, and section poles. Shackle insulator occurs in small size on the overhead distribution system. At present, the usage of this insulator has decreased because of the underground cable used for distribution purposes. It includes a conductor within the groove and can be fixed by using a soft binding wire.
Shackle insulator specifications
It is used in a distribution system by arranging in between tower & conductors to support & insulate.
Can be used in overhead lines with low & medium voltage
It is used with a bolt by placing on the pole otherwise telegraph to avoid outflow current from conductors
Can be used in both horizontal & vertical position.
Shackle insulator pros
Extremely dependable for conductors
Designed to meet up the demands of electricity
The best solution for maintaining protection in different electrical appliances
Bears a high amount of current and temperature
Shackle insulator cons
These apply to low voltage distribution networks only.
Here we provide a table of voltage capacity and use of each types of insulator .
Insulator
Voltage capacity
Use
Pin insulator
< 33 kV
Distribution system
Post insulator
11 kV to 765 kV
Substation system
Suspension insulator
> 11 kV (High)
Transmission system
Shackle insulator
< 33 kV
Distribution system
So, there you have a detailed description of different types of insulator and their specifications. If you have any points to discuss in this article in Linquip, let us know by leaving a reply in the comment section. Is there any question we can help you through? Feel free to sign up on our website to get the most professional advice from our experts.
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It is obvious that if
Overhead line insulators should have the following properties:
high mechanical strength in order to withstand the conductor load, wind load etc.
high electrical resistance in order to minimize the leakage currents
high relative permittivity of insulating material so that the dielectric strength is high
high ratio of puncture strength to flashover
Most commonly used material for overhead line insulators is porcelain. But glass, steatite and some other special composite material may also be used sometimes.
For the successful operation of power lines, proper selection of insulators is very essential. There are several types of overhead line insulators. Most commonly used types are
Pin type insulators
Suspension type insulators
Strain insulators
Shackle insulators
Pin type insulators or pin insulators are popularly used in
A pin insulator is usually made from porcelain, but glass or plastic may also be used in some cases. As pin insulators are almost always employed in open air, proper insulation while raining is also an important consideration. A wet pin insulator may provide a path for current to flow towards the pole. To overcome this problem, pin insulators are designed with rain sheds or petticoats. Beyond operating voltage of 33kV, pin insulators become too bulky and uneconomical.
Insulation failure
An insulator must be properly designed so as to withstand mechanical as well as electrical stresses. Electrical stress on insulator depends on the line voltage, and hence, proper insulators must be used according to the line voltage. Excess electrical stress can break-down the insulator either by flash-over or puncture.
Flash-over: In insulator flash-over, electrical discharge occurs by forming an arc between the line conductor and the insulator pin (which is connected to the cross-arm). The discharge jumps through the air surrounding the insulator following the shortest distance. In case of a flash-over, the insulator continues to act according to its designed capacity unless it gets destroyed due to the excess heat.
Puncture: In case of insulator puncture, electrical discharge occurs from conductor to pin through the body of the insulator. Sufficient thickness of porcelain (or the insulator material) must be provided to avoid a puncture breakdown. When such breakdown is involved, the insulator is permanently damaged.
Safety factor of insulator: The ratio of puncture strength to flash over voltage is called as safety factor. It is desirable to have high value of safety factor so that a flash-over takes place before the insulator gets punctured. For pin type insulators, the value of safety factor is about 10.
As it is already mentioned above, pin insulators become too bulky an uneconomical beyond 33 kV. So, for voltages higher than 33 kV, suspension insulators are used. A suspension insulator consists of a number of porcelain discs connected to each other with metal links in the form of a string. Line conductor is suspended at the bottom end of the suspension string which is secured to cross-arm of the tower. Each disc in a suspension insulator string is designed for a low voltage, say 11 kV. The number of discs in a string depends on the working voltage. Suspension insulators are preferred for
Advantages of suspension insulators
Each unit of disc is designed for a low voltage, say 11 kV. Hence, depending upon the working voltage, desired number of discs can be connected in series to form an insulator string suitable for particular voltage.
If any of the discs in insulator string is damaged, it can be replaced easily. Replacement of the whole string is not required.
In case of increased demand on the line, the line voltage can be increased and the additional insulation required for the raised voltage can be easily provided by adding the desired number of discs in the insulator strings.
As the line conductors are suspended by suspension strings, they run below the earthed cross-arms of the towers. This arrangement provides partial protection from lightning.
The suspension arrangement provides greater flexibility to the line. Suspension insulators are allowed to swing so that they can take up the position where mechanical stresses are minimum.
At a dead end of a transmission line or at a corner or sharp curve, the transmission line is subjected to a great tensile load. In order to sustain this great tension, strain insulators are used at dead ends or sharp corners. For high voltage transmission lines, stain insulator consists of an assembly of suspension insulators. In this case, the suspension string is arranged horizontally and the insulator discs are in vertical plane. Two or more suspension strings can be assembled in parallel to sustain greater tensions. For low voltage lines (less than 11 kV), shackle insulators are used as strain insulators.
Some additional types of insulators are: post insulators, glass insulators, polymer insulators, long-rod insulators, stay insulators etc. Read about these additional types of insulators here
It is obvious that if overhead power lines are not properly insulated from their support poles/towers, the current will flow towards the ground through the poles/towers which also become hazardous. Of course, the power line won't even work in that case! Hence, overhead power lines are always supported on insulators mounted on their support poles/towers.should have the following properties:Most commonly used material for overhead line insulators is porcelain. But glass, steatite and some other special composite material may also be used sometimes.For the successful operation of power lines, proper selection of insulators is very essential. There are several. Most commonly used types areorare popularly used in electric distribution systems up to 33 kV voltage level. They are secured on the cross arms of the pole to carry power lines. There is a groove on the upper end of a pin insulator for housing the conductor. Conductor wire is passed through this groove and secured by binding with the same wire as of conductor.An insulator must be properly designed so as to withstand mechanical as well as electrical stresses. Electrical stress on insulator depends on the line voltage, and hence, proper insulators must be used according to the line voltage. Excess electrical stress can break-down the insulator either byorAs it is already mentioned above, pin insulators become too bulky an uneconomical beyond 33 kV. So, for voltages higher than 33 kV, suspension insulators are used. A suspension insulator consists of a number of porcelain discs connected to each other with metal links in the form of a string. Line conductor is suspended at the bottom end of the suspension string which is secured to cross-arm of the tower. Each disc in ais designed for a low voltage, say 11 kV. The number of discs in a string depends on the working voltage. Suspension insulators are preferred for transmission lines At a dead end of a transmission line or at a corner or sharp curve, the transmission line is subjected to a great tensile load. In order to sustain this great tension, strain insulators are used at dead ends or sharp corners. For high voltage transmission lines, stain insulator consists of an assembly of suspension insulators. In this case, the suspension string is arranged horizontally and the insulator discs are in vertical plane. Two or more suspension strings can be assembled in parallel to sustain greater tensions. For low voltage lines (less than 11 kV), shackle insulators are used as strain insulators.Shackle insulators are used in low voltage distribution lines as strain insulators. A shackle insulator can be used vertically as well as horizontally and it can be directly fixed to a pole with a bolt or to the cross arm. However, the use of such insulators is decreasing after increasing the use of underground cables for distribution purpose.
An insulator is a material that does not allow electricity to flow freely. This is due to the insulator’s electrons being more tightly bonded and unable to move freely. Paper, plastic, rubber, glass, and air are all common insulators. Semiconductors and conductors are non-insulator materials, meaning they can easily conduct electric currents. Insulators have higher resistivity than semiconductors or conductors. They’re mostly used to protect materials that conduct electricity.
For instance, the plastic cover that surrounds the wires stops electricity from flowing where it isn’t required. Furthermore, insulators are utilized to connect power distribution and transmission cables to utility poles and transmission towers. In this article, you’ll learn the different types of insulators used in power transmission lines. You’ll also the advantages and disadvantages of these insulators.
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Standard Insulating Materials Used in Electrical Engineering.
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Contents
Types of Power Transmission Insulators
The following are the common types of insulators used in power transmission lines:
Disc insulators
Post insulators
Pin insulators
Strain insulators
Suspension insulators
Shackle insulators
Stay insulators
Polymer insulators
Glass insulators
Long rod insulators
Disc insulators
These types of insulators get their name from the shape of the insulator, which resembles a disc. In high-voltage transmission and distribution lines, these insulators are utilized. The requisite electro-mechanical strength is met by disc insulators.
Furthermore, they are a cost-effective option for polluted regions with medium to low levels of pollution. Transmission lines and industrial and commercial applications are among the uses for these insulators, which have high-efficiency qualities such as reduced corrosion and a strong design. In suspension and tension systems, they provide insulation as well as support for line conductors. It can also maintain high voltages in heavy-load situations.
Post insulators
This type of transmission line insulator is a high-voltage insulator that can handle a variety of voltage levels, making it ideal for use in substations. These are used to ensure that electricity generated in power plants is distributed safely and reliably.
Post insulators are constructed of ceramic or a single piece of composite material (silicone rubber) and may hold up to 1100 kV of power. Because of its outstanding mechanical qualities, it is commonly used to protect transformers, switchgear, and other connected equipment when mounted vertically.
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Pin insulators
Pin types of insulators are typically seen in power distribution lines. It’s a device that protects a wire from physical support, such as a utility pole pin (wooden or metal dowel). It’s a single-layer, non-conducting shape composed of porcelain or glass.
Depending on the voltage application, one or multiple pin insulators might be utilized on the physical support. The pin insulator is developed with a high mechanical strength material and can carry voltages up to 11kV. These can be positioned either vertically or horizontally.
Strain insulators
These types of insulators are made to withstand the stretch of a hung electrical wire or cable when subjected to mechanical stress. It is used to support radio antennae and overhead power lines, similar to a suspension insulator.
Between two lengths of wire, a strain insulator is used to electrically disconnect them while preserving a mechanical connection. Alternatively, it can be utilized to deliver the pull of wire to support while electrically insulating it when a wire links a pole or tower. The voltage potential of these insulators is around 33kV.
Suspension insulators
Insulators like this are commonly employed as conductors to safeguard overhead transmission lines. The suspension insulator is a type of insulator that is widely used in towers and is composed of porcelain. They have a form string with a succession of insulators linked to it.
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It is hinged on the tower’s cross arm and has a power conductor at its lowest point. When a higher voltage of around 33 kV is required, they are employed. As the size and weight of the insulator increase, the pin insulator becomes more cost-effective. A suspension insulator is utilized to solve these challenges.
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Shackle insulators
Shackle types of insulators are utilized in low voltage distribution systems and are typically tiny in size. This kind of insulator can be utilized both vertically and horizontally. This insulator can be connected with a metal strip and has a voltage carrying capacity of roughly 33 kV.
It has a tapered hole that evenly distributes the load force, lowering the risk of fracture when highly loaded. After the widespread usage of subterranean cables for distribution, the use of insulators has declined recently.
Stay insulators
Stay types of insulators are low-voltage insulators that combine a stay wire and a primary grip to balance and fasten dead-end poles. These insulators are rectangular and come in smaller sizes than other types of insulators.
Between the line conductor and the earth, these insulators can be placed. Furthermore, they serve as protection devices, guarding against abrupt voltage changes due to faults. When the poles collapse to the ground or the stay wires are accidentally damaged owing to increased mechanical load, the value of these insulators is evident.
Polymer insulators
These types of insulators are electrical devices that are typically made of polymer materials with metal fittings. Furthermore, these insulators are enclosed by polymer weather shelters and are formed of fiberglass rods. The insulator core is protected from the elements by weather shades.
Polymer insulators are lighter than porcelain insulators and provide more power. It is generally thought to be a good heat and electrical insulator. Because of its unusual electrical, mechanical, chemical, and thermal qualities, it is utilized as an insulator.
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Glass insulators
These types of insulators are made of annealed or toughened glass that is used in power transmission lines. This insulator’s job is to insulate electrical lines so that electricity does not leak into all of the poles and the ground.
In the past, glass insulators were employed in telegraph and telephone lines, but in the 19th century, ceramic and porcelain varieties took their place. Toughened glass kinds were produced to counter the glass’s frailty, and they quickly became popular due to their extended lifespan.
Long rod insulators
To insulate transmission lines, long rod insulators are commonly hinged on steel towers. Furthermore, they serve as safety devices by properly supplying power. Long rod insulators are usually made up of many insulators, depending on the usage and demand.
On the outside, these are porcelain rods with weather sheds and metal end fittings. This type of insulator has the advantage of being able to be used in both tension and suspension applications.
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That is all for this article, where the common types of insulators used in transmission lines are been discussed. I hope you learn a lot from the reading, if so, kindly share with other students. Thanks for reading, see you around!
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