What Is An Insulator?: Material that will not allow electricity to easily flow through

Are you in need of information on Insulators? How about you read this article to get all the required information.

This article has all the details you need on insulators and insulating materials.

For clarity and easy reading, I will begin this article with an overview. After which, I will explain how it works using the energy band.

Furthermore, in the next section, I will discuss insulating materials and classify them according to substance and materials and according to temperature.

Subsequently, I will discuss the types of insulators. Then, I will distinguish between cross-linked polyethylene (XLPE) and polyvinyl chloride (PVC).

Even so, I will state the properties of good insulating materials. Then, I will conclude by providing answers to some frequently asked questions.

What Is An Insulator: Overview

What Is An Insulator_ Overview

In transmitting electricity from the generator plants to the consumer, conductors and insulators play a vital role. Generally, conductors, semiconductors, and insulators are the materials applicable to electrical engineering.

In electronic systems, these three classes of materials come to play fully. The conductors, as you know, allow the free passage of electrons through them.

Also, insulators are generally known as materials that do not allow current flow through them. On the other hand, semiconductors are materials that behave like conductors in certain conditions and like insulators in other states.

In the definition of electricity, the main aim is to transport electrical charges from one point to another.

Considering this, you may ask why we use insulators in electrical and electronic systems since they do not allow electricity to pass through them.

In electrical engineering, an insulator is a material that offers infinite resistance to the flow of electric current. This infinite resistance is the amount of resistance that is much higher than the value of the current.

When the resistance is extremely high, it blocks the flow of current through the insulator. However, if you have a higher current whose value is higher than the insulating material, the insulation will break down, and the material might conduct.

Hence, insulators function properly according to the voltage or current rating of the line they are used.

Furthermore, the essence of insulators in electrical and electronic devices is to prevent current from flowing to unwanted paths. As such, without insulators, there will be a high level of electrocution in electrical systems, especially when it involves non-electrical engineers.

Thus, electricity would not be safe to use. This implies that insulators offer more than 60% safety to electrical systems.

What Is An Insulator: How It Works

Since we have gotten an overview, this section will explain how they work and what gives them infinite resistance to the flow of electrical current.

Unlike conductors, the particles of insulators are held rigidly in place. As such, they do not move around easily and they transfer a minimal amount of energy to other particles.

A good insulator prevents both current and heat from passing through it. Nevertheless, the generation of heat is also an effect of current flowing through a conductor.

I will explain how insulators work using an energy band diagram. The energy band diagram consists of the valence band, the conduction band, and the energy gap.

The valence band is the last band of an atom and they contain valence electrons. These electrons leave the valence band and cross the forbidden energy gap to the conduction band.

If the electrons in the material gain energy that enables it to cross the energy gap to conduction, the material will conduct an electric current. This is common in conductors and semiconductors.

However, insulators have a very wide energy gap, such that when the electrons gain energy, they can not cross the energy gap to the conduction band. Hence, the electric current does not flow.

Furthermore, if you continue applying current and heat to the insulator, the insulating material will break down. Even so, some strong insulators will not melt, but you will feel shocked if you touch the insulator as a result of an electromagnetic field.

This is because the current is too much for the insulator to carry. Thus, the capacity of insulating materials differs. As such, you should not use an inferior one for high voltages and current.

What Is An Insulator: Insulating Materials

What Is An Insulator_ Insulating Materials

Insulating materials are classified according to substances and materials, and according to temperature.

Classification According To Substances And Materials

The classification of insulating materials according to substances and materials identifies the state of matter of the insulating material. According to substances and materials, insulating materials are further classified into solids, liquids, and gases.


Solids are the most popular insulating materials. They are useful in electrical power transmission and distribution lines to carry bare conductors.

Also, they are useful in insulating and sheathing cables like armored cables. Even so, their application includes signal cables. They could be organic or inorganic.

Examples of these insulating materials are mica, slate, quartz, glass, rubber, porcelain, ceramics, cotton, silk, terylene, paper, cellulose materials, etc. Some of these materials serve as dielectric materials in electronic components like capacitors.


Liquid insulating materials are oils and varnishes. In addition to their insulating ability, they also extinguish arcs, which protects the equipment from a potential fire outbreak.

They are used in devices like transformers, oil circuit breakers, etc. These liquid insulating materials include refined hydrocarbon mineral oils, synthetic varnishes, spirit, linseed oil, etc.


The gaseous insulating materials include dry air, argon, carbon dioxide, nitrogen, etc. On transmission and distribution lines, the bare conductors use the air around them as their insulating material.

Even so, the gas insulating materials are also useful in air circuit breakers.

Classification According To Temperature

Insulators are also classified according to their assigned limiting insulating temperature. When current passes through a conductor, it causes a rise in the temperature of the conductor.

This rise in temperature occurs as a result of a heating effect on the conductor due to the current flowing through it. If the temperature goes above that of the insulating material, the insulator will get burnt.

Class Y

This class of insulating materials deteriorates easily. Hence, they are not suitable for electrical machines and apparatus.

They are hygroscopic. Also, they are neither impregnated nor immersed in oil. These insulating materials include silk, cotton, cellulose, wood, paper, etc.

However, they do not operate above a temperature of 90 degrees celsius. They were formally referred to as class O insulating materials.

Class A

This class of insulating materials is impregnated with natural resin, insulating oils, cellulose esters, etc. These insulating materials include laminated wool, varnished paper, etc.

However, these insulating materials can not operate above 105 degrees celsius.

Class E

This class of insulating materials consists of cotton, synthetic resin enamels, and paper laminates with formaldehyde bonding, etc. The temperature limit for this class is 120 degrees celsius.

Class B

The class B insulating materials consist of mica and mica laminates, glass and glass laminates, fiber and fiber laminates, asbestos and asbestos laminates, etc with suitable bonding.

They operate with a temperature that does not exceed 130 degrees celsius.

Class F

The class F insulating materials are class B materials with higher thermal stability bonding materials. Their limiting insulating temperature is 155 degrees celsius.

Class H

The insulating materials in class H are glass fiber and asbestos materials. They also include built-up mica, with silicon resins.

Their limiting insulating temperature is 180 degrees celsius.

Class C

This consist of mica, ceramics, glass, quartz, etc. However, the class C insulating materials have no binders but with silicon resins of higher thermal stability.

Their limiting insulating temperature is above 180 degrees celsius.

The term limiting insulating temperature is the highest temperature at which an insulating material can operate without breaking down.

What Is An Insulator: Types Of Insulators

What Is An Insulator_ Types Of Insulators

From the explanation above, I believe that you know insulating materials. Now, let us talk about the types of insulators.

In transmitting and distributing electricity, insulators play a vital role, even in signal transmission. Thus, I will explain the types of insulators in overhead transmission and distribution lines.

Pin Type Insulator

In overhead lines, electricians mount the pin-type insulator on the cross-arm of a pole with the aid of a pin. The pin insulator has a groove on its upper end.

More so, the conductor passes through this groove and engineers tie the conductor to the insulator with a few strands of wire. Also, these few strands of wire must be the same material as the conductor.

Furthermore, they are useful in the transmission and distribution of electric power at voltages of about 33kV.

Although, some of these pin insulators can be useful on transmission lines of voltages ranging from 33kV to 69kV. However, these types of insulators are always bulky and uneconomical.

Post-Type Insulator

The post-type insulator is an insulator in the 1930s that is more compact than the pin-type insulator. They replace the pin-type insulators on lines up to 69kV.

However, some configurations can operate on a 115kV line.

Suspension Insulator

In practice, it is usual to use suspension insulators on lines greater than 33kV. These insulators usually consist of several glasses or porcelain discs with a serial connection by metal links in the form of a string.

You suspend the conductor at the bottom end of the string. Also, you secure the top end to the cross-arm of the tower.

However, the voltage of the line determines the number of disc units.

Strain Insulator

The strain insulator is used in a dead-end or anchor pole or tower, where the straight section of a line ends. It is also applicable where the line angles off in another direction.

However, these poles must be able to withstand the mechanical stress as a result of the horizontal tension of the line. Nevertheless, shackle insulators can be used as strain insulators for low voltage lines less than 11kV.

Also, suspension insulators can replace the strain insulators on high voltage transmission lines. In the case of exceedingly high tension like long river spans, you can use two or more strains in parallel.

Shackle Insulator

The shackle insulators were used as strain insulators in the early days. However, they are used for low voltage lines for distribution nowadays.

You can arrange them in a position either horizontally or vertically. Also, you can fix them to the pole with a bolt or to the cross-arm.

Bushing Insulator

Bushing insulators enable one or several conductors to go through a partition like a wall or a tank. Hence, it insulates the conductors from the body of the tank, such as transformers.

Glass Insulators

These are products of glass. They had been in use since the 18th century in telephone/telegraph lines.

Even though porcelain and ceramic insulators took it over in the 19th century, its toughened forms made it more durable.

Polymer Insulators

This type of insulator consists of s fiberglass rod and polymer weather shed a layer. More so, this polymer weather shed is a product of silicon rubber, although it can also be a product of other substances.

They are about 90% lighter than porcelain types of are almost equal if not better in strength.

Long Rod Insulators

A long rod insulator consists of a porcelain rod, an outside weather shield, and metal end sections. This long rod model improves the insulating strength by removing metal components between its units.

You can use these long rod types for suspension cases and tension locations.

Stay Insulators

The use of a stay insulator is at the end of a distribution line with a stay wire. Also, this stay wire aims to hold the last pole in the distribution line erect.

Click here to read more on the types of insulators and the effect of air and moisture on insulation.

What Is An Insulator: PVC Vs XLPE

What Is An Insulator_ PVC Vs XLPE

Now that you know the types of insulators on transmission and distribution lines, it is necessary to also know about PVC and XLPE. These are plastic products that provide insulation in electrical cables and wires.

Polyvinyl Chloride (PVC)

Polyvinyl Chloride (PVC) is a thermoplastic material with high strength. It is applicable in the production of pipes, medical devices, wire and cable insulation, etc.

Also, pure PVC is a white, brittle solid that is insoluble in water and ethanol. However, it is slightly soluble in tetrahydrofuran. Its chemical formula is (C2H3Cl)n.

Polyvinyl Chloride (PVC) comes in 2 forms. These are the rigid and the flexible form.

The rigid form is used in the production of pipes, bottles, plastic cards, etc. However, pipes produced from PVC are used in electrical engineering for conduit wiring.

Conduit wiring is a system of electrical installation in which the wires are buried inside the wall using pipes. Thus, the wires are not visible.

On the other hand, flexible PVC is used in electrical cable insulation, imitation leather, flooring, etc. These cables are used on low voltage lines as service cables as well as in domestic installation.

Cross-Linked Polyethylene (XLPE)

This is a thermoset material that provides insulation in an electrical system. It is a product of crosslinking polymers.

The process of crosslinking polymers changes the molecular structure of polymer chains. Done either by physical or chemical means, this process makes polyethylene materials more tightly bound together.

Also, it has high thermal insulation qualities that make it useful in both high voltage and low voltage lines. It has excellent electrical, thermal, and physical properties.

Even so, it can resist moisture, flame, crush, and heat deformation. However, they can withstand temperatures up to 120 degrees celsius.

Properties Of A Good Insulating Material

Properties Of A Good Insulating Material
  • It has high dielectric strength.
  • Also, it has infinite and specific resistance to the flow of current and heat.
  • Even so, its mechanical strength should be high.
  • More so, it should be able to resist high temperatures.
  • In addition, it should not absorb water.
  • It can not be easily set ablaze.
  • Lastly, it can come in any shape.

What Is An Insulator: Frequently Asked Questions

Frequently Asked Questions
What is an insulator’s simple definition?

An insulator is a material that is a poor conductor of heat, sound, or electric current.

What is the difference between an insulator and a conductor?

Conductors are materials that allow the free flow of electrons through them. Contrary to conductors, insulators do not allow electrons to flow through them freely.

What is a conductor?

A conductor is a material or substance that allows electric current to pass through them. When you apply voltage to a conductor, electrical charges will flow.

What are the 3 types of insulation?

Cellulose, mineral wool, and fiberglass are the most common types of loose-fill insulation materials.

What is a heat conductor?

It is any material that allows heat to pass through it easily.

Is plastic an insulator?

They can trap heat efficiently. Thus, plastics are good insulators.

Is a vacuum a good insulator?

Due to its complete lack of atoms, vacuum is the best-known insulator.

Why are plastics a good insulator?

Plastics have no free electrons in their conduction band. As such, there is no conduction mechanism.
Therefore, plastics are poor heat and electricity conductors.

Is air an insulator?

Even though air can transmit heat via convection, it is generally a good thermal insulator.

What are insulators made of?

Insulators used in the transmission of high voltage are products of glass, porcelain, or composite polymer materials.

What Is An Insulator: My Final Thoughts

What Is An Insulator_ My Final Thoughts

This article explains everything you need to know about insulators. However, I expect you to open every link on this article to broaden your level of understanding.

Insulatorsprevents the system from leakage and provides protective boundaries for current to flow. Hence, they play a great safety role in any electrical or electronics system.

However, if you have read through this article line by line, then you have every information you desire to have about insulators.

I hope you found this article helpful. Kindly, fill out the “Leave A Reply” form to share your thoughts.

However, kindly visit our tech-explained categories for more of these kinds of articles.

Christian Jerome
Akan Christian writes for PowerVersity.com. He holds an HND in Electrical/Electronic Engineering. Christian enjoys reading, listening to solemn music, singing, and playing sports. For PowerVersity.com, Christian writes reviews, buying guides, and best pick articles.


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