What are electrical insulators used for?

November 7, 2023


Electrical insulators are essential materials in the electrical field and are used for various purposes. Their primary function is to prevent the passage of electric current, thus protecting people and equipment.

In this article, we will look in detail at all the uses of electrical insulators, their properties, and the various materials used as insulators. So, what are electrical insulators used for?

What are electrical insulators?

In electrical engineering, electrical insulators are defined as those materials that have very low electrical conductivity. Because of this property, insulators are used to prevent current from escaping from conductors and to protect people from electrocution hazards.

Insulating materials have a very high electrical resistivity, on the order of 10^12 to 10^16 Ohms per meter. This means that current cannot flow through them and is confined to metal conductors.

Electrical insulators are opposed to electrical conductors, such as metals, which instead have low resistivity and allow current to flow through them.

What electrical insulators are used for?

Electrical insulators perform several essential functions in electrical engineering. The main uses are:

  • Electrical cable insulation: insulators cover the conducting wires inside cables, separating them and preventing short circuits and current leakage. The most commonly used materials are PVC, polyethene and rubber.
  • Insulation of electrical components: live parts of switches, sockets, plugs, etc., are separated from accessible metal parts by insulators to prevent electrocution.
  • Equipment insulation: inside home appliances, computers, and automobiles, insulators separate live components from parts that the user can touch.
  • Insulators on poles and towers: porcelain or glass insulators used on light poles and high-voltage pylons serve to insulate bare wires from metal supports.
  • Insulation of electric generators: in alternators and electric motors, the windings are insulated from the metal casing to prevent leakage and erosion.
  • Insulation of photovoltaic panels: in photovoltaic systems, silicon cells are encapsulated between insulating layers to protect them and insulate electrical contacts.
  • Transformer insulation: the metal core and windings of transformers are immersed in liquid (oil) or solid insulation to prevent discharges.
electric insulators

Properties of electrical insulators

Electrical insulators must possess specific basic properties to perform their function adequately:

  • Dielectric strength: maximum voltage that can be withstood before an electrical discharge occurs across the insulator. It must be higher than the operating voltage.
  • Resistivity: a measure of resistance to the passage of current. The higher the value, the better the insulation.
  • Dielectric permittivity: the measure of the polarizability of the material in the presence of an electric field. It affects the accumulation of charges.
  • Thermal stability: the ability to maintain insulating properties even at high temperatures. Important for machinery insulations with overheating.
  • Mechanical strength: toughness against impacts, abrasions, and cuts that can damage the insulation. Requirement for cables and mobile equipment.
  • Chemical resistance: the ability not to degrade when exposed to solvents, acids, bases, and weather pollutants. Required in industrial environments.

Materials used as electrical insulators.

There are various types of materials used industrially as electrical insulators. The most common are:

  • PVC: Polyvinyl chloride is the most common material for electrical cable insulation. It is flexible, durable and inexpensive. It has dielectric strengths of 20-40 kV/mm.
  • Rubber: often used for flexible cables and insulation of moving parts. Fair dielectric strength but poor thermal resistance.
  • Polyethylene: used both solid and expanded for insulation of power and telecommunication cables. It has excellent dielectric and mechanical properties.
  • Polyester: used in motor and transformer windings. Excellent thermal stability.
  • Mica: used in sheets or as paint to insulate high voltages. Dielectric strength >100 kV/mm.Expensive.Bakelite: thermosetting resin with high resistivity and dielectric strength.Used for switch supports and insulators.Ceramic and porcelain: used for very high voltage insulators due to high dielectric strength.
  • Glass: glass tubes and beads are used in high-voltage overhead power line insulators. Paper and plant fibres are impregnated with resins to make inexpensive insulators with decent dielectric properties.


Electrical insulators are, therefore essential materials for the operation and safety of electrical systems and equipment at all voltage levels. Their properties enable them to confine and control electric fields and currents, protecting users and preventing short circuits and dangerous leakage.

The choice of the most suitable insulation is made by evaluating factors such as working voltage, operating temperatures, flexibility, and chemical and mechanical resistance according to the specific application for which it is intended. Materials such as PVC, polyethene, mica and ceramics are the most versatile and most widely used.

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