November 15, 2021

IEC60383:Definitions of insulators

The definitions of insulators here refer to the circumscription of the electrical insulators on overhead power lines or high voltage power substations in standard IEC 60383-1:1993.

Why should we clarify the definitions of insulators?

Because in IEC 60383 standard, it describes each test, whether a mechanical or electrical test, that should be carried out. And these tests to insulators are designed and applied according to the different types, materials, or purposes of insulators. We shall make clear what they are, and that’s why the definition should be the basic knowledge and the very beginning of IEC60383.

Is this the only definition of insulators we have in IEC?

Not really. Here’s what IEC 383 writes:

The definitions given below are those which either do not appear in IEC50(471)or differ from those given in IEC 50(471).

Quoted from IEC official site

What types of insulators do we have in IEC 60383?

There are 4 major types listed in the standard.

  1. Insulator string
    One or more connected string insulator units intended to give flxible support to overhead line conductors and stressed mainly in tension.
  2. Pin insulator
    A rigid insulator consisting of an insulating component intended to be mounted rigidly on a supporting sutrcutre by means of a pin passing up inside the insulator. The insulating component may consist of one or more pieces of insulating material permanently connected together. The fixing of the insulating component to the pin can eighter be separable or permanent (pininsulator with integral pin.)
  3. Line post insulator
    A rigid insulator consisting of one or more pieces of insulating material permanently assmebled with a metal base and sometimes a cap intended to be mounted rigidly on a suppoirting sutrcture with the metal base attached by means of a stud or one or several bolts.
  4. Traction insulator
    And insulator or insulator set intended to give flexible or rigid support for overhead electric traction lines. All types of overhead line insulators may be used for this purpose.

So, from the above text, we can see the 4 types include insulators that we commonly see in electrical power transmission, distribution, and substations. If you feel the words are difficult to understand, let’s put it in this way with some images:

  1. Insulator string means normally the string include more than one insulators. And for most of the time, it is a collection of tension insulators. For exmaple, it can be several pieces of ceramic disc insualtors, glass disc insulators,or some connections of polymeric insulators.

2. Pin insulator usually appears on top of the tower. It gives a supporting force from the downside fighting against the gravity of the conductor. Due to this purpose, the metal connection part is different from tension insulators.

11kV composite insulator pin type

Let’s see an example. This is a pin insulator, its housing material is silicone rubber, which is also known as polymer. It’s mounted on the tower of 11KV overhead power lines.

3. Line post insulator often serves in power substations or transmissions. It supports a much bigger conductor or switch. Thus it’s bigger in size and bears a bigger bending or torsion force.

4. Traction insulators are the most common types of insulators. From the photos in explanation 1, you may see the ceramic disc insulator, glass disc insulator, or polymeric insulator, they are all traction insulators. They have this name because they are used in traction line and usually works by supporting tension load.

Above all, these are the 4 definitions of insulator types in section 1 of IEC 60383-1:1994. In the rest part of IEC 383, we will gradually introduce different tests to insulators, including test purpose, test methods, acceptance criteria, and etc. We will also give reader recommendations of test equipment to carry out the tests, as well as operations. We also give an example of test equipment. The below link is a tensile testing machine for mechanical tension tests of traction insulators.

Insulator Test Machine for Tensile Test | ContuneINTL (

For more test equipment of insulators, please view “Our products” – “Insulator test equipment“column

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About Tester of HV insulator

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