How to Test the Integrity and Performance of Electrical Insulators Over Time

February 6, 2024

Introduction to Electrical Insulators

Electrical insulators are materials that impede or limit the flow of electric current. They are essential to ensure safety and efficiency of electrical systems. However, over time, insulators can degrade and lose their insulating properties, with the risk of generating short circuits, current leakages and overheating. It is therefore critical to periodically test their performance.

In this article we will analyze the most effective methods to check the integrity and performance of electrical insulators over time, with a specific focus on the polymeric and composite materials most widely used in industrial and civil applications.

electrical insulators

Why Testing Electrical Insulators is Important

Insulators are materials designed to withstand the passage of electrical current. However, during their service life, they can be subjected to electrical, mechanical, thermal and environmental stresses that undermine their insulating properties.

The main degradation mechanisms of insulators include:

  • Thermal and oxidative aging
  • Dielectric and partial discharge stresses
  • Moisture absorption
  • Chemical aggression
  • Mechanical stress

The degradation of the insulator can lead to an increase in its electrical conductivity, with greater current losses, overheating and eventually faults and short circuits. To prevent these problems it is essential to periodically perform tests to check their integrity and performance.

Non-Destructive Testing Methods

There are several non-destructive methods that allow assessing the condition and properties of insulators without damaging them. Among the most utilized:

  • Dielectric strength measurements – provide indications on the dielectric strength of the insulator by subjecting it to increasing voltages up to breakdown.
  • Partial discharge measurements – detect minute current losses due to micro cavities or flaws within the insulator.
  • Dielectric spectroscopy – analyzes dielectric properties versus frequency to investigate polarization and conductivity.
  • Thermographic analysis – locates localized overheating due to high dielectric losses.
  • Aging index evaluation – combining dielectric, mechanical and chemical data to estimate the residual life of the insulator.

Laboratory Testing on Specimens

In addition to field testing, destructive analyses can be performed on specimens in the lab to obtain detailed information on the condition and performance of insulators:

  • Tensile, flexural and hardness testing – to evaluate mechanical properties and embrittlement.
  • Water absorption measurements – to estimate the tendency for aging in a humid environment.
  • Thermal analysis DSC, TGA, DMA – provide indications on thermal stability of the material and its glass transitions.
  • FTIR spectroscopy – detects chemical modifications and oxidative degradations.
  • Optical and electron microscopy – to analyze defects and cracks at the micro and nanostructural level.


The periodic verification of the conditions and performance of electrical insulators is essential to ensure reliability and safety of electrical systems. Non-destructive testing techniques and lab analyses allow monitoring the aging state of insulating materials and preventing catastrophic failures. It is advisable to rely on specialized laboratories to perform these tests in accordance with the applicable technical standards.

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