substation

HOW TO SELECT INSULATORS FOR POLLUTED ENVIRONMENTS

2025-11-17 15:08

In recent years, with the substantial increase in electricity demand, utilities must enhance the efficiency of their transmission lines to avoid economic losses caused by power line failures. Investigations have revealed that insulator flashover is one of the causes of power supply interruptions. 

  • What's the flashover in the insulator?

The insulator begins to fail when the pollutants that exist in the air settle in the surface of the insulator and combine with the humidity of the fog, rain, or dew. The mixture of pollutants, plus the humidity form a layer that can become conductor and allow passing currents that will facilitate the conditions of short circuit. This is due to a decrease of the resistance of the insulator surface. Unless there is a natural cleaning or an adequate maintenance, the electrical activity will be affected by a possible flashover in the insulator. 

porcelain insulators

  • Three main types of pollution:

  1. Industrial pollution

  2. Marine pollution

  3. Desert pollution

According to IEC 60185, procelain insulators and glass insulators are selected for three phase a.c. systems.


Pollution levelExamples of typical environments
I-Light

  • Areas without industries and with low density of houses equipped with hcating plants

  • Areas with low density of industries or houses but subjected to frequent winds and/or rainfall

  • Agricultural areas

  • Mountainous areas

All these areas shall be situated at least 10 km to 20 km from the sea and shall not be exposed to winds directly from the sea

II-Medium

  • Areas with industries not producing particularly polluting smoke and/or with average density of houses equipped with heating plants

  • Areas with high density of houses and/or industries but subjected to frequent winds and/or rainfall

  • Areas exposed to wind from the sea but not too close to the coast (at least several kilometres distant)

III-Heavy

  • Areas with high density of industries and suburbs of large cities with high density of heating plants producing pollution

  • Areas close to the sea or in any case exposed to relatively strong winds from the sea

IV - Very heavy

  • Areas generally of moderate extent, subjected to conductive dusts and to industrialsmoke producing particularly thick conductive deposits

  • Areas generally of moderate extent, very close to the coast and exposed to sea-spray or to very strong and polluting winds from the sea

  • Desert areas, characterized by no rain for long periods, exposed to strong winds carrying sand and salt, and subjected to regular condensation


For a.c. porcelain and glass insulators, a utility would typically specify maximum connection length taking into account live line work, minimum dry arcing distance, and minimum creepage distance. Then, it would be stated that insulator profile must comply with IEC/TR 60815, the focus being on simplicity and ease of use.



Get the latest price? We'll respond as soon as possible(within 12 hours)
This field is required
This field is required
Required and valid email address
This field is required
This field is required
For a better browsing experience, we recommend that you use Chrome, Firefox, Safari and Edge browsers.