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Sedicoat A story of hydrophobicity

We are continuing our journey through the pollution and how does it impact the performance of T&D overhead lines.

First you need to understand what is pollution and how characterized it by reading our Pollution Starter Kit.

What is pollution?

After many years of operations a series of elements can be deposited over the surface of the insulator. All these elements can have an impact on the performance of the string and may lead to a flashover…

bird pollution
industrial pollution
corrosive environment

How flashover occurs in polluted environment?

In contaminated conditions, contaminants deposit on the insulator surface can lead to the formation of a conductive layer, resulting in a flow of leakage current, dry band formation and, under certain conditions, flashovers.

  1. Pollution is deposited on the insulator surface
  2. Solid layer (A) is wetted by rain, dew, fog etc..
  3. Surface leakage current in the pollution forms dry bands.
  4. Localised drying causes partial flashover of dry bands
  5. If the resistance of the remaining layer is low enough, arcs can extend along the insulator
  6. Flashover

How avoids any flashover?

Several solutions can be used to avoid any flashover in polluted environment.

The first one is to wash regularly the insulators, but this solution is expensive and not safe for the linemen.

Another solution is to use RTV coating over glass insulators.

How Sedicoat insulator RTV silicone coated glass limits flashover appearance?

A drop on a hydrophilic surface
  A drop on a hydrophobic surface (like Silicone).

The water repellent property of the RTV coating keeps the water droplets apart on the surface of the insulator: no formation of conductive water film on the surface.

Leakage currents are reduced on the surface of the insulator:

  • No dry band
  • No flashover

But what is the point of coated glass?

Sedicoat insulator = Toughened Glass Insulator with a coating

You will keep the unique property of TGI under its silicone layer: Binary status due to the toughening process, with no hidden puncture or crack.

the only material which allows a complete, reliable “at a glance” inspection from a distance. Safest maintenance with no need for any instruments or emergency maintenance.

Reliable “at a glance” inspection

Benefits of glass insulators with silicone coating

Specific properties of Silicone

  • Eliminates the need for insulators to be washed regularly
  • Eliminates the risk of flashover due to pollution

Inherent properties of toughened glass

  • Infallible visual inspection
  • Safe live-line working
  • Long-term reliability

Do not require any line design modification

To discover more about Sedicoat, please see our product section.