In the past many years, a large variety of polymeric
insulating materials have been developed, but only some have shown success in
outdoor insulation. Now days, there are basically three classes that are in
significant used:
1. Epoxy resins
2. Ethylene propylene rubbers
3. Silicone rubbers
Epoxy resins for polymer insulator
The epoxy resins have shown successful long term performance
in clean environments, but under contaminated conditions their performance has
been far from satisfactory. Therefore, epoxy resins use has been restricted to
specific conditions. They are suitable for distribution class insulators up to
about 69kV.
Ethylene propylene rubbers for polymer insulator
Three types of ethylene rubbers are in use for outdoor
polymer insulator:
1: ethylene propylene monomer (EPM)
2: ethylene propylene diene monomer (EPDM)
3: co-polymer of ethylene propylene and silicone (ALLOY)
They are suitable for insulators up to 765kV. Their long
term performance has been successful in clean environments.
Silicone rubber for polymer insulator
Silicone rubber has proven to be the most reliable polymer
material for outdoor electrical insulation. It has three common types:
1. room temperature
vulcanized(RTV)
2. high temperature
vulcanized(HTV)
3. liquid silicone
rubber(LSR)
Silicone rubber is able to maintain their hydrophobicity for
longer periods of time. This is very important as it has the ability to
suppress leakage current activity therefore preventing flashover and power
system outages. Todays ,the trend is toward using silicone rubber for the
housing of all types of overhead line polymer insulators.
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