Polymer insulator (composite) is an electrical device
consisting of insulation section made of polymer materials and metal fittings.
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| Polymer Suspension Insulator |
Polymer Insulators are characterized by small size, light
weight, high mechanical strength, no zero value detection, easy installation
and less maintenance have become a new generation insulators for high voltage
transmission lines.
Polymer Insulators, just like its porcelain counterparts
have two basic purposes on transmission lines:
1. To support conductors and attach them to structures
2. To electrically isolate conductors from other components
on a transmission line
The second purpose is very important to operation since
without some form of insulating material, electrical circuit cannot operate and
any insulation deficiency oftentimes would result to trouble, say flashovers.
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| Polymer Insulators |
Polymer Insulators differs in the fact that the protective
ribbed mold is made of silicon organic rubber. The insulation unit is still
made of fiberglass as well as flanges are made of antitrust alloy thus providing
safe long-term operation under various climatic conditions.
Three major parts of polymer insulators:
2. Insulation core unit – a rod made of composite dielectric
substance – fiberglass, as a rule (tar reinforced with fiberglass) or
consisting of separate elements assembled at the unit in a particular order.
3. Insulator fittings – flanges (end terminals) and screen
fittings.
Polymeric Insulators
Composition
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| Polymer Pin Insulator |
Polymer insulators have been increasingly accepted by
electric utilities as suitable replacements for porcelain and glass insulators
since it was first introduced early 70s. Polymers that comprise the insulators
are ethylene propylene polymers. The type of polymers that are used as
insulators could either be EPR, EPDM, or Silicon Rubber.
EPRs are among the best weathering resistant synthetic
polymers. It has excellent electrical, chemical and mechanical properties with superior
aging and color stability. In general
all EPRs have outstanding resistance to heat, oxygen, ozone and sunlight. In fact, the resistance of EPDM rubber to sunlight
is rated equal to that of silicone rubber.
Silicone rubber but it are resistant to sunlight heat and are
flexible over a wide range of temperatures.
Silicone rubber is a hydrophobic material (repels water). But, unlike the EPR backbone, the
silicon-oxygen bond is susceptible to attack by acids and bases.
EPDM/Silicone Alloy is an alloy developed by some insulators
manufacturers. They combined the best properties of these two materials and call
the compound ESP.
How to Specify
Polymer Insulators
Polymer Insulator specifications are basically similar to
that of porcelain. The two basic components of its specifications are the
Mechanical and Electrical Characteristics.
Depending on the type of insulators here the different specs
requirements
Mechanical
Tensile Strength
Cantilever Strength
Vertical, Transverse, Longitudinal Load Requirements
Weight
Electrical
Voltage Class
Length
Arcing Distance
Leakage Distance
Impulse Withstand Voltage
Low Frequency Flashover
Also during specifications, it is important to specify the
end fittings, or terminals, so that there will be consistencies in the lines hardware
that you are going to use.
More of Polymer Insulators and its comparison to porcelain
on the succeeding post.
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