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Реферат Development of Composite Insulators for Overhead Lines

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Текст реферата Development of Composite Insulators for Overhead Lines

Tomsk Polytechnic University
Electrotechnical Institute
Electrical Systems and
Networks Departments
Development of Composite Insulators for Overhead Lines
Made by
Group
Checked by
Tomsk
Cont ents
1. Introduction
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3; . 3 2. Design of composite insulators
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……... . 4 2.1. Structure of composite insulators
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…... 4 2.2 Designing composite insulators
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…….. . 5 3. Predicting service life
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3;.. 1 0 5. Words list
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3;… 11 6. References
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1. INTRODUCTION
Overhead power transmission lines require both cables to conduct the
electricity and insulators to isolate the cables from the steel towers
by which they are supported. The insulators have conventionally been
made of ceramics or glass. These materials have outstanding insulating
properties and weather resistance, but have the disadvantages of being
heavy, easily fractured, and subject to degradation of their withstand
voltage properties when polluted. There was therefore a desire to
develop insulators of a new structure using new materials that would
overcome
these drawbacks.
The 1930s and '40s saw the appearance of the first insulators to
replace inorganic materials with organic, but these suffered problems
of weather resistance, and their characteristics were unsatisfactory
for outdoor use. In the 1950s epoxy resin insulators were developed,
but they were heavy, suffered from UV degradation and tracking, and
were never put into actual service. By the mid-1970s a number of new
insulating materials had been developed, and the concept of a
composite structure was advanced, with an insulator housing made of
ethylene propylene rubber (EPR), ethylene propylene diene methylene
(EPDM) linkage, polytetrofluoro ethylene (PTFE), silicone rubber (SR)
or the like, and a core of fiberreinforced plastic (FRP) to bear the
tensile load.
Since these materials were new, however, there were many technical
difficulties that had to be remedied, such as adhesion between
materials and penetration of moisture, and the endfittings, which
transmit