Wood Pole Overhead Lines
Concentrating on the mechanical aspects of distribution wood pole lines, this informative text includes coverage of live line working, environmental influences, climate change and international standards.
TABLE OF CONTENTS Wood Pole Overhead Lines
Chapter 9: Bare, Insulated and Covered Conductors
9.1 Introduction
This chapter looks briefly at the various types of conductor on the market with particular reference to covered and insulated conductors. Aspects such as current carrying capacity, weather loads and line design have been covered in other chapters. A brief introduction to novel conductors that may be used in the future on wood pole lines is given at the end of the chapter.
9.2 Types of overhead distribution system
There are four basic types of overhead line system in use at distribution voltages:
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bare wire
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XLPE/HDPE covered conductors
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aerial cable systems
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spacer cable concept.
XLPE (cross-linked polyethylene) and HDPE (high density polyethylene) are the two materials of which the sheaths of covered conductors are made.
The range of characteristics that are normally of most importance are:
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electrical
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mechanical
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size
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chemical/physical
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cost
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reliability
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environmental.
Environmental covers susceptibility to wind/ice/snow etc. as well as pollution such as salt.
9.2.1 Electrical
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conductor type high or low conductivity
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current ratings
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thermal uprating.
The conductor material can be a high conductivity copper or aluminium or a conductor designed to give a balance between strength and conductivity. The terms used to describe conductors are given in chapter 8, as well as the thermal treatments that can help to give the desired characteristics. Thermal uprating is of importance as an alternative to re-conductoring or raising the voltage level when higher power levels are required. If a conductor can be raised in temperature without a reduction in lifetime or an increase in sag so much that it...
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