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 16: Line and Component Susceptibility to Weather Effects
16.1 Scope
16.1.1 Components
The various components of an OHL that will be considered are:
-
conductors
-
insulators
-
poles
-
supports and fittings
-
foundations
-
pole-mounted transformers
-
pole-mounted switchgear
-
lightning protection arc gaps
-
lightning protection surge arresters
-
line design.
16.1.2 Weather environment
The weather effects that will be considered are:
-
lightning
-
snow
-
ice
-
wind gales
-
wind low wind speeds
-
pollution
-
temperature
-
others.
Lightning is covered in detail in chapter 18; however, the effects on particular components are also covered briefly here for the sake of completeness.
16.1.3 Procedure
Each OHL component will be considered for all relevant weather effects. There will inevitably be an interaction with other components. These will be considered at the time and backreferenced later.
16.2 Conductors
16.2.1 Lightning
Lightning can affect overhead lines, either by:
-
direct strike, causing the lightning strike current to travel along the conductors until a route to earth is found
-
an indirect strike where a voltage surge is induced in the line by the magnetic field associated with a strike to an objector ground near the line.
16.2.1.1 Bare conductor
Direct strike
Neither a direct nor indirect strike to a line will cause conductor damage directly, except in extremely rare occasions in the case of a direct strike with a high strike current (>100 kA), where localised heating at the struck point may be sufficient to cause strand failure. This has sufficiently low probability not to be considered as part of a condition assessment.
Local arcing
Lightning overvoltage surges on OH lines can cause air breakdown across insulators at...
Copyright The Institution of Electrical Engineers 2005 under license agreement with Books24x7
