15-11-2012, 06:18 PM
An Overview on Transmission Towers
An Overview on Transmission.pptx (Size: 2.47 MB / Downloads: 82)
Introduction
The transmission lines are the connecting links between generating stations and distribution systems.
Since the rate of growth being greater in the developing countries which in turn had led to the increase in the number of power stations, so consequent increase in power transmission lines and towers was observed.
This presentation deals in detail about towers and their renovation techniques for improvisation.
Tower components:
Peak –It supports ground wire.
Cage-In between peak & tower body.
Cross arm-It supports conductors.
Bracing-To resist lateral loads.
Towerbody-Mainportion which connects cage & foundation.
Body Extension-For more clearance.
Stub-It projects tower body into the foundation.
Types of Towers:
General classification as follows:
Self supporting -They are rigid in both longitudinal as well as transverse directions. Normally they are vertical configured.
Self supported wide base-Horizontally configured.
Flexible-They are not rigid in the transmission cable direction
Guyed type-They are grouted into the surrounding area in tension.
Classification as per IS:802(part-I)-1977 code of practice :
Tangent towers -(2° line deviation)
Small angle towers -(10° line deviation)
Medium angle towers -(30° line deviation)
Large angle towers -(60° line deviation)
Renovation techniques:
Some methods of renovation and strengthening are as follows:-
To install pre-tensioned guy wires at midpoint and at one quarter heights to provide additional stiffness.
To insert additional horizontal diagonal elements at every one quarter height of the tower to create diaphragms.
To assess overload factors by computing a ratio of maximum stresses versus allowable stress used in design.
Failed connections can also be strengthened by using new stiffeners and bolts at failed joints.
Conclusions:
The renovation of towers requires a non-linear analysis, and redesign of connections, and replacement of some elements.
Buckled elements could be replaced with new connections could also be replaced, where they have failed.
Horizontal tie members will help form diaphragms at top and middle height of towers.
The software indicates that under a certain wind speed and direction, the tower will fail: but guying and bracing the tower will help to resist lateral forces which will reduce the leg loads to acceptable levels.