[NTYNUT (OP)]

hello
how electricity tower are designed ?
there is lot of iron and wire on it how should we design it

[chris]

 

how electricity tower are designed

Do you mean "pylons" - the free-standing, tall, metal structures that support overhead cables?

[NTYNUT (OP)]

hello
how it is design yes

[alancalverd]

Start with the statutory clearance of the conductors from each other and whatever they pass over.

Specify the conductors according to the intended maximum working current

Calculate the insulator length required for the voltage and assumed weather conditions

Calculate the catenary drops between pylons for the specified design tension of the conductors

Design the simplest tree structure (single vertical insulators) required to support a straight run, allowing for windage and the weight of the wires between pylons

Calculate the straight-run pylon spacing required by the clearance, insulator lengths and catenary drops

Determine the maximum tolerable angular deflection between adjacent straight runs

Design the tree structure required to anchor each turn that exceeds that value (pairs of horizontal insulators)

Consider whether additional tensioning or tension relief trees (horizontal insulators) are required between the simple trees

Design any junction or terminal trees that may be required

Now go to an applied maths textbook and look up "just stiff structures" to support the outline trees you have drawn

At this point the geologists, accountants, countryside preservation planners and electrical load planners will tell you that the proposed route and capacity have changed.

[evan_au]

AC transmission towers carry power wires in multiples of 3, for 3 phases.

High Voltage DC transmission towers carry power lines in multiples of 2.

The distance between the wires, and between the wires and ground is calculated to be above the breakdown voltage of air (on a rainy day).

The height of the wires above the ground or trees is calculated for the hottest day, when everyone has their air conditioners on maximum, as the wires sag more when they are hot. A program of active tree lopping stops the trees from growing up into the wires.

Above the power conductors, there is usually a lightning arrestor wire, to redirect lightning away from the power-carrying wires.

As you mentioned, often optical fibers are installed in the towers too - and often mobile base stations.

The steel structure and foundations must be strong enough to support the weight of the wires, plus wind forces, and any sideways forces if the transmission line takes a bend.
See: https://en.wikipedia.org/wiki/Transmission_tower

Ooops... overlap with alancalverd

[NTYNUT (OP)]

Calculate the insulator length required for the voltage and assumed weather conditions

how to calculate insulator length 

[alancalverd]

Talk to the manufacturers.

There are all sorts of patented designs for various applications. You probably wouldn't need an ice-storm-resistant insulator to cross the Sahara but whilst it would be a sensible precaution in Canada, Iceland or even Shetland, it's probably not necessary in East Anglia. That's where the accountants, meteorologists and geologists come in: at some point it may be more sensible to bury a megavolt DC cable rather than run a 400 kV 3-phase on pylons.

[evan_au]

Another factor relates to oscillations in the wires. Wind will cause the wires to sway from side to side, and the wire spacing must not let the wires to get too close to each other, or the metal tower.

If you look at wires between towers, you may see some weights or spacers attached to the wires. I expect this is intended to break up oscillations in the wires.