Use Aluminum Wire or Tubular Busbar

And the "tubular busbar" is made from what material?

Dear sir

tubular busbar also aluminum

Regards

So then, building on what RAMConsult said about skin effect, which choice would have more, "skin"?

That would be the one I'd use, but I'm not into electricity.

Google on "Skin Effect" and apply what it says to answer your question.

Like all things in life it depends on the application.

For high voltage substations use tubular bus bar.

_{Jack - We design and build tubular aluminium substation bus bar systems.}

Dear sir

thank you very much

but we have existing sub station 400kV consist of Four diameters all diameter are

tubular aluminium .one company added new fifth diameter

and made of aluminum wire .please What is the difference between them?

Regards

Without seeing the site it is hard to say, but both systems have their advantages and disadvantages depending on the site (cost, flexibility, structural support ease over long distances, wind loading, thermal expansion, connection, life, transport and erection on site, etc).

Tubular is better overall, but not best for all situations. Perhaps cost was the driving factor for the fifth run, or perhaps something on the site made bus bar too difficult to fit.

Is there some reason why the company that installed the fifth item cannot be contacted by telephone directly?

As was already said, for each application you have to choose the suitable system and material. For voltage above 230 kV, tubular aluminum is preferred due to reduced skin effect and corona losses. See for instance:

Bus Conductor Design and Applications

Usually all substation design group has a software in order to calculate the efforts and choose the switchyard -included short-circuit current dynamical resistance and so on.