what are criteria for selecting 500KV conductor

[apple001]

what are criteria for selecting 500KV conductor in electrical transmission system.thanks

 

[mpparent]

How about ampacity for one?

Mike

 

[apple001]

thanks,any other ideas please?

 

[RalphChristie]

Would it not be basically the same for all kinds of lines?

Some other criteria:
Short circuit capacity
Environmental factors (maybe corrosive and salt-laden atmospheres require certain conductors)
Sags and tension (limited by the strength of the conductors)
Cost factors
Future growth
etc.

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[jghrist]

Also corona. This will require larger diameter conductor.

Bundled conductors are used to reduce surge impedance.

 

[cuky2000]

Other factor that affect the conductor selection are audible noise (AN), communication interference (RI, TV), electromagnetic field, losses (corona, dielectric, ohmic), mechanical strength, environment conditions (wind speed, snow, ambient temperature, altitude, sun radiation,), economic factors, etc.

Beware that transmission lines are typically operated under the cable ampacity rating to satisfy its thermal limit, voltage drop or stability limits.

 

[fsmyth]

"Bundled conductors are used to reduce surge impedance."

Could you expand on this a bit? Sounds backwards.
<als>

 

[jghrist]

The surge impedance is sqrt(L/C). Inductance L is proportional to the log of phase spacing divided by self-GMD. Bundling increases the self-GMD thus decreases the inductance.

 

[tinfoil]

Some conductors are made to be 'smoother' on their outside to minimize corona.

Longer spans for 500kV may also dictate stronger (more or better steel in the core) conductors.

 

[cuky2000]

All line impedances parameters are heavily influenced by the geometric of conductors such as subconductor radius, number and spacing of subconductors, conductor spacing and shield wire(s) and phase conductor clearances.

The characteristic impedance, Zc and the inductive and capacitive reactance (Xl & Xc) are all reduced with the increase of the equivalent bundle conductor radios. For the same reason, the line loadability, expressed as a function of the surge impedance load (SIL), will increase for the same voltage level of a particular transmission line configuration.

The enclose example may be used to illustrates how the bundle conductor radio will help to increase the SIL.

http://cuky2000.250free.com/SIL.jpg

I hope this help to clarify this concept.