Increase transmission line voltage to over 500KV

[frankiee]

In Ontario Canada, why cant 500 KV transmission lines be upgraded by adding a transformer uping the voltage to lets say 700 KV with the existing lines?
Instead of building a new power corridor.
Is there a law that states the max voltage?

 

[Overvoltage]

Lots of reasons:
1. There may not be sufficient clearance on the line as-built for the higher voltage to avoid arcing to the earth or other corona effects.
2. The equipment may not be designed (insulators, buswork, breakers, etc) to handle the higher voltage and would have to be rebuilt at the higher rating.
3. As you get into the UHV designs, often the line configurations change drastically to avoid corona effects, audible noise, and other issues, that may be entirely different than the current 500kV line configuration.

It is not unheardof that a line can be rebuilt to a higher voltage, but often it has been designed to the higher voltage in the first place but operated at a lower voltage for a period. Otherwise, a significant amount of rebuilding may be required, and often it is not much more expensive to build a completely separate line on a different right-of-way and also be able to maintain the existing line to maintain power flows.

 

[itsmoked]

500kV lines run things like states and major cities. So turning them off for long enough to change lots of stuff isn't an option. And lots of stuff would need to change to increase the voltage 50%.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davidbeach]

Keith, there is no line that can't be turned off; a basic aspect of contingency planning. As Overvoltage indicated, unless the line was originally designed for the higher voltage it would take a total rebuild and that isn't likely to happen. That's why there is still a tremendous amount of 230kV transmission because conversion to 500kV in not practical.

 

[itsmoked]

You could turn off the western interstate tie for several months?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davidbeach]

Unplanned loss of the DC, if that is what you are talking about, can have profound impacts because at times it runs in an N-0 contingency case. On the other hand it was out for many months following the '94(?) earth quake. The 500kV AC component of the intertie relies on four lines. Scheduled outages are also much easier to deal with than sudden unplanned outages.

Besides turning off the intertie would generally have no impact on the side of the California-Oregon border that has generation; it would only impact the side that won't build a sufficient amount of generation.

 

[itsmoked]

I was referring to the 500kVAC stuff that runs up the center of CA. Thanks.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

And if you build a new line you will probably keep the old one in service. You will have two lines instead of one. Some of the benefits are less total losses and the greater redundancy of two lines instead of one.


Bill
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"Why not the best?"
Jimmy Carter