Maximum Continuous System Voltage

[cuky2000]

1) Why the maximum rated continuous voltage at 500 kV is 10% above nominal system while all other voltages are limited only to 5%?

2) There is any overvoltage vs. time curve available?

Any reference or standard number could be helpful

Thanks

 

[waross]

It's nice to see you back in the forum Cuky. Welcome back.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[dpc]

I think ANSI C84.1 would be the applicable standard in the US. But I can't seem to find our copy.....

dpc

David Castor

http://www.cvoes.com

 

[cuky2000]

Hello friends

I am glad to be back.

Appears that the ANSI/NEMA C84.1 was Withdrawn. The IEEE Std 141 still is based in this standard.

As far as I recalled there is not explanation why only the 500 kV is 10% above. I am suspecting that the switching surge, the system charging current may influence this 10%.

However, what is confusing is that higher voltage such as 765 kV the max. rated voltage is 5% and the limited experience in 1100 kV increase this rating again to about 9%.

 

[magoo2]

ANSI C84.1 has not been withdrawn. It is still up to date. In fact it's in the process of being updated for next year.

The development of the 500 kV line design was done back in the 60's by Westinghouse working with VEPCO and GE working with TVA on competing 500 kV projects. My understanding is that they couldn't control the voltage to meet +/- 5% like the other transmission voltages at the time so they wound up with +/- 10%. This of course impacted their equipment ratings (primarily transformers and arresters). It's still in effect to this day and the 500 kV approaches 550 kV at light load in northern Virginia and the PJM interconnection.

 

[jghrist]

1) It does seem strange. C84.1-2006 has 10% for 500 kV, but 5% for 400 kV and 4.6% for 765 kV. Maybe this is why Duke Power uses a nominal 525 kV voltage.

2) There are overvoltage vs time curves available from many surge arrester manufacturers.