Operating 230 kV Breakers at 115 kV

[BLadewig]

We have been directed to purchase 230 kV breakers for operation at 115 kV. The thought is that in the future the system will be upgraded and it won't be necessary to purchase new breakers.

It is a generally accepted practice around here, apparently, and I was hoping for any comments from others who might know of some red flags that we should be aware of.

Actually, I'm hoping there aren't any red flag comments....

 

[DanDel]

Will all the equipment be 230kV rated, or just the C/Bs?
If the switchyard does not encorporate the correct distances, structures, and bushings needed for the higher voltage, you may have trouble later when you switch over to the higher voltage.

 

[busbar]

Are clearances/creep/strike dimensions intended to be initially 550 or 1050kVBIL? What about arrestors and instrument transformers?

 

[dpc]

As far as application of 230 kV circuit breakers at 115 kV, this should not present any problems, as long as fault current is within the rating of the breaker.

 

[cuky2000]

It is common practice in the power industry design substation with provision to uprate the operating voltage in the future. Continuous current, interrupting rating, clearances, BIL SIL, grounding grid, etc should be satisfactorily designed for worst-case scenario at 115 kV or 230 kV.

Some power transformers and auxiliary service units could be designed for dual voltages for extra charges. Provision for modest investment replacing little equipment should be considered. Some of those equipment are surge arresters and voltage transformers (PT or CVT).

One of the biggest challengers could be the setting and coordination of the protection system to minimize the downtime during the transition from 115 kV to 230 kV. Therefore, a good plan in advance is strongly suggested.

 

[jbartos]

Suggestion: Considering the equipment sizing for 115kV with respect to 230kV sizing, there will be a substantial increase in the power rating at 230kV. E.g. 2000A at 115kV yields about 398MVA and at 230kV yields about 797MVA, which is to be linked to larger consumers to be added to the power distribution. If this is the case, then as much as possible should be designed to fit 230kV, not only circuit breakers.

 

[BLadewig]

Yes, the rest of the yard will be sized for 230 kV issues such as clearance, etc.

 

[neps3]

BLadewig

In general the switchyard and the entire equipment should be deisgned for 230kV. If this is so then what is your concern.

The only concern I have is that the extra $$$ you are investing with an intention of future expansion program has no return. Therefore you must do an investment analysis and include all the costs and benefits for this project. Who knows in two years time the cost of 230kV gear may be reduced by x%. Just a hope?. Plus the $$$ would have depreciated in two years time at the discount rate. Therefore an investment analysis is a must act for investments.

Kind regards