The reliability comparison between 3.3 kV versus 6.6 kV supply (Motor)

[SUNBCP]

I plan to introduce the 6.6 kV power supply to HV motors instead of the exisitng that using 3.3 kV for HV motors. And I have some questions about the reliability & cost comparison between 3.3 kV versus 6.6 kV. If you have any recommendations/experience for using 6.6 kV. Pls advise us.

Thank you.

 

[RRaghunath]

6.6kV is more popular in power projects in India, though 3.3kV together with 11kV is being used as auxiliary power supply for motors in power plants with unit size of 500MW for some time now.

Generally speaking, 6.6kV motors are more commonly used and hence chance of getting a competetive quote from vendors is better.

 

[jraef]

SUNBCP,
I think that the issue of what is most commonly used is specific to where in the world you are. I am in the US, and of course we have absolutely no 3.3 or 6.6kV! Just 2.3 or 4.2kV all over, and a little 6.9kV here and there.

Seriously though, I do a lot of work in other parts of the world, and in the Middle East for instance what I see is predominantly 3.3kV. with you being in Thailand, I think that you need to investigate the commonality of any motor voltage you intend to use. The availability of replacements and knowledgable service people will be the most important factor. The motor voltage itself has little to do with reliability or even power consumption. As voltage gets higher, the current goes down so the wires can get smaller. However, as voltage goes up the cost of switchgear and controls goes up as well.

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