No. of Generating units 2

[Snippet]

Hi everyone, I asked this Q in another forum and the people there advised me to put it up in here. This is the reference thread of my Question.

http://www.eng-tips.com/viewthread.cfm?qid=267729&page=1

I would appreciate some help.

"Common sense is genius dressed in its working clothes." -- Ralph Waldo Emerson

 

[racookpe1978]

For convenience, I'm duplicating the orgignal question below:

"We have: Alternative I: Two generating units of 105 MW each initially for total design discharge of 30 cumecs and Net head of 820 m.
Due to transportation constraints of bulky machine, we are exploring the alternative II of having smaller but more no. of units.
So what should be the minimum discharge for each unit? Some standard says 10% while other says (20-25%). Can you all enlighten me on it? I would appreciate."

 

[racookpe1978]

The original question didn't address ooperating costs, but only shipping (and lifting ?) and installation costs.

Seems like foundations, power controllers and breakers, extra pipe runs (for the third or fourth pumps), extra valves, and extra spares ould have to be considered.

On the other hand, the client gets betters reliability.

But at low operating levels, only one small pump is running rather than a single over-sized pump at low efficiency.
However, should they size the small pumps so only 2 of 3 are needed at full load? Or only 2 of 4?

 

[MikeHalloran]

Just so we're clear, you're asking about 'turndown' of Pelton turbines, right?

About that, and claiming essentially zero expertise, I think they can be had with variable area nozzles and automatic controls to keep the velocity constant at reduced flows.





Mike Halloran
Pembroke Pines, FL, USA

 

[21121956]

Hello everybody:

With that head, flow and power generated, I think you are talking about Pelton turbines. It is widely accepted that, for these turbines, the minimum flow for operation at a good efficiency is 20% of design flow.

Regarding with the number and size of the units for the plant, I am sending the specifications EM 1110-2-1701 of 31 Dec 1985, clause f, page 6-20. This document even today is as fresh as it can be.

 

[Snippet]

Hi 21121956, now that was really informative! Thanks for clearing the doubt. A star for your answer from me.

Thank you Rakoo and Mike for the insights too. I really appreciate it.


"Common sense is genius dressed in its working clothes." -- Ralph Waldo Emerson