The author is working in captive power plant of 51 MW capacity. Of these 4 machines, 3 are of 12MW 2-pole, Russian design, 1957 make. The 4th machine is of 15MW Bhel, India make, 4 pole m/c.

My concern is that we're going for phased replacement of older 12 MW M/Cs. So should I go for 12-15 MW 2 pole OR 4 pole m/c? Economics say that 4 pole is cheaper. Performance-wise 4 pole is more stable and less maintenance prone. I want more info this topic.

sanjay sharma

 

Sanjay, you pointed out that economics, maintenance, and stability concerns point to 4-pole machines as the solution. The stability concern is true only if the GD^2 values of the replacement machines are equal to or greater than 4 times that of the original 2-pole machines!

Please note, my statement is valid as long as the prime-movers aren't replaced!

Regards, Phil Corso, PE ([email protected])

 

Thanks Phil for the reply. We're going for complete phasing out of turbomachines. Also at other location (not in the power plant premises) we are going for TRT (Top Recovery Turbine) with BF gas as fuel. There we're having one no. 14 MW generator. This machine also we were thinking of going for 4-pole rather than 2-pole. Your advice is needed for both above cases.

Thank You.

 

Anonymous, I’m not sure what advice you are expecting! My earlier answer was to emphasize the importance of machine selection to resolve or head-off a stability problem. That is, a larger GD^2 factor has a greater impact on system stability than does any control strategy one can devise! The TRT, although a winner with regard to energy conservation, doesn’t have a large GD^2 factor. That said, my advice is, “Make sure you carry out a stability study!!

Regards, Phil Corso, PE ([email protected])