Hello,
My company has acquired a 450 MW 60 Hz Steam Turbine driven Generator. I have been tasked with working through a solution on how to convert the 60 HZ to 50 Hz.

The Equipment Specifications are:
Nominal rating 400MW. Max continuous rating 450MW, Type TC4R-26, 24,000V, 3 phases, 60Hz. double star connection.

Any advice?

 

Rogerthat,,,
As a start I suggest you obtain two threads from the Control.Com Archives:

o Http://www.control.com/thread/1026249406

o Http://www.control.com/thread/1245027301

Regards,
Phil Corso

 

Hello, Rogerthat,

After re-reading your post, you may be saying that your company has only acquired the generator, in which case all of the information below may not be applicable. There have been other posts on control.com about re-purposing generators at different frequencies; there is a very helpful 'Search' function cleverly hidden at the far right of the Menu Bar at the top of every control.com webpage which can be used to find past posts. (It's suggested you use the Search Help to form search terms to find related posts.)

A synchronous generator produces AC (Alternating Current) power at a particular frequency in proportion to the speed of the generator rotor per the formula:<pre> F = (P * N)/120
where F = Frequency (Hz)
P = Number of poles of generator rotor
N = Speed of generator rotor (RPM)</pre>So, a two-pole generator producing 50 Hz must be spun at 3000 RPM, and a two-pole generator producing 60 Hz must be spun at 3600 RPM.

For machines of the size you are describing he steam turbine is usually directly coupled to the generator and is most likely designed to run at 3600 RPM (since most synchronous generators of the size your company has taken possession of usually have two-pole generators), and that means that it likely can't operate very well at any other speed. The design of the turbine nozzles and turbine blades are all based on a particular RPM, and steam flow-rate at a particular inlet pressure and temperature. As such, it probably can't be easily operated at 3000 RPM.

Further, the voltage developed by a generator is also proportional to the speed of the generator rotor, and so simply reducing the speed of the steam turbine output isn't going to solve all of the issues with the generator.

About the only suggestion I can offer would be to obtain a different generator (one rated for 50 Hz operation) and a reduction gear to install between the turbine and generator to convert the 3600 RPM output of the generator to 3000 RPM. This way the steam turbine can be operated at its most design speed and efficiency, and the generator can be operated at its design speed without modification.

I suppose a different alternative would be to install a very large (VERY large) static converter using thyristors/SCRs to convert the current from 60 Hz to 50 Hz--but that would also be extremely costly and would likely require a cooling system (water-based) of its own.

You may be surprised at what the OEM (Original Equipment Manufacturer) may be able to help with. It's not likely but they may have some options which could be helpful.

Please write back to let us know what your company decides to do with this turbine-generator.