Industrial generation dynamic behaviour

Hello, This isn't strictly a control question, but it relates to a current control problem. We're modelling parts of a plant power generating system
and need an indication of approximate process dynamics. Following may not be in correct terminology.
Can anyone give me an indication of the natural frequency for a pair of steam turbine driven alternators, about 15MVA each, parallelled on a bus? That is, the frequency of torsional oscillation and power slew following a step disturbance. TIA
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bruce varley wrote:

I don't do big power stuff, so I'll also use terminology that may not be correct: This would depend quite heavily on the generators' moments of inertia, but more importantly on their torque 'constants'. This torque vs. position relationship would be the apparent spring constant in a spring-mass system, and would in turn be proportional to the field current. Since the field current would depend on whatever the current demands were from the generating plant, I would expect a wide range of resonant frequencies.
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Tim Wescott
Wescott Design Services
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Bruce,
Are you talking about a step-change in electrical load, or a step-change in steam supply to the turbines?
Kelvin B. Hales Kelvin Hales Associates Limited Consulting Process Control Engineers Web: www.khace.com
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