What will be the effect on Steam Turbine rotor and blading if it runs at 2900 rpm instead of rated 3000 rpm?

Question

Turbine rating 500 MW, 3000rpm and TG is connected to the grid. Turbine inlet steam pressure is 160 kg/cm2 and 550deg C.

Answer 1

They say it takes the turbine out of its "ideal" flow design and higher erosion on the blading can be expected running it at a lower than rated rpm.

For this to happen, the frequency of the whole network must be lowered, which can only be done in a concerted way. All generators on the same network run sychronously.

This is usually done when demand is very high and the network is too close to its maximum generating capacity. By lowering the frequency, motors on the network run slower and load drops, in the same proportional amount. In this particular case, less than 4 percent.

It will not affect the output capacity of the turbine, per se. On the contrary, it may increase it, somewhat.
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Answer 2

The power plant were I worked had steam turbines attached directly to the generators, that turned 3,600 R.P.M.They were built by Westinghouse. A full sign wave in electricity is 360 degrees, so a unit turning 3,600 R.P.M makes things mathematically correct. The governor on the turbine works like this. As demand for power increases, it puts a load on the generator just like a brake, it's harder to turn so the governor opens to let more steam enter the turbine. Boiler pressure starts droping , so more fuel is added to make more fire to generate more steam. This is only a small part of how a power plant works.

Answer 3

you'll loose a little of the HP output which will translate to a littel less in the MW aoutput as well

Answer 4

It should last longer.