Limits on MVAR out of older generators

[mns15451]

Is there any limits or change in the capability (curve) of the older generators. In other words is there any limit for the MVAR output of the generators. If so, what is the correction factor to find out the new Limits of the MVAR.

 

[wolf39]

There is no such correction factor available. A generator capability curve is individually linked to the generator design. For instance: At a given rated output (MVA) an old generator with a low synchronous reactance does permit a higher under-excited figure (MVAr) than a modern generator with a higher synchronous reactance, under the assumption that suitable design features were applied to the stator core end regions.

Wolf

http://www.hydropower-consult.com

 

[edison123]

Only temperature limits. You might want to reduce the allowable temp limits, both for stator & rotor, to extend the life a bit. But there is no thumb-rule or standard about what is that reduction. Past history and original OEM's generosity play a big role in such matters.

I have seen 50-70 year old machines with original windings still running with the original temp limits while the so called 'state-of-art' machine fail miserably well within their expected life even they were operated conservatively.

Muthu

http://www.edison.co.in

 

[burnt2x]

Agree with edison123. We did experience a metering calibration screw-up on a circa '63 steam turbine generator such that meter read-out was lower than actual by about 42%. We got temp hi alarm when unit indicated a load of around 50%

 

[mns15451]

Thanx a lot for your resposes. I conclude that its only the temperature which is concerned in this regard. This, anyway is always a consideration on the new machines as well.
Regards to all.

 

[wolf39]

Of course, generally speaking high temperatures are always indications that something is wrong. However, the original question was more or less dealing with capability curves and MVAr output limits. Excessive under-excited MVAr figures don't show up in slot RTD readings if rated MVA data are not exceeded. In such cases the only indicator left before stator failure occurs is the operator's nose, in case the power plant is manned and the generator in question is not sealed (like hydrogen-cooled turbogenerators).

Wolf

http://www.hydropower-consult.com