The machine is 27.6MW Bharat Type HGT 410/110-14D hydrogenerator. The 1X shaft amplitude were 30 micron pk-pk at FSNL, 60 micron at exitation and 130 micron at 20MW. Is it normal? because from my experienced with gas and steam generator the 1X different from FSNL and base load not so much different

I can't help you with what's normal.

But just a few thoughts. 130 micron is around 5 mils I think. How does that compare to the bearing clearance (should be below half)? What is the machine speed?

The speed is 430 RPM and the brg clearence is 0.2mm

Your vibration at 130 microns = 0.13 mm is over half of your 0.2 mm bearing clearance. I would think the bearings won't last long at those levels (assuming the vibration at the location of your prox probe is representative of vibration at the location of your bearings... is it?).

But maybe there's something different about hydro's? Now I'll show my ignorance about hydro's... are these vertical machines? Are the bearings oil lubricated babbit bearings?

Could we be talking 130 micrometres pp and .2 mm radial? This would make a big difference. What is the shaft diameter?

I haven't seen that many hydro TG's, but I have seen this type of variation due to the genrator or a gas turbine. Is it normal? I'd rather answer, is it desirable? No!

Also to characterise the shift, you need phase and frequency information. Is this 1X? The vector change that occurs has much greater importance than just an amplitude change. Also, you want the curve from this period in a polar plot to see how the change occured.

If this is a larger onsite built stator arrangement or otherwise hard to center it is not unusual to make a "electrical compensation" balancing session with data from on grid loaded condition so the run is as good as possible at the majority of operating hours that should be on full load. Once in a while a compromise must be found so the thing can run up w/o problems and then run acceptably when on load. If the vibration on the other hand goes up by temperature and not by load, things are different. Olov

From the 2004 report the 1X vibration increased from 60 micron pp at FSNL to 120 at 20MW at X and maintain 80 micron pp at Y.

This problem occured after several damaged stator slots were changed last month

Could this due to electrical problem? what type of test should be carried out, pls advice

quote:

This problem occured after several damaged stator slots were changed last month

What is different about the vibration now than the vibration described in 2004? It sounds the same to me.

quote:

Could this due to electrical problem? what type of test should be carried out, pls advice

I don't work much with generators, so take my comments with skepticism. But I would think that a 1x frequency if electrical in nature would be associated with the rotor (1x associated with stator field assymetry would give vibration at 14 times running speed on this 14-pole machine). Most likely thermal bow of the rotor if it slowly increases over time just after a load increase. Shorted rotor turns could contribute to uneven heating and thermal bow. The simplest check for shorted turns would be ac impedance unbalance test (pole-drop test) of the rotor while shutdown. There are quite a few other checks for shorted turns that I'm not familiar with (RSO for example).

This sounds like generator rotor being thermally unstable. While loaded reactive power generates more heat and rotor is being bowed.

Ahmad,

I recently worked on a steam turbine generator that had 1xSS vibration increase with excitation on and then go higher when put under load. Vibration ar both generator bearings were in-phase using the proximity probes. The rotor was believed to have an electrical fault. The rotor was repaired by factory and fault was confirmed.

Walt