Turbine Generator Vibration Limits. Non-rotating parts.

[Dmitry]

Hello All

One of the most important aspects of any vibration analysis is Vibration Limit. So one may expect that for most powerful generators (steam turbine driven generators) these data are readily available. It is not true.

What is available - Vibration Limits on bearings and rotor. Non-rotating parts such as end winding (coil ends), core and frame are not covered by international standards. At the moment, it looks like national standards tend to ignore these parts.

But companies who run power stations (EDF – France, RAO UES – Russia, etc) do have vibration related issues on end windings so they have to have internal standards on vibration. Comparison of these standards should be very instructive.

Unfortunately “internal standards” are published in local language so they are difficult to find.

At the moment I found standards:
1) RD 34.45-51.300, 2001 Electrical equipment testing extent and specification limits. Russia
2) Modal Test Analyses and Natural Frequency Measurement Methods of Large Turbo-Generators on Stator End Windings and Evaluation Criteria, Chinese Engineering Industry Standard JB/T 8990-1999, Jan. 2000
3) Measurement and Evaluation of the Dynamic Characteristic on Stator End Windings of the Large Turbo-Generator, Chinese Power Industry Standard, DL/T 735-2000, Jan. 2001

They are quite different. Russian standard specifies allowable vibration level for end winding, while Chinese – allowable range of natural frequencies.

Would be interesting to know if any other countries/companies have such standards published.

Best regards,
Dmitry

 

[MotorVib]

A long time ago I look over eather the GE or Westtinhouse old desgine books but I have no idea were you could find a copy of the book. I belive that there was something in the book about coil and rotor windings deflection and Vibration.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[cbrn]

Hi,
I find it a bit a curious problem. International Standards, as you have already noticed, cover vibration performance of shaftlines in their whole (both rotating parts and statoric parts, but always related to the fact that "something" is revolving inside "some kind" of supports).
Vibrational issues on machine parts are not covered by International Standards because, I think, it is a matter of design-intent. I mean, you could design a machine part so that it can stand an X vibration level (which causes an X stress-state and an X displacement/deformation field) or you could also design the same machine part so that it can withstand a 2X vibration level, and so on.
Of course, all the problem is to have the opportunity to carry a full vibrational response analysis over the components of interest, and to be able to define correctly all the possible variable forces involved (mechanical, electrical, thermal...). All this will have an influence over the fatigue analysis of the parts involved.
Then, any manufacturer can choose by internal standardization to be more severe from a vibrational point of view so that the design of connections and structural elements is easier, or on the opposite to be more tolerant on vibrations with the drawback of being obliged to take more care on the structural / connections aspects...

I'm not an expert of generators, but if I was concerned about end windings, bus-bars and so on, I'd first of all check which is the vibrational limit allowed for the rotor (zone A/B?...), and which are the max unbalances allowed; then with the help of a response analysis I'd try to find the deflections and the orbits (deflection-in-time function) of the rotor in correspondence of the stator windings, then calculate the electro-magnetic field variations caused by this "oscillating eccentricity", then calculate the forces; parallelly, I'd check which displacement amplitudes are allowable at the supports of the shaftline, in the case that some supports are directly connected to the statoric structure (I know it's seldom the case for hydroset generators, but I don't know for steam turbogenerators); then, I'd calculate the response of the stator to all the incoming variable forces and check that the induced vibrations are tolerable by all elements involved.

Regards

 

[MotorVib]

I forgot the one vibrastion standered out ther is an old Germany one but I would not count on that one bacause of it age I belive it was over 60 years old. There is also ISO 1945 but this is Blance Limits. Blance is not vibration but it good blance helps with vibration.

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[Dmitry]

Thank you gentlemen for the comments.

Just to highlight the practical aspect of my question. When generator is opened (end shield/bell) is removed, there is dust (if there is oil than - dark grease) visible on end winding. This is result of insulation wear. If insulation wears out – sooner or later there is an electrical failure.
Before trying to reduce vibration any engineer would like to know if current vibration is acceptable or not. If it is acceptable – generator will work for ~25 years without any fuss.
This is where standards come into play!

Best regards,
Dmitry