locating a shorted turn in field winding

[Yuma]

Dear all,

Are you aware of a method of locating a shorted turn in the field winding of a turbogenerator? I don't mean to tell whether there is a shorted turn or not, but to physically locate it so you know which retaining ring you shold dismantle in order to fix it.

I remember an old timer from ABB claiming to be able to do so using an RSO test and a schematic of the field winding. It sounds feasible to me that, looking at the RSO curve and taking into account the speed of the wave, one could tell where the short is, but I've been asking around and it can't find anybody that can do it.

Also I've been google-ing a bit and found a description of a method which consisted of injecting and monitoring a current in the field winding, and then tapping all over the winding and watch for some change in the current. I don't really have more details on it.

Any experiences, opinions, suggestions, etc appreciated.
Thanks

 

[potteryshard]

Could you inject current and look at it with an IR camera?

 

[ScottyUK]

You might try Doble Powertest - they have a few 'old timers' in the UK who know the RSO test inside out.


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If we learn from our mistakes I'm getting a great education!

 

[waross]

Question:
Is the RSO test similar to a TDR test? Would a TDR test give any useful information?
Thanks.

Bill
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"Why not the best?"
Jimmy Carter

 

[Yuma]

Yes Waross, they are somehow similar techniques. RSO consists of injecting a low voltage wave from one slipring and then from the other. Record both waves and compare them. If the field winding is perfectly symmetrical - i.e. without shorts - then the superimposed waves are exactly the same.

Your idea makes sense although it is the first time I hear about using TDR for this. Maybe it would give some good information if we had first the signature of the 'healthy' field winding, and then repeat the test now that I'm sure that there is a short, and compare both results. But I'm just guessing...

Thanks, I will propose it to the manufacturer