Vibration in Power Transformers and Reactors
Vibration in Power Transformers and Reactors
(OP)
Dear sirs:
I am interested in measuring vibrations in HV Power Transformers and Shunt (line) Reactors.
Could you be kind enough for giving me some help in this?
- where to find information of the tests and analisys?
- which are the most suitable test sensors and equipment?
Thanks in advance
hy
I am interested in measuring vibrations in HV Power Transformers and Shunt (line) Reactors.
Could you be kind enough for giving me some help in this?
- where to find information of the tests and analisys?
- which are the most suitable test sensors and equipment?
Thanks in advance
hy






RE: Vibration in Power Transformers and Reactors
If you were really bored, theoretically you might be able to look for increase in 120hz vibration as a symptom of core problems or overvoltage or unbalanced conditions. Likewise very high frequencies >1mhz acoustic are sometimes associated with internal electrical discharge activity... but that has not been developed as a practical diagnostic tool yet.
The bread and butter tests for monitoring the health of the transformer are oil sampling (including dissolved gas analysis) and off-line electrical testing (power factor, turns ratio, excitation current winding resistance etc).
RE: Vibration in Power Transformers and Reactors
RE: Vibration in Power Transformers and Reactors
RE: Vibration in Power Transformers and Reactors
So we are not so bored as you see.
We are aware of bread, butter and coffee tests but, that is another story. Although excitation current and leakage reactance measures are suitable for mechanical movements in core.
Factory test are normally regarding "noise", not vibration.
Also in some 150kV class transformers we had found loosen windings and core wooden separators, due to vibration.
From some of makers we have the points where to take measures, so as to compare with factory tests results, but would want to see if there is anyone who had dealt with this kind of problem, and que test equipment used.
RE: Vibration in Power Transformers and Reactors
From what little I know, the primary factors involved in transformer winding loosening have historically been thought to be through-faults, and thermal aging of the insulation. Related tests as you mention are single-phase leakage reactance and excitationi current and internal inspection. Recently there have been a lot of papers on Frequency Response Analysis for detecting winding movement. I'm certainly not trying to dispute the importance of vibration... I hadn't heard any discussion on that aspect before, but it makes sense that it could be another factor in winding loosening. Also I have never heard of fatigue failures of connections within a transformer.
At our power plant we use Entek IRD Datapak together with desktop software for vibration monitoring of rotating equipment. There is a range of vib monitoring equipment available starting with "vibration pens" sold by skf, giving magnitude only. You can add capability to provide spectrum display, then capability to interface with pc program, do multi-channel analysis, balancing etc). If you have any friends in a power plant or industrial plant with rotating equipment, they will have specialists in vibration monitoring. Vendors include Rockwell/Entek, SKF, CSI and a few others.
One other story that comes to mind on the subject of transformer vibration (not related to your question) ... I heard a report where a generator stepup transformer had a fan blade which apparently developed a crack which went unnoticed.... resulted in increasing imbalance and vibration until the fan blade finally fell apart... shrapnel cut into the cooler tubes resulting, in sucking air into the transformer (cooler was under suction), caused relief valve to lift, and then operators took unit offline in response. Other fan blades showed cracks near the bases of the blade. I have seen similar cracks myself but never a catastrophic failure. It certainly seems like on-line vib monitoring would detect the cracked fan blade as evidenced by vibration at the rotating speed of the fan.
RE: Vibration in Power Transformers and Reactors
RE: Vibration in Power Transformers and Reactors
You are confusing frequency response analysis and measurement of sound level with measurement of vibration on tank surface.
Tank vibration is more relevant for shunt reactors.There are cases in olden days , when poorly designed or made shunt reactor tanks broke open in service due to severe vibration of tank.So when EHV shunt reactors are tested at factory tank vibration will be measured by puting the sensor on tank surface and applying 110% of rated votageto winding. Limit of vibration will be specified ,say 150 microns etc
Modern trfs,tank vibration is negligible and rarely measured ,even though not uncommon to specify.
You can get test instument from reputed makers like Bruell&Jarr
RE: Vibration in Power Transformers and Reactors
RE: Vibration in Power Transformers and Reactors
http://www.elexp.com/sec_040b.htm
http://www.cosmotron.se/products/sheets/CMVVS302E.pdf
http://www.grindosonic.com/products.html
etc. for more info