Abstract

The rotor thermal sensitivity often affects the dynamic behavior of power unit generators. Owing to this phenomenon, increments of field current and other process parameters that are related to it may cause a shaft thermal bow and significant changes in the synchronous vibration. This symptom can also be caused by many other common malfunctions that affect rotating machines. Therefore, diagnostic techniques aimed at identifying the actual fault are very useful for optimizing maintenance activities. The thermal sensitivity of generator rotors can be deemed as a fault because it is commonly caused by a local deterioration of the winding insulation as well as by jamming phenomena between conductors and rotor slots, caused by friction forces due to the different thermal expansions of these components. This paper shows the results obtained by applying a diagnostic method, based on multiple linear regression models, which has been developed for the analysis of generator vibrations caused by thermal sensitivity. Nevertheless, nonlinear relationships between vibration and process parameters have also been taken into account. The capabilities of this diagnostic technique have been validated using the analysis of experimental data collected in a power plant. The results of this investigation are shown and discussed in the paper.

References

1.
Yang
,
Y.
, and
Zhao
,
Q.
,
2010
, “
Generator Thermal Sensitivity Analysis With Support Vector Regression
,”
American Control Conference
,
Baltimore, MD
, June 30–July 2, pp.
944
949
, Paper No. 5530699.http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1072.3794&rep=rep1&type=pdf
2.
Irwanto
,
B.
,
Eckert
,
L.
, and
Prothmann
,
T.
,
2015
, “
Thermal Unbalance Behaviour of Turbogenerator Rotors
,”
Ninth IFToMM International Conference on Rotor Dynamics
,
Milan, Italy
, Sept. 22–25, pp.
2231
2242
.10.1007/978-3-319-06590-8_183
3.
Klempner
,
G.
, and
Kerszenbaum
,
I.
,
2004
,
Operation and Maintenance of Large Turbo-Generators
,
Power Engineering, Wiley
,
Hoboke, NJ
.
4.
Stone
,
G. C.
,
Boulter
,
E. A.
,
Culbert
,
I.
, and
Dhirani
,
H.
,
2004
,
Electrical Insulation for Rotating Machines: Design, Evaluation, Aging, Testing, and Repair
,
Wiley-IEEE Press
, Hoboken, NJ.
5.
Paxton
,
J. G.
,
1994
, “
Turbine Generator Rotor Thermal Unbalance
,”
EPRI Proceedings: Utility Motor and Generator Predictive Maintenance and Refurbishment Conference
, San Francisco, CA, Dec. 7–9, Paper No. EPRI TR-104625, pp.
112
116
.
6.
Febriyanto
,
A.
, and
Sandewan
,
H. T.
,
2011
, “
Rotor Thermal Sensitivity Experience on 143.4 MVA Hydrogen-Cooled Turbo Generator With Direct-Cooled Rotor Design
,”
International Conference on Electrical Engineering and Informatics—ICEEI 2011
, Bandung, Indonesia, July 17–19, Paper No. 6021643.10.1109/ICEEI.2011.6021643
7.
Rakow
,
A. S.
,
Edmonds
,
J. S.
,
Rakow
,
J. F.
, and
Brody
,
R. D.
,
2011
, “
Root Cause Failure Analysis of a 373 Megawatt Steam Turbine Generator Exhibiting Both Reversible and Irreversible Thermal Sensitivity
,”
ASME
Paper No. POWER2011-55011.10.1115/POWER2011-55011
8.
Pennacchi
,
P.
, and
Vania
,
A.
,
2004
, “
Accuracy in the Identification of a Generator Thermal Bow
,”
J. Sound Vib.
,
274
(
1–2
), pp.
273
295
.10.1016/j.jsv.2003.05.014
9.
Vania
,
A.
,
Pennacchi
,
P.
, and
Chatterton
,
S.
,
2013
, “
Identification of a Shaft Thermal Bow by Means of Model-Based Diagnostic Techniques
,”
Surveillance Seven International Conference
,
Chartres, France
, Oct. 29–30, pp.
1
11
.https://www.semanticscholar.org/paper/Identification-of-a-Shaft-Thermal-Bow-by-Means-of-Vania-Pennacchi/4f0ccc4788bd4e6e3116afaa2fbbd58e5a0c3a79
10.
Singh
,
A. N.
,
Cronje
,
W. A.
, and
Doorsamy
,
W.
,
2017
, “
Investigation of Thermal Instability Testing on Synchronous Generator Rotors Using an Experimental Direct Mapping Method
,”
IEEE International Symposium on Industrial Electronics
,
Edinburgh, Scotland
, June 19–21, pp.
321
328
, Paper No. 8001267.10.1109/ISIE.2017.8001267
11.
Freedman
,
D. A.
,
2009
,
Statistical Models: Theory and Practice
,
Cambridge University Press
,
Cambridge, UK
.
12.
Rencher
,
A. C.
, and
Christensen
,
W. F.
,
2012
,
Methods of Multivariate Analysis
, 3rd ed.,
Wiley
,
Hoboken, NJ
.
13.
Badrieh
,
F.
,
2018
, “
Time Convolution With the Unit Step Response
,”
Spectral, Convolution and Numerical Techniques in Circuit Theory
,
Springer
,
Cham, Switzerland
.
14.
Zawoysky
,
J. R.
, and
Genovese
,
W. M.
,
2011
, “
Generator Rotor Thermal Sensitivity—Theory and Experience
,” GE Power Systems, Schenectady, New York, Paper No. GER-3809.
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