Improvement of Stator Slot Structure based on Insulation Stresses Analysis in HV Generator
High voltage generators are being subject to higher
voltage rating and are being designed to operate in harsh conditions.
Stator windings are the main component of generators in which
Electrical, magnetical and thermal stresses remain major failures for
insulation degradation accelerated aging. A large number of
generators failed due to stator winding problems, mainly insulation
deterioration. Insulation degradation assessment plays vital role in the
asset life management. Mostly the stator failure is catastrophic
causing significant damage to the plant. Other than generation loss,
stator failure involves heavy repair or replacement cost. Electro
thermal analysis is the main characteristic for improvement design of
stator slot-s insulation. Dielectric parameters such as insulation
thickness, spacing, material types, geometry of winding and slot are
major design consideration. A very powerful method available to
analyze electro thermal performance is Finite Element Method
(FEM) which is used in this paper. The analysis of various stator coil
and slot configurations are used to design the better dielectric system
to reduce electrical and thermal stresses in order to increase the
power of generator in the same volume of core. This paper describes
the process used to perform classical design and improvement
analysis of stator slot-s insulation.
 F. Tim Emery and Dennis Pavlik, "Electrostatic field analysis of high
voltage generator stator insulation systems" 2000 conference on
electrical insulation and dielectric phenomena, IEEE.
 Muhammad Arshad, Abdul Khaliq and Syed M. Islam, "Turbo
generator stator winding condition assessment",2004 international
conference on power system technology, POWERCON 2004,
Singapore, 21-24 November 2004.
 Sang Bin Lee, Jinkyu Yang, Karim Younsi and Raj Mohan
Bharadwaj, ÔÇÿAn On-Line groundwall and phase to phase insulation
quality assessment technique for AC machine stator winding-, IEEE
Transactions on Industry Application, vol. 42 no.4, July/August 2006.
 P. O-Donnell, "Report of large motor reliability survey of industrial
and commercial installations: Part I," IEEE Trans. Ind. Appl., vol. IA-
21,no. 4, pp. 853-864, 1985.
 ÔÇöÔÇö, "Report of large motor reliability survey of industrial and
commercial installations: Part II," IEEE Trans. Ind. Appl., vol. IA-21,
no. 4, pp. 865-872, 1985.
 P. F. Albrecht, J. C. Appiarius, and D. K. Sharma, "Assessment of
reliability of motors in utility applicationsÔÇöUpdated," IEEE Trans.
Energy Convers., vol. EC-1, no. 1, pp. 39-46, Mar. 1986.
 G. C. Montanari and M. Cacciari, ÔÇÿÔÇÿA probabilistic insulation life
model for combined thermal-electrical stresses--, IEEE Transactions
on Electrical Insulation vol. EI-20 no.3, June 1985.
 G. J. Anders, SM J. Endrenyi, F G.L. Ford, M G.C. Stone, SM, ÔÇÿÔÇÿA
probabilistic model for evaluating the remaining life of electrical
insulation in rotating machines--, lEEE Transactions on Energy
Conversion, vol. 5, no. 4, December 1990.
 S.B.Pandey, ÔÇÿÔÇÿEstimation for a life model of transformer insulation
under combined electrical & thermal stress--, IEEE Transaction on
reliability. vol.41, no.3, 1992 September.
 H.S.Endicott, B.D.Hatch, R.G.Sohmer, ÔÇÿÔÇÿApplication of eyring model
to capacitor aging data--, IEEE Trans. Component parts, vol 12, 1965
Mar, pp 34-41.
 T.S.Ramu, ÔÇÿÔÇÿOn the estimation of life power apparatus insulation
under combined electrical and thermal stress-, IEEE Trans. Electrical
insulation, vol EI-20, 1985 Feb, pp 70-78.
 Diako Azizi, Ahmad Gholami, Abolfazl Vahedi, ÔÇÿÔÇÿAnalysis of the
deterioration effects of stator insulation on the its electro-thermal
property--, International Journal of Energy and Power Engineering.,
vol. 2, no. 3, 2009.