1. GAP 1
generator assessment process
a solution to life assessment of large generators
anilscoob@gmail.com omsaiempl@gmail.com

2. 1 GAP 2
GAP
GAP*
GAP 4 GAP 3
anilscoob@gmail.com

3. GAP1 evaluates the thermal residual
life from experience and the
accumulated data
Optionally diagnosis of faults through
on-line testing - vibration signature
analysis, current signature analysis and
infrared thermal imaging

4. Methodology
The methodology employed is estimation of
consumed life and residual life
Consumed life is estimated by operational
history
Residual life is estimated by consumed life,
establishment of calculation method for
residual break-down voltage and operation
pattern in the future

5. Unit Condition
The generator is in operation
Inspection & tests Performed
OEM data and specification
Operational history
Operational parameters
Thermal profile
Maintenance history

6. Benefits
Extent of thermal life degradation
Preventive maintenance plan
Schedule for GAP2, GAP3 and GAP4
Final Report
Standardized format in electronic form
Photographs of critical areas
Thermal residual life
Analysis and recommendation

7. Expected Downtime
Zero days
Option
Vibration severity level
Vibration signature analysis
Electrical Signature analysis
Infrared thermal imaging

8. Life Assessment
Thermal Life Assessment

9. Ageing of an Electrical Insulation
System

10. Assessment of Condition
and Residual Life Time

11. Inverse Power Law and Arrhenius Law

12. Single Stress and Multi Stress
Ageing of EIS

13. Thermal Life Assessment
Arrhenius Equation

14. Thermal Electrical
Stress
Mechanical Ambient
anilscoob@gmail.com

15. Thermal Ageing Model
The thermal ageing in insulating materials is complex
and the mechanisms vary in different materials and
under different service conditions.
To a first approximation, the oxidation process can be
expressed by the Arrhenius rate law.
It is evident that, the higher the temperature, the
shorter is the life expectancy of the insulation. The
Arrhenius law is the basis of all accelerated ageing
tests which are used to estimate the thermal life of a
winding and is also used to define the insulation
thermal classes

17. Arrhenius Equation
Dr. Svante August Arrhenius was a Swedish scientist,
professor of physics, and the founder of physical
chemistry. In 1903, he received the Nobel Prize for
Chemistry for his study of ionic theory

18. Lr ∝ f (Y, Yo, N, Tmax, Tavg, Tamb)
Lr = Residual thermal life (years)
Y = Operating years
Yo = Equivalent operating years
N = Number of starts/stops
Tmax = Maximum allowable temperature (oC)
Tavg = Average operating temperature (oC)
Tamb = Ambient temperature (oC)

19. T HE R MAL L IF E
C urves plotted at different winding temperature in o C
100
90
80
70
60
% L ife
50
40
30
100 95 90 85 81
20
10
0
0 5 10 15 20 25 30 35
x 10000
Hours of O peration
81 85 90 95 100 pres ent

20. R emaining T hermal L ife vs Winding T emperature
25
x 10000
81
20
R eamaining L ife (No. of hours )
15 85
10
90
95
5
100
0
80 82 84 86 88 90 92 94 96 98 100
T emperature (deg C )

21. Thermal Life Estimation by Arrhenius Equation
BHEL 46.25 MVA, 11 KV, 3000 rpm Turbo-generator @ Monnet Ispat, Raipur
100
present life
90
80
70
Residual Thermal Life(%)
60
50
40
30
thermal life
20
10
0
10
15
20
25
30
0
5
Operating Years
residual thermal life present life thermal life

22. GAP Estimation by Arrhenius Equation
BHEL 46.25 MVA, 11 KV, 3000 rpm Turbo-generator @ Monnet Ispat, Raipur
100
90
80
Residual Thermal Life(%)
70
60
50
40
30
20
10
0
0
5
10
15
20
25
30
Operating Years
GAP11 GAP21 GAP31 GAP41 GAP12 GAP22 GAP32 GAP42

23. Life Index
1 2 3 4 5 6 7 8 9 10

24. Thermal Life Assessment
N-Y Map Method

25. Thermal Electrical
Stress
Mechanical Ambient
anilscoob@gmail.com

26. Electrical aging and thermal aging both depend on
service operation in year (Y), and aging due to
heating and cooling is proportional to the number of
starts-stop of a machine (N)
From empirical data based on the insulation system
study i.e. the electrical, thermal aging characteristics
and the heating and cooling cycle characteristics, a
NY-map is derived
From the equation by experimental data, the residual
breakdown strength (%) is as
Vr ∝ f (Y, N, No, Tmax, Tavg, Tamb)

27. Vr ∝ f (Y, N, No, Tmax, Tavg, Tamb)
Vr = Residual breakdown strength (%)
Y = Operating years
N = Number of starts/stops
No = Equivalent number of starts/stops
Tmax = Maximum allowable temperature (oC)
Tavg = Average operating temperature (oC)
Tamb = Ambient temperature (oC)

28. Thermal Life Estimation by N-Y Method
BHEL 46.25 MVA, 11 KV, 3000 rpm Turbo-generator @ Monnet Ispat, Raipur
90
present life
85
80
Residual Breakdown Strength (%)
75
70
thermal life
65
60
55
50
45
40
0 5 10 15 20 25 30 35 40
Operating Years
Residual Breakdown Strength Minimum Breakdown Strength present life thermal life

29. Life Index
1 2 3 4 5 6 7 8 9 10

31. THANK YOU
ध यवाद
‫ا‬
‫ﮨﮯ‬ ‫ﯾہ ادا‬
ந றி
ಧನ ಾದಗಳ