dga analysis
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This is a presentation on DGA analysis
using a ratio method of hot metal gases
Will show results from four examples
Three DGA ratios and one fluid quality
This method is a proven tool in NHECPredictive Maintenance
Gary B. Ell iott
New Horizon ElectricNew Horizon ElectricNew Horizon Electric
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A New Way To F ind Regulator Problems
Through Gas Ratios?
Objectives:
Establ ish a Pattern
Recognize Potential Problems
Establ ish Solid Gas Ratio Formulas
Keep I t Simple As Possible
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Which Gases Should Be Evaluated?
C CH
H
H
H
C
H
H
H
H
C
H
H
H
C
H
H
H
C
C C
C
C
H HH H H
HH HH
H
C CH H H HAcetylene
Ethylene
Methane
Ethane
Hydrogen
HeatingHeating
Arcing Corona
Heating
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NHEC Gas Ratio Standards
1-Ethane .5 to 1.0 of Methane
2-Ethylene .5 to .75 of Acetylene 3-Ethylene .75 to 1.0 of Acetylene
4-Ethane 1 to 1 or Greater of Methane
5-Ethylene 1 to 1 or Greater of Acetylene
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Regulator was last serviced 4-99 Regulator was in service
Regulator seen normal duty Regulator load was about 75% normally
Had no previous DGA or F luid Quali ty
data
Example #1
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333 kva Regulator at Fairplay Sub
TOA Software
Targeted
Regulator
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DGA Report 5-25-2001
TOA Software
Ethylene 19224ppm
Acetylene 7246ppm
Ratio 2.65
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DGA Report 10-29-2001
TOA Software
Ethylene 14143ppm
Acetylene 5601ppm
Ratio 2.52
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DGA Report 12-11-2001
TOA Software
Ethylene 12792ppm
Acetylene 5098ppm
Ratio 2.50
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F luid Quality Report
TOA Software
Color on 5-25-2001
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Reversing Switch Assembly
(Load Carrying)
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Reversing Switch Stationary Contact
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Stationary Contact
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Reversing Switch Moveable Contact
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Regulator fai lure was inevitable Regulator was last serviced 4-99
Contacts were damaged due to not
exercising the selector (reversing) switch
Conclusion
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Regulator at McCormick Sub
Targeted
Regulator
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DGA Report 4-23-2001
TOA Software
No indication of a
problem
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DGA Report 4-22-2002
TOA Software
No indication of a
problem
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F luid Quality Report 2002
Moistur e 45ppm
IFT 13
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Untanking The Regulator
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Rust Present
Moisture
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333kva regulator currently in service Not scheduled for maintenance
Example #3
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DGA Report 5-09-2002
Ethylene 10911ppm
Acetylene 3432ppm
Ratio 3.18
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DGA Report 6-13-2002
Ethylene 11059ppm
Acetylene 3746ppm
Ratio 2.95
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F luid Quality Report 5-09-2002
No indication of a
problem
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Contact Lead Termination Point
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Contact Lead Termination PointClose-Up
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Found contact wire lead missing fasteningnuts
Failure was inevitable
Only reason hadn t fai led is lack of
frequency on that step
Conclusion
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333kva regulator currently in service Not scheduled for maintenance
Regulator had been serviced in the field
previously
Regulator load was around 75% normally
Had no previous DGA or F luid Quali tydata
Example #4
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Regulator at Westminster Sub
Targeted
Regulator
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DGA Report
Ethylene 203063ppm
Acetylene 4390ppmRatio 46.26
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F luid Quality Report
No indication of a
problem
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Ratio Results Ethylene > Acetylene
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Reversing Switch Assembly
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Reversing Switch Assembly
(Continued)
S
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Reversing Switch Assembly
Moveable Contact
R i S it h A bl
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Reversing Switch Assembly
Stationary Contacts
N l S t f R i S it h
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Normal Set of Reversing Switch
Stationary and Moveable Contacts
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Questions ?