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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 ?