On Site Dissolved Gas Analysis for Transformer Condition Assessment

Robin Watson - Kelman UKKarl Smith - Kelman AfricaHenk Fourie - Kelman Africa

Catastrophic Failure of Transformers

The state of the oil is the key

These gases are a clue to the heat sources in the oil

Also Carbon Monoxide and Carbon Dioxide to state of Paper Insulation

Dissolved Gas Analysis - DGA

Most utilities use DGA to assess transformer conditionLimited sampling of larger transformers with suspected issuesThis approach does not identify developing faultsSome have a scheduled DGA program (eg annually)Tap Changer condition is also important Transformers & LTC’s mostly sampled annuallyMore critical transformers (GSU’s and large system autos) sampled quarterlyMost utilities would do more than 5000 samples per year

However there are difficulties

Large distances to the labDelays up to 2 weeks for standard samplesEven critical rushed samples can take many hoursLoss of transformer can cause significant loss of revenue

Kelman saw this as an opportunity and joined up with 2 key customers to develop a new approach

• Room for improvement..?• Interested in new ideas• Often skeptical of new technology

- pie in the sky?• Reliable portable DGA in small box?

- is that possible?• The 2 customers agreed to Beta Test

Transport X- lab and field testing

Photo-Acoustic Spectroscopy:

Principle discovered in 1880s by Alexander Graham Bell.Infra Red radiation absorbed by gas.Each gas has an unique IR absorption spectrum.Level of absorption is proportional to gas concentration.

Photo-Acoustic Spectroscopy:

Absorbed IR radiation causes rise in temperature, hence rise in pressure.If the radiation is pulsed at an audible rate the resultant pressure wave can be detected by sensitive microphones.Technique capable of measuring accurate concentrations in a complex cocktail of compounds.

DGA Target Gas IR absorption spectra

Overall system used for Transport X

Overall system used for Transport X

Beta Trials: TXU and Alabama Power

Danny Bates

Alabama Power

Randy Cox

TXU Electric Delivery(shown here with colleague Tracy Nolan)

Laboratory Investigations

Laboratory created large number of identical oil samples of known concentrationRan samples through 3 different GCs and Transport XPerformed by Alabama Power personnel, September to November 2003Gases shown separately for clarityCompares GC and Transport X for amplitude and variability

Comparison with GCC2H6

0

2

4

6

8

10

12

14

16

18

20

1 2 3 4 5 6 7 8 9 10

Test Number

ppm

TheoreticalConcentration

GC Readings

GC Average

Transport prototype

Transport pre-prod

CH4

8 9 10

umber

TheoreticalConcentration

GC Readings

GC Average

Transport prototype

Transport pre-prod

CO2

0

50

100

150

200

250

300

350

400

450

500

1 2 3 4 5 6 7 8 9 10

Test number

ppm

TheoreticalConcentrationGC Readings

GC Average

TransportprototypeTransport pre-prod

0

5

10

15

20

25

30

1 2 3 4 5 6 7

Test N

ppm

CO

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10

Test numberpp

m

TheoreticalConcentrationGC readings

GC Average

TransportprototypeTransport pre-prod

C2H4

0

2

4

6

8

10

12

14

1 2 3 4 5 6 7 8 9 10

Test Number

ppm

TheoreticalConcentration

GC Readings

GC Average

Transport prototype

Transport pre-prod

C2H2

0

0.5

1

1.5

2

2.5

1 2 3 4 5 6 7 8 9 10

Test Number

ppm

TheoreticalConcentration

GC Readings

GC Average

Transport prototype

Transport pre-prod

Analysis of Laboratory Tests

Spread of Transport X results smaller than GC results –indicates better repeatabilityAccuracy of Transport X at least as good as GCs – often better

However:Not conclusive testsSmall number of testsOnly tested at one concentrationSO WE CARRIED OUT SOME FIELD TESTS

Field Tests to Compare Transport X results to GCs

Many samples taken in US and in EuropeMain tanks, LTCs, CBs and bushings tested.Wide range of conditions – temperature and humidity Data incorporates different labs, different Transport X units, different sampling techniques, and different electrical equipment etc.

Field Test results

Field Test Results (cont)

CO2 Scatter

0

2000

4000

6000

8000

10000

0 2000 4000 6000 8000 10000

Various LAB ppm

Tran

spor

t-10

ppm

CO2X=YLinear (CO2)

Ethane Scatter

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500Various LAB ppm

Tran

spor

t-10

ppm

EthaneX=YLinear (Ethane)

CO Scatter

0

100

200

300

400

500

600

700

800

0 200 400 600 800

Various LAB ppm

Tran

spor

t-10

ppm

COX=YLinear (CO)

Analysis of Field Testing

Despite differing gas extraction and analysis techniques, overall correlation and linearity are excellent for all gasesRemarkably low scatter for Methane, Ethane, Ethylene and Acetylene Slightly larger spread for CO and CO2Hydrogen exhibits excellent linearity, but more mid-range data points required to test scatter

Worldwide

TRANSPORT X tested & adopted worldwide

UK, Ireland, Germany, Norway, Denmark, Sweden, Iceland, Croatia, Russia, Slovakia, Israel, Saudi Arabia, South Africa, Namibia, Kenya, Morocco, USA, Canada, Mexico, China, Mongolia, Korea, Singapore, Malaysia, Philippines, Indonesia, and growing by the day.

Field Application

Complements current DGA program– Primarily for confirmation & rush

samplesEasy to use – little expertise required

If you can take good sample, you can use Transport X

• Reliable portable DGA...?– ‘…given us the upper hand’ (D. Bates)

Developments

Software supportPC software for record download and storageTOA compatibilityEmbedded diagnosis algorithms

Key Gas; Rogers’ Ratios; Duval’s Triangle; Settable Caution & Warning thresholds

Moisture measurementON-Line DGA!

Embedded Diagnostic Tools

Testing at Cahora Bassa in Mozambique

Transfix – On-Line DGA

Uses same core technologySame Beta Test sites (TXU and Alabama)Adopted by many other worldwide utilitiesNo consumables8 gases + moistureExtensive Alarm optionsRemote and Local comms optionsHourly sampling – real-time DGA

Transfix – On-Line DGA

May ’04Transfix design review at Kelman withDanny Bates, Dr. Colin McIlroy & Robin Watson

(engineering prototype in background)

Transfix – Beta Test Sites

Transfix – Alabama Installation

Installed early November ’04 – very simpleNew LTC chosen for Beta Test – See more ‘action’ in a short period of time

Resistive-type LTC – small gassing per tap changeSimulate developing fault on transformer

Results remotely downloaded into TransCom®

Transfix – Alabama Installation

Conclusions

DGA front line tool for transformer monitoringTransport X reliable DGA toolMeets real industry needs – helps save $’s!

On-line DGA of real interest for critical equipmentTransfix – has taken the market by storm and in Africa alone more than 50 units are installed.

Thank you.

Any Questions?