Трансформаторы: эксплуатация, диагностирование, ремонт и продление срока службы

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Ðèñ. 12. Òàíãåíñ äåëüòà êàê ôóíêöèÿ òåìïåðàòóðû (ºC)

äëÿ ÷åòûðåõ ðàçëè÷íûõ òðàíñôîðìàòîðîâ [11]

Ñ ïîìîùüþ ìåòîäà ×ÕÄ è ìåòîäà ïðåîáðàçîâàíèÿ äàííûõ â òåìïåðàòóð-

íóþ çàâèñèìîñòü ìîæíî âûïîëíÿòü ïðàâèëüíóþ èíäèâèäóàëüíóþ êîìïåíñàöèþ

òåìïåðàòóðíûõ âîçäåéñòâèé (ïàòåíò çàÿâëåí). Äëÿ õîðîøåé èçîëÿöèè òåìïå-

ðàòóðíàÿ çàâèñèìîñòü ñëàáàÿ. Êîãäà èçîëÿöèÿ ñòàðååò è/èëè èçíàøèâàåòñÿ,

êîýôôèöèåíò ïîïðàâêè íà òåìïåðàòóðó ñòàíîâèòñÿ çíà÷èòåëüíî áîëüøå, ò. å.

ïîïðàâêà íà òåìïåðàòóðó – ýòî ôóíêöèÿ îò ñòàðåíèÿ, ÷òî ñîãëàñóåòñÿ ñ ðåçóëü-

òàòàìè íåñêîëüêèõ ïðîåêòîâ è èññëåäîâàíèé [8, 10].

Ïðèìåðû èíäèâèäóàëüíûõ ïîïðàâîê íà òåìïåðàòóðó äëÿ âûñîêîâîëüòíûõ ââî-

äîâ ïîêàçàíû íà ðèñ. 13. Äàííûå òàáëèöû, ïðåäñòàâëåííîé ïðîèçâîäèòåëåì, âåðíû

òîëüêî äëÿ íîâûõ âûñîêîâîëüòíûõ ââîäîâ. Êàê òîëüêî ó âûñîêîâîëüòíûõ ââîäîâ

ïîÿâëÿþòñÿ ïðèçíàêè ñòàðåíèÿ, òåìïåðàòóðíàÿ çàâèñèìîñòü óâåëè÷èâàåòñÿ. «Ïëî-

õèå» âûñîêîâîëüòíûå ââîäû èìåþò î÷åíü áîëüøóþ ïîïðàâêó íà òåìïåðàòóðó.

Ðèñ. 13. Ñòàíäàðòíàÿ ïîïðàâêà íà òåìïåðàòóðó ïî ñðàâíåíèþ

ñ èíäèâèäóàëüíîé ïîïðàâêîé íà òåìïåðàòóðó

äëÿ îáðàçöîâ âûñîêîâîëüòíûõ ââîäîâ GE Type U

Èíäèâèäóàëüíàÿ ïîïðàâêà íà òåìïåðàòóðó äëÿ òðàíñôîðìàòîðîâ ÿâëÿåòñÿ

áîëåå ñëîæíîé ïî ñðàâíåíèþ ñ ïîïðàâêîé äëÿ èçäåëèé èç îäíîãî ìàòåðèàëà, íà-

ïðèìåð âûñîêîâîëüòíûõ ââîäîâ. Ïîñòîÿííàÿ àêòèâàöèè ýíåðãèè ìàñëîáóìàæ-

íîé èçîëÿöèè W

, ñîãëàñíî çàêîíó Àððåíèóñà,

κ = κ

·exp(–W

/kT),

ãäå W

– ýíåðãèÿ àêòèâàöèÿ; k

– ïîñòîÿííàÿ Áîëüöìàíà.

Ýíåðãèÿ àêòèâàöèè äëÿ ïðîïèòàííîé ìàñëîì áóìàãè îáû÷íî ñîñòàâëÿåò

0,9–1 eV, â òî âðåìÿ êàê äëÿ ìàñëà òðàíñôîðìàòîðà W

– îáû÷íî îêîëî 0,4–

0,5 eV.

Èíäèâèäóàëüíûå ïîïðàâêè íà òåìïåðàòóðó äëÿ òðàíñôîðìàòîðîâ ñ ðàç-

íûì èçíîñîì ïîêàçàíû íà ðèñ. 14. Äàííûå äëÿ òðàíñôîðìàòîðà îáîáùåíû â

òàáë. 2.

Òàáëèöà 2

Äàííûå äëÿ òðàíñôîðìàòîðà

Ïðîèçâîäèòåëü Ãîä Âëàæíîñòü,

Íîìèíàëüíàÿ

ìîùíîñòü, MÂA

Ñòàòóñ

Pauwels 2005 0,4 80 Íîâûé, íà çàâîäå

Pauwels 2000 0,3 20 Íîâûé, íà ýíåðãîïðåäïðèÿòèè

Westinghouse 1985 1,5 40 Áûâøèé â óïîòðåáëåíèè,

çàïàñíîé

íà ýíåðãîïðåäïðèÿòèè

Yorkshire 1977 4,5 10 Áûâøèé â óïîòðåáëåíèè

è ñïèñàííûé

Ðèñ. 14. Ïîïðàâêà íà òåìïåðàòóðó äëÿ òðàíñôîðìàòîðîâ â ðàçíîì ñîñòîÿíèè

Êàê âèäíî èç ðèñóíêà, êàæäûé òðàíñôîðìàòîð èìååò ñâîþ èíäèâèäóàëüíóþ

ïîïðàâêó íà òåìïåðàòóðó. Íîâûå åäèíèöû èìåþò «îòðèöàòåëüíóþ» ïîïðàâêó

äëÿ íåçíà÷èòåëüíî ïîâûøåííûõ òåìïåðàòóð è áóäóò ïîêàçûâàòü ñîâåðøåííî

äðóãèå ðåçóëüòàòû, åñëè èñïîëüçîâàòü ñòàíäàðòíóþ òàáëèöó.

Ñòàðûå òðàíñôîðìàòîðû ïîêàçûâàþò òå æå õàðàêòåðèñòèêè, ÷òî è ñòàíäàðò-

íûå òàáëèöû, íî ñ áîëåå ñèëüíîé òåìïåðàòóðíîé çàâèñèìîñòüþ ïî ñðàâíåíèþ

ñî ñðåäíèìè çíà÷åíèÿìè IEEE.

Ðåçóëüòàòû ýêñïåðèìåíòîâ

Ïðîïèòàííàÿ ìàñëîì êðàôò-áóìàãà. Îáðàçöû êðàôò-áóìàãè ñ ðàçëè÷íûì

âëàãîñîäåðæàíèåì áûëè ïðîàíàëèçèðîâàíû ïðè ðàçíûõ òåìïåðàòóðàõ [13]. Ðå-

çóëüòàòû èçìåðåíèé äëÿ ñóõîé áóìàãè ñ âëàãîñîäåðæàíèåì <0,5 % ïîêàçàíû

íà ðèñ. 15.

Ðèñ. 15. Êîýôôèöèåíò ðàññåÿíèÿ êàê ôóíêöèÿ ÷àñòîòû äëÿ ñóõîé êðàôò-áóìàãè

Ðèñ. 16. Òàíãåíñ äåëüòà ïðè 50 Ãö äëÿ ñóõîé êðàôò-áóìàãè êàê ôóíêöèÿ òåìïåðàòóðû

Èñïîëüçîâàíèå ìåòîäà ×ÕÄ äëÿ îöåíêè òåìïåðàòóðíîé çàâèñèìîñòè íà

îñíîâå èçìåðåíèé òîëüêî ïðè îäíîé òåìïåðàòóðå äàåò ðåçóëüòàòû, ïðåäñòàâ-

ëåííûå íà ðèñ. 16. Êàê ïîêàçàíî íà äèàãðàììå, ðàññ÷èòàííàÿ òåìïåðàòóðíàÿ

çàâèñèìîñòü õîðîøî ñîãëàñóåòñÿ ñ äåéñòâèòåëüíî èçìåðåííûìè çíà÷åíèÿìè

òàíãåíñà äåëüòà.

Òðàíñôîðìàòîðû. Èçìåðåíèÿ ×ÕÄ íà ðàñïðåäåëèòåëüíîì òðàíñôîðìàòîðå

ïðè ðàçëè÷íûõ òåìïåðàòóðàõ ïîêàçàíû íà ðèñ. 17. Êàê è îæèäàëîñü, àíàëèç

íà âëàæíîñòü (âëàãîñîäåðæàíèå áóìàæíîé èçîëÿöèè) ïîêàçûâàåò îäèíàêîâûå

çíà÷åíèÿ âíå çàâèñèìîñòè îò òåìïåðàòóðû èçîëÿöèè (òåìïåðàòóðà èçîëÿöèè

îïðåäåëÿëàñü ïî òåìïåðàòóðå îáìîòêè, îöåíåííîé ïî ñîïðîòèâëåíèþ îáìîòêè

ïîñòîÿííîìó òîêó).

Ðèñ. 17. Ðåçóëüòàòû èçìåðåíèé ×ÕÄ è àíàëèçà âëàæíîñòè

ïðè ðàçëè÷íûõ òåìïåðàòóðàõ

Ìàñëÿíóþ è áóìàæíóþ èçîëÿöèþ íóæíî ðàññìàòðèâàòü îòäåëüíî ïðè ìî-

äåëèðîâàíèè òðàíñôîðìàòîðà äëÿ îöåíêè òåìïåðàòóðíîé çàâèñèìîñòè. Ýòî ïî-

êàçàíî íà ðèñ. 18.

Ðèñ. 18. Òàíãåíñ äåëüòà êàê ôóíêöèÿ ÷àñòîòû

äëÿ ìàñëÿíîé è áóìàæíîé èçîëÿöèè

Ñî÷åòàíèå ðåçóëüòàòîâ ìîäåëèðîâàíèÿ è ïðåîáðàçîâàíèÿ â òåìïåðàòóðíóþ

çàâèñèìîñòü ïîçâîëèëî ïîëó÷èòü êðèâûå, ïðåäñòàâëåííûå íà ðèñ. 19. Òàêæå

äëÿ ýòîé ñèñòåìû èçîëÿöèè, ñîäåðæàùåé äâà ðàçíûõ çàâèñÿùèõ îò òåìïåðàòó-

ðû ìàòåðèàëà, ïðåîáðàçîâàíèå äàåò ðåçóëüòàòû, î÷åíü áëèçêèå ê äåéñòâèòåëü-

íûì èçìåðåííûì çíà÷åíèÿì òàíãåíñà äåëüòà.

Ðèñ. 19. Òàíãåíñ äåëüòà ïðè 50 Ãö äëÿ ðàñïðåäåëèòåëüíîãî òðàíñôîðìàòîðà

êàê ôóíêöèÿ òåìïåðàòóðû

Âûñîêîâîëüòíûå ââîäû. Âûñîêîâîëüòíûé ââîä ASEA/ABB GOB ïðåäïî-

ëîæèòåëüíî â õîðîøåì ñîñòîÿíèè áûë èñïûòàí ïðè ðàçëè÷íûõ òåìïåðàòóðàõ.

Èçìåðåíèÿ òàíãåíñà äåëüòà è ×ÕÄ áûëè âûïîëíåíû ïðè òðåõ ðàçíûõ òåìïå-

ðàòóðàõ: â ïîìåùåíèè ïðè 22 °C, íà îòêðûòîì âîçäóõå ïðè –8 °C è â íàãðåòîé

êàìåðå ïðè 42 °C. Ðåçóëüòàòû èñïûòàíèÿ ïðèâåäåíû â òàáë. 3.

Òàáëèöà 3

Èçìåðåíèÿ òàíãåíñà äåëüòà íà âûñîêîâîëüòíîì ââîäå ABB GOB

Òåìïåðàòóðà

èçîëÿöèè, °C

Èçìåðåííûé òàíãåíñ äåëüòà

ïðè 200Â ïðè 1–10 kÂ Êîììåíòàðèé

–8 0,86 1,04 – 1,14 Çàâèñèìîñòü îò íàïðÿæåíèÿ ïðè

íèçêîé òåìïåðàòóðå

22 0,46 0,46 –

42 0,34 0,32 –

Íà ðèñ. 20 ïðåäñòàâëåíû ðàññ÷èòàííûå ïîïðàâêè íà òåìïåðàòóðó ñ èñïîëü-

çîâàíèåì ðåçóëüòàòîâ ïî ×ÕÄ âìåñòå ñ äàííûìè îò ïðîèçâîäèòåëÿ î ïîïðàâêàõ

íà ñðåäíþþ òåìïåðàòóðó.

Ðèñ. 20. Êðèâûå ïîïðàâîê íà òåìïåðàòóðó äëÿ âûñîêîâîëüòíîãî ââîäà ABB/ASEA GOB

Äëÿ êîíêðåòíîãî âûñîêîâîëüòíîãî ââîäà èíäèâèäóàëüíàÿ ïîïðàâêà íà òåìïå-

ðàòóðó êàê ïðè 22 °C, òàê è ïðè 42 °C ïðåêðàñíî ñîãëàñóåòñÿ ñ äàííûìè îò ïðîèç-

âîäèòåëÿ, ïîêàçûâàþùèìè âûñîêîâîëüòíûé ââîä â íîðìàëüíîì ñîñòîÿíèè.

Çàêëþ÷åíèå è âûâîäû

Èçìåðåíèå ÷àñòîòíîé õàðàêòåðèñòèêè äèýëåêòðèêà (×ÕÄ/Ñ×Î) – ýòî ìå-

òîä/ìåòîäîëîãèÿ èñïûòàíèÿ è äèàãíîñòèêè îáùåãî ñîñòîÿíèÿ èçîëÿöèè. Ïî

ñðàâíåíèþ ñ òðàäèöèîííûìè èçìåðåíèÿìè òàíãåíñ äåëüòà ïðè 50/60 Ãö èçìå-

ðåíèÿ ×ÕÄ èìåþò ñëåäóþùèå ïðåèìóùåñòâà:

– ñïîñîáíîñòü âûïîëíèòü èíäèâèäóàëüíóþ ïîïðàâêó íà òåìïåðàòóðó èçìå-

ðåííîãî çíà÷åíèÿ òàíãåíñà äåëüòà 50/60 Ãö;

– ñïîñîáíîñòü îöåíèòü âëàãîñîäåðæàíèå ïðîïèòàííîé ìàñëîì áóìàæíîé

èçîëÿöèè â ñèëîâûõ òðàíñôîðìàòîðàõ è âûñîêîâîëüòíûõ ââîäàõ;

– ñïîñîáíîñòü îöåíèòü çíà÷åíèå òàíãåíñà äåëüòà ïðè ðàáî÷åé òåìïåðàòóðå

äëÿ îöåíêè ðèñêà íåîáðàòèìîãî îòêàçà â ñëó÷àå òåïëîâîãî ïðîáîÿ;

– ñïîñîáíîñòü èññëåäîâàòü óâåëè÷åíèå òàíãåíñà äåëüòà èç-çà àêòèâíûõ ñî-

ñòàâëÿþùèõ.

Ñâîéñòâà èçîëÿöèè èìåþò áîëüøîå çíà÷åíèå äëÿ îïðåäåëåíèÿ ñîñòîÿíèÿ

ýíåðãîñèñòåìû â öåëîì. Íàëè÷èå èíôîðìàöèè î åå ñîñòîÿíèè ïîìîãàåò èçáå-

æàòü âîçìîæíîãî íåîáðàòèìîãî îòêàçà, îïðåäåëèòü «õîðîøèå» åäèíèöû è ïðè-

íÿòü ðåøåíèå î ïðàâèëüíîì òåõîáñëóæèâàíèè, ÷òî ïîçâîëÿåò îòñðî÷èòü çàòðà-

òû íà èíâåñòèðîâàíèå è, êàê ñëåäñòâèå, ñýêîíîìèòü çíà÷èòåëüíûå ñðåäñòâà.

1. IEEE Guide for Diagnostic Field Testing of Electric Power Apparatus; Pt. 1: Oil Filled Power Transf-

ormers, Regulators, and Reactors”, IEEE 62-1995.

2. Werelius P. et al. Diagnosis of Medium Voltage XLPE Cables by High Voltage Dielectric Spectros-

copy, paper presented at ICSD 1998.

3. Gäfvert U. et al. Dielectric Spectroscopy in Time and Frequency Domain Applied to Diagnostics of

Power Transformers // 6th Intern. Conf. on Properties and Applications of Dielectric Materials, June

21–26, 2000, Xi’an, China.

4. Gubanski S. M. et al. Dielectric Response Methods for Diagnostics of Power Transformers, Electra,

No. 202. June 2002. Ð. 23–34 (CIGRE Technical Brochure, No. 254. P. 2004).

5. Gubanski S. M. et al. Reliable Diagnostics of HV Transformer Insulation for Safety Assurance of Po-

wer Transmission System. REDIATOOL – a European Research Project, paper D1–207 CIGRE 2006.

6. Swedish Bushings Plant Sees Growth in RIP Designs, INMR Quarterly, Issue 68, 2005.

7. Braun J. M et al. Accelerated Aging and Diagnostic Testing of 115 kV Type U Bushings, paper

presented at IEEE Anaheim 2000.

8. Kane C. Bushing, PD and Winding Distortion Monitoring, paper presented at ABB Seminar «Power

Transformer Health Monitoring and Maintenance» Johannesburg, 2008.

9. Blodget R. B. Influence of Absorbed Water and Temperature on Tan Delta and Dielectric Constant of

Oil-Impregnated Paper Insulation, Trans. AIEE, 1961.

10. Brusetti R. Experience with On-line Diagnostics for Bushings and Current Transformers, NETA Fall

2002, paper A335.

11. Tyagi R. K., Victor S., Sodha N. S. Application of Temperature Correction Factors for dissipation fa-

ctor Measurements for Power Transformers – A case study, Doble Client Conf., Vadodara, India, 2006.

12. Werelius P., Ohlen M. Dielectric Frequency Response Measurements on Power Transformers,

EuroTechCon 2008, Liverpool, UK.

13. Niemanis R. et al. Determination of Moisture Content in Mass Impregnated Cable Insulation Usi-

ng Low Frequency Dielectric Spectroscopy, IEEE Power Engineering Society Summer Meeting 2000,

Seattle, Washington, USA.

COMPARISON STUDY BETWEEN GAS CROMATOGRAPHY

AND PHOTOACOUSTIC INFRARED SPECTROSCOPY

V. Sokolov

, D. Skelly, A. de Pablo, W. Ferguson, GE Energy

1. Introduction

Transformers are a critical part of an electrical utility’s asset base. Many utilities

have an ageing fleet of transformers that were installed as the system developed and ex-

panded. In numerous instances, transformers are being operated for many years beyond

their predicted useful life of 25 or 40 years. As electricity demand has increased, tran-

sformers in some regions are being loaded beyond their rated capacity in order to cope

with the demand. Generator transformers are heavily loaded as operators wish to max-

imize their profits and meet the demand. In some industries, e.g., aluminium smelting

or steel plants, transformers are also a critical part of the process. Loss of a transformer

in a utility, generation plant or process can cost many millions of dollars, depending on

how long it is out-of-service. Replacing a transformer is a costly and time-consuming

process. Demand for transformers and raw materials has increased in recent years, so

the cost and lead-time for delivery of a new transformer has increased.

Although the fact that a transformer not properly working generates gases is

known since the 1920´s [1], monitoring and diagnostics of transformers by means of

Dissolved Gas Analysis (DGA) has been developing since the 1950’s.

Dissolved gas analysis is indisputably the best detector of abnormalities in po-

wer transformers. Well-known Guides for Interpretation of Gases [2–4] give clear

suggestions how to identify defective transformers and what type of faults could

occur. Experience has shown that DGA can detect and give warning of 70 % of the

most common failures in power transformers [5].

Traditionally, DGA has been carried out by taking a sample of oil from the tran-

sformer, sending it to a laboratory and waiting for the results. Inadequate sampling

procedures, however, can lead to significant errors in the analysis. For example, bad

sampling techniques can introduce contaminants into the oil, and inappropriate stor-

age can mean loss of gas from the oil between taking the sample and analysis in the

laboratory. Results can vary from laboratory to laboratory, and even between users

of the same equipment. A CIGRE Round Robin test [6] showed spreads of several

hundreds of percent between identical samples tested in different laboratories using

various techniques (Table 1).

Table 1

Statistical data for gas chromatography analyses [6]

Deviation from true value, %

Sample A Sample B

Vacuum single stroke 13 40

Vacuum multiple strokes 23 35

Stripping 22 27

Best laboratory 7 14

Worst laboratory 39 70

Worst deviation on one gas 150 400

Sample A: hydrocarbons 6–60 ppm; CO, CO

: 100–500 ppm.

Sample B: hydrocarbons 1–10 ppm; CO, CO

: 30–100 ppm.

Another possible reason for this is that gas chromatographs are calibrated with

the aid of in-house prepared gas-in-oil standards or more normally gas mixtures

whose actual concentrations are not well established. This can lead to uncertainty in

diagnosing the results, especially when looking at trending of gas concentrations.

As an example of this, Table 2 shows the results of DGA analysis, Toepler pump

extraction method, of several 400 kV grid transformers in service with different gas

contents [7].

Table 2

DGA results of transformers in service

Vs,

Vg,

%g H

CO CO

Σg %R

49 0,7 1,46 6 1777 10272 1 40 98 0 1 0 12195 83,5

49 1,1 2,24 6 2537 14880 8 25 443 2 10 0 17911 80,0

70 2,1 3,00 5 2278 21858 6 232 1499 0 1 0 25879 86,3

63 2,6 4,13 7 6173 29105 30 45 1096 6 17 0 36479 88,3

46 2,9 6,30 11 8963 46078 5 181 1439 1 2 0 56680 90,0

41 3,0 7,32 16 6950 52848 62 182 3691 39 116 0 63904 87,3

45 3,7 8,22 8 6837 52998 70 0 1003 63 118 0 61097 74,3

35 3,3 9,43 22 10561 60833 121 175 9736 7 172 0 81627 86,6

48 5,2 10,83 14 9156 59969 70 120 31469 0 125 0 100923 93,2

48 5,7 11,88 6 12568 68396 29 800 22251 0 11 0 104061 87,6

Where Vs is sample volume, Vg is volume of gas, %g is percentage of gas, Σg is the sum of all gases

analyzed and %R is percentage of gases recovered.

2. Experimental procedure

Comparison between laboratory gas chromatography and photo acoustic spectros-

copy was done with gas-in-oil standards prepared according to ASTM 3612. Gas chr-

omatograph is a modern Agilent® GC. This GC employs a flame ionisation detector,

a thermal conductivity detector and a methanizer for CO and CO

quantification,. The

carrier gas is Argon. Gas extraction from the oil is by means of a headspace gas samp-

ling system, also by Agilent. The photo-acoustic spectroscope is a TRANSPORT X®

by GE Energy. The TRANSPORT X employed was a standard unit.

An external dedicated oil laboratory carried out gas chromatography. GE Ener-

gy technicians operated photo-acoustic spectrometer.

Standard Quantitative Gas-in-oil samples were created by spiking degassed new

transformer oil with known concentrations of fault gases. Additionally samples were

created using aged oil and separate samples were created containing only hydrogen

(because of practical difficulties in obtaining a mix of gases containing all the fault

gases and hydrogen, a separate hydrogen-in-oil sample was produced to verify acc-

uracy of hydrogen detection). All these samples were created according to ASTM

3612 Appendix 1. Multiple samples were created at various concentrations.

Gas chromatograph was calibrated with the aid of commercially available gas

standards. Photo-acoustic spectroscope TRANSPORT X unit was calibrated at the

manufacturer facilities using multiple gas standards and was verified on known gas-

in-oil standards.

3. Results and discussion

The results show very poor correlation between methods, laboratory gas ch-

romatography and photo-acoustic spectroscopy, despite good consistency within

individual methods.

These data suggest that the result reported from the GC and presented as gas-

in-oil, may in fact be the mass-of-gas result, in µl/l, and that this result was not cor-

rected for volumetric ratio and partition coefficients as demanded by the headspace

method. Essentially the results are raw data in the gas phase and are not correlated

back to the oil phase for the transformer oil. In addition the GC results were possi-

bly not corrected to normal temperature and pressure (NTP) (however no effort has

been made here to make an NTP correction).

Table 3 to 8 and Figures 1 to 4 below present the reported result from PAS, from

the GC and a set of corrected GC result assuming the above assertion is correct. The

correction factor was taken directly from ASTM 3612. The corrected results show

much improvement over the non-corrected with regard to absolute accuracy.

Table 3

New degassed oil sample spiked with 50 µl/l gas mixture

Spiked, µl/l Measured concentration, µl/l Corrected, µl/l

PAES GC

0 9 0 0

47 50 40 31

46 51 15 36

46 47 19 34

50 47 20 25

CO 49 48 38 17

46 97 164 221

Table 4

New degassed oil sample spiked with 100 µl/l gas mixture

Spiked, µl/l Measured concentration, µl/l Corrected, µl/l

PAES GC

0 10 0 0

94 98 73 56

92 101 29 70

92 90 36 65

101 96 42 53

CO 97 97 76 34

92 140 127 171

Table 5

New degassed oil sample spiked with 200 µl/l gas mixture

Spiked, µl/l Measured concentration, µl/l Corrected, µl/l

PAES GC

0 12 0 0

202 190 144 111

197 202 60 145

197 180 75 135

216 194 91 115

CO 208 191 176 79

197 228 247 333

Table 6

New degassed oil sample spiked with 250 µl/l gas mixture

Spiked, µl/l Measured concentration, µl/l Corrected, µl/l

PAES GC

0 61 0 0

253 242 175 135

246 245 75 182

246 226 93 167

270 252 115 145

CO 260 246 218 98

246 232 282 381

Table 7

Used degassed oil sample spiked with gas mixture

Spiked, µl/l Measured concentration, µl/l Corrected, µl/l

PAES GC

0 32 0 0

189 212 149 115

183 206 60 145

183 190 74 133

201 194 90 113

CO 194 224 197 89

183 286 297 401