Gas

Normal Limit

IEC 60599:199

(Guideline)

Abnormal Limit

IEC 60599:1999

(Guideline)

Production rates

IEC 60599:1999

Solubility

H₂ – Hydrogen

≤ 60

≥ 150

≤ 5 ppm/day

7 %

CH₄ – Methane

≤ 40

≥ 110

≤ 2 ppm/day

30 %

CO – Carbon Monoxide

≤ 540

≥ 900

≤ 50 ppm/day

9 %

CO₂ – Carbon Dioxide

≤ 5100

≥ 13000

≤ 200 ppm/day

120 %

C₂H₄ – Ethylene

≤ 60

≥ 280

≤ 2 ppm/day

280 %

C₂H₆ – Ethane

≤ 50

≥ 90

≤ 2 ppm/day

280 %

C₂H₂ – Acetylene

≤ 3

≥ 50

≤ 0.1 ppm/day

400 %

CO / CO₂ Ratio

Between 3 and 11

Possible Paper Breakdown – Check with Furanic Test

Transformers ≥ 132 kV

Limit

Unit of Measure

Moisture

20 ppm (Max.)

ppm

Acidity

0.20 (Max.)

Mg KOH/g Oil

Dielectric

60kV (Min.)

kV

PCB

50 ppm (Max)

ppm

Transformers ≤  132 kV

Limit

Unit of Measure

Moisture

20 ppm (Max.)

ppm

Acidity

0.20 (Max.)

Mg KOH/g Oil

Dielectric

50kV (Min.)

kV

PCB

50 ppm (Max)

ppm

Drums and Switchgear

Limit

Unit of Measure

Moisture

30 ppm (Max.)

ppm

Acidity

0.20 (Max.)

Mg KOH/g Oil

Dielectric

30kV (Min.)

kV

PCB

50 ppm (Max)

ppm

Note1

< 200

Test indicates extensive paper degradation has taken place, and has exceeded the critical point. The transformer is now a serious risk of failure.

Note 2

200-250

The paper is near or at the critical condition. Recommend that the transformer be taken out of service as soon as possible and thoroughly inspected.

Note 3

260-350

The paper is approaching the critical condition. Suggest inspection be scheduled and/or re-sample within 3/6/12 months to reassess condition. Paper samples can be taken for direct DP testing.

Note 4

360-450

The paper is starting to approach the critical condition. Suggest a re-sample in 6-12 months time.

Note 5

460-600

Significant paper deterioration but still well away from the critical point.

Note 6

610-910

Mild to minimal paper ageing.