IS CODE for transformer oil

Answer 1

Refer to:

International Electrotechnical Commission IEC 836"Specifications for silicone liquid for electrical purposes" (Silicone Fluid Type T-1) and

ASTM D 4652 "Silicone Fluids for Electrical Insulation" specifications for repair or top-off of existing liquid-filled units.

These standards cover both the physical and electrical properties of fluid suitable for dielectric applications.

Also refer following:

IS-335/1993 - Specification for uninhibited new insulating oils.

IS-12463/1988 - Specification for inhibited mineral insulating oils.

IEC -60296/2003 - Specification for unused mineral insulating oils for Transformers and switchgear. This standard cover both uninhibited and inhibited oils.

ASTM - D3487/2000-StandardSpecification for Mineral Insulating Oil used in Electrical apparatus. This standard also covers both uninhibited and inhibited oils.

Unused Mineral Insulating oils filled inNew transformers

IS -1866/2000-Code of Practice for Electrical Maintenance and supervision of Mineral Insulating oil in Equipment. (Refer Table.1 for limiting values of various parameters)

IEC -60422/1998-Supervision and maintenance guide for mineral insulating oils in electrical equipment.

In service Mineral Insulating oils:

IS -1866/2000 -Code of Practice for Electrical Maintenance and supervision of Mineral Insulating oil in Equipment.(Refer Table for limiting values of various parameters)

IS-335/1993

Appearance ------------ Clear and transparent

Density at 29.5 deg.C (Max) 0.89 g/cm2

Kinematic Viscosity (Max)

1) at 27deg.C ------------------ 27 cSt

2) at 40deg.C ------------------ Under consideration

IFT at 27deg.C (Min) ---------0.04 N/m

Flash Point (Min) --------- 140deg.C

Pour Point (Max) ---------- 6deg.C

Neutralization Value

1) Total Acidity (Max) ---- 0.03 mg KOH/gm

2) Inorganic acidity ------ Nil

Corrosive Sulphur ------- Non-corrosive

Electric Strength (BDV)

1) New unfiltered Oil (Min) 30 KV (rms)

2) After filteration (Min) If the above value is not attained, the oil shall be filtered to 60 KV (rms)

Dielectric dissipation factor (tan ) at 90deg.C(max) 0.002

Specific resistance (Resistivity)

1) at 90deg.C (Min) 35 x 10 12 ohm-cm

2) at 27deg.C (Min) 1500 x 10 12 ohm-cm

Oxidation Stability

1) Acidity (max) 0.4 mg KOH/gm

2) total sludge (max) 0.1 % by weight

Ageing characteristics

a) Resistivity (Min)

1) at 27deg.C 2.5 x 10 12 ohm-cm

2) at 90deg.C 0.2 x 10 12 ohm-cm

b)Tanδ at 90deg.C (Max) 0.20

c) Total acidity (Max) 0.05 mg KOH/gm

d) Total sludge (Max) 0.05 % by weight

Presence of Oxidation inhibitor -The oil shall contain natural anti oxidant additives.

Water content - 50 ppm

S K value - Under consideration

IS-1866/2000-Recommended Limits of Unused Mineral Oil filled in NewTransformer

Property

Highest Voltage of Equipment (KV)

< 72.5

72.5-170

>170

Appearance

Clear, free from sediment and suspended matter

Density at 29.5 deg.C (g/cm2), Max.

0.89

0.89

0.89

Viscosity at 27 deg C (cst), Max

27

27

27

Flash Point deg. C, Min

140

140

140

Pour Point Deg. C , Max

-6

-6

-6

Total acidity (mg KOH/gm), Max

0.03

0.03

0.03

Water Content (ppm), Max

20

15

10

IFT at 27 degC,(mN/m), min

35

35

35

Tanδ at 90 deg C, Max

0.015

0.015

0.01

Resistivity at 90 deg.C (x10e12 ohm cm Min.

6

6

6

BDV Kv Min

40

50

60

IS-1866/2000-Violation Limits for in service oils

Property

Highest Voltage of Equipment (KV)

< 72.5

72.5-170

>170

Flash Point deg. C, Min

Maximum decrease of 15deg.C from initial value

Pour Point Deg. C , Max

-6

-6

-6

Total acidity (mg KOH/gm), Max

0.3

0.3

0.3

Water Content (ppm), Max

No free water

40

20

IFT at 27 degC, (mN/m), min

1

1

1

Tanδ at 90 deg C, Max

1

1

0.2

Resistivity at 90 deg.C (x10e12 ohm cm Min.

1

1

1

BDV Kv Min

30

40

50

Sediment and Sludge

No sediment or precipitable sludge should be detected.

Results below 0.02% by mass may be neglected

IS-1866/2000 - Frequency of testing

Property

Frequency of Testing

Appearance

In conjunction with other Quantitative tests

Water content

After filling or refilling prior to energizing, then after

three and 12 months, subsequently along with DGA

BDV

After filling or refilling prior to energizing, then yearly

Total acidity

Yearly

IFT

After filling or refilling prior to energizing, then yearly

Resistivity

After filling or refilling prior to energizing, then yearly

Tanδ

After filling or refilling prior to energizing, then yearly

Flash Point

Yearly

Sediment and sludge

Yearly

IS-1866/2000-Recommended Actions

Property

Recommended Actions

Appearance

As dictated by other tests

Water content

Check Source of water and consider reconditioning

BDV

Recondition the oil or alternatively, if more economical or other tests dictate replace oil

Total acidity

Replace or reclaim oil

IFT

Replace or reclaim oil

Resistivity

Replace or reclaim oil

Tanδ

Replace or reclaim oil

Flash Point

Replace the oil, equipment may require inspection

Sediment and sludge

Where sediment is detected recondition the oil

IS-1866/2000 - Classification of oils in service.

Group 1:

This group contains oils that are in satisfactory condition for continued use. The frequency can be followed as described earlier.

Group 2:

This group contains oils that requires reconditioning for further service. (LOW BDV and High water content). The frequency can be followed as described earlier after reconditioning.

Group 3:

This group contains oils in poor condition that it can restore satisfactory properties only after reclaiming. Insulating oils this group should be reclaimed or replaced depending on economic considerations.

Group 4:

This group contains oils, in such poor state that it is technically advisable to dispose of them.

IEC -60296 - General Specification

Functional Properties: Viscosity, Pour point, Water content, BDV, Density, Tan.

Stability Properties: Appearance, Acidity, IFT, corrosive Sulfur, Antioxident additive

Performance Properties: Oxidation Stabillity, Sludge

HSE Properties: Flash Point, PCB content, PCA content

Ashok

Head Engineering & Project Execution

EVI, India