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
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