Answer Posted / arvind singh

There is not any technical name for the transformer oil,
its only the specification which made the crude oil to
transformer oil(insulating oil). Nepthanic oil, Peraphenic
oil, Mineral Oil (its the specification which process the
crude oil to the nepthane base for the cooling of
transformer which have various acceptance norms as
specified in IS:335 below
Sl No. Characteristics Requirement Method of test as
per latest revision of IS as indicated below
1. Appearance The oil shall be clear and
transparent and free from suspended matters/sediments A
representative sample of oil shall be examined in a 100 mm
thick layer at the ambient temperature
2. Density at 29.5 Deg. C. Max. 0.89 g/cm3
IS:1448[P:16]
3.
Kinematic Viscosity at 27oC Max. 27 cst
IS:1448[P:25]
4. Interfacial tension at 27oC Min. 0.04 N/m
IS:6104
5. Flash point Pensky Marten (closed),Min.
140oC IS:1448[P:21]
6. Pour point Max. -6 deg. C IS:1448[P:10]
7. Neutralisation value (Total acidity) Max.
0.03 mg KOH/G IS:1448 [P:2]
8. Corrosive Sulphur Non-corrosive IS:335
9. Electric Strength (breakdown voltage)
IS:6792
a) New unfiltered oil, Min. 30 kV (rms)
b) After filtration, Min. 60 kV (rms)
10. Dielectric dissipation factor (Tan delta) at 90º C,
max. 0.002 IS:6262
11. Specific resistance (resistivity)
IS:6103
a) at 90oC min. 150x1012 ohm-cm *
b) at 27oC min. 2500x1012 ohm-cm *
12. Oxidation stability IS:335
a) Neutralisation value after oxidation Max.
0.40 mg KOH/g
b) Total sludge value after oxidation Max.
0.10 percent by weight.
13. Presence of oxidation inhibitor present by weight
The oil shall not contain anti-oxidant additives
IS:13631
14. Water content maximum 50 ppm IS:13567
15. Aging characteristics after accelerated ageing
(open beaker method with copper catalyst)
IS:12177
Method A
a) Specific resistance (resistivity) Min.
IS:6103
1) at 27oC, Min. 4.5x1012 ohm-cm
2) at 90oC, Min. 0.2x1012 ohm-cm
b)Dielectric dissipation factor (Tan delta) at 90oC
Max.
0.20 IS:6262
c) Total acidity, Max. 0.05 mg KOH/gm IS:1448
[P:2]
d) Total sludge, Max. 0.05 percent by weight
Annex A of IS 12177
16. SK value, max. 4-8% volume increase IS : 335

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