Insulating Paper, Corrugated Paperboard for Transformers

Thickness tolerance

IEC 641-2

≤ 1.6 mm 6.00 %
> 1.6 - 8.0 mm 4.00 %

±7.5 %
± 5.0 %

Apparent density

IEC 641-2

≤ 1.6 mm 1.09 g/cm³
> 1.6 - 4.0 mm 1.15 g/cm³

1.00 - 1.20 g/cm³
1.10 - 1.25 g/cm³

Min. tensile strength M.D. unfolded

IEC 641-2

≤ 1.6 mm 107 N/mm²
> 1.6 - 4.0 mm 128 N/mm²

70 N/mm²
80 N/mm²

Min. tensile strength C.M.D, unfolded

IEC 641-2

≤ 1.6 mm 77 N/mm²
> 1.6 - 4.0 mm 83 N/mm²

50 N/mm²
55 N/mm²

Min. elongation M.D, unfolded

IEC 641-2

3.9 %

6.0 %

Min. elongation C.M.D, unfolded

IEC 641-2

4.1 %

8.0 %

Max. moisture content

IEC 641-2

4.2 %

8.0 %

Max. ash content

IEC 641-2

0.3 %

2.0 %

pH of aqueous extract

IEC 641-2

6.3

6.0 - 9.0

Max. shrinkage M.D

IEC 641-2

0.4 %

0.5 %

Max. shrinkage C.M.D

IEC 641-2

0.6 %

0.7 %

Max. thickness shrinkage

IEC 641-2

3.9 %

5.0 %

Min. oil absorption

IEC 641-2

≤ 1.6 mm 13.7 %
> 1.6 - 4.0 mm 10.6 %

11.0 %
9.0 %

Compressibility C

IEC 641-2

≤ 1.6 mm 9.4 %
> 1.6 - 4.0 mm 5.7 %

10.0 %
7.5 %

Revers. part of compressibility Crev

IEC 641-2

≤ 1.6 mm 54 %
> 1.6 - 4.0 mm 71 %

45 %
50 %

Min. breakdown voltage in oil

IEC 641-2

≤ 1.6 mm 50 kV/mm
> 1.6 - 4.0 mm 45 kV/mm

12 kV/mm
10 kV/mm

Max. conductivity of aqueous extract

IEC 641-2

≤ 1.6 mm 3.3 mS/m
> 1.6 - 4.0 mm 3.5 mS/m

10.0 mS/m
10.0 mS/m