Natural Ester

Paper

Standard

Temperatures

Duration

Results

Palm kernel oil alkyl ester (PKOAE) [14]

TUK paper 0.255 mm thickness

ASTM D149

150˚C

672, 1344 and 2016 h

Breakdown strength (BDS) of TUK dipped in MO is comprised between 55 and 54 kV/mm, while the BDS of TUK dipped in PKOAE is comprised between 78 and 75 kV/mm.

Not specified [16]

Kraft paper 0.5 mm thickness

ASTM D149

110˚C, 140˚C, 160˚C and 185˚C

336 h at 110˚C, then 336 h and 140˚C, next 336 h at 160˚C, finally 336 h at 185˚C for a total of 1344 h

Initial BDV of fresh paper equal to 4 kV. At the end of the aging tests, BDV of paper dipped in natural ester was the highest (16 kV), followed by paper dipped in synthetic ester (12 kV) then a mixture of mineral oil and synthetic ester (10 kV).

Soya bean oil [17]

TUK and Nomex-910, each of 0.077 mm thickness

ASTM D149

120˚C, 150˚C and 180˚C

48, 72 and 96 h

Initial Breakdown strength (BDS) of NP-910 equal to 92 kV/mm and TUK 62 kV/mm. After 180˚C after 96 hours, the BDS of Nomex-910 falls by 37.83, while the BDS of TUK falls by 52%.