Insulating oils with high surge resistance - based on high-aromatics reformate fractions

摘要

Insulating oils with a negative d.c. surge resistance of 200 kV, a positive d.c. surge resistance of 130 kV and a negative gas evolution value of is not -20 mu l/min, comprise a high-aromatics reformate having a boiling range of 204-371 degrees C, contg. 1.0 wt.% polar cpds., contg. 2.5 wt.% polynuclear aromatics (=4 fused rings), and having a 100 degrees F viscosity of 50-300 SUS, a pour point -9.4 degrees C and a flash point of =130 degrees C. As well as their good electrical properties, the oils have good oxidative stability and convective heat transfer properties. An insulating oil was prepd. by blending (i) 57 pts. vol. of an aromatic oil (212-316 degrees C, 99.6 wt.% aromatics, 0.18 wt.% polar cpds.) prepd. by reforming a hydrotreated naphtha and fractionating the product, with (ii) 43 pts. vol. of a raffinate (13.5 wt.% aromatics) obtd. by phenol extraction of a middle distillate (247-392 degrees C) derived from a naphthenic crude. The prod. had surge breakdown voltages of 246 kV (negative) and 143 kV (positive) and a gas evolution value of -106 mu l/min.