This paper discusses recent, new impregnant developments and evaluations for capacitor dielectrics. These dielectric fluids are isopropylbiphenyl (Wemcol), di-2 ethylhexyl phthalate plus trichlorobenzene (Dielektrol II) butylated monochlorodiphenyl oxide (Edisol) phenyl xylyl ethane (PXE) and benzyl neocaprate (BMC). The film-paper dielectrics impregnated with these were extensively tested for thermal stability under voltage and resistance to overvoltages with partial discharges: Considerable attention is now being devoted to practically significant partial discharge testing, to determine service reliability. Also included here is the evaluation of windings where one foil is narrower and folded at the edges to reduce the voltage stress at the foil edges.
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