Dielectric strength of oil-immersed transformer insulation with superimposed AC and lightning impulse voltage

Author

Kamata, Y. ; Endoh, K. ; Furukawa, S. ; Endoh, F. ; Nonomura, K. ; Iwata, Yoshiyuki ; Horiuchi, S. ; Takasu, N.

Author_Institution

Hitachi, Ltd., Tokyo, Japan

Volume

25

Issue

4

fYear

1990

fDate

8/1/1990 12:00:00 AM

Firstpage

683

Lastpage

687

Abstract

The 50-Hz AC partial discharge (PD) triggered by a lightning impulse voltage of 1.2/50 μs and breakdown characteristics under superimposed voltage conditions are studied for several modes of oil-immersed transformer insulation, representing typical combinations of mineral oil and oil-impregnated paper. It is concluded that (1) no AC PD phenomena are triggered by lightning impulse voltage when the preapplied 50-Hz voltage is less than 50% of the RMS value of the AC PD inception voltage for all combinations of polarities, and (2) peak breakdown values of the superimposed voltage are reduced by 10 to 19% for a single applied lightning impulse with a low solid-to-liquid dielectric packing fraction (SLPF) for oil-impregnated paper in the intercoil model, but the difference in breakdown voltage between the superimposed voltage and a single lightning impulse is very small for a high SLPF for oil-impregnated paper, i.e. above about 30%

Keywords

electric strength; impulse testing; insulating oils; insulation testing; partial discharges; transformer insulation; 50 Hz; AC partial discharge; SLPF; breakdown characteristics; dielectric strength; inception voltage; intercoil model; lightning impulse voltage; mineral oil; oil-immersed transformer insulation; oil-impregnated paper; peak breakdown values; solid-to-liquid dielectric packing fraction; superimposed voltage conditions; Breakdown voltage; Dielectric breakdown; Dielectrics and electrical insulation; Lightning; Minerals; Oil insulation; Partial discharges; Petroleum; Power transformer insulation; Solid modeling;

fLanguage

English

Journal_Title

Electrical Insulation, IEEE Transactions on

Publisher

ieee

ISSN

0018-9367

Type

jour

DOI

10.1109/14.57090

Filename

57090