History
1930xx. First 110 and 220 kV bushings

In autumn 1931, Izolyator Plant manufactured an oil-filled bushing for 115 kV for the first time.
The first Russian high voltage bushings were non-sealed. Oil-barrier insulation was used as their inner insulation. In 1932, non-sealed oil-barrier bushings rated 110 kV were developed, and their serial production commenced.