GB1430418A - Electrical bushing assembly - Google Patents

Abstract

1430418 Bushing assembly WESTING- HOUSE ELECTRIC CORP 16 April 1973 [27 April 1972] 18236/73 Heading H2C An electrical bushing assembly for power transformers comprises a lead tube 10 coaxial within an upper casing member 20; and stressrelieving means 28 comprising a cap 30 having an opening 32 for the end 12 of the lead tube 10 to which it is secured by a nut 34, and a cup 40 having a flange 48 positioned between the cap 30 and the upper edge of the casing member 20. Coiled compression springs 38 enclosed between the cap 30 and the bottom 44 of the cup 40 maintain the lead tube 10 under tension and the casing member 20 under compression via a gasket 50, and relieve stresses due to differential expansion of the lead tube and casing member. A resilient 0-ring 54 compressed between the cap 30 and the flange 48 provides a fluid-tight expansion seal. The cup 40 gives the stressrelieving means 28 a shape which avoids any substantial increase in length of the bushing assembly. In another embodiment, Fig. 3, the compression springs 38 are disposed in an annular slot of an inverted telescopic member 64 which bears upward on the lower edge of the upper casing member 20 via a gasket 50, the slot being telescopically engaged with an annular wall 72 of a bushing support member 24 attached to the lower casing member 22. A fluid-tight expansion seal is provided by a flexible band 74 attached at its first end 76 to the cup 64 and at its second end 78 to the bushing support member 24. Such a flexible band (56, Fig. 2, not shown) may be used in the first embodiment instead of the O-ring expansion seal 54; furthermore in any embodiment it may be shaped to provide a larger space and thus act as an oil expansion chamber. In a further modification (Fig. 4, not shown) the springs (38) are compressed between internal projections or annular shoulders of an inverted cup (80) and of a bushing support member (24) which telescopes into the cup (80).