Patent GB-290651-A (GB)
Title: Improvements in or relating to high voltage insulators
IPC: H01B17/28
Filed: 1928-02-28
Abstract: 290,651. Associated Electrical Industries, Ltd., (formerly Metropolitan-Vickers Electrical Co., Ltd.), (Assignees of Mateer, J. E.). May 19, 1927, [Convention date]. Transformers.-A lead-in bushing for oil-filled high voltage circuit interrupters &c. comprises a well structure at the inner end of the bushing adapted for insertions through the bushing opening in the interrupter tank, the well structure and the flexible conductor ready for threading through the bushing being mounted for shipment separately from the bushing in such a way that the parts will require no further adjustments during assembly. The well structure 4 consists of an open ended metal well 12, having a flauge 19 to carry a transformer 5, and a flange 20 engaging the end of an insulating structure 14. A lateral flange 18 on the well 12 receives bolts 27 which rest on bosses 28 on the cover 2 of the interrupter casing to hold the well in adjusted position. The well cover 15 rests on a sealing gasket 30 and is bolted to the flange 18. The insulating structure 14 is preferably of porcelain and is formed with downwardly-converging sidewalls 35 with surface creeping flanges 36. The structure 14 is secured to the flanges 19, 20 by rubber compound. A collar 39 is secured by cement 40 round the lower part of the side walls 35, as shown, a metal plate 42 being secured across the end of the structure 14. A screwthreaded conducting stud 46, integral or secured to the plate 42, projects for the reception of a stationary contact member of the interrupter, a cable 48, extending through the bushing, being welded to the plate 42. The current transformer 5 comprises a laminated ring core 50 and a low voltage secondary 51, the cable 48 forming a oneturn primary winding. An oil-tight low voltage terminal device for the transformer 5 comprises an insulating bushing 53 in which the conductor 54 is preferably sealed, washers 55, and nuts 57 attaching adjacent conductors 58, 59 in the circuit of the windings 51. The condenser bushing structure comprises an inner condenser 64, a metal supporting cylinder 65, a collar 67, outer porcelain protective shells 68 and a top terminal structure 70. The condenser 64 is preferably formed of alternate layers of metal foil and hard moulded fibrous insulating material, such as paper impregnated with phenolic condensation product, and is tapered or stepped from a uniform cylindrical mid-portion 71 to its outer end. The cylinder 65 is sealed to the portion 71 and to the well 12, and is formed with an annular flange 74 sealed and secured in position on a flange 32 of the cover 15 by a gasket. 78 and) screws 79. The collar 67 is formed with a cylindrical portion 80, a projecting flange 85 bolted to a flange 74 on the cylinder 65, the under part of the flange 85 being bevelled to rest on a sealing gasket carried on the bevelled edge 77 of the flange 74. A flange 87 of the lowest of the nested shells 68 rests on a gasket 88 on the collar 67 and is cemented to the collar portion 80. The top terminal structure 70 comprises a collar 94 secured to the top shell 68, and a member 95 comprising lifting hooks 99 and a terminal clip 100. After the well structure has been placed in position through the flanged opening 7 in the casing 2, the stud 46 may be laterally adjusted' by moving the flange 18 on the flange 9 of the casing 2. For shipment, the condenser bushing, as one unit, and the well structure, with the cable detached from the terminal 70, and the remaining interrupter parts, as a second unit, may be separately packed, no adjustments being necessary on reassembly. In a modified construction, the wellstructure is permanently fixed to the cover 2, thus preventing adjustment of the stud 46, and the flange 20 is a separate element secured to the well-structure by screws.