Patent GB-410826-A (GB)
Title: Improvements in or relating to metal-clad liquid-insulated electrical apparatus
IPC: H02B1/00
Filed: 1932-11-25
Abstract: 410,826. Oil-break switches. REYROLLE & CO., Ltd., A., Hebburn-on-Tyne, and ALLAN, A., Cragside, Ashleigh Grove, Tynemouth. Nov. 25, 1932, No. 33383. [Class 38 (v).] Cases.-Metal-clad, liquid - immersed apparatus such as switches, is provided with spaced barriers of solid insulating material inserted in the liquid between the apparatus and the casing walls in order to increase the resistance to flash-over in the direction normal to their surfaces, and the inner barrier or barriers are interrupted to break the surface flash-over path between conducting parts of the apparatus which may be at different potentials, and have their edges at the interruptions bent over at an angle to the surface, whilst the outer barrier or barriers lie between the walls and the gaps formed by the interruptions. As applied to the oil-filled isolating switch chamber disclosed in Specifications 410,206 and 410,207, equi-spaced contacts B, D are mounted for example on insulators B<1>, D' and their connections taken through insulators C<2>, D<2> to, for instance, cables F<1> G<1>, and also to a main breaker through insulator E<1>, withdrawable conductor E, and sluice valve E<2> for closing the orifice in the tank A when E is withdrawn. The cable-ends F, G are arranged to be withdrawable without loss of oil from the tank A or admission of air (which may be moist) thereto, and a cock F<4> is provided for draining and filling each insulator with oil. Rotary isolating blades G, G<1> are mounted, respectively, on the insulator B<1> and an insulator G<2> independently movable inside B<1>, but in an alternative form, B, C are connected to main breaker contacts and a single arm G is mounted on the third contact D. The upper part H containing the operating mechanism (not shown) acts as an oil conservator and expansion chamber for the tank A, with which it communicates bv two small holes, and is provided with a "breathing" device for admitting dried air. Six equallyspaced barriers J<1> ... J<4> are used for 132 kV switchgear, and are arranged in three parts, each part extending from about the middle of one wall, round the apex, to the middle of the next wall, where it overlaps the edge of the neighbouring part. The innermost barrier or barriers, two as shown, are bent inwards as at K<1> and are slotted top and bottom to receive metal securing strips K<5> carried by brackets K<4> on the framework K<2>, to which the outer strips are bolted at K<3>. Spacing strips K<6> are also provided. Adjacent the central parts of the walls the barriers extend to the full height of the wall, but adjacent the apexes, they are cut away by amounts gradually increasing towards the innermost barrier, the two outer ones being left at full height. Suitable material is compressed paper, cardboard, or compressed wood-pulp, or other fibrous material readily absorptive of oil, care being taken to remove all traces of moisture during preparation and assemblage in the apparatus, and to dry the oil. In a modification, Figs. 4, 5 (not shown) the invention is applied to an isolating blade, which can be lowered about its pivot to an earthing position and is located in a tank having its flat sides parallel to one another and its ends rounded.