GB1404931A - Electrical switchgear - Google Patents

Abstract

1404931 Metal-clad switchgear REYROLLE PARSONS Ltd 11 Sept 1972 [22 June 1971] 29269/71 Heading H1N In high voltage metal-clad switchgear filled with gas under pressure (e.g. SF 6 , compressed air) the adjoining sections of bus-bar or connection chambers have bellows-type expansion joints which permit relative movement, provide compensating means to minimize end loading on the chambers, and also cater for any assmebly misalignment, each joint comprising a main bellows 13, Fig. 1, attached in a gas-tight manner between end flanges 14, 15 of chambers 11, 12 and a group of pressure-compensating auxiliary bellows 16 mounted between these end flanges by means of overlapping brackets 17, 18 (detailed in Fig. 2, not shown) so that the two sets of bellows act in opposition. The interior of each compensating bellows is connected by a pipe 19 to the interior of chamber 11 so that all bellows and chambers are at a common pressure. The total effective internal cross-sectional area of the compensating bellows 16 is preferably equal to that of the main bellows 13 so that any end loading on the chambers arising from gas pressure and/or thermal expansion stresses transmitted to the chamber supporting structure is compensated since movement of the chambers tending to compress the main bellows 13 is accompanied by a similar expansion movement of the compensating auxiliary bellows 16 and vice versa. The group of compensating auxiliary bellows is normally distributed around the flange mounting for the main bellows (Fig. 3, not shown) but combination into a single double walled unit of annular cross-section with its inner wall surrounding the main bellows is referred to. The main bellows are of non-magnetic material to eliminate heating from induced electric currents.