GB1228101A - - Google Patents

Abstract

1,228,101. Metal clad switchgear; gas blast switches. "COQ" N.V. 16 April, 1969 [22 April, 1968], No. 19496/69. Heading H1N. A metal clad, gas filled switchgear has a high pressure compartment 2 containing arc extinguishing SF 6 gas and a low pressure compartment 14 containing insulating SF 6 gas and has a gas control system which adjusts the density of gas in the two compartments such that the pressure difference between the two compartments is maintained substantially constant and the density in the low pressure compartment is maintained substantially constant. As shown the high pressure compartment 2 which contains a multibreak gas blast switch 3 is located inside the low pressure compartment 14 which also contains a series isolating switch 4; earthing switch 10; spark gap 11; duplicate bus-bar selectors 5, 6; and current transformers 12, 13. The gas blast vents into a chamber 15 from where it is returned to the compartment 14 through filters 38 and non-return valves. The pressures in the two compartments are applied to opposite sides of a differential pressure switch 48. If the pressure difference is too high a contact 50 is closed and a solenoid valve 34 opened to allow gas to leak from one chamber to the other. If the difference is too small another contact 49 is closed to energize a compressor 36 to pump gas from the low pressure to the high pressure compartment. The density of gas in the low pressure compartment 14 is sensed by a switch 45; if too low a contact 46 energizes a valve 28 to introduce more gas from a bottle 30; if too high a contact 47 energizes a valve 31 to vent some gas to the atmosphere. To avoid unnecessary loss of gas valve 31 is energized by way of a contact 53 of switch 48 so that valve 31 is not operated while the pressure difference is low, e.g. during a switching operation. If due to low temperature some gas condenses in the high pressure compartment 2 it flows to a chamber 44 and a float switch 52 energizes a heater 43 to revapourize it. In a modification (Fig. 3, not shown) to avoid loss of gas to the atmosphere low and high pressure gas storage tanks (54, 60) are connected to compartment 14 and gas is recirculated between them by a second compressor (59). In this case chamber 15 feeds the filtered gas to the low pressure tank (54) and valve 48 senses the difference between the high pressure compartment 2 and chamber 15 whose pressure rises more rapidly and therefore causes a quicker response during an interruption. In a further modification (Fig. 4, not shown) the storage tanks (54, 60) and compressor (59) are shared by a plurality of switchgear assemblies.