Device for cooling hot gases in a high-voltage equipment

Abstract

The invention relates to a device for cooling hot gases generated by an internal arc in high voltage metal-enclosed switchgear and controlgear or prefabricated high voltage/low voltage stations. This device comprises a metal foam cooling filter having a honeycomb structure.

Claims

1. An enclosure, comprising: a high voltage switchgear; and a device configured to cool hot gases generated by an internal arc in the high voltage switchgear, the device including a metal foam cooling filter disposed on an opening of the enclosure and having an alveolar structure of variable dimensions obtained by assembling at least six cells to form a honeycomb structure of hexahedral cells, the metal foam cooling filter being configured to slow a speed of expansion of the hot gases within the enclosure, openings of each hexahedral cell being obstructed by structural members of adjacent hexahedral cells in contact therewith.

2. The enclosure according to claim 1 wherein the hexahedral cells are connected together so as to have openings in all directions.

3. The enclosure according to claim 1 wherein the hexahedral cells form meshes.

4. The enclosure according to claim 3 wherein the hexahedral cells have a diameter lying between 1 and 4 cm.

5. The enclosure according to claim 1 wherein the cooling filter is made of aluminium.

6. The enclosure according to claim 1 wherein the cooling filter is made of cast iron.

7. The enclosure according to claim 1, wherein the enclosure is a metal enclosure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other characteristics and advantages of the invention will become clear from the description that follows, taken as a non-limiting example, while referring to the appended figures in which:

(2) FIG. 1 schematically illustrates a top view of a cell of a cooling filter in a preferred embodiment according to the invention;

(3) FIG. 2 schematically illustrates several side views of the cell of FIG. 1;

(4) FIG. 3 schematically illustrates a three-dimensional view of an assembly of several cells of FIG. 1;

(5) FIG. 4 shows a partial view of an example of embodiment of a cooling filter equipping a cooling device constituted by the assembly of FIG. 3;

(6) FIGS. 5 to 7 represent three possibilities of installation of a cooling filter in high voltage metal-enclosed switchgear and controlgear or a prefabricated high voltage/low voltage station.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

(7) FIGS. 1 and 2 schematically represent, respectively, a top view and a side view of a hexahedral cell 2 for manufacturing a metal foam cooling filter, made of aluminium or cast iron for example, intended to equip a metal enclosure containing HV switchgear or controlgear. The metal foam cooling filter may also be installed between two expansion volumes in a prefabricated high voltage/low voltage station or a prefabricated electrical room.

(8) FIG. 3 represents a 3D meshed honeycomb structure obtained by assembly of six cells 2. As may be seen in this FIG. 3, the cells 2 are assembled such that each of them has openings in all spatial directions. This structure favours an increase in turbulence within the cells, increasing the transfer of heat in internal arc conditions. It ensures at the same time a high overall porosity, substantially limiting the increase in internal pressure upstream of the filter. The gain in flow (speed, temperature, etc.) is thus obtained without notable impact on the switchgear or controlgear.

(9) FIG. 4 represents an example of cooling filter 4 equipping a device obtained by the assembly mode illustrated by FIG. 3 intended to be installed in a metal-enclosed module containing high voltage switchgear or controlgear. This cooling filter has a high porosity which favours an increase in turbulence in the cells and an increase in heat transfers in internal arc conditions.

(10) Preferentially, the diameter of the cells 2 lies between 1 and 4 cm and the thickness of the cooling filter 4 is from 4 to 20 cm, for example 10 cm.

(11) In another embodiment, not represented, the metal foam cooling filter comprises cells forming square meshes.

(12) The structure of the cooling filter 4 is closely linked to the dimensions of the high voltage metal enclosure in which it will be installed. In fact, the cooling filter 4 creates an obstacle to the flow of hot gases resulting from the appearance of an internal arc in the module containing the high voltage switchgear or controlgear. The result is a pressure jump through this cooling filter which induces an increase in pressure in the high voltage enclosure upstream of the filter. Yet, the resulting pressure must remain within the structural limit of the metal enclosure. If the resistance to flow is too low, the thermal effect will not be significant. Also, the dimensions of the cooling filter according to the invention are defined while take into account the following two situations: In the case where the internal arc occurs far from the cooling filter 4 and near the bottom of the metal enclosure, the first pressure peak in the arc compartment is not influenced by the cooling filter 4. In fact, more than 10 ms are required for the pressure wave to reach the cooling filter 4 and return to the arc area. The power of the arc drops after having reached a peak at the end of 10 ms. The dimensions of the cooling filter 4 are thus calculated so as to limit the increase in pressure due to the cooling filter 4, to the same level as the first pressure peak that would have been observed within the metal enclosure, in the absence of the cooling filter 4. In the case where the internal arc occurs near to the cooling filter 4, the impact of the latter on the increase in pressure is negligible. In fact, although the passage of gases through the cooling filter 4 accelerates the rise in pressure in the metal enclosure, this pressure drops considerably in several milliseconds when the hot gases reach the cooling filter 4 due to the fact that it is directly proportional to the density of the gas. This phenomenon makes the increase in pressure due to the cooling filter 4 almost negligible at the end of several milliseconds.

(13) The device according to the invention makes it possible to: slow down the gas speed in a metal enclosure containing HV switchgear or controlgear or in an insufficient expansion volume situated downstream of the metal enclosure; cool the temperature of these gases and create turbulences inside the metal enclosure, or the downstream volume; contain the combustion of flammable gases inside the metal enclosure, or the downstream volume; attain these objectives without increasing the pressure peaks in the metal enclosure, or the downstream volume.

(14) FIGS. 5 to 7 schematically represent a metal enclosure 10 containing high voltage switchgear or controlgear 12 arranged in an electrical room 14.

(15) In FIG. 5, a cooling filter 16 is arranged on an orifice 18 pierced on the upper face 20 of the enclosure 10 so as to cool and to reduce the speed of evacuation of the hot gases in the room 14.

(16) FIG. 6 represents another embodiment of a cooling filter which differs from the filter of FIG. 5 in that an additional buffer volume 21 is arranged above the module containing the high voltage switchgear or controlgear, in particular to limit the pressure, notably, in high performance modules (40-50 kA). A cooling filter 22 is arranged on an orifice 24 pierced on the upper face 26 of the enclosure 10.

(17) In FIG. 7, a cooling filter 36 is arranged in an expansion cavity 38 below the electrical room 14. The hot gases generated in the metal enclosure 10 are evacuated to the expansion cavity 38 via a first orifice 40 and a second orifice 42. The cooling filter 36 divides the expansion cavity 38 into two areas 44 and 46. A second cooling filter 48 is arranged on a third orifice 50 linking the second area 46 and the inside of the electrical room 14.

(18) The cooling filter 36 slows down the flow of hot air which is evacuated via the orifice 40 to the first area 44 whereas the second cooling filter 48 slows down the flow of hot air which is evacuated via the third orifice 50 from the second area 46 to the inside of the electrical room 14.