WO2014137336A1

WO2014137336A1 - Deforming pressure ring seal for an arc-resistant switchgear duct

Info

Publication number: WO2014137336A1
Application number: PCT/US2013/029406
Authority: WO
Inventors: Jeffrey T. JORDAN; Sergio Flores VÁZQUEZ; Alberto Guerrero VEGA; Gregory O. MOTLEY
Original assignee: Schneider Electric USA Inc
Current assignee: Schneider Electric USA Inc
Priority date: 2013-03-06
Filing date: 2013-03-06
Publication date: 2014-09-12
Anticipated expiration: 2015-09-06
Also published as: RU2015135183A; EP2965392B1; EP2965392A4; RU2624468C2; CN105009390B; CN105009390A; EP2965392A1

Abstract

An electrical enclosure assembly includes a duct chamber with two adjacent duct sections having respective first and second flanges fastened to form a flanged butt joint. The duct sections are in a path through which a pressure wave travels during an arc-fault event from an arc-fault device to an exhaust vent. A pressure ring is fastened internally to at least one of the first and second panels to cover the flanged butt joint. In response to a peak pressure of the pressure wave, the pressure ring deforms with the respective adjoining panels of the duct sections. Although the peak pressure creates gaps in the flanged butt joint, the deformation causes the pressure ring to fill-in those gaps and, thus, block ventilation through the flanged butt joint.

Description

DEFORMING PRESSURE RING SEAL

FOR AN ARC-RESISTANT SWITCHGEAR DUCT

FIELD OF THE INVENTION

[0001] This invention is directed generally to electrical systems, and, more particularly, to a pressure ring for protecting a joint between two adjacent duct sections.

BACKGROUND OF THE INVENTION

[0002] Arc-resistant switchgear enclosures are designed to withstand the effects of an internal arc-fault event. Such event typically causes an explosive reaction that results in a violent pressure wave traveling in the enclosure towards an exhaust vent and causing severe mechanical and thermal stress on the structural components of the enclosure.

[0003] One problem with current enclosures occurs at a flanged connection between adjacent duct sections. The connection is typically a flanged butt joint in which respective flanges of the adjacent duct sections are fastened to each other. To meet safety standards, structural integrity is required such that accidental blow-out of the pressure wave through the flanged connection is prevented. For example, industry standards require that indicators placed at certain positions relative to the enclosure do not burn during a test as a result of escaping arc products. IEEE Standard C37.20.7, Paragraph 5.4.2, Indicator Placement. This requirement creates a significant design challenge for modular duct extensions that are joined at respective flanges.

[0004] To comply with the industry standards, current enclosures are reinforced with added structural components and strengthening materials to restrict the deformation of the flanged connection. However, disadvantages of the current enclosures include cost of the added materials, increased time to assemble the added structural components, and the likelihood of developing a kink in the reinforced flanged connection that inadvertently permits escape of the pressure wave and arc products.

[0005] What is needed is an arc-resistant enclosure that embraces the deformation of the flanged connection.

SUMMARY OF THE INVENTION

[0006] In an implementation of the present invention, an electrical enclosure assembly for a medium or high voltage system includes a duct chamber with two duct panels joined by a butt joint. Typically, the butt joint is screwed (or otherwise fastened) to side flanges of the duct panels. A pressure ring is screwed to the underside of the butt joint. When an arc fault occurs, an arc-blast force causes a pressure wave to travel through the duct chamber, causing the duct panels to distort. The pressure wave tends to seek an unintended ventilation path through the butt joint. In response to the pressure wave, however, the pressure ring expands to absorb the pressure wave and fills-in any gaps in the butt joint caused by the distortion of the duct panels. As such, the pressure ring blocks the escape of exhaust through the butt joint and allows the duct panels to temporarily conform to the deforming pressure caused by the arc fault.

[0007] In another implementation of the present invention, an electrical enclosure assembly includes a first duct section having a first panel with a first flange. A second duct section is adjacent to the first section and has a second panel with a second flange. The second flange is fastened to the first flange of the first panel to form a flanged butt joint between the first and second duct sections. The first and second sections are in a path through which a pressure wave travels, during an arc-fault event in the enclosure, to an exhaust vent. A pressure ring is fastened internally to at least one of the first and second panels and covers the flanged butt joint. The pressure ring deforms with the first and second panels in response to a peak pressure of the pressure wave, the deforming causing the pressure ring to fill-in gaps created in the flanged butt joint by the peak pressure during the arc-fault event.

[0008] In another alternative implementation of the present invention, an electrical enclosure assembly includes two adjacent duct sections having rectangular profiles formed by respective top, bottom, left, and right panels. The first and second duct sections are in a path through which a pressure wave travels during an arc-fault event towards an exhaust vent. A top butt joint is formed by two fastened top flanges, each of the top flanges being attached to a respective top panel. A bottom butt joint is formed by two fastened bottom flanges, each of the bottom flanges being attached to a respective bottom panel. A pressure ring is mounted within and has a matching rectangular profile to the rectangular profiles of the duct sections. The pressure ring is attached to at least one of the top panels and at least one of the bottom panels to cover both the top butt joint and the bottom butt joint. The pressure ring deforms in response to a peak pressure of the pressure wave, the deforming causing the pressure ring to seal the top and bottom butt joints during the arc-fault event.

[0009] The foregoing and additional aspects and embodiments of the present invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments and/or aspects, which is made with reference to the drawings, a brief description of which is provided next.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

[0011] FIG. 1 is an exploded view of two adjacent duct sections with a partial pressure ring.

[0012] FIG. 2 is perspective view of the partial pressure ring of FIG. 1.

[0013] FIG. 3A is an elevation view illustrating a prior art duct arrangement prior to an arc-fault event.

[0014] FIG. 3B is an elevation view illustrating the duct arrangement of FIG. 3A during a peak pressure of the arc-fault event.

[0015] FIG. 3C is an elevation view illustrating the duct arrangement of FIG. 3A after the peak pressure of the arc-fault event.

[0016] FIG. 4A is an elevation view illustrating a duct arrangement with a pressure ring prior to an arc-fault event.

[0017] FIG. 4B is an elevation view illustrating the duct arrangement of FIG. 4A during a peak pressure of the arc-fault event.

[0018] FIG. 4C is an elevation view illustrating the duct arrangement of FIG. 4A after the peak pressure of the arc-fault event.

[0019] FIG. 5 is a perspective view illustrating a duct arrangement with a full pressure ring.

[0020] FIG. 6 is a perspective view illustrating the full pressure ring of FIG. 5.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0021] Referring to FIG. 1, an enclosure duct 100 for an arc-resistant enclosure assembly includes two adjacent duct sections 100a, 100b. A left duct section 100a has a top panel 102a with a top flange 104a and, similarly, a right duct section 100b has a top panel 102b with a top flange 104b. The enclosure duct 100 further includes a pair of side panels 106a, 106b and bottom panels 108a, 108b. The bottom panels 108a, 108b includes respective bottom flanges 110a, 110b. [0022] In an alternative embodiment, such as illustrated in FIGs. 5 and 6, each of the side panels 106a, 106b is optionally separated into two adjacent panels with respective adjacent flanges. In other words, in the alternative embodiment each of the duct sections 100a, 100b has its own separate side panels. The top panels 102a, 102b are parallel to the bottom panels 108a, 108b, and the side panels 106a, 106b are parallel to each other.

[0023] Adjacent flanges of the enclosure duct 100 are fastened to each other to form flanged butt joints between the left duct section 100a and the right duct section 100b. For example, when assembled, the top flange 104a of the left duct section 100a is fastened to the top flange 104b of the right duct section 100b to form a top flanged butt joint. Optionally, a gasket (not shown) is inserted between the flanges for an enhanced sealing of the joint.

[0024] The enclosure duct 100 further includes a top pressure ring 112a that is fastened to the top panels 102a, 102b to cover the top flanged butt joint. A bottom pressure ring 112b is fastened to the bottom panels 108a, 108b to cover a respective bottom flanged butt joint. Each pressure ring 112a, 112b is spaced away from the respective top panels 102a, 102b and bottom panels 108a, 108b.

[0025] Optionally, the enclosure duct 100 includes a central support 114 that is centrally mounted between the top panels 102a, 102b and the bottom panels 108a, 108b, and is oriented parallel to the side panels 106a, 106b. The central support 114 increases the structural strength of the top panels 102a, 102b and the bottom panels 108a, 108b by, for example, preventing buckling of the panels.

[0026] The panels of the duct sections 100a, 100b form an internal space that is in a path through which a pressure wave travels in an X direction during an arc-fault event. The pressure wave travels from the point of origination 116 of the arc-fault event, e.g., at a switchgear, to an exhaust vent 118. The effects of the pressure wave on the pressure rings 112a, 112b are described in more detail below in reference to FIGs. 3A-4C.

[0027] Referring to FIG. 2, a pressure ring 112 is a plate with a main surface 120 having an array of attachment holes 122. The pressure ring 112 is identical to the top and bottom pressure rings 112a, 112b and is described separately for ease of understanding. The attachment holes 122 are provided for fastening the pressure ring 112 to either the top panels 102a, 102b (as the top pressure ring 112a) or the bottom panels 108a, 108b (as the bottom pressure ring 112b).

[0028] The pressure ring 112 further includes side walls 124 extending perpendicularly from the main surface 120. Notches 126 in a central location between the side walls 124 accommodate placement of the pressure ring 112 over the central support 114. The side walls 124 create a separation between the pressure ring 112 and the respective top or bottom panels 102a, 102b, 108a, 108b. The separation is an optional features that allows a separation between the main surface 120 of the pressure ring 112 and the respective top or bottom panels 102a, 102b, 108a, 108b. As discussed in more detail below in reference to FIGs. 3A-4c, the separation is helpful in part for absorbing the pressure wave without allowing leaks in-between flanged butt joints.

[0029] The pressure ring 112 further includes a pair of brackets 128 extending away from the main surface 120. The brackets 128 are bendable for attachment to respective top, side, or bottom panels of the enclosure duct 100.

[0030] Referring to FIGs. 3A-3C, a time sequence is illustrated showing the effects of the pressure wave on a top and bottom flanged butt joints 201a, 201b of a prior art enclosure duct 200. In FIG. 3A, the enclosure duct 200 is illustrated prior to a peak pressure X caused by the arc-fault event. As such, the flanged butt joints 201a, 201b are shown intact with top and bottom fasteners 203a, 203b in their fastened positions. The peak pressure is formed by a pressure wave traveling horizontally and along a central axis between top and bottom panels 202a, 202b, 208a, 208b of the enclosure duct 200.

[0031] In FIG. 3B, the enclosure duct 200 is illustrated during the peak pressure X, e.g., 50 ms (milliseconds). The peak pressure X has caused a rupture in the top flanged butt joint 201a with some of the pressure X' escaping through the rupture. The top fastener 203a, which provided a rigid reinforcement to the top flanged butt joint 201a, has been blown off from the top flanged butt joint 201a. Furthermore, the ruptured joint 201a is asymmetric relative to the bottom flanged butt joint 201b, which remains intact in this example. The escaped pressure X' is a safety hazard, likely causing fire and damage to nearby equipment and personnel.

[0032] In FIG. 3C, the enclosure duct 200 is illustrated after the peak pressure X. The ruptured joint 201a remains in its ruptured position with severe and permanent deformation to the enclosure duct 200. Thus, the rigid connection provided by the fasteners 203a, 203b has been ineffective. Although the bottom flanged butt joint 201b has remained intact, the rigid connection is in reality counter-productive because it helps in rupturing the top flanged butt joint 201a.

[0033] In another example, the peak pressure X causes severe and permanent deformation to both flanged butt joints 201a, 201b. In this example, the rigid reinforcement fails to protect either of the flanged butt joints 201a, 201b. Moreover, the deformation in this example is asymmetric, i.e., each flanged butt joint 201a, 201b is ruptured in a different way.

[0034] Referring to FIGs. 4A-4C, a time sequence is illustrated showing the effects of the pressure wave on top and bottom flanged butt joints 101a, 101b of the enclosure duct 100, in accordance with one aspect of the present invention. In FIG. 4A, the enclosure duct 100 is illustrated prior to the peak pressure X caused by the arc-fault event. The peak pressure is formed by a pressure wave traveling horizontally and along a central axis between top and bottom panels 102a, 102b, 108a, 108b of the enclosure duct 100. Both flanged butt joints 101a are shown intact with respective flanges of the joints in sealed contact with each other.

[0035] In FIG. 4B, the peak pressure X has caused symmetric deformation of the top flanged butt joint 101a relative to the bottom flanged butt joint 101b. Furthermore, the respective pressure rings 112a, 112b have deformed to absorb the pressure and fill-in (or seal) gaps 204a, 204b created in the respective flanged butt joints 101a, 101b. Consequently, the pressure rings 112a, 112b divert pressure flows X', X" towards the exhaust vent and, thus, prevent unintended escape of pressure through the temporarily deformed flanged butt joints 101a, 101b.

[0036] The separation between the main surface of each pressure ring 112a, 112b and the respective top or bottom panels 102a, 102b, 108a, 108b (described above in reference to FIG. 2) is helpful in providing a space for the pressure rings 112a, 112b to deform prior to making contact with the respective panels.

[0037] In FIG. 4C, the enclosure duct 100 is illustrated after the peak pressure X. The flanged butt joints 101a, 101b have returned to their original positions after being elastically deformed. In other examples, the flanged butt joints 101a, 101b plastically deform to some degree but in an uniform manner. By way of example, the flanged butt joints 101a, 101b may deform similarly to a balloon that has been inflated beyond the elastic limit (prior to rupturing, or popping) and, then, deflated. The deflated balloon has been uniformly stretched. Similarly, the flanged butt joints 101a, 101b may plastically deform in an uniform and/or symmetrical manner without rupturing.

[0038] Thus, instead of restricting the deformation with added flange reinforcements (such as fasteners 203a, 203b of the prior art duct enclosure 200) and/or heavier gauge duct panels, the pressure rings 112a, 112b allow the enclosure duct 100 to deform while maintaining the integrity of the joints 101a, 101b. In other words, the pressure rings 112a, 112b anticipate and embrace the deformation, instead of attempting to prevent it.

[0039] Referring to FIG. 5, an enclosure duct 300 includes an alternative arrangement of a pressure ring 312. The enclosure duct 300 includes two adjacent duct sections 300a, 300b having a rectangular cross-sectional profile and in which there is no common panel (like the side panels 106a, 106b of the enclosure duct 100 described in reference to FIG. 1). Specifically, in addition to having separate top and bottom panels (not shown in FIG. 5), the duct sections 300a, 300b have separate side panels. A left duct section 300a has its own front and back side panels 306ai, 306bi and a right duct section 300b has its own front and back side panels 306aii, 306bii.

[0040] The duct sections 300a, 300b are adjoined all-around at each flanged butt joint 301a-301d between respective adjacent panels. The flanged butt joints 301a-301d are standing seams facing outward and include a top flanged butt joint 301a, a bottom flanged butt joint 301b, a left flanged butt joint 301c, and a right flanged butt joint 30 Id. As such, the duct sections 300a, 300b have a flanged butt joint at each side of its rectangular cross- sectional profile.

[0041] Referring to FIG. 6, the pressure ring 312 has a matching rectangular cross-sectional profile to the profile of the duct sections 300a, 300b. The pressure ring 312 has a top side 301a, a bottom side 301b, a left side 301c, and a right side 30 Id. Each of the four sides 301a-301d is a sheet metal plate having attachment holes 322 for fastening the respective side to a corresponding flanged butt joint 301a-301d (e.g., the top side 301a is attached to the top flanged butt joint 301a, the bottom side 301b is attached to the bottom flanged butt joint 301b, etc.). Similar to the embodiment illustrated in FIG. 2, the pressure ring 312 bends and conforms to absorb the pressure created by the arc-fault event while maintaining the integrity of the seal between the flanged butt joints 301a-301d.

[0042] The pressure rings 112, 312 can be used especially in all medium voltage and high voltage switchgear and control-gear enclosures. For example, the enclosures include medium voltage enclosures for voltage ranging between about 600 volts and 36,000 volts. In another example, the enclosures include high voltage enclosures for voltage of about or greater than 36,000 volts. Potentially catastrophic effects of arc-fault events in such enclosures are eliminated, or greatly reduced, by the pressure rings 112, 313 described above.

[0043] While particular embodiments, aspects, and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

What Is Claimed Is:

1. An electrical enclosure assembly comprising:

a first duct section having a first panel with a first flange;

a second duct section adjacent to the first section and having a second panel with a second flange, the second flange being fastened to the first flange of the first panel to form a flanged butt joint between the first and second duct sections, the first and second sections being in a path through which a pressure wave travels during an arc-fault event in the enclosure to an exhaust vent; and

a pressure ring fastened to at least one of the first and second panels and internally covering the flanged butt joint, the pressure ring deforming with the first and second panels in response to a peak pressure of the pressure wave, the deforming causing the pressure ring to fill-in gaps created in the flanged butt joint by the peak pressure during the arc-fault event.

2. The electrical enclosure assembly of claim 1, wherein the path of the pressure wave through the first and second duct sections is horizontal.

3. The electrical enclosure assembly of claim 1, wherein the pressure ring is fastened to both the first and second panels.

4. The electrical enclosure assembly of claim 1, wherein the flanged butt joint is a standing seam facing outward.

5. The electrical enclosure assembly of claim 1, wherein the pressure ring and the first and second duct sections have matching rectangular cross-sectional profiles.

6. The electrical enclosure assembly of claim 5, wherein the first panel further includes a third panel with a third flange and the second panel includes a fourth panel with a fourth flange, the third flange and the fourth flange forming another flanged butt joint between the first and second duct section, the pressure ring being fastened to at least one of the third and fourth panels to cover the additional flanged butt joint.

7. The electrical enclosure assembly of claim 6, wherein the first and second panels are parallel to the third and fourth panels.

8. The electrical enclosure assembly of claim 7, wherein the first and second panels are respective top panels of the first and second duct sections and the third and fourth panels are respective bottom panels of the first and second duct sections.

9. The electrical enclosure assembly of claim 8, wherein the pressure ring deforms symmetrically along a central axis between the top and bottom panels.

10. The electrical enclosure assembly of claim 1, wherein the pressure ring deforms elastically in response to the peak pressure.

11. The electrical enclosure assembly of claim 1 , wherein the pressure ring is a sheet metal plate.

12. An electrical enclosure assembly comprising:

two adjacent duct sections having rectangular profiles formed by respective top, bottom, left, and right panels, the first and second duct sections being in a path through which a pressure wave travels during an arc-fault event towards an exhaust vent;

a top butt joint formed by two fastened top flanges, each of the top fianges being attached to a respective top panel;

a bottom butt joint formed by two fastened bottom flanges, each of the bottom fianges being attached to a respective bottom panel; and

a pressure ring mounted within an internal space of the duct sections and having a matching rectangular profile to the rectangular profiles of the duct sections, the pressure ring being attached to at least one of the top panels and at least one of the bottom panels to cover both the top butt joint and the bottom butt joint, the pressure ring deforming in response to a peak pressure of the pressure wave, the deforming causing the pressure ring to seal the top and bottom butt joints during the arc-fault event.

13. The electrical enclosure assembly of claim 12, wherein the path of the pressure wave through the duct sections is horizontal.

14. The electrical enclosure assembly of claim 12, wherein the top and bottom butt joints are each a standing seam facing outward.

15. The electrical enclosure assembly of claim 12, wherein the pressure ring deforms symmetrically along a central axis of the duct sections.

16. The electrical enclosure assembly of claim 12, wherein the pressure ring is a sheet metal plate.

17. The electrical enclosure assembly of claim 12, wherein the pressure ring deforms elastically in response to the peak pressure.