Underground junction chamber

Abstract

A junction chamber (10) comprises a base (20); a plurality of side walls (24, 26, 28, 30) extending away from the base (20) to define a receptacle, two of the side walls include: first and second cable gland lower plates (28, 30) which each include one or more lower arcuate notches (32); and first and second cable gland upper plates (40, 42) which each include one or more upper arcuate notches (44), and a lid (60) configured to enclose the junction chamber (10); wherein when each cable gland lower plate (28, 30) is located adjacent to a respective cable gland upper plate (40, 42), the corresponding lower and upper arcuate notches (32, 44) define generally circular cable openings (55).

Description

[0001] Underground junction chamber

[0002] Field of the invention

[0003] [1] The present invention relates to an underground junction chamber. In particular, the underground junction chamber is intended for use with onshore wind farms as a connecting point for cable-jointing and branching applications. However, it will be appreciated that the underground junction chamber may have applications in other industrial settings.

[0004] Background of the invention

[0005] [2] Onshore wind farms utilise an array of wind turbines which are designed to capture and convert wind energy into rotational energy which can subsequently be connected to a generator that converts the rotational energy into electricity.

[0006] [3] Each wind turbine typically has a transformer which receives AC (alternating current) electricity at one voltage and increases or decreases the voltage to deliver the electricity as needed. A wind power plant often uses a step-up transformer to increase the voltage, and reduce the required current, which reduces power losses that occur when transmitting large amounts of current over long distances. The electricity is subsequently transferred to a substation in which the electricity is converted from high to low voltage prior to distribution to consumers.

[0007] [4] The design of a wind farm requires the consideration of several variables to optimise the design and minimise materials, and also minimise power losses.

[0008] [5] The wind farm includes a collector system, which is defined by the network of cables that connect the turbines underground. Typically the cables that define the collector system are buried at a depth of around one metre below the surface. The process of trenching the ground to insert the collector system is costly and time consuming.

[0009] [6] In wind farm applications, cables of the collector system have historically been connected end to end with “in-line” joints. These joints are often subject to failure, with water getting into the cables, resulting in damage. [7] Junction boxes have been designed for connecting and branching cables of the collector system. The use of junction boxes may reduce cable distance by allowing multiple turbines to arrive at a common junction box. This can result in significant cost savings.

[0010] [8] A junction box may provide several advantages for the wind farm. In addition to reducing the total cable length, they may enable the designer / operator to optimise the cable layout considering cable ampacity, which is the maximum allowable current a cable can carry before it starts to overheat.

[0011] [9] Furthermore, junction boxes may enable the designers to address issues of cable derating, which is the phenomenon in which multiple cables laid side-by-side will result in the cables having lowered ampacities due to the heat dissipation of the cables.

[0012]

[0010] Whilst junction boxes provide several operational advantages, in practice they are also prone to failures, predominantly due to water ingression, noting the subterranean conditions encountered when buried for prolonged periods. Failure of a junction box is particularly problematic, noting that in many wind farm installations, a group of turbines are connected to a common radial feeder. In such installations, if a fault occurs at a connection point, such as a junction box, the fault may result in all turbines on the common feeder being rendered temporarily unusable. In order to minimise downtime, it is important that cable connections and junction boxes are able to withstand prolonged exposure to environmental conditions without maintenance or failure.

[0013]

[0011] Any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the priority date of this application.

[0014] Summary of the invention

[0015]

[0012] A junction chamber comprising: a base; a plurality of side walls extending away from the base to define a receptacle, two of the side walls include: first and second cable gland lower plates which each include one or more lower arcuate notches; and first and second cable gland upper plates which each include one or more upper arcuate notches, and a lid configured to enclose the junction chamber; wherein when each cable gland lower plate is located adjacent to a respective cable gland upper plate, the corresponding lower and upper arcuate notches define generally circular cable openings.

[0016]

[0013] The lid preferably includes a perimeter having downwardly folded edges which overhang an upper peripheral portion of each of the side walls.

[0017]

[0014] A seal assembly is preferably located between the lid and the side walls, the seal assembly including a polymer gasket and a plurality of hexserts gaskets.

[0018]

[0015] The hexserts are preferably between around 1 ,0mm and 2.0mm in thickness.

[0019]

[0016] The hexserts are preferably about 1 ,5mm in thickness.

[0020]

[0017] Gland seals are preferably located within the cable openings.

[0021]

[0018] The junction chamber further preferably comprises an external frame which includes a plurality of external cable holders, each cable holder being axially aligned and longitudinally separated relative to an adjacent one of said cable openings.

[0022]

[0019] The receptacle preferably includes a first cable layer and a vertically separated second cable layer defining a dual layer configuration.

[0023]

[0020] The junction chamber further preferably comprises at least two intermediate cable gland plates, each intermediate cable gland plate having arcuate notches formed on both upper and lower laterally extending contact surfaces defined by flanges.

[0024]

[0021] The intermediate cable gland plates are preferably located between the adjacent cable gland lower plate and the respective cable gland upper plate.

[0025]

[0022] Preferably the arcuate notches are each located on flanges.

[0026]

[0023] The flanges are each preferably stiffened by at least one stiffening gusset which extends between the flange and an adjacent generally perpendicular surface of one of the cable gland upper plates or the cable gland lower plates or the intermediate cable gland plate.

[0027]

[0024] The flanges preferably each include a plurality of holes for receiving fasteners to secure adjacent flanges.

[0025] The holes are preferably located on rectangular planar surfaces.

[0028]

[0026] In a second aspect, the present invention provides a junction chamber comprising: a base; a plurality of side walls extending away from the base to define a receptacle, two of the side walls include: first and second cable gland lower plates which each include one or more lower arcuate notches; and first and second cable gland upper plates which each include one or more upper arcuate notches, at least two intermediate cable gland plates, each intermediate cable gland plate having arcuate notches formed on both upper and lower laterally extending contact surfaces, and a lid configured to enclose the junction chamber; wherein each intermediate cable gland plate is located between a cable gland lower plate and a respective cable gland upper plate, to define two vertically separated rows of generally circular cable openings.

[0029]

[0027] The junction chamber further preferably comprises an external frame which includes two or more vertically separated layers of external cable holders, each cable holder being axially aligned and longitudinally separated relative to an adjacent one of said cable openings.

[0030] Brief description of the drawings

[0031]

[0028] Figure 1 is a perspective top view of an underground junction chamber according to a first embodiment in an open configuration;

[0032]

[0029] Figure 2 is a partially exploded perspective top view of the underground junction chamber of figure 1 with the lid removed;

[0033]

[0030] Figure 3 is a top and side view of the underground junction chamber of figure 1 , including an external frame;

[0034]

[0031] Figure 4 is a perspective top view of the underground junction chamber of Figure 1 in a closed configuration, including the external frame;

[0032] Figure 5 is a perspective top view of an underground junction chamber according to a second embodiment in a closed configuration, including the external frame;

[0035]

[0033] Figure 6 is a top view of the interior of the junction chamber;

[0036]

[0034] Figure 7 is a schematic diagram depicting the junction box installed within an array of wind turbines;

[0037]

[0035] Figure 8 is a schematic view depicting a length of cable for use with the underground junction chamber;

[0038]

[0036] Figure 9 is a perspective view depicting one of the cable gland seals in isolation;

[0039]

[0037] Figure 10 depicts the cable gland seals being installed on the underground junction chamber;

[0040]

[0038] Figure 11 is a schematic view depicting a hexsert seal in use;

[0041]

[0039] Figure 12 is an end view of the underground junction chamber of the second embodiment;

[0042]

[0040] Figure 13 is a perspective view showing the external frame in isolation according to the second embodiment; and

[0043]

[0041] Figure 14 is a further perspective view of the junction chamber showing the cable securement to the external frame.

[0044] Detailed description of preferred embodiments

[0045]

[0042] An underground junction chamber 10 is depicted in the drawings for use with the collector system of a wind turbine farm 100. Whist the junction chamber 10 is described in the context of underground installations, it will be appreciated that the junction chamber 10 may also be used in applications other than wind turbines.

[0046]

[0043] With reference to the drawings, a first embodiment of the junction chamber 10 is depicted in Figures 1 - 4 and W and 14, and a second embodiment of the junction chamber 15 is depicted in Figures 5 and 12 and 13.

[0047]

[0044] The junction chamber 10 includes a base 20 which defines an internal receptacle or chamber having an internal volume generally in the form of a rectangular prism. As shown in Figures 1 and 2, the base 20 has a floor or support surface 22 and four upwardly extending side walls 24, 26, 28, 30. When the junction chamber 10 is installed in a trench or pit, the walls 24, 26, 28, 30 are configured to extend generally vertically to define a receptacle.

[0048]

[0045] The opposing end walls 28, 30 each define cable gland lower plates which each include a plurality of lower arcuate notches 32 which are semi-circular and configured for receiving cables.

[0049]

[0046] In the embodiment depicted, the opposing walls 24 and 26 are longer than the perpendicular end walls 28, 30. However, it will be appreciated that other base configurations may be embodied, and the size of the receptacle can be configured for a given cable diameter, or number of junctions. In one arrangement, the junction chamber 10 is around 1500mm long and 800mm wide.

[0050]

[0047] Cable connectors 85 are housed within the underground junction chamber 10. The cable connectors 85 include at least one pair of electrically connected pins to engage with corresponding right angle connectors secured to each cable end. The junction chamber 10 includes a copper bus bar mounted on insulators to ground the cables 200. The arrangement of pins and right-angle connectors readily facilitates the connection of cables having different diameters.

[0051]

[0048] The junction chamber 10 includes at least one, and in the embodiment depicted in figures 1 to 3, two cable gland upper plates 40, 42. The two cable gland upper plates 40, 42 are located at opposing ends of the base 20. Each cable gland upper plate 40, 42 includes a plurality of upper arcuate notches 44 which are generally semi-circular.

[0052]

[0049] The upper arcuate notches 44 (of the cable gland upper plates 40, 42) when brought into abutment with the lower arcuate notches 32 (of the cable gland lower plates 28, 30) define a plurality of generally circular cable openings 55 which allow cables 200 to pass into the underground junction chamber 10.

[0053]

[0050] Each of the arcuate notches 32, 44 includes a laterally extending contact surface 50, 52 defined by a flange. The contact surfaces 50, 52 increase the surface area with the cable 200 which when installed is positioned in abutment with the cable gland lower plates 28, 30 and the cable gland upper plates 40, 42.

[0051] Referring to Figure 2, each flange defined by the contact surfaces 50, 52 extends along the full width of the junction chamber 10. On each side of each arcuate notch 32, 44 is an engagement formation defined by a generally rectangular surface 65 having holes formed therein. In the embodiment depicted, the rectangular surfaces 65 are generally planar and square and there are holes 67 located at each of the four corners of the surfaces 65. By inserting bolts or other suitable fasteners through the holes 67, the cable gland upper plates 40, 42 and the cable gland lower plates 28, 30 can be removably secured. A gasket or other suitable seal may be placed between the cable gland upper plates 40, 42 and the cable gland lower plates 28, 30 to improve the seal quality.

[0054]

[0052] The arrangement of the cable gland upper plates 40, 42 and the cable gland lower plates 28, 30 may be customised for a specific cable arrangement. In the embodiment depicted in figure 2, there are three cable openings 55 at each end of the junction chamber 10. However, other arrangements such as 1 , 2, 4, 5, 6 or more cable openings 55 may be located in one or both of the opposing ends of the junction chamber 10. Furthermore, the number of cable openings 55 located in each end of the junction chamber 10 may be different.

[0055]

[0053] In the arrangement shown in figure 4, each of the laterally extending contact surface 50, 52 includes a stiffening gusset 53, extending between two generally perpendicular surfaces of the cable gland upper plates 40, 42 and the cable gland lower plates 28, 30. The stiffening gussets 53 are welded, cast or otherwise secured to the laterally extending contact surface 50, 52 to provide increased rigidity, and reduce the risk of seal failure due to in ground deformation.

[0056]

[0054] The cable openings 55 each include a gland seal 56, as depicted in isolation in figure 9. The cable gland seal 56 is a two part seal that can be separated for placement around the cable 200. A hose clamp 57 (or another suitable locking band) secures the two halves of the cable gland seal 56 together. As depicted in figure 10, the flange 61 of each cable gland seal 56 is brought into abutment against one of the circular cable openings 55, and the cable gland seal 56 may then be tightened.

[0057]

[0055] Screws 63 are mounted on longitudinally opposing press plates 65, the screws 63 being seated on a common pitch circle diameter on the cable gland seal 56. The screws 63 are tightened to compress a rubber seal (in a direction generally extending parallel with the longitudinal axis of the cable 200). This causes the cable gland seal 56 to partially radially expanding both inwardly and outwardly, sealing against the circular cable openings 55 and also the cable 200.

[0058]

[0056] The cable gland seal design improves water barrier sealing, and increases range taking capability and rationalises the junction chamber 10 by reducing the combinations required.

[0059]

[0057] With reference to figure 6, the underground junction chamber 10 includes an interface 102 with protective caps, an earthing system 103 and a compression gland 104 for an earthing cable.

[0060]

[0058] A lid 60 encloses and seals the underground junction chamber 10. A plurality of holes 62 are positioned around the perimeter of the lid 60. The holes 62 are configured to be aligned with corresponding holes 64 formed around the upper perimeter of both upwardly extending walls 24, 26 and the two cable gland upper plates 40, 42.

[0061]

[0059] Suitable fasteners, such as bolts and nuts are configured to pass through the holes 62, to secure the lid 60 to the base 20.

[0062]

[0060] In the arrangement depicted, the lid 60 has downwardly folded edges which overhang the upper peripheral portions of each of the walls 24, 26 and the two cable gland upper plates 40, 42.

[0063]

[0061] A seal assembly is located between the lid 60 and the upwardly extending side walls 24, 26, 28, 30.

[0064]

[0062] The seal assembly includes a polymer gasket 51 (such as a neoprene gasket) seen in figure 11 , which is located between the lid 60 and the walls 24, 26 and the two cable gland upper plates 40, 42. The gasket 51 has an adhesive strip one side so that it adheres in place.

[0065]

[0063] In addition, the seal assembly includes a plurality of hesxerts 49 which are preferably between around 1 .0mm and 2.0mm in thickness, and more preferably around 1 ,5mm thick and located between the lid 60 and each of the walls 24, 26 and the two cable gland upper plates 40, 42.

[0064] Hexserts 49 are basically a fixed nut which is installed similar to a pop rivet. The flange of the hexsert has been made to be 1 ,5mm to assist in not completely compressing the gasket 51 .

[0066]

[0065] The inclusion of the hexserts 49 prevents the gasket from being overly compressed.

[0067]

[0066] The hexserts 49 also assist in the rebounding of the neoprene gasket by preventing the gasket from being over compressed.

[0068]

[0067] In the arrangement depicted in figure 1 , the junction chamber 10 is configured with a cable glands arrangement, to join 6 single core cables having outer cable diameters ranging from 26 to 98 mm. However, larger or smaller cables 200 may also be used.

[0069]

[0068] Referring to Figures 3 and 4 and 13, the underground junction chamber 10 includes an external frame 80. The frame 80 supports a plurality of external cable holders 97. The external cable holders 97 are defined by straps (or other suitable brackets), best seen in figure 14. The external frame 80 includes two longitudinally extending support beams 82 which assist to resist flexing and maintain IP68 waterproof rating. The support beams 82 are secured to an underside of the underground junction chamber 10. The beams 82 may also be connected to perpendicular secondary beams 84, located at each end of the underground junction chamber 10.

[0070]

[0069] As shown in Figures 4 and 13, the external cable holders are seated on a sub-frame assembly 86 which extends upwardly away from the longitudinally extending support beams 82. The sub-frame assembly 86 has a generally inverted “U” shaped profile and serves to raise the external cable holders so they are located coaxial with the cable openings 55.

[0071]

[0070] The external cable holders serve the purpose of bracing the cable at a location that is longitudinally separated from the underground junction chamber 10. This ensures the cable 200 is correctly aligned with the cable openings 55, as the cable 200 is secured at two locations, namely by the external cable holder 81 and also the internal electrical connector 85. As a result, the cable passes through the cable openings 55 with good axial alignment. This improves the hermetic seal achieved by the cable openings 55, as the external frame 80 reduces any axial cable misalignment. The external frame 80 also prevents any movement of the cable, for example during backfilling of trenches, which could otherwise create problems with the seal quality due to axial misalignment of the cables 200.

[0072]

[0071] A second embodiment of the underground junction chamber 15 is depicted in Figure 5 and 12. The underground junction chamber 15 of the second embodiment shares many features with the first embodiment, and only the areas of difference are described in detail below. Within the underground junction chamber 15 there are two layers of cable 200 which are vertically separated.

[0073]

[0072] With reference to figure 5, there are two layers of cable openings 55 which are vertically separated. In this dual layer embodiment there are two levels and 4 circuits.

[0074]

[0073] The components of the underground junction chamber 10 may be provided flat packed for site installation. Alternatively, the underground junction chamber 10 may be semi-assembled, packed in a wooden (or other suitable) crate along with all necessary components for each particular installation.

[0075]

[0074] In the embodiment depicted in figure 5, there are two layers of 3 cable openings 55, that is a dual level arrangement. It will be appreciated that other arrangements are permissible, such as two layers of two cable openings 55, two layers of four cable openings, 55 or three or more layers of vertically separated cable openings 55. The number of openings at each end of the underground junction chamber 15 may be non-equal.

[0076]

[0075] As shown in figure 5, the underground junction chamber 15 of the second embodiment includes a dual level cable holder structure 87, so that two (or more) layers of cables 200 can be braced relative to the sub-frame assembly 86, and to ensure each cable 200 is coaxial with its respective cable opening 55.

[0077]

[0076] In order to achieve the second and subsequent layers, the second embodiment incudes at least two intermediate cable gland plates 91 , 93, best seen in figure 12.

[0078]

[0077] The intermediate cable gland plates 91 , 93 each have arcuate notches formed on each of the upper and lower laterally extending contact surfaces defined by flanges. As such, the intermediate cable gland plates 91 , 93 can be selectively stacked to provide a multi-layer underground junction chamber 10 to any desired number of layers, but most commonly two layers.

[0078] The junction chamber 10 may include internal monitoring equipment configured to convey data to the surface. For example, this may include one or more thermometers or moisture sensors which can transmit data back to the surface which may be used to identify whether the junction chamber 10 has any moisture ingression issues, or if the collection system is overheating. Data may be transmitted by wired or wireless communication.

[0079]

[0079] The underground junction chamber 10, 15 is fabrication from a material suitable for deployment below ground with anti-corrosive properties such as stainless steel.

[0080]

[0080] The underground junction chamber 15 can be customised to single one end, dual the other, or other variations depending on the local site-specific requirements.

[0081]

[0081] The cables and earthing system are mounted above the base of the junction chamber 10, which enables a small amount of water ingression without compromising the electrical installation.

[0082]

[0082] Advantageously, the junction chamber 10 enables a reduction of land footprint for the wind turbine farm installation.

[0083]

[0083] Advantageously, the junction chamber 10 enables the joining / branching of cables having different cross-sections and conductor material.

[0084]

[0084] Advantageously, the junction chamber 10 has an IP68 rating which provides for water and dust resistance.

[0085] [1] Wherever it is used, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of’. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear.

Claims

Claims:1 . A junction chamber (10) comprising: a base (20); a plurality of side walls (24, 26, 28, 30) extending away from the base to define a receptacle, two of the side walls include: first and second cable gland lower plates (28, 30) which each include one or more lower arcuate notches (32); and first and second cable gland upper plates (40, 42) which each include one or more upper arcuate notches (44), and a lid (60) configured to enclose the junction chamber; wherein when each cable gland lower plate is located adjacent to a respective cable gland upper plate, the corresponding lower and upper arcuate notches (40, 42) define generally circular cable openings (55).

2. The junction chamber of claim 1 , wherein the lid includes a perimeter having downwardly folded edges which overhang an upper peripheral portion of each of the side walls.

3. The junction chamber of claim 2, wherein a seal assembly is located between the lid and the side walls, the seal assembly including a polymer gasket and a plurality of hexserts.

4. The junction chamber of claim 3, wherein the hexserts are between around 1 .0 mm and 2.0 mm in thickness.

5. The junction chamber of claim 4, wherein the hexserts are about 1 .5 mm in thickness.

6. The junction chamber of any one of the preceding claims, wherein gland seals are located within the cable openings.

7. The junction chamber of any one of the preceding claims, further comprising an external frame which includes a plurality of external cable holders, each cable holder(81 ) being axially aligned and longitudinally separated relative to an adjacent one of said cable openings.

8. The junction chamber of any one of the preceding claims, wherein the receptacle includes a first cable layer and a vertically separated second cable layer defining a dual layer configuration.

9. The junction chamber of claim 8, further comprising at least two intermediate cable gland plates, each intermediate cable gland plate having arcuate notches formed on both upper and lower laterally extending contact surfaces defined by flanges.

10. The junction chamber of claim 9, wherein the intermediate cable gland plates are located between the adjacent cable gland lower plate and the respective cable gland upper plate.11 . The junction chamber of claim 9, wherein the arcuate notches are each located on flanges.

12. The junction chamber of claim 11 , wherein the flanges are each stiffened by at least one stiffening gusset which extends between the flange and an adjacent generally perpendicular surface of one of the cable gland upper plates or the cable gland lower plates or the intermediate cable gland plate.

13. The junction chamber of claim 11 , wherein the flanges each include a plurality of holes for receiving fasteners to secure adjacent flanges.

14. The junction chamber of claim 12, wherein the holes are located on rectangular planar surfaces.

15. A junction chamber comprising: a base; a plurality of side walls extending away from the base to define a receptacle, two of the side walls include: first and second cable gland lower plates which each include one or more lower arcuate notches; andfirst and second cable gland upper plates which each include one or more upper arcuate notches, at least two intermediate cable gland plates, each intermediate cable gland plate having arcuate notches formed on both upper and lower laterally extending contact surfaces, and a lid configured to enclose the junction chamber; wherein each intermediate cable gland plate is located between a cable gland lower plate and a respective cable gland upper plate, to define two vertically separated rows of generally circular cable openings.

16. The junction chamber of claim 15 further comprising an external frame which includes two or more vertically separated layers of external cable holders, each cable holder being axially aligned and longitudinally separated relative to an adjacent one of said cable openings.

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