NO347187B1 - Grounding device for a concrete structure and system comprising the grounding device - Google Patents

Description

EARTHING SYSTEM FOR A CONCRETE STRUCTURE AND PROCEDURE FOR ARRANGEMENT OF THE EARTHING SYSTEM IN THE CONCRETE STRUCTURE

The invention relates to an earthing system for a concrete structure, where the earthing system comprises an earthing device that comprises an electrically conductive fixing bracket for a fixing element in the form of a post bracket, and an earthing element for casting in the concrete structure. The invention also relates to a procedure for arranging the grounding system in a concrete structure. A system for grounding an electrical element belonging to the concrete structure is also described.

Known technique and its disadvantages

Offshore wind turbines are particularly susceptible to lightning strikes, and solutions are therefore sought to reduce the risk of damage in the event of lightning strikes.

One measure is turbine platforms in concrete, where handrails are made of a non-current-conducting material, preferably a composite material. Various electrical components can be fitted to the turbine platform, for example navigation lights, sign lights and antennas. A well-known and commonly used method for grounding concrete structures is the use of an earth wire. A first end of the grounding wire is attached to a reinforcement element in the concrete structure, while a free second free end of the grounding wire extends out of the concrete structure, after which the free end is attached to the electrical component or a cable rail, for example using a screw connection.

The publications DE 202005003458 U and DE 10227632 A1 describe embedded grounding devices designed for connection to a grounding cable, where a fastener for the grounding cable is electrically conductively connected to an arming element. In DE 202005003458 U, the attachment is connected to the reinforcing element via a welding connection. In DE 10227632 A1, the fastener is connected to the reinforcing element via a screw connection. The grounding cable rests against a connection surface belonging to the fixture, and is screwed to the fixture with one screw. The connection surfaces in DE 202005003458 U and DE 10227632 A1 have a size that corresponds to the electrically conductive end of the earthing cable.

The publication US 2009272557 A1 describes an earthing cable which is partially embedded and connected to a busbar inside a mast for a wind turbine.

A significant disadvantage of known technology is that the ground wire is exposed to corrosion. This problem is particularly large offshore, due to moist and salty air. An earth wire that extends outside the concrete structure, for example in an arch, can also function as an electrical antenna that can cause disturbances to electrical equipment and devices, referred to in the technical language as EMC.

The purpose of the invention is to remedy or to reduce at least one of the disadvantages of known technology, or at least to provide a useful alternative to known technology.

The purpose is achieved by the features indicated in the description below and in the subsequent patent claims.

General description of the invention

The invention is defined by the independent patent claims. The independent claims define advantageous embodiments of the invention.

In a first aspect, the invention relates more specifically to a grounding device for a concrete construction, where the grounding device comprises: a post bracket; and a grounding device. The grounding device comprises: an electrically conductive fixing bracket with a first connection surface for the post bracket and at least one embedment part for fixing in the concrete structure; and an electrically conductive grounding element which in a first end part is electrically conductively attached to a second connection surface of the fastening bracket, and in a fastening part is arranged for an electrically conductive connection with a reinforcement element in the concrete structure. The grounding element and the second connection surface are designed to be covered by the concrete structure, the post bracket being electrically conductively attached to the bracket via a screw connection.

The first coupling surface can be an outer coupling surface. The outside can be understood as a surface or a side that faces away from the concrete construction. The second coupling surface can be an internal coupling surface. In this context, interior can be understood as a surface or a side that faces inwards in the concrete construction.

The effect of the earthing element's first end part being electrically conductively attached to the second connection surface of the fastening bracket is that the earthing element can be cast in its entirety into the concrete structure and thus protected against corrosion.

As the earthing element is electrically conductively attached to the second connection surface of the fixing bracket, the fixing bracket and the first connection surface of the fixing bracket can function as an external grounding point for the concrete structure. Thus, elements that need grounding can be connected directly to the mounting bracket. In this context, electrically conductive means that the earthing element is made of an electrically conductive material.

In a preferred embodiment, the fastening bracket can be made of stainless metal. The fixing bracket can be a profile. The profile can be made of a plate with one or more cracks. The profile can comprise a center part where the center part forms a connecting part. The first coupling surface may be an outside coupling portion. The second coupling surface can be an inside of the coupling part. The embedment part can comprise a plurality of recesses so that concrete can flow through the recesses so that the fixing bracket is firmly cast in the concrete structure. In an advantageous embodiment, the fastening bracket comprises two embedment parts positioned on each side of the coupling part.

Between the coupling part and the embedment part there can be a mutual angle which is equal to or greater than 90 degrees. In one embodiment, the angle can be 120 degrees.

The grounding element's first end part can be attached to the second connection surface by means of heat treatment, for example welding. The advantage of welding is that a strong electrically conductive connection is formed.

The grounding element's first end part can, as an alternative or addition, be attached to the second connection surface via a screw connection.

The effect of the screw connection is that the attachment of the earthing element to the mounting bracket can be done using elements that are normally part of an ordinary mounting bracket, in that an ordinary mounting bracket typically has a nut on the inside to receive a screw. The screw may be adapted to attach the fixing bracket to a formwork element.

When the grounding element is attached to the coupling part, the grounding element will typically protrude perpendicularly from the coupling part, which makes the grounding device space-consuming. The screw connection makes it possible to store and transport the grounding element and the connecting part separately. In this way, the grounding element and the connecting part can be stacked in a way that makes maximum use of space.

A further effect of the screw connection is that it is possible to easily combine different fixing brackets and different grounding elements, depending on the construction in which the grounding element is to be arranged. For example, one type of grounding element can be used for different fixing brackets, or vice versa.

The grounding element can be an electrically conductive rail.

The effect of the grounding element being an electrically conductive rail is that the grounding element can protrude rigidly from the connection part and provide a correct and repeatable position in relation to the fixing bracket.

The rail can have an elasticity that makes it possible to brace the rail against at least one reinforcement element. The rail can be flexible so that the rail can be alternately positioned above and below a plurality of rebars which lie in a common plane. Through this, a plurality of electrically conductive contact points between the rail and the reinforcement can be achieved.

In comparison, a cable typically has little or no elasticity, and will therefore not be able to provide a corresponding tension to the reinforcement element such as the rail. When casting the concrete structure, it is therefore likely that a cable will move in relation to the reinforcing elements so that there is no contact between the cable and the reinforcing element.

The grounding device may comprise a clamp for securing the grounding element to the reinforcement element.

The effect of the clamp is that a secure and electrically conductive connection can be provided between the grounding element and the reinforcing element, also if the grounding element has a deviant or incorrect position in relation to the reinforcing element.

Another effect is that the clamp can keep the grounding element in an electrically conductive contact with the reinforcing element when the grounding element and/or the reinforcing element is exposed to stress during casting, for example when concrete that is added presses the grounding element and/or the reinforcing element downwards.

A further effect is that the clamp can provide an electrically conductive contact with the reinforcing element which prevents slurry from pressing in between the grounding element and the reinforcing element.

The clamp can be displaceable in the longitudinal direction of the earthing element.

The effect of the clamp being displaceable in the grounding element's longitudinal direction is that the clamp can provide a secure and electrically conductive connection between the grounding element and the reinforcement element at varying distances between the fastening bracket and the reinforcement element.

The clip can be displaceable along a slot in the electrically conductive rail. The effect of the slot is that a large contact surface is achieved between the clamp, the rail and the reinforcing element.

The bracket may comprise a screw connection. The effect of the screw connection is that the clamp can be easily fixed in a simple way using simple tools. The screw connection can include a locking screw so that the clamp can be fixed with just one tool, for example a spanner.

In a second aspect, the invention relates more specifically to a concrete structure for a wind turbine, where the concrete structure comprises an earthing device according to the first aspect of the invention.

The effect of the concrete structure including the earthing device is that the earthing of the wind turbine is protected against corrosion, in that the earthing element is protected and hidden by the concrete structure.

The concrete structure can be a platform for the wind turbine.

Wind turbines can include a platform under the turbine itself, also known as a turbine platform. The platform can be a platform from service personnel. Various electrical components can be mounted to the platform, for example navigation lights, sign lights and antennas.

As the platform is made of concrete, the risk of lightning strikes is reduced. However, the electrical components will be exposed to lightning strikes and overvoltages, which places great demands on the grounding of the electrical components. In a concrete construction, it is known to connect one or more reinforcing elements with soil. By providing the concrete structure with the grounding device described herein, a concrete platform for a wind turbine can be provided with a secure grounding at the same time as the grounding is hidden in the concrete structure.

Concrete construction can be positioned offshore.

Wind turbines that are positioned offshore have a greater risk of lightning strikes than wind turbines on land. A concrete platform including the grounding device described here is therefore particularly well suited for an offshore installation.

A system for grounding an electrical element for a concrete structure is also described, where the system comprises a grounding device according to the first aspect of the invention, and an electrically conductive fastening element arranged for the fastening bracket.

The effect of attaching an electrically conductive fastening element to the fastening bracket is that the electrically conductive fastening element can be used for grounding an electrical element on the outside of the concrete structure. The electrical element can, for example, be a cable.

The electrically conductive attachment element can be a post bracket.

The effect of the electrically conductive element being a post bracket is that the post bracket can both be used to house a part of a post, for example a railing post, and function as an earthing point for an electrical element. The post bracket can be arranged to house an end part of the railing post.

The electrically conductive fastening element can comprise at least one oblong recess for a screw, where the at least one oblong recess is arranged perpendicular to a longitudinal axis of the fastening element.

The effect of the oblong hole is that a post positioned in the electrically conductive fastening element can be turned axially about the longitudinal axis of the fastening element in order to obtain a correct positioning in relation to adjacent elements. If the concrete structure is elliptical and provided with a plurality of fastening elements along a perimeter of the concrete structure, it may be necessary to adjust the axial position of the post, which is possible when the screw hole is elongated.

A fastening device for an electrical component can lie electrically conductive against the fastening element.

The effect of the fastening device being electrically conductive against the fastening element is that the fastening device can be used as an earthing element, so that a separate earthing cable is not necessary.

The fastening device can be a cable rail.

The effect of the fastening device being a cable rail is that the cable rail can house electrical cables and at the same time protect the cables against electrical disturbances, known in technical terms as a faraday cage. The cable rail can also include a function such as a kick plate, known in the technical language as a kick plate.

A further effect is that electrical components that are mounted in close proximity to the cable rail can use the cable rail as an earthing point.

In a third aspect, the invention relates to a method for arranging an earthing system according to the invention's first aspect in a concrete construction, where the method comprises the steps;

• to position the fixing bracket to an inside of a formwork element for the concrete construction so that the first connecting surface of the fixing bracket rests against a part of the formwork element;

• to screw the fixing bracket to the formwork element with a screw, the grounding element's first end part being positioned between the inside of the fixing bracket and a nut;

• to attach the grounding element's fastening part to the reinforcing element;

• adding concrete to the inside of the formwork element so that the reinforcing element, the grounding element and the nut are covered by the concrete;

• to remove the screw; and

• to screw a fastening device for an electrical component to the fastening bracket.

The method may further comprise the step;

• to screw a fastening element to the fastening bracket's first connection surface.

In what follows, an example of a preferred embodiment is described which is illustrated in the accompanying drawings, where:

Fig. 1 shows the grounding system's grounding device in perspective;

Fig. 2 shows the grounding device from above in its individual components;

Fig. 3 shows the grounding device from above and attached to a formwork element;

Fig. 4 shows in perspective the earthing system in a concrete structure;

Fig. 5 shows how an electrical voltage is led through the grounding system for grounding an electrical element for the concrete structure; and

Fig. 6 shows a concrete structure that includes the earthing system.

Figures 1 and 2 show an earthing device 1 for a concrete structure 9 (figures 3 - 6), where the earthing device 1 comprises an electrically conductive attachment bracket 10 with a first connection surface 101 for a post bracket 5 (figures 4 and 5) and at least one embedment part 12 for solid casting in the concrete construction 9, and a grounding element 2 which in a fastening part 21 is arranged for an electrically conductive connection with a reinforcing element 91 in the concrete construction 9. The grounding element 2 is electrically conductively attached in a first end part 22 to a second connection surface 102 belonging to the fastening bracket 10, and the grounding element 2 and the second connecting surface 102 is designed to be covered by the concrete structure 9.

The fastening bracket 10 shown as a broken profile comprising a coupling part 100 and two embedding parts 12. The first coupling surface 101 is positioned on a first side of the coupling part 100. The second coupling surface 102 is positioned on a second side of the coupling part 100. The two fastening parts 12 are shown with a mutual angle of 60 degrees, so that the angle between each of the embedding parts and the connecting part is 120 degrees, and is provided with a plurality of recesses 121 so that concrete can flow through the recesses 121 to give the fixing bracket 10 additional anchoring in the concrete structure..

The grounding element 2 is shown as an electrically conductive rail, where the fastening part 21 is arranged perpendicular to the first end part 22, so that the first end part 21 protrudes from the fastening bracket 10. The first end part 22 rests against the second coupling surface 102 of the fastening bracket 1, and is fixed to the attachment bracket 10 with a screw connection 31.

The fastening part 21 of the grounding element 2 comprises a recess 210. The recess 210 makes it possible to move a clip 3 with a second screw connection 32 in the longitudinal direction of the fastening part 21, so that the clip 3 can be screwed to the grounding element 2 in various positions along the recess 21.

Figure 3 shows the grounding device 1 embedded in concrete structure 9, and attached to a formwork element 99. When the grounding device 1 is to be firmly cast in the concrete structure 9, the fixing bracket 10 is positioned to an inside 990 of the formwork element 99 so that the first connecting surface 101 of the fixing bracket 10 rests against the inside of the formwork element 99 and the connecting surface 101 becomes level with the outside of the concrete structure 9 when the formwork element 99 is removed.

The grounding device 1 is attached to the formwork element 99 with the first screw connection 31. A nut 311 belonging to the screw connection 31 is arranged for casting in the concrete structure 9. A first screw 310 is arranged to be able to be unscrewed from the screw connection 31 after the nut 311 has been cast and the formwork element 99 is removed .

Figure 4 shows a partially cross-sectional sketch of the grounding system for grounding an electrical element (not shown) for the concrete structure 9. The grounding system comprises the grounding device 1 and an electrically conductive post bracket 5 arranged to the fixing bracket 10. The electrically conductive post bracket 5 is arranged to house a part of a railing post 6. The post bracket 5 is attached to the fastening bracket 10 via two screw connections 31, and at the same time secures the railing post 6 to the post bracket 5, as an electrically conductive connection is formed between the reinforcement element 91, the fastening bracket 10, the post bracket 5 and the screw connection. The railing post 6 shown in the figure is made of a non-electrically conductive material, for example composite.

A cable rail 55 is attached to an outside of the post bracket 5 via two screw connections 33, in which an electrically conductive connection is formed between the reinforcement element 91, the fastening bracket 10, the post bracket 5 and the cable rail 55.

Figure 5 shows how an earthing circuit G can be provided between the reinforcing element 91 and to an outside of the concrete structure 9 via the earthing element 2, the fixing bracket 10 and the post bracket 5 and the cable rail 55. Because the cable rail 55 is connected to earth, an electrical element (not shown) will be able to be connected to earth by connecting the ground wire of the electrical element to the cable rail 55. The cable rail 55 can house electrical cables and at the same time protect the electrical cables against electrical disturbances, by the cable rail forming a faraday cage.

Figure 6 shows a concrete construction 9 for a wind turbine, where the concrete construction 9 comprises a plurality of grounding devices 1 and a plurality of electrical elements 7.

The plurality of grounding devices 1 are cast into the concrete structure 9 along the outer side of the concrete structure 9. The concrete structure 9 also comprises a plurality of non-electrically conductive fixing brackets (10X). The non-electrically conductive attachment brackets 10X are identical to the electrically conductive attachment bracket 10, but are not electrically conductively connected to any reinforcing element 91.

Along the edge of the concrete structure 9, a plurality of cable rails 55 have been mounted. These house electrical wires for an electrical installation 7. An electrical wire P can be passed through corresponding recesses in the cable rail 7, the fixing bracket 10 and the post bracket 5, in order to thereby be threaded inside the post bracket 5 and to the electrical installation 7.

The use of the verb "to comprise" and its various forms does not exclude the presence of elements or steps not mentioned in the claims. The indefinite articles "an", "ei" or "et" before an element do not exclude the presence of several such elements.

Claims (9)

Patent claims 1. Grounding system for a concrete structure (9), where the grounding system comprises: - a post bracket (5); and - an earthing device which (1) includes: i) an electrically conductive fixing bracket (10) with a first connection surface (101) for the post bracket (5) and at least one embedment part (12) for fixing in the concrete structure (9); and ii) an electrically conductive grounding element (2) which in a first end part (22) is electrically conductively attached to a second connection surface (102) of the fastening bracket (10), and in a fastening part (21) is arranged for an electrically conductive interconnection with a reinforcing element (91) in the concrete structure (9), where the grounding element (2) and the second connecting surface (102) are arranged to be covered by the concrete structure (9), c a r a c t e r i s e r t w e e d that: - the post bracket (5) is electrically conductively attached to the fixing bracket (10) via a screw connection (31). 2. Earthing system according to claim 1, where the grounding system comprises a fastening device (55) for an electrical component, where the fastening device (55) is electrically conductive against the post bracket (5). 3. Grounding system according to claim 2, where the fastening device (55) is a cable rail. 4. Grounding system (1) according to any of the preceding claims, wherein the grounding system (1) comprises a clamp (3) for fixing the grounding element (2) to the reinforcing element (91), and where the clamp (3) is displaceable in the longitudinal direction of the earthing element (2). 5. Concrete structure (9) for a wind turbine, wherein the concrete structure (9) comprises an earthing system according to any one of claims 1 - 4. 6. Concrete structure (9) according to claim 5, where the concrete structure (9) is a platform for the wind turbine. 7. Concrete structure (9) according to any one of claims 5 - 6, where the concrete structure (9) is positioned offshore. 8. Method for arranging an earthing system according to any one of claims 1-5 in a concrete structure (9), wherein the method comprises the steps; • to position the fastening bracket (10) to an inside (990) of a formwork element (99) for the concrete construction (9) so that the first connection surface (100) of the fastening bracket (10) rests against a part of the formwork element (99); • to screw the fixing bracket (10) to the formwork element (99) with a screw (110), the first end part (22) of the grounding element (2) being positioned between the inside of the fixing bracket (102) and a nut (311); • to attach the grounding element (2) attachment part (21) to the reinforcement element (91); • adding concrete (90) to the inside of the formwork element (99) so that the reinforcing element (91), the grounding element (2) and the nut (311) are covered by the concrete (90); • to remove the screw (110); and • to screw the post bracket (5) to the first connecting surface (101) of the fixing bracket (10). 9. Method according to claim 8, where the method further comprises the step; • to screw a fastening device (55) for an electrical component to the post bracket (5).