ELECTRICAL DEVICE AND METHOD FOR ESTABLISHING AN ELECTRICAL CONNECTION

Description

[0001] Electrical joints are used for providing connections between two electrically conducting elements in an electrical circuit, such as in electrical busbar systems. The electrically conducting elements may be made of a conducting metal or a conducting alloy. Assume that the electrically conducting elements are composed of a metal. Typically, when two metallic conducting elements are brought in contact with each other by means of a fastening mechanism to form an electrical joint, the actual metal-to-metal contact area is small compared to the total contact area physically touching. Therefore, the current flow is restricted to the metal-to-metal contact area. In other words, there is an Electrical Contact Resistance (ECR) associated with the contact area. The magnitude of the ECR may vary with contact mechanics such as a surface structure of the contact area and a physical load applied on the electrical joint. For example, the surface structure of the contact area may include crests and troughs which trap air in the contact area when the metallic conducting elements are closed. This leads to an increase in the ECR associated with the contact area. The increase in ECR leads to generation of heat in the contact area, resulting in high temperatures in the contact area.

[0002] In view of the above, there exists a need for reducing the ECR by increasing a conduction area within the contact area of an electrical joint.

[0003] In the document Mg Chemicals: "Technical Data Sheet 847 Carbon Conductive Assembly Paste", 3 October 2018, pages 1-5, XP055712514 an electrically conductive carbon paste with a bulk density of 1.07 g / cm 3< is disclosed.

[0004] US Patent Application Publication US 2010 / 0 240 265 A1 discloses an electrical interface with a nano-particle layer. Mg Chemicals: "Electrically Conductive Grease Comparison Chart", 3 October 2018, XP 055711312 discloses an overview over different electrically conductive carbon pastes with bulk densities of above 1 g / cm 3< .

[0005] Chinese Patent CN 106 816 202 B discloses a graphene modified conductive silver paste and a preparation method thereof. Korean Patent Application KR 2016 0 044 356 A discloses a conductive paste having carbon nanotubes as conductive particles, the carbon nanotubes having a bulk density of 0.07 to 4 g / cm 3< .

[0006] Japanese Patent Application JP 2019 061 916 A discloses a conductive auxiliary agent dispersion with carbon materials as conductive aid having a specific surface area of 300 to 1400 m 2< / g or 10 to 200 m 2< / g respectively.

[0007] Therefore, it is an object of the present invention to provide an electrical device comprising an electrical joint having a reduced ECR and a method of forming the electrical joint.

[0008] The object of the present invention which is defined by the appended claims is achieved by an electrical device comprising a first electrical component and a second electrical component forming an electrical joint therebetween and a conductive solution deposited between the first electrical component and the second electrical component in the electrical joint. The term 'contact surface', as used herein, may refer to an overlapping area between the first electrical component and the second electrical component, where the the first electrical component and the second electrical component are joined in order to form the electrical joint. The conductive solution increases a current conduction area between the first electrical component and the second electrical component in order to reduce the ECR.

[0009] In accordance with one embodiment of the present invention, an electrical device comprising a first electrical component and a second electrical component forming a contact surface therebetween. The electrical joint comprises a contact surface between the first electrical component and the second electrical component deposited with at least one layer of a conductive solution. The present invention is characterized in that the conductive solution has a bulk density between 0.4 g / cm 3< and 0.6 g / cm 3< . Each of the first electrical component and the second electrical component may be composed of a conducting metal such as aluminum, copper etc., or a conducting alloy such as brass. As used herein, the conductive solution may be in the form of a paste or a liquid.

[0010] Advantageously, the deposition of the conductive solution at the contact surface results in levelling of surface irregularities in the contact surface. Consequently, trapping of air in the contact area between the first electrical component and the second electrical component is eliminated.

[0011] In accordance with one embodiment of the present invention, the conductive solution is at least one of thermally conducting and electrically conducting. When the conductive solution is thermally conducting, heat generated at the contact surface due to ECR is easily dissipated. Similarly, when the conductive solution is electrically conducting, conduction of electric current between the first electrical component and the second electrical component is improved.

[0012] In accordance with the present invention, the conductive solution comprises at least a conducting carbon allotrope. The carbon allotrope may include, but are not limited to, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, fullerenes, graphite, or a combination or a derivative thereof. In a preferred embodiment, the carbon allotrope is single-walled carbon nanotubes.In another preferred embodiment, the carbon allotrope is multi-walled carbon nanotubes. In one embodiment, the carbon allotrope has a surface area between 110 m 2< / g and 350 m 2< / g. Advantageously, the present invention uses carbon allotropes to impart conductive properties to the conductive solution. In accordance with one embodiment, the carbon allotrope may be 10 to 20 percent by weight of the conductive solution . The conductive solution is formed by dispersing the carbon allotrope in a base oil. The base oil may be one of a group I base oil, a group II base oil, a group III base oil, a group IV base oil or a group V base oil. The group I base oil may comprise more than 90% saturates, less than 0.3% sulphur and a viscosity index in the range of 80 to 120. The group II base oil may comprise less than 90% saturates, less than 0.3% percent and a viscosity index in the range of 80-120. The group III base oil may comprise more than 90% saturates, less than 0.3% percent and a viscosity index greater than 120. The group IV base oil are polyalphaolefins and are synthesised synthetic base oils. The group V base oil may comprise including silicone, phosphate ester, polyalkylene glycol (PAG), polyolester, biolubes, etc. In one embodiment, the at least one layer of the conductive solution has a thickness between 100 micron and 500 micron.

[0013] Advantageously, the use of the base oil helps in creating a homogenous conductive solution from the carbon allotrope.

[0014] In accordance with one embodiment of the present invention, the electrical device is a an electrical busbar system.

[0015] Advantageously, the electrical busbar system has a reduced Electrical Contact Resistance (ECR) compared to existing electrical busbar systems due to the presence of the condcutive solution in the electrical joint.

[0016] In accordance with one embodiment of the present invention, a switchgear arrangement comprising an electrical device as described above is disclosed. The switchgear arrangement may be one of a medium voltage switchgear and a high voltage switchgear. The medium voltage switchgear are intended for use in the voltage range of 1 kV to 36 kV, while the high voltage switchgear is intended for voltages above 36 kV. The switchgear may be one of an air insulated switchgear, a vacuum insulated switchgear, and a gas insulated switchgear.

[0017] In accordance with one embodiment of the present invention, a method of forming an electrical joint between a first electrical component and a second electrical component is disclosed. The method comprises depositing at least one layer of a conductive solution as described above, on a contact surface between the first electrical component and the second electrical component. The layer of the conductive solution may be deposited on the contact surface by manual coating methods such as using a brush or using mechanical devices such as grease guns, spraying systems and so on. The present invention is characterized in that the conductive solution has a bulk density between 0.4 g / cm 3< and 0.6 g / cm 3< .

[0018] The method further comprises forming the electrical joint by superposing the first electrical component and the second electrical component at the contact surface. In one embodiment, the first electrical component and the second electrical component are superposed at the contact surface by a mechanical fastener. The mechanical fastener may include nuts, bolts, washers, screws and so on.

[0019] The above-mentioned and other features of the invention will now be addressed with reference to the accompanying drawings of the present invention. The illustrated embodiments are intended to illustrate, but not limit the invention.

[0020] The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which: FIG 1Aillustrates a cross sectional view of an electrical joint, in accordance with one embodiment of the present invention; FIG 1Billustrates a top view of the electrical joint, in accordance with one embodiment of the present invention; FIG 2illustrates a flowchart of a method of forming the electrical joint, in accordance with one embodiment of the present invention; FIG 3Aillustrates an electrical busbar system including the electrical joint, in according with one embodiment of the present invention; and FIG 3Billustrates a switchgear arrangement including the electrical busbar system, in accordance with one embodiment of the present invention.

[0021] Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide thorough understanding of one or more embodiments. It may be evident that such embodiments may be practiced without these specific details.

[0022] Referring to FIG 1A, a cross-sectional view of an electrical joint 100 is shown, in accordance with one embodiment of the present invention. Similarly, FIG 1B shows a top view of the electrical joint 100.

[0023] The electrical joint 100 is part of an electrical busbar system comprising a first busbar 105 and a second busbar 110. Each of the first busbar 105 and the second busbar 110 may be composed of at least one of aluminum and copper. Further, each of the first busbar 105 and the second busbar 110 may have a solid cross section or a hollow cross section. The first busbar 105 and the second busbar 110 serve as the electrically conducting elements of the electrical joint 100.

[0024] The first busbar 105 and the second busbar 110 are superposed at a contact surface 115. The contact surface 115 may indicate an overlapping area between the first busbar 105 and the second busbar 110. The contact surface 115 is deposited with a layer 120 of a conductive solution. The conductive solution consists of at least 50% by weight of carbon nanotubes dispersed in a base oil. The base oil in the present embodiment is Vaseline 8422 Vara AB. The carbon nanotubes may be single-walled carbon nanotubes that have current carrying capacity of approximately 1010 A / cm 2< . The first busbar 105 and the second busbar 110 are held together to form the electrical joint 100, using a bolting mechanism 125. The bolting mechanism 125 consists of a first nut 130 passing through the first busbar 105 and the second busbar 110, secured using a first bolt 135 and a second nut 140 passing through the first busbar 105 and the second busbar 110, secured using a second bolt (not shown).

[0025] Referring to FIG 2, in conjunction with FIGS 1A and 1B, a flowchart of a method 200 for forming the electrical joint 100 is shown, in accordance with one embodiment of the present invention. The method 200 comprises steps 205 and 210.

[0026] In order to form the electrical joint 100, at first, the contact surface 115 is deposited with the layer 120 of the conductive solution as shown in step 205. The layer 120 of the conductive solution may be deposited on the contact surface 115 by manual application, such that the conductive solution levels any unevenness associated with the contact surface 115 that may cause formation of air bubbles in the electrical joint 100. In other words, the deposition of the layer 120 of conductive solution prevents formation of airgaps in the electrical joint 100. Further, the conductive solution also improves conduction of heat and electricity across the electrical joint 100. As a result, heat is easily dissipated, thus leading to decreased electrical contact resistance in the electrical joint 100. Upon superposing, the first busbar 105 and the second busbar 110 is joined using the bolting mechanism 125 to form the electrical joint 100, as shown in step 210.

[0027] FIG 3A shows an electrical busbar system 305 including the aforementioned electrical joint 100, in accordance with one embodiment of the present invention.

[0028] FIG 3B shows a switchgear arrangement 310 including the electrical busbar system 305, in accordance with one embodiment of the present invention. The switchgear arrangement 310 comprises a cable compartment 315, a switching compartment 320, and a busbar compartment 325 including the electrical busbar system 305 all coupled with one another. The electrical busbar system 305 includes one or more electrical joints similar to the aforementioned electrical joint 100. In the present embodiment, the switchgear arrangement 310 may be a clean air switchgear for use in medium voltage ranges.

[0029] The foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention disclosed herein. While the invention has been described with reference to various embodiments, it is understood that the words, which have been used herein, are words of description and illustration, rather than words of limitation. Further, although the invention has been described herein with reference to particular means, materials, and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all electrical devices and methods that are within the scope of the appended claims.List of reference numerals

[0030] 100electrical joint 105first busbar 110second busbar 115contact surface 120layer of conductive solution 125bolting mechanism 130first nut 135first bolt 140second nut 305electrical busbar system 310switchgear arrangement 315cable compartment 320switching compartment 325busbar compartment

Claims

1. An electrical device comprising: a first electrical component (105) and a second electrical component (110) forming an electrical joint (100) therebetween, wherein the electrical joint (100) comprises a contact surface (115) between the first electrical component (105) and the second electrical component (110) deposited with at least one layer (120) of a conductive solution wherein the conductive solution comprises at least a conducting carbon allotrope dispersed in a base oil, characterized in that the conductive solution has a bulk density between 0.4 g / cm3 and 0.6 g / cm3.

2. The electrical device according to claim 1, wherein the conductive solution is at least one of thermally conducting and electrically conducting.

3. The electrical device according to claim 2, the carbon allotrope is 10 to 20 percent by weight of the conductive solution.

4. The electrical device according to claim 1, wherein the at least one layer (120) of the conductive solution has a thickness between 100 micron and 500 micron.

5. The electrical device according to claim 1, wherein the carbon allotrope has a surface area between 110 m2 / g and 350 m2 / g.

6. The electrical device according to claim 1, wherein the electrical device is an electrical busbar system (305).

7. A switchgear arrangement (310) comprising an electrical device (305) according to any of the preceding claims 1 to 5.

8. The switchgear arrangement (310) according to claim 7 is one of a medium voltage switchgear and a high voltage switchgear.

9. A method of forming an electrical joint (100) between a first electrical component (105) and a second electrical component (110), the method comprising: depositing at least one layer (120) of a conductive solution, on a contact surface (115) associated with at least one of the first electrical component (105) and the second electrical component (110); and forming the electrical joint (100) by superposing the first electrical component (105) and the second electrical component (110) at the contact surface (115), wherein the conductive solution comprises at least a conducting carbon allotrope dispersed in a base oil, characterized in that the conductive solution has a bulk density between 0.4 g / cm3 and 0.6 g / cm3.

10. The method according to claim 9, wherein the first electrical component (105) and the second electrical component (110) are superposed at the contact surface (115) by a mechanical fastener (125).