Patent Description:
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.

In the document Mg Chemicals: "<NPL> an electrically conductive carbon paste with a bulk density of <NUM>/cm<NUM> is disclosed.

US Patent Application Publication <CIT> discloses an electrical interface with a nano-particle layer. Mg Chemicals: "<NPL> discloses an overview over different electrically conductive carbon pastes with bulk densities of above <NUM>/cm<NUM>.

Chinese Patent <CIT> discloses a graphene modified conductive silver paste and a preparation method thereof. Korean Patent Application <CIT> discloses a conductive paste having carbon nanotubes as conductive particles, the carbon nanotubes having a bulk density of <NUM> to <NUM>/cm<NUM>.

Japanese Patent Application <CIT> discloses a conductive auxiliary agent dispersion with carbon materials as conductive aid having a specific surface area of <NUM> to <NUM><NUM>/g or <NUM> to <NUM><NUM>/g respectively.

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.

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.

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 <NUM>/cm<NUM> and <NUM>/cm<NUM>. 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.

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.

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.

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 <NUM><NUM>/g and <NUM><NUM>/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 <NUM> to <NUM> 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 <NUM>% saturates, less than <NUM>% sulphur and a viscosity index in the range of <NUM> to <NUM>. The group II base oil may comprise less than <NUM>% saturates, less than <NUM>% percent and a viscosity index in the range of <NUM>-<NUM>. The group III base oil may comprise more than <NUM>% saturates, less than <NUM>% percent and a viscosity index greater than <NUM>. 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 <NUM> micron and <NUM> micron.

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

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

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.

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 <NUM> kV to <NUM> kV, while the high voltage switchgear is intended for voltages above <NUM> kV. The switchgear may be one of an air insulated switchgear, a vacuum insulated switchgear, and a gas insulated switchgear.

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 <NUM>/cm<NUM> and <NUM>/cm<NUM>.

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.

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.

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.

Referring to <FIG>, a cross-sectional view of an electrical joint <NUM> is shown, in accordance with one embodiment of the present invention. Similarly, <FIG> shows a top view of the electrical joint <NUM>.

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

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

Referring to <FIG>, in conjunction with <FIG>, a flowchart of a method <NUM> for forming the electrical joint <NUM> is shown, in accordance with one embodiment of the present invention. The method <NUM> comprises steps <NUM> and <NUM>.

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

<FIG> shows an electrical busbar system <NUM> including the aforementioned electrical joint <NUM>, in accordance with one embodiment of the present invention.

<FIG> shows a switchgear arrangement <NUM> including the electrical busbar system <NUM>, in accordance with one embodiment of the present invention. The switchgear arrangement <NUM> comprises a cable compartment <NUM>, a switching compartment <NUM>, and a busbar compartment <NUM> including the electrical busbar system <NUM> all coupled with one another. The electrical busbar system <NUM> includes one or more electrical joints similar to the aforementioned electrical joint <NUM>. In the present embodiment, the switchgear arrangement <NUM> may be a clean air switchgear for use in medium voltage ranges.

Claim 1:
An electrical device comprising:
a first electrical component (<NUM>) and a second electrical component (<NUM>) forming an electrical joint (<NUM>) therebetween,
wherein the electrical joint (<NUM>) comprises a contact surface (<NUM>) between the first electrical component (<NUM>) and the second electrical component (<NUM>) deposited with at least one layer (<NUM>) 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 <NUM>/cm<NUM> and <NUM>/cm<NUM>.