Electrostatic shielding element, electrostatic shielding device, and transformer device including electrostatic shielding device

Abstract

The present disclosure relates to an electrostatic shielding element (1) disposed on a first axis (z) and comprising an electrostatically shielded volume (14) at least partially enclosed by an electrically conductive coating (12), the thickness (d) and conductivity (σ) of the coating (12) being selected to allow a magnetic field of a predetermined frequency (f) to penetrate the coating and enter the volume (14). The present disclosure also relates to an electrostatic shielding apparatus (2) and a transformer apparatus (3).

Description

[Technical Field]

[0001] Technical Field The present disclosure relates to an electrostatic shielding device including an electrostatic shielding element and at least two electrostatic shielding elements. More particularly, the present disclosure relates to an electrostatic shielding element including an electrostatically shielded volume that is permeable by a magnetic field up to a predetermined frequency. [Background technology]

[0002] background Electronic devices are difficult to place in environments where they are exposed to high voltages due to the interaction of the device with background electric fields, leading to complex considerations regarding the isolation of both the electronic device and surrounding devices in the high-voltage environment. Complexities increase when the device also requires magnetic coupling to equipment or appliances outside the electric field.

[0003] Electronic devices in high-voltage environments require electrostatic shielding because conductive objects in high-electric field environments cause field enhancement, resulting in an increased probability of partial discharge and accelerated degradation of any adjacent dielectric components and / or materials. Electrostatic shielding can terminate electric field lines at the boundary of the shielded area, preventing magnetic fields from penetrating the shield. Therefore, it is difficult to provide magnetic interactions, such as power and / or signal transmission, with shielded devices from outside the shielded area.

[0004] Electrostatic shielding must meet at least three requirements: -The conductivity of the shielding material must not be too low in order to provide an equipotential surface.

[0005] - the conductivity of the shielding material must not be too high to avoid induced eddy currents that repel the incident magnetic flux, - The thickness of the shield should be sufficient to achieve mechanical stability, but less than the skin depth of the magnetic field. Summary of the Invention [Problem to be solved by the invention]

[0006] overview It is therefore an object of the present disclosure to provide an improved electrostatic shield, and in particular to provide an electrostatic shield that allows power and / or signal transmission to and from a shielded electronic device. [Means for solving the problem]

[0007] According to a first aspect of the present disclosure, the object is at least partly achieved by an electrostatic shielding element as set forth in claim 1.

[0008] Thus, an electrostatic shielding element is provided, comprising an electrostatically shielded volume disposed on a first axis and at least partially enclosed by a conductive coating, the thickness and conductivity of the coating being selected to allow a magnetic field of a predetermined frequency to penetrate the coating and enter the volume. The conductivity and thickness of the coating are:

[0009]

number

[0010] Preferably, the hardness is selected such that c≦40000 Sm / s, more preferably c≦5000 Sm / s, and most preferably c≦1000 Sm / s.

[0011] The electrostatically shielded volume is constructed to be protected from electric fields at operating frequencies of 50 Hz / 60 Hz. For this purpose, the coating material must be sufficiently conductive. The coating material must also be continuous to completely close the volume.

[0012] By appropriately selecting the conductivity and thickness of the coating, magnetic fields can be allowed to penetrate the volume, allowing power and signal transmission to electrical devices contained within the volume.

[0013] The coating is preferably a conductive metal coating. When the coating is exposed to an incident magnetic field, eddy currents are induced in the coating. The eddy current effect increases as the frequency of the magnetic field increases, preventing the magnetic field from penetrating the shielded volume. The eddy current effect decreases as the conductivity of the coating material decreases.

[0014] Thicker coatings require lower electrical conductivity than thinner coatings to allow the magnetic field to penetrate, but thicker coatings have better mechanical strength than thinner coatings.

[0015] The frequency of magnetic fields for power and signal transmission applications is traditionally between 20 kHz and 20 MHz. Designing electrical devices and electronic components for a given frequency within this range limits the range of coating conductivities / materials and coating thicknesses that can be selected. The constant c can be selected to ensure that at least a portion of the signal power of the magnetic field can penetrate the coating. At c = 40,000 Sm / s, approximately 10% of the signal power penetrates the coating. At c = 5,000 Sm / s, approximately 50% of the signal power penetrates the coating. At c = 1,000 Sm / s, approximately 90% of the signal power penetrates the coating.

[0016] Optionally, the electrostatically shielded volume is completely enclosed by a conductive coating.

[0017] In the case of a single shielding element, the electrostatically shielded volume must be completely closed by the conductive coating. The volume may be partially closed, i.e., partially open, if the open area of ​​the volume is covered by an adjacent galvanically connected conductor, such as another shielding element.

[0018] Optionally, the volume extends laterally from the first axis. The volume may be disc-shaped, extending significantly more laterally from the first axis than along the first axis.

[0019] Optionally, the volume is circular or elliptical about a first axis. A circular volume has a radius extending orthogonally from the first axis. An elliptical volume extends a first distance along a second (major) axis orthogonal to the first axis, and extends a second distance along a third (minor) axis orthogonal to both the first and second axes.

[0020] Because field enhancement occurs at sharp corners and edges, a circular or elliptical volume about the first axis is envisioned. Furthermore, the radially outer edge of the volume may have a rounded shape in a plane parallel to the first axis. The radius of curvature of the radially outer edge may preferably be half the thickness of the volume at the radially outer edge as viewed along the first axis.

[0021] Optionally, the conductive layer has a thickness of 1 mm or less. Optionally, the conductivity of the conductive layer is between 1 S / m and 10 8 S / m range, preferably 10 3 S / m~10 8 S / m range, most preferably 10 5 S / m~10 8 Located in S / m.

[0022] 10 8 Conductivity less than 10 S / m includes conductive materials. 5 It is also conceivable to use coatings of semiconducting materials such as S / m and materials such as carbon / graphite at about 1 S / m.

[0023] Optionally, the electrostatic shielding element comprises at least one electrical device enclosed within the volume, the electrical device configured to receive power by inductive coupling and / or to be communicatively coupled to a magnetic field of a predetermined frequency.

[0024] Thus, an electrical device may be enclosed and electrostatically shielded within the coated volume. Power may be inductively received and transmitted to another electrical device or component. Additionally, the electrical device may be communicatively coupled to the magnetic field to receive and / or transmit signals via the magnetic field to a receiver / transmitter outside the electrostatically shielded volume. This allows the electrostatic shielding element to be placed within a high-voltage electric field without risk of damaging the electrical device or surrounding instruments and / or equipment.

[0025] Optionally, the electrical device comprises at least one LC circuit. The LC circuit may comprise a single LC circuit or multiple LC circuits, such as an array of LC circuits.

[0026] According to a second aspect of the present disclosure, the object is at least partly achieved by an electrostatic shielding device as set forth in claim 9.

[0027] Accordingly, there is provided an electrostatic shielding device comprising at least two electrostatic shielding elements according to any one of the embodiments of the first aspect of the present disclosure, galvanically connected to each other, the at least two electrostatic shielding elements being disposed spaced apart from each other along a first axis to form an electrostatically shielded space therebetween.

[0028] Thus, the DC electrical connection between the at least two electrostatic shielding elements ensures an equipotential surface across the entire surface of the electrostatic shielding device. They are both disposed on a first axis, e.g., parallel to the first axis. Thus, the electrostatically shielded space between the electrostatic shielding elements also extends laterally from the first axis. The space may include any components that require shielding from the electric field but also require contact with the environment outside the electrostatic shielding elements.

[0029] Optionally, the at least two electrostatic shielding elements are mechanically and galvanically connected to each other via at least one conductive fastening element.

[0030] The galvanic connection may be realized by a conductive fastening element, such as a screw or bolt, that engages with the at least two electrostatic shielding elements. The fastening element may also be electrically conductive by being provided with a conductive coating, such as the same coating as the at least two electrostatic shielding elements.

[0031] Optionally, the electrostatic shielding apparatus comprises at least one electronic component disposed within the electrostatically shielded space, the electrical device being electrically connected to the electronic component.

[0032] Electronic components may be placed within the electrostatically shielded space without risk of interference from electric fields, and the electrical components may be electrically connected to electrical devices inside the electrostatic shielding element in areas bordering the electrostatically shielded space via electrical conductors passing through the coating of the electrostatic shielding element.

[0033] Optionally, the at least two electrostatic shielding elements are spaced apart from one another by at least a separation distance, and the electronic component is positioned within the shielded space at least the separation distance from a radial periphery of the at least two electrostatic shielding elements.

[0034] As a rule of thumb, the electric field is negligible at a distance equal to the radial perimeter separation of at least two electrostatic shielding elements, and therefore a component is protected when it is located within an electrostatic shielded space at least the radial perimeter separation distance of the electrostatic shielding elements.

[0035] Optionally, the electronic component is a sensor powered by and / or communicatively coupled to the electrical device.

[0036] A sensor placed within an electrostatically shielded space is exposed to the environment in which the electrostatic shielding device is positioned. Therefore, such a sensor may measure properties such as temperature, pressure, and humidity without exposure to electric fields and without the risk of field buildup and / or electrical breakdown of the medium in which it is installed, which could lead to arcing. The sensor may be powered by an electric device inductively coupled to a magnetic field. Any sensor data may be wirelessly transmitted to a remote control unit via the electric device and magnetic field. "Remote" as used herein should be understood as being away from or outside of the electric / magnetic field.

[0037] Optionally, the shielded volume comprises a field grading material or a dielectric material. The field-grading material may also be a nonlinear resistive field-grading material. The primary characteristic of a nonlinear resistive field-grading material is that its electrical conductivity increases above a threshold electric field amplitude, and thus it can be used to reduce the maximum electric field stress at a location within an insulation system. Field-grading material composites generally may be constructed from a base polymer, such as SiR, ethylene propylene-diene monomer rubber, epoxy resin, or thermoplastic resin, and may be filled with single or multiple fillers, often conductive or semiconductive, to achieve nonlinear behavior. The composite's nonlinear conductive behavior comes from the semiconducting filler. The filler material may be silicon carbide, although alternatives exist.

[0038] Any suitable dielectric material may be used, such as pressboard, paper, cellulose or impregnated cellulose, dielectric polymers, etc. Fluid dielectric materials may be used alternatively or to complement solid dielectric materials. Fluid dielectric materials may be exemplified by air, oil, etc. The field grading material or dielectric material may partially or completely fill the shielded space.

[0039] According to a third aspect of the present disclosure, the object is at least partly achieved by a transformer arrangement as claimed in claim 15.

[0040] Thus, there is provided a transformer arrangement comprising a transformer and an electrostatic shielding device according to any one of the embodiments of the second aspect of the present disclosure.

[0041] An electrostatic shielding device may be provided in the transformer device to protect and drive sensors to monitor the transformer during operation. Due to the shielding properties of the electrostatic shielding element, no sensor needs to disconnect the transformer to perform measurements.

[0042] The above aspects, the appended claims, and / or the examples disclosed hereinabove and below may be combined with each other as appropriate, as would be apparent to one skilled in the art.

[0043] Additional features and advantages are set forth in the following description, claims, and drawings, and in part will become readily apparent to those skilled in the art from or may be learned by practice of the disclosure set forth herein.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS Further objects, advantages, and features of the present disclosure will become apparent from the following description of one or more embodiments, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0045] [Figure 1] 1A and 1B are diagrams illustrating an example of an electrostatic shielding element according to a first embodiment of the present disclosure. [Figure 2] 1A and 1B are diagrams illustrating an example of an electrostatic shielding element according to a first embodiment of the present disclosure. [Figure 3] 1A and 1B are diagrams illustrating an example of an electrostatic shielding element according to a first embodiment of the present disclosure. [Figure 4] 1A and 1B are diagrams illustrating an example of an electrostatic shielding element according to a first embodiment of the present disclosure. [Figure 5] FIG. 10 is a diagram illustrating an example of an experimental result. [Figure 6] FIG. 2 illustrates an example of an electrostatic shielding device according to a second aspect of the present disclosure. [Figure 7]FIG. 2 illustrates an example of an electrostatic shielding device according to a second aspect of the present disclosure. [Figure 8] FIG. 10 illustrates an example of a transformer device according to a third aspect of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0046] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION The present disclosure will be developed in more detail below with reference to the accompanying drawings, which show example embodiments. The present disclosure should not be considered limited to the example embodiments described. Like numbers refer to like elements throughout the description.

[0047] The terms used herein are for the purpose of describing particular embodiments of the present disclosure only and are not intended to be limiting of the present invention. As used herein, the singular forms "A," "AN," and "THE" are intended to include the plural forms unless the context clearly dictates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0048] FIG. 1 illustrates an electrostatic shielding element 1 for protection against electric fields. The electrostatic shielding element 1 is shown disposed on a first axis Z when viewed along the first axis Z. The electrostatic shielding element 1 includes an electrostatically shielded volume 14 at least partially enclosed by a conductive coating 12, the thickness D and conductivity σ of which are selected to allow a magnetic field of a predetermined frequency F to penetrate the coating and enter the volume 14. The volume 14 may extend laterally from the first axis Z. The volume 14 may be disk-shaped, extending significantly more laterally from the first axis Z than along the first axis Z. As shown in FIG. 1, the volume 14 may be circular about the first axis Z with a radius R. In the case of a single shielding element 1, the electrostatically shielded volume 14 may be completely enclosed by the conductive coating 12. If the open area of ​​the shielded volume 14 is covered by an adjacent galvanically connected conductor, such as another shielding element 1, the shielded volume 14 may be partially closed, i.e. partially open.

[0049] As shown in Figure 2, volume 14 may alternatively be elliptical about a first axis Z. Elliptical volume 14 may extend a first distance R1 along a second (major) axis X that is orthogonal to first axis Z. Elliptical volume 14 may also extend a second distance R2 along a third (minor) axis Y that is orthogonal to both first axis Z and second axis X. A circular or elliptical volume 14 about first axis Z is preferred to reduce the risk of field enhancement at corners and edges.

[0050] 3 and 4 show side views of an example of an electrostatic shielding element 1 according to a first embodiment of the present disclosure. The electrostatic shielding element 1 is viewed along either the second axis x or the third axis y, i.e., perpendicular to the first axis z. In FIG. 3, the volume 14 has a slightly conical or parabolic shape around the first axis z, while in FIG. 4, the volume 14 is substantially flat around the first axis z. Both shapes are equally contemplated.

[0051] Furthermore, the radial periphery or edge 13 of the volume 14 may have a rounded shape in a plane parallel to the first axis Z. The radius of curvature RC of the radial outer edge may preferably be half the volume thickness T at the radial outer edge 13 as viewed along the first axis Z.

[0052] Figure 3 shows a detailed view of the coating 12. The electrostatically shielded volume 14 is configured to be protected from electric fields at operating frequencies of 50 Hz / 60 Hz. For this purpose, the coating material must be sufficiently conductive. The coating material must also be continuous to completely enclose the volume 14.

[0053] Appropriate selection of the electrical conductivity σ and thickness D of coating 12 allows magnetic fields to penetrate into volume 14, enabling power and signal transmission to electrical devices contained within volume 14.

[0054] The coating 12 is preferably a conductive metallic coating 12. When the coating 12 is exposed to an incident magnetic field, eddy currents are induced in the coating 12. The eddy current effect increases as the frequency of the magnetic field increases, preventing the magnetic field from penetrating the shielded volume. The eddy current effect decreases as the electrical conductivity σ of the coating material decreases.

[0055] A thicker coating 12 requires a lower conductivity σ than a thinner coating 12 to allow penetration of the magnetic field into the volume 14. However, a thicker coating 12 has better mechanical strength than a thinner coating 12.

[0056] For a given frequency f, the conductivity σ and thickness d of coating 12 may be selected such that:

[0057]

number

[0058] where c is a constant less than or equal to 40,000 Sm / s, allowing approximately 10% of the magnetic field's signal power to be transmitted through coating 12. Preferably, c is less than or equal to 5,000 Sm / s, resulting in approximately 50% of the signal power being transmitted through coating 12. Most preferably, c is less than or equal to 1,000 Sm / s, thereby allowing approximately 90% of the signal power to be transmitted through coating 12.

[0059] The frequency (f) of the magnetic field for power and signal transmission applications is traditionally between 20 kHz and 20 MHz. Designing electrical devices and electronic components for a given frequency (f) within this range limits the range of selectable coating conductivities / materials and coating thicknesses.

[0060] The thickness of the conductive layer may be between 1 mm and less. The conductivity σ of the conductive layer (or coating) 12 is 1 S / m to 10 8 S / m range, preferably 10 3 S / m~10 8 S / m range, most preferably 10 5 S / m~10 8 Located in S / m. 10 8 Conductivity less than 10 S / m includes conductive materials such as metals. 5 It is also conceivable to use a coating of semiconductor material with 0.5 S / m and a material such as carbon / graphite with about 1 S / m.

[0061] 3 and 4, the electrostatic shielding element 1 comprises at least one electrical device 18 enclosed within a volume 14. The electrical device 18 may be configured to receive power by inductive coupling and / or to be communicatively coupled to a magnetic field of a predetermined frequency f.

[0062] An electrical device 18 may be enclosed and electrostatically shielded within the coated volume 14. Power may be inductively or wirelessly received and transmitted to another electrical device 18 or component. Additionally, the electrical device 18 may be communicatively coupled to the magnetic field to receive and / or transmit signals via the magnetic field to a receiver / transmitter (not shown) outside the electrostatically shielded volume. This allows the electrostatic shielding element 1 to be placed within a high-voltage electric field without risk of damage to the electrical device or surrounding fixtures and / or equipment.

[0063] The electrical device 18 may include at least one LC circuit. The LC circuit may include a single LC circuit or multiple LC circuits, such as an array of LC circuits. The electrical device 18 that can receive power from a magnetic field and perform wireless power and signaling is a conventional device and will not be described in detail in this disclosure.

[0064] Figure 5 shows the simulation results of the variation of the magnetic field penetration into volume 14. The vertical axis represents how well the magnetic field penetrates coating 12 into volume 14. A value of 1 is very good penetration, and a value of 0 is no penetration. The horizontal axis is the product fσ. Three examples are shown for different coating thicknesses d1, d2, and d3, where d1=100 μm, d2=10 μm, and d3=1 μm.

[0065] As the simulated example shows, for d2, the magnetic field is 13 When the product is less than 10, the coating 12 is almost completely penetrated. 15 When the voltage exceeds 10, it is almost completely blocked. 13 <Frequency f×conductivity σ<10 15 There are various degrees of magnetic field penetration in the range of . Therefore, for a given frequency f of 1 MHz for the magnetic field to penetrate completely through a 10 μm thick coating 12, the following must be guaranteed:

[0066]

number

[0067] 6 shows an electrostatic shielding device 2 according to a second embodiment of the present disclosure. The electrostatic shielding device 2 includes at least two electrostatic shielding elements 1 according to any one of the above-described examples. The electrostatic shielding elements 1 are galvanically connected to each other, and the at least two electrostatic shielding elements 1 are disposed spaced apart from each other along the first axis z to form an electrostatically shielded space 16 therebetween.

[0068] The DC electrical connection between the at least two electrostatic shielding elements 1 therefore ensures an equipotential surface over the entire surface of the electrostatic shielding device 2, which in turn ensures negligible electric potential within the shielded space 16. They are both disposed on the first axis z, for example, parallel to each other along the first axis z. The electrostatic shielded space 16 between the electrostatic shielding elements 1 therefore also extends laterally from the first axis z. The shielded space 16 may include any components that require shielding from electric fields but that require contact with the environment outside the electrostatic shielding elements 1, i.e., the environment in which the electrostatic shielding device 2 is installed.

[0069] The at least two electrostatic shielding elements may be mechanically and galvanically connected to each other via at least one conductive fastening element.

[0070] The galvanic connection may be realized by means of a conductive fastening element 20, such as a screw or a bolt, which engages with the at least two electrostatic shielding elements 1. The fastening element 20 may also be electrically conductive by being provided with a conductive coating, such as the same coating 12 as the at least two electrostatic shielding elements 1.

[0071] The electrostatic shielding apparatus 2 may include at least one electronic component 22 disposed within the electrostatically shielded space 16 , and the electrical device 18 may be electrically connected to the electronic component 22 .

[0072] Electronic component 22 may be placed within electrostatically shielded space 16 without risk of interference from electric fields external to electrostatic shielding device 2. Electrical component 22 may be electrically connected to electrical device 18, an electrical device located inside electrostatic shielding element 1, via electrical conductor 26 passing through coating 12 of electrostatic shielding element 1 through a wall of the electrostatic shielding element that borders electrostatic shielded space 16. Alternatively, electrical component 22 may be wirelessly connected to electrical device 18, such as when electrical component 22 is inductively coupled to the electrical device. Electrical component 22 may comprise at least one LC circuit, in this example.

[0073] The at least two electrostatic shielding elements 1 may be spaced apart from one another by at least a separation distance D. The electronic components 22 may be disposed within the shielded space 16 at least a separation distance D from the radial peripheries 13 of the at least two electrostatic shielding elements 1. Typically, the separation distance is defined as the distance along the first axis z between the radial peripheries 13 of the electrostatic shielding elements 1. Preferably, the separation distance D is significantly smaller than the radii r, r1, and r2 of the electrostatic shielding elements 1. As an example, the separation distance D is equal to or less than one-fifth of the radii r, r1, and r2. In the case of an elliptical electrostatic shielding element, the separation distance is determined relative to the extension along the minor axis of the ellipsoid, i.e., along the third axis y.

[0074] The distance between the at least two electrostatic shielding elements 1 may vary throughout the shielded space. As a rule of thumb, the electric field is negligible at a distance equal to the separation distance D from the radial periphery 13 of the at least two electrostatic shielding elements 1. Thus, an electronic component 22 is protected when positioned within the electrostatic shielded space 16 at least the separation distance from the radial periphery of the electrostatic shielding elements. The shielded space 16 is illustrated as bounded by the dashed area in FIG. 7 .

[0075] The electronic component 22 may be a sensor 22 powered by and / or communicatively coupled to the electrical device 18 .

[0076] Sensors 22 disposed within electrostatically shielded space 16 are exposed to the environment in which electrostatic shielding apparatus 2 is positioned. Thus, such sensors may measure properties such as temperature, pressure, humidity, etc. without exposure to electric fields and without risk of field buildup and / or electrical breakdown of the medium in which they are installed, which could lead to arcing. Sensors 22 may be powered by electrical devices 18 inductively coupled to the magnetic field.

[0077] The shielded volume 16 may contain a field-graded material or a dielectric material. The field-graded material may be a nonlinear resistive field-graded material. The key characteristic of a nonlinear resistive field-graded material is that its conductivity increases above a threshold electric field amplitude, and therefore it can be used to reduce the maximum electric field stress at a location within the insulation system. Field-graded material composites generally may be composed of a base polymer, such as SiR, ethylene propylene-diene monomer rubber, epoxy resin, or thermoplastic resin, and may be filled with one or more fillers, often conductive or semiconductive, to achieve nonlinear behavior. The composite's nonlinear conductive behavior comes from the semiconducting filler. The filler material may be silicon carbide, although alternatives exist.

[0078] Any suitable dielectric material may be used, such as pressboard, paper, cellulose or impregnated cellulose, dielectric polymers, etc. Fluid dielectric materials may be used alternatively or to complement solid dielectric materials. Fluid dielectric materials may be exemplified by air, oil, etc. The field grading material or dielectric material may partially or completely fill the shielded volume 16.

[0079] 8 conceptually illustrates a transformer apparatus 3 according to a third embodiment of the present disclosure. The transformer apparatus 3 includes a transformer 24 and an electrostatic shielding device 2 according to any one of the above-described examples. Accordingly, the electrostatic shielding device 2 may be provided in the transformer apparatus 3. The electrostatic shielding device 2 may protect and drive a sensor 22 to monitor the transformer 24 during operation. Due to the shielding properties of the electrostatic shielding element 1, no sensor needs to disconnect the transformer 24 to perform measurements.

[0080] Any transformer apparatus 3 may include a monitoring unit 28 and may be configured such that the electronic components 22 are wirelessly coupled to the control unit 28 via the electric device 18 and via a magnetic field. The control unit 28 may be configured to transmit power to the electric device 18 via the magnetic field and to receive signals, such as sensor data, from the electronic components 22 via the electric device 18 via the magnetic field.

Claims

1. an electrostatic shielding element (1) disposed on a first axis (z) and comprising an electrostatically shielded volume (14) at least partially enclosed by an electrically conductive coating (12), the thickness (d) and conductivity (σ) of the coating (12) being selected to allow a magnetic field of a predetermined frequency (f) to penetrate the coating and enter the volume (14); For the given frequency (f), the conductivity (σ) and the thickness (d) of the coating (12) are: [Equation 1] and c≦40,000 Sm / s.

2. Electrostatic shielding element (1) according to claim 1, wherein the volume (14) extends laterally from the first axis (z).

3. 3. The electrostatic shielding element of claim 2, wherein the volume is circular or elliptical about the first axis, the circular volume having a radius extending perpendicularly from the first axis, the elliptical volume extending a first distance along a second axis that is perpendicular to the first axis and a second distance along a third axis that is perpendicular to both the first axis and the second axis.

4. Electrostatic shielding element (1) according to any one of claims 1 to 3, wherein the thickness (d) of the coating (12) is 1 mm or less.

5. The conductivity (σ) of the coating (12) is between 1 S / m and 10 ８ Electrostatic shielding element (1) according to any one of claims 1 to 4, in the range of S / m.

6. Electrostatic shielding element (1) according to any one of claims 1 to 5, comprising at least one electric device (18) enclosed within the volume (14), the electric device (18) being configured to receive power by inductive coupling and / or to be communicatively coupled to a magnetic field of the predetermined frequency (f).

7. Electrostatic shielding element (1) according to claim 6, wherein the electrical device (18) comprises at least one LC circuit.

8. An electrostatic shielding device (2) comprising at least two electrostatic shielding elements (1) according to any one of claims 1 to 7, which are galvanically connected to each other, the at least two electrostatic shielding elements (1) being arranged spaced apart from each other along the first axis (z) and forming an electrostatically shielded space (16) therebetween.

9. 9. The electrostatic shielding device (2) according to claim 8, wherein the at least two electrostatic shielding elements (1) are mechanically and galvanically connected to each other via at least one electrically conductive fastening element (20).

10. When claim 6 or 7 is cited, the electrostatic shielding device (2) according to any one of claims 8 to 9 further comprises at least one electronic component (22) disposed within the electrostatically shielded space (16), and the electrical device (18) is electrically connected to the electronic component (22).

11. 11. The electrostatic shielding device (2) of claim 10, wherein the at least two electrostatic shielding elements (1) are spaced apart from each other by at least a separation distance (D), and the electronic component (22) is disposed in the shielded space (16) at least the separation distance (D) from the radial periphery (13) of the at least two electrostatic shielding elements (1).

12. Electrostatic shielding apparatus (2) according to any of claims 10 to 11, wherein the electronic component is a sensor (22) powered by and / or communicatively coupled to the electrical device (18).

13. Electrostatic shielding device (2) according to any of claims 10 to 12, wherein the shielded volume comprises a field grading material or a dielectric material.

14. A transformer arrangement (3) comprising a transformer (24) and an electrostatic shielding device according to any one of claims 9 to 13.

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