Voltage divider device having a rod-like structure

Abstract

The invention relates to a voltage divider device (1), comprising a core region (2) having a capacitor device and a resistor (3) arranged in the core region (2); a first electrode (4) of the capacitor device having a coupling member (5) for connecting to a voltage-carrying element; a second electrode (6) of the capacitor device having a grounding member (7) for connecting to a grounding element; and wherein the first electrode (4) and the second electrode (6) are connected in an electrically conductive manner via the resistor (3), wherein the first electrode (4) and the second electrode (6) comprise a plurality of electrically conductive, substantially finger-shaped or rod-shaped modulation elements (9). The invention also relates to the arrangement of such a voltage divider device on a connection part of a switchgear of a power network.

Description

Technical Field

[0001] The invention relates to a voltage divider arrangement according to the preamble of the independent claim. Background Art

[0002] Voltage divider devices, also called voltage dividers, are used to measure voltages in grid switchgear. With the increasing input of energy from different source types, such as solar or wind power, into the grid, it is becoming increasingly important to determine and monitor certain power parameters of the grid. This includes, for example, the actual line voltage.

[0003] In the prior art, so-called conventional transformers are used for the measurement. Usually, conventional transformers are inductive voltage dividers with a ferromagnetic core, which are very sensitive to interference. As an alternative, so-called unconventional transformers are known, which can basically be divided into the basic technologies of resistor-type voltage dividers, resistor-capacitor-type voltage dividers and capacitor-type voltage dividers.

[0004] Resistive voltage dividers operate using one or more resistors, but have the obvious disadvantage that stray capacitance and / or parasitic capacitance from connecting cables or other structural elements can have a significant influence on the actual measured value and thus affect the accuracy of the measurement. As an evolution of such resistive voltage dividers, resistive-capacitive voltage dividers are known, which basically have at least one resistor and one capacitor with a defined capacitance.

[0005] If the capacitance of the capacitor is large enough, the above-mentioned stray capacitance and parasitic capacitance become relatively very small and can be ignored, thereby improving the measurement accuracy.

[0006] One of the main problems with this type of resistor-capacitor voltage divider is that the capacitance of the capacitor should remain as constant as possible over a long period of time (usually years or even decades) to prevent the actual measured value from drifting. In addition, the capacitance of the capacitor must remain constant when the external temperature changes or the current frequency changes slightly. In addition, moisture is absorbed into the dielectric located between the capacitor elements, which can cause the capacitance to change during the service life of the voltage divider.

[0007] Typically, the dielectric used in the prior art is an epoxy casting resin, in which the capacitor elements and resistors of the voltage divider are cast. The capacitor arrangement of the known voltage divider arrangement is designed, for example, as two concentrically arranged circular capacitor elements.

[0008] The capacitor element may separate from the dielectric after the casting resin has cured or due to temperature changes, resulting in parts of the capacitor no longer having surfaces in direct contact with the dielectric, but instead forming cavities. These in turn affect the overall capacitance of the capacitor.

[0009] Furthermore, cavities in the dielectric increase the likelihood of partial discharges, which ultimately lead to voltage flashovers and should therefore be avoided. Summary of the invention

[0010] The object of the present invention is to overcome the disadvantages of the prior art and to provide a voltage divider arrangement which has a constant capacitance over a long period of time, in particular over years or decades, and a constant dielectric strength over the entire service life of the voltage divider arrangement.

[0011] The objects of the invention are achieved by the characteristic features of the independent claims.

[0012] The voltage divider device according to the present invention comprises a core region, a capacitor device and a resistor arranged in the core region. The first electrode of the capacitor device comprises a coupling member, wherein a voltage-carrying element can be connected to the voltage divider device in an electrically conductive manner via the coupling member. The second electrode of the capacitor device comprises a grounding member, wherein a grounding element can be connected to the voltage divider device in an electrically conductive manner via the grounding member. The first electrode and the second electrode are connected in an electrically conductive manner via the resistor.

[0013] According to the present invention, the first electrode and the second electrode include a plurality of electrically conductive substantially finger-shaped or rod-shaped modulation elements.

[0014] The finger- or rod-like design of the modulation element reduces the possibility of formation of separations, such as gas-filled cavities due to dielectric shrinkage, during the manufacturing process of the voltage divider device.

[0015] Furthermore, the rod-shaped modulating elements can adapt to temperature changes more easily than a ring electrode arrangement.The finger-shaped or rod-shaped modulating elements can essentially "travel along" the dielectric medium during the manufacturing process and in the event of temperature changes.

[0016] The gas-filled cavity increases the likelihood of voltage flashovers and prevents complete discharge of the voltage divider arrangement, which is detrimental to reliable operation. This is particularly important if the capacitor arrangement is embedded in a solid dielectric medium or if the core region is filled with a solid dielectric medium. Optionally, a polymer filling the core region may be provided for this purpose.

[0017] Optionally, the modulation elements defining the first electrode and the modulation elements defining the second electrode are arranged in substantially concentric circles relative to each other.

[0018] This allows the largest possible capacitor surface area to be obtained with a minimum space requirement.The arrangement in the shape of concentric circles also allows the distance between the capacitor elements to remain constant.

[0019] Optionally, the arrangement radius of the modulation elements defining the outer ring electrode is approximately 50% greater than the arrangement radius of the modulation elements defining the inner ring electrode.

[0020] Optionally, the arrangement radius of the modulation elements of the inner ring electrode is between 8 mm and 22 mm, and the arrangement radius of the modulation elements of the outer ring electrode is between 15 mm and 40 mm.

[0021] If the distance between the modulation elements is large enough, the risk of voltage flashovers between the modulation elements and any damage to the dielectric associated therewith can be prevented.

[0022] The distance can be adapted to the operating conditions, in particular to the input voltage.

[0023] Optionally, the length of the modulation element is defined as 10 mm-60 mm, and the diameter of the modulation element is defined as 1.5 mm-10 mm.

[0024] Optionally, the modulation element is defined to have a substantially electrically insulating substrate and an electrically conductive coating.

[0025] Optionally, the modulating element is defined to include an electrically conductive additive and a substantially electrically insulating matrix.

[0026] By using an electrically insulating matrix and / or by adding conductive additives to the essentially electrically insulating matrix, the expansion coefficients of the dielectric and the modulation element can be adjusted and brought closer together. This further reduces the separation of the modulation element and the associated undesirable formation of cavities. Preferably, epoxy resin is used as the matrix / substrate. This leads to a significant reduction in the formation of cavities, in particular compared to all-metal modulation elements.

[0027] Optionally, the additive includes carbon nanoparticles or is made of carbon nanoparticles.

[0028] Optionally, a direction defining a longitudinal extension of the modulation element of the first electrode and a direction defining a longitudinal extension of the modulation element of the second electrode are substantially parallel.

[0029] This allows to achieve a substantially continuous constant distance between the modulation elements. This may be particularly advantageous for a constant capacitance of the capacitor arrangement.

[0030] Optionally, the modulation element defining the first electrode and the modulation element defining the second electrode have an overlapping region in a direction parallel to their longitudinal extension direction. The width of the overlapping region can determine the capacitance of the capacitive device.

[0031] Optionally, it is defined that the first electrode has 6-14 modulation elements, preferably 8-12 modulation elements, and the second electrode has 14-26 modulation elements, preferably 18-22 modulation elements.

[0032] Optionally, under the conditions of a temperature of 20° C., a relative humidity of 50%, a pressure of 1000 mbar, and a current frequency of 50 Hz, the capacitor device has a capacitance of 1 pF-30 pF, preferably a capacitance of 1 pF-15 pF.

[0033] If the capacitance of the capacitor arrangement is sufficiently large, stray and parasitic capacitances can be neglected during the voltage measurement. Thus, the residual capacitance including the mentioned stray and parasitic capacitances becomes so low compared to the main capacitance of the capacitor that it no longer has a substantial influence on the measurement accuracy.

[0034] The invention further relates to the arrangement of a voltage divider arrangement according to the invention on a connecting part of a switchgear of an electrical network.

[0035] Optionally, the core region is defined to include a dielectric medium, and the dielectric medium includes a siloxane-based polymer or is made of a siloxane-based polymer.

[0036] Siloxane-based polymers, in particular solid siloxane polymers, also known as silicone polymers, have diffusion-inhibiting properties. Such polymers are generally insensitive to water vapor diffusion when used as dielectric media and the dielectric constant does not change significantly when exposed to humid air. In addition, silicone polymers have better frequency transmission properties than known dielectric media and are therefore able to meet compliance requirements in accordance with standards, in particular those of the international standard IEC 60044-7. In addition, frequencies up to 10 kHz can be transmitted within predetermined boundaries.

[0037] Siloxane polymers, in particular solid siloxane polymers, also known as silicone polymers, have elastic properties. In the voltage divider device according to the invention, this allows the polymer to adapt well to the structure of the electrode arrangement during operation. In the case of non-elastic materials, cracks may be generated in the material when the temperature changes, or the material of the capacitor device may be partially separated from the dielectric medium. This may lead to the formation of gas-filled cavities, which not only prevent the capacitance of the capacitor device from being constant, but may also lead to voltage flashovers and incomplete discharge of the voltage divider device. The use of siloxane polymers can avoid these problems because it ensures a good connection with the elements of the capacitor device.

[0038] Optionally, it is defined that the core region is designed substantially as a truncated cone or cylinder. Optionally, it is provided that a sheath region, preferably a sheath region of an epoxy-based polymer, is provided which at least partially, preferably completely surrounds the core region.

[0039] In view of the characteristic elastic properties of silicone polymers, it may be advantageous to surround a core region made of silicone polymer with a mechanically more stable sheath region to protect the core region from deformation and damage.

[0040] Optionally, the dielectric medium defining the core region has a relative permittivity of 4 to 6.

[0041] Optionally, the relative permittivity of the dielectric medium of the core region in the temperature range of -40°C to 80°C differs by at most 3%, preferably by at most 0.75%, compared to the relative permittivity of the dielectric medium at 20°C.

[0042] Since the voltage divider device according to the invention is usually used in non-air-conditioned areas or heated areas, the dielectric constant of the dielectric medium is advantageously as constant as possible under normal temperature conditions. This ensures a constant capacitance of the capacitor device, which is advantageous for measuring the voltage as accurately as possible.

[0043] Optionally, the relative permittivity of the dielectric medium of the core region in the frequency range of 50 Hz to 10000 Hz differs by a maximum of 0.6%, preferably by a maximum of 0.4%, compared to the relative permittivity of the dielectric medium at 50 Hz.

[0044] In modern power grids, the feed-in of different energy sources leads to changes in the grid frequency. Therefore, the dielectric constant of the dielectric is also advantageously constant within the frequency range typical of the grid to ensure accurate measurement of the voltage.

[0045] Optionally, the relative permittivity of the dielectric medium of the core region when its water content is 5‰ to 30‰ differs by a maximum of 3%, preferably by a maximum of 2.9%, compared to the relative permittivity of the dielectric medium when its water content is 30‰.

[0046] Since the voltage divider device according to the invention is usually used under normal ambient conditions, it may occasionally be exposed to increased air humidity. Generally, siloxane polymers have a reduced water absorption. However, the dielectric constant of the dielectric medium is advantageously as constant as possible within a certain water content range, so that a constant voltage measurement result can be obtained even over a long period of time.

[0047] In particular, if more and more water diffuses into the dielectric medium over the service life of the voltage divider arrangement, this would lead to an undesirable drift of the measured values ​​over time in the case of a strong dependence of the dielectric constant on the water content of the dielectric medium.

[0048] Optionally, the defined core region is cast from a two-component thermosetting silicone system.

[0049] Alternatively, the maximum water absorption is defined as 30‰ of the weight of the polymer matrix at a temperature of 20° C. The maximum water absorption can be determined, for example, by storing the silicone polymer in an aging test chamber for about 1000 days.

[0050] Optionally, finger-shaped or rod-shaped modulation elements may be provided on the first electrode and the second electrode.

[0051] Optionally, the present invention also relates to a method for manufacturing a voltage divider device according to the present invention, comprising the following steps:

[0052] Casting the core region from a silicone-based casting material, in particular a two-component casting material, and

[0053] - Solidifying the core region.

[0054] Optionally, the method may include the following steps:

[0055] - casting the jacketing region from a casting compound, in particular an epoxy-based casting compound, and

[0056] - Curing the jacket zone.

[0057] Further features of the invention are apparent from the patent application claims, the exemplary embodiments and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In the following, the present invention is discussed in detail based on non-exhaustive exemplary embodiments, wherein:

[0059] Figure 1 shows a side cross-sectional view of a voltage divider arrangement according to the present invention;

[0060] Figure 2 The voltage divider device according to the present invention is shown along Figure 1 Sectional view along axis AA. DETAILED DESCRIPTION

[0061] Figure 1 The voltage divider arrangement 1 according to the invention is shown in a sectional view along a plane extending through a central axis 13 of the voltage divider arrangement 1 .

[0062] The voltage divider device comprises a capacitor device, which comprises a first electrode 4 and a second electrode 6. The first electrode 4 is formed integrally with a coupling member 5, which comprises a thread, by which the coupling member 5 can be connected to a voltage-carrying element. Alternatively, the energizing element as a voltage-carrying element can be a power line in a distribution box of a power grid.

[0063] The second electrode 6 is formed integrally with a grounding member 7, which also includes a thread for attaching a grounding element. In addition, the second electrode 6 includes a measuring terminal 8, through which a measuring instrument for measuring voltage can be connected. The first electrode 4 and the second electrode 6 have modulation elements 9 arranged in a concentric circle and in the form of fingers.

[0064] In this exemplary embodiment, the longitudinal extension directions of the finger-like modulation elements 9 of the first electrode 4 and the finger-like modulation elements 9 of the second electrode 6 are substantially parallel, wherein the modulation elements 9 of the first electrode 4 and the modulation elements 9 of the second electrode 6 have an overlapping portion B.

[0065] The first electrode 4 and the second electrode 6 are connected in an electrically conductive manner via a resistor 3 .

[0066] In this exemplary embodiment, the capacitor device and the resistor 3 are surrounded by a core region 2 made of a silicone polymer-based elastic material. Since the silicone polymer in this exemplary embodiment is an elastic soft material, the core region 2 in this exemplary embodiment is surrounded by a sheath region 12 made of an epoxy-based polymer to improve mechanical stability.

[0067] In this exemplary embodiment, the siloxane polymer has low water diffusivity compared to commonly used plastic materials such as epoxy polymers.

[0068] Figure 2 Shows Figure 1 The voltage divider arrangement 1 is shown in a cross-sectional view along the axis AA. Figure 2 The substantially concentric configuration of the elements of the voltage divider device 1 according to the invention is shown, in particular the concentric configuration of the resistor 3 extending centrally along the central axis 13 and the modulation elements 9 of the first electrode 4 located in the inner circle and the modulation elements 9 of the second electrode 6 located in the outer circle.

[0069] In this exemplary embodiment, the modulation element 9 has a substantially electrically insulating base body 10 which is coated with an electrically conductive coating 11 , in particular with an electrically conductive lacquer, in order to be electrically conductively connected to the first electrode 4 / the second electrode 6 .

[0070] In other exemplary embodiments, the modulation element 9 may also be made entirely of a conductive material or an electrical insulator that becomes conductive due to the addition of additives.

[0071] In this exemplary embodiment, the difference between the radii of the two circles described by the arrangement of the modulation elements 9 of the first electrode 4 and the arrangement of the modulation elements 9 of the second electrode 6 is about 7.6 mm. However, in other exemplary embodiments, this distance may be different.

[0072] The voltage divider arrangement 1 described in this exemplary embodiment has a maximum insulation value of 24 kV. However, in other exemplary embodiments, this maximum insulation value can also be 36 kV. Depending on the field of application, any other maximum insulation value is also possible.

[0073] The voltage divider device 1 according to this exemplary embodiment is configured to have a rated voltage of a maximum of 24,000 / √3 V at a frequency of 50 Hz. In this exemplary embodiment, the secondary voltage is approximately 3.25 / √3 V, but this value may be adjusted in other exemplary embodiments depending on the application.

[0074] In this exemplary embodiment, the response factor of the voltage divider device, ie in particular the capacitance of the capacitor device therein, is constant in the temperature range of -40° C. to 80° C. In particular, in this exemplary embodiment, the capacitance of the capacitor device is 8 pF.

[0075] Reference numerals:

[0076] 1 voltage divider device, 2 core region, 3 resistor, 4 first electrode, 5 coupling member, 6 second electrode, 7 grounding member, 8 measuring terminal, 9 modulation element, 10 substrate, 11 coating, 12 sheath region, 13 central axis, B overlapping portion.

Claims

1. A voltage divider device comprising, A core region (2) having a capacitor device and a resistor (3) arranged in the core region (2), The first electrode (4) of the capacitor device has a coupling member (5) for connecting to a voltage-carrying element, The second electrode (6) of the capacitor device has a grounding member (7) for connecting to a grounding element. And among them, The first electrode (4) and the second electrode (6) are connected in an electrically conductive manner via the resistor (3). The invention is characterized in that the first electrode (4) and the second electrode (6) comprise a plurality of conductive modulation elements (9) in the form of fingers or rods; wherein the modulation element (9) of the first electrode (4) and the modulation element (9) of the second electrode (6) form an inner circle and an outer circle respectively, and the inner circle and the outer circle are arranged in a concentric circle manner relative to each other; The modulation element (9) of the first electrode (4) and the modulation element (9) of the second electrode (6) have an overlapping portion B in a direction parallel to their longitudinal extension direction.

2. The voltage divider device according to claim 1, characterized in that The arrangement radius of the modulation element (9) of the outer ring electrode is approximately 50% greater than the arrangement radius of the modulation element (9) of the inner ring electrode.

3. The voltage divider device according to claim 1 or 2, characterized in that: The arrangement radius of the modulation elements of the inner ring electrode is between 8 mm and 22 mm, and the arrangement radius of the modulation elements of the outer ring electrode is between 15 mm and 40 mm.

4. The voltage divider device according to claim 1, characterized in that The length of the modulation element is 10 mm-60 mm, and the diameter of the modulation element is 1.5 mm-10 mm.

5. The voltage divider device according to claim 1, characterized in that The modulation element (9) has an electrically insulating base body (10) and an electrically conductive coating (11).

6. The voltage divider device according to claim 1, characterized in that The modulation element (9) comprises an electrically conductive additive and an electrically insulating matrix.

7. The voltage divider device according to claim 6, characterized in that The additive includes carbon nanoparticles or is made of carbon nanoparticles.

8. The voltage divider device according to claim 1, characterized in that The longitudinal extension direction of the modulation element (9) of the first electrode (4) is parallel to the longitudinal extension direction of the modulation element (9) of the second electrode (6).

9. The voltage divider device according to claim 1, characterized in that The first electrode (4) has 6-14 modulation elements (9), and the second electrode (6) has 14-26 modulation elements (9).

10. The voltage divider device according to claim 1, characterized in that Under the conditions of a temperature of 20° C., a relative humidity of 50%, a pressure of 1000 mbar, and a grid frequency of 50 Hz, the capacitor device has a capacitance of 1 pF-30 pF.

11. The voltage divider device according to claim 1, wherein: The core region (2) comprises a dielectric, which comprises a siloxane-based polymer or is made of a siloxane-based polymer. 12 . Arrangement of a voltage divider device ( 1 ) according to claim 1 on a connecting part of a switchgear of a power network.

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