Measuring transducer arrangement with a voltage sensor

Abstract

The invention relates to a measuring transducer arrangement (1) with an annular support element (7) made of an electrically conductive material and a voltage sensor (3) comprising a conductor foil (15) arranged on the support element (7) with a first layer (23) and a second layer (24). The first layer (23) has at least one strip-like measuring electrode (27) which is connected to an electrical measuring potential. The second layer (24) has at least one strip-like ground electrode (28) which is connected to an electrical ground potential. The support element (7) is connected either to the measuring potential or to the ground potential.

Description

[0001] The invention relates to a measuring transducer arrangement with a voltage sensor.

[0002] The invention relates in particular to a measuring transducer configured for measuring an alternating voltage in a switchgear, especially in a gas-insulated switchgear. The measuring transducer may furthermore include a current sensor configured for measuring an alternating current.

[0003] For current and voltage measurement, coils with ferromagnetic cores are used, for example. However, these are large and expensive. Alternative solutions already exist, so-called Low-Power Instrument Transformers, abbreviated LPITs. These use, for example, a Rogowski coil for AC current measurement and a solid, cylindrically bent sheet for AC voltage measurement.

[0004] DE 10 2020 212 404 B4 discloses a field probe combination for use in medium and high voltage applications, comprising a first field probe and a second field probe. The first field probe and the second field probe are formed by a first conductive field probe layer applied to an insulator for the first field probe and by a second conductive field probe layer applied to the insulator for the second field probe. The insulator has the form of a hollow cylinder or a hollow cylinder slotted parallel to an axis of symmetry of the field probe combination and has an insulator thickness perpendicular to the axis of symmetry, i.e., in the radial direction, that separates the first conductive field probe layer from the second conductive field probe layer.

[0005] WO 2013 / 135506 A1 discloses a transducer arrangement comprising a voltage sensor and a current sensor. The voltage sensor has a measuring electrode for detecting an electrical voltage, wherein the measuring electrode has a receptacle in which a probe of the current sensor is positioned. The receptacle is, for example, formed as a recess in the measuring electrode and arranged on the outer sheath side of the measuring electrode. The measuring electrode and the probe are, for example, embedded in an insulating body, which is a supporting insulator for one or more electrical conductors. The insulating body is manufactured, for example, by a casting process in which the measuring electrode and the probe are cast into a liquid insulating material, which then hardens. One problem with this process is that the insulating material shrinks upon cooling. This can lead to partial detachment of the insulating material from the measuring electrode, resulting in the risk of partial discharges.

[0006] The invention is based on the objective of providing an improved measuring transducer arrangement with a voltage sensor.

[0007] The problem is solved according to the invention by a measuring transducer arrangement with the features of claim 1.

[0008] Advantageous embodiments of the invention are the subject of the dependent claims.

[0009] A measuring transducer arrangement according to the invention comprises - a ring-shaped support element made of an electrically conductive material, and - a voltage sensor comprising a conductor foil arranged on the carrier element with a first layer and a second layer, wherein - the first layer has at least one strip-like measuring electrode that is placed on an electrical measuring potential, - the second layer has at least one strip-like ground electrode that is placed on an electrical ground potential, and - the support element is either placed on the measuring potential or on the ground potential.

[0010] The transducer assembly is used to detect an electrical voltage applied to an electrical conductor. For this purpose, the transducer assembly is arranged such that its support element runs around the conductor in a ring-like fashion, spaced apart from the conductor. The voltage is detected capacitively as a voltage between a ground potential and at least one measuring electrode of the conductor foil. Alternatively, a displacement current through the capacitance between the conductor and at least one measuring electrode of the conductor foil is measured.

[0011] The ring-shaped support element stabilizes the conductive foil and allows it to be arranged in a ring around an electrical conductor to measure the voltage applied to the conductor. Due to its mechanical flexibility, the conductive foil can be easily adapted to the dimensions of the support element, or conductive foils of the same design can be used for support elements of different diameters by adjusting the length of the conductive foil to the circumference of the respective support element. In contrast, a mechanically rigid ring-shaped voltage measuring element must have a diameter that is tailored to the specific requirements.

[0012] The at least two-layer design of the conductor foil, with a first layer comprising at least one measuring electrode and a second layer comprising at least one ground electrode, enables the formation of a high secondary capacitance between the at least one measuring electrode and the at least one ground electrode by making the insulating layer between the first and second layers as thin as possible. A high secondary capacitance is advantageous to avoid dangerously high output voltages of the transducer assembly in the case of high-voltage measurements.

[0013] Furthermore, the mechanical flexibility of the conductor foil allows for improved encapsulation of the conductor foil into a plastic (insulating material), as the conductor foil can adapt to the insulating material during its curing process due to its flexibility.

[0014] One embodiment of the measuring transducer arrangement, in which the support element lies at the same measuring potential as each measuring electrode of the conductor foil, increases the area lying at the measuring potential for capacitive detection of the voltage applied to the conductor and thus the sensitivity of the voltage measurement.

[0015] A configuration of the transducer arrangement in which the support element is at ground potential enables the shielding of each measuring electrode from electric fields in the vicinity of the conductor. This configuration is useful, for example, when measuring a voltage applied to a conductor in the vicinity of other conductors, since these other conductors can also generate electric fields. This is particularly relevant when the conductor is a phase conductor of a multi-phase electrical connection. Such phase conductors are arranged, for example, parallel to each other and spatially adjacent to one another, or, in the case of three phases, in a triangular configuration, where the term "triangular configuration" refers to the arrangement of the phase conductors at the vertices of a triangle in a plane perpendicular to the path of the phase conductors.

[0016] In one embodiment of the invention, the conductive foil is arranged in a ring shape on the inner side of the support element. The inner side of the support element refers to a side of the support element that faces a space enclosed by the support element and thus a conductor enclosed by the support element. With this arrangement of the conductive foil on the support element, the conductive foil faces the conductor, thereby increasing the sensitivity of the voltage measurement, for example, compared to an arrangement of the conductive foil on the outer side of the support element.

[0017] In a further embodiment of the invention, the transducer arrangement includes a current sensor configured to measure an electric current and arranged on the support element. For example, the current sensor has at least one Rogowski coil that extends in a ring shape along the support element. Each Rogowski coil is arranged on the support element, for example, via at least one retaining element, wherein the retaining element has a recess in which the Rogowski coil is arranged and is connected to the support element by frictional and / or positive locking. This embodiment of the invention advantageously makes it possible to use the transducer arrangement also for measuring an electric current through a conductor around which the support element is arranged.

[0018] In a further embodiment of the invention, the support element is made of an electrically conductive plastic or expanded metal.

[0019] In a further embodiment of the invention, the measuring transducer arrangement has at least one holding device which is manufactured integrally with the support element or a component of the support element.

[0020] The aforementioned embodiments of the invention advantageously make it possible to manufacture the support element or the support element and the at least one holding device cost-effectively, for example by injection molding.

[0021] In a further embodiment of the invention, the first layer is arranged on an inner side of the conductor foil. This ensures that each measuring electrode of the first layer is positioned as close as possible to the conductor surrounded by the support element.

[0022] In a further embodiment of the invention, the first layer comprises two measuring electrodes running parallel to each other and spaced apart from each other. The design of the first layer with two measuring electrodes advantageously provides a redundant design of the measuring electrodes, which, for example, allows the failure of one measuring electrode to be compensated for and increases the measurement accuracy.

[0023] In a further embodiment of the invention, the carrier element is placed on the measuring potential and has a component for each measuring electrode of the first layer, which is connected to the measuring electrode. In this embodiment of the invention, the conductor film has, for example, a third layer comprising at least one strip-like measuring electrode connected to a measuring electrode of the first layer, and the second layer is arranged between the first layer and the third layer. The third layer is, for example, arranged on an outer surface of the conductor film. In particular, the third layer has, for example, a measuring electrode for each measuring electrode of the first layer, which is connected to the measuring electrode of the first layer and, for example, runs parallel to the measuring electrode of the first layer.If the support element has several components, these components and their respective holding devices are, for example, electrically isolated from one another. As already explained above, this embodiment of the invention improves the measurement sensitivity of the voltage sensor by increasing its measuring area through the support element. The third layer is particularly advantageous if the transducer arrangement includes a current sensor in addition to the voltage sensor, since the measuring electrode(s) of the third layer on the outside of the support element can create an electric field-free space, a so-called Faraday cage, between outwardly bent edge regions of the support element and the measuring electrodes of the third layer, in which the current sensor, in particular Rogowski coils of the current sensor, can be arranged.

[0024] In a further embodiment of the invention, the support element is placed at ground potential and connected to each ground electrode. In this case, the second layer is arranged, for example, on an outer surface of the conductor foil. The support element is designed, for example, to shield electric fields that are not generated by an electrical conductor around which the support element runs. As already explained above, this embodiment of the invention particularly enables the shielding of the measuring electrode(s) of the voltage sensor from electric fields in the vicinity of a conductor whose voltage is being measured. This is particularly advantageous for voltage measurements on phase conductors of multiphase electrical devices.

[0025] In a further embodiment of the invention, each measuring electrode and each ground electrode is designed as a copper layer. This is advantageous because of the high electrical conductivity of copper.

[0026] In a further embodiment of the invention, the support element is designed such that the electric field strengths between the support element and an electrical conductor around which the support element runs do not exceed the dielectric strength of an insulating medium between the measuring transducer arrangement and the conductor. In other words, the support element controls the electric field generated by the conductor in such a way that the electric field strength in the insulating medium does not become too high or too inhomogeneous, so that the dielectric strength of the insulating medium is not exceeded.

[0027] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings. These drawings show: Fig. 1 a sectional view of a section of a gas-insulated switchgear, Fig. 2 a sectional view of a section of an embodiment of a measuring transducer arrangement according to the invention, Fig. 3 a sectional view of a conductor foil of a first embodiment of a measuring transducer arrangement according to the invention, Fig. 4 a cross-sectional view of a conductor foil of a second embodiment of a measuring transducer arrangement according to the invention.

[0028] Corresponding parts are marked with the same reference symbols in the figures.

[0029] Fig. 1 ( Fig. Figure 1 shows a sectional view of a gas-insulated switchgear 100. The switchgear 100 has two enclosures 101, 102 through which an electrical conductor 103 is routed. A feedthrough 105 is arranged between the enclosures 101, 102. The feedthrough 105 has an annular frame 106, which is arranged between two opposing flanges 107, 108 of the enclosures 101, 102. A measuring transducer arrangement 1 according to the invention is arranged on the frame 106.

[0030] The measuring transducer arrangement 1 comprises a voltage sensor 3, configured to measure an electrical voltage applied to the conductor 103, and a current sensor 5, configured to measure an electric current flowing in the conductor 103. The measuring transducer arrangement 1 further comprises an annular support element 7 on which the voltage sensor 3 and the current sensor 5 are arranged. The support element 7 extends around the conductor 103. The voltage sensor 3 is arranged on an inner surface of the support element 7 facing the conductor 103. The current sensor 5 is arranged on an outer surface of the support element 7 facing away from the conductor 103. The measuring transducer arrangement 1 also comprises retaining devices 8 by which the support element 7 is connected to the frame 106.The support element 7 and the holding devices 8 are made of an electrically conductive material, in particular an electrically conductive plastic, for example a polyphenylene ether, in which carbon fibers are embedded. For example, the support element 7 and the holding device 8 are manufactured by injection molding. The support element 7 with the voltage sensor 3 and the current sensor 5 and the holding devices 8 are embedded in a plastic 9. The plastic 9 is, for example, a casting resin.

[0031] Fig. 2 ( Fig. Figure 2) shows a sectional view of a section of an embodiment of a measuring transducer arrangement 1 according to the invention. The voltage sensor 3 has a conductor foil 15 that runs in a ring shape on the inside of the support element 7. Conductor foils 15 of different embodiments of the measuring transducer arrangement 1 are shown below with reference to the Fig. 3 and Fig. 4 is described in more detail. The current sensor 5 comprises two Rogowski coils 17 that run in a ring shape along the carrier element 7. The carrier element 7 consists of two ring-shaped components 7.1, 7.2 that are connected to each other by friction and / or form-fitting means. The Rogowski coils 17 are arranged on the carrier element 7 by several clamp-like retaining elements 19, which have a recess 21 for each Rogowski coil 17 and also hold the components 7.1, 7.2 of the carrier element 7 together by friction and / or form-fitting means, for example by a snap or latch connection. The retaining elements 19 are made of an electrically non-conductive material and are mechanically deformable in order to be connected to the components 7.1, 7.2 of the carrier element 7.

[0032] Fig. 3 ( Fig. Figure 3) shows a cross-sectional view of the conductor foil 15 of a first embodiment of the measuring transducer arrangement 1 with a section plane that is perpendicular to a longitudinal direction of the conductor foil 15. The conductor foil 15 is formed in three layers with a first layer 23, a second layer 24 and a third layer 25. The first layer 23 is arranged on an inner side of the conductor foil 15, which is in Fig. 1 is facing the conductor 103. The third layer 25 is arranged on an outer side of the conductor foil 15, which is in Fig. The second layer 24 is positioned between the first layer 23 and the third layer 25 and is electrically insulated from both. The first layer 23 and the third layer 25 each have two strip-like measuring electrodes 27, which run parallel to each other and spaced apart. The second layer 24 has a ground electrode 28. Each measuring electrode 27 extends to an edge of the conductor foil 15 and contacts the support element 7. The measuring electrodes 27 and the support element 7 are connected to an electrical measuring potential. The ground electrode 28 is electrically insulated from the support element 7 and connected to an electrical ground potential.

[0033] Fig. 4 ( Fig. 4) shows one to Fig.Figure 3 shows an analogous sectional view of the conductor foil 15 of a second embodiment of the measuring transducer arrangement 1. The conductor foil 15 is formed in two layers, with a first layer 23 and a second layer 24. The first layer 23 is arranged on an inner side of the conductor foil 15. The second layer 24 is arranged on an outer side of the conductor foil 15. The first layer 23 has two strip-like measuring electrodes 27, which run parallel to each other and spaced apart. The second layer 24 has a ground electrode 28. The ground electrode 28 extends over the entire width of the conductor foil 15 to its edges and contacts the support element 7. The ground electrode 28 and the support element 7 are connected to an electrical ground potential. The measuring electrodes 27 extend from the edges of the conductor foil 15 and are electrically insulated from the support element 7 and connected to an electrical measuring potential.

[0034] In both embodiments, the measuring electrodes 27 and the ground electrode 28 are each designed, for example, as a copper layer.

[0035] Although the invention has been further illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived from them by the person skilled in the art without leaving the scope of protection of the invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 212 404 B4

[0004] WO 2013 / 135506 A1

[0005]

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