Transducer with a flexible voltage sensor

Abstract

The invention relates to a transducer (1) having an annular carrier element (7) and a voltage sensor (3) that has a mechanically flexible voltage measuring element (15) arranged on the carrier element (7).

Description

[0001] Description

[0002] TRANSDUCER WITH A FLEXIBLE VOLTAGE SENSOR

[0003] The invention relates to a measuring transducer with a voltage sensor.

[0004] In particular, the invention relates to a measuring transformer configured to measure an alternating voltage in a switchgear, particularly in a gas-insulated switchgear. The measuring transformer may further comprise a current sensor configured to measure an alternating current.

[0005] For current and voltage measurement, for example, large coils with ferromagnetic cores are used. However, these are large and expensive. Alternative solutions already exist, so-called Low-Power Instrument Transformers, abbreviated to LPIT. These use, for example, a Rogowski coil for AC current measurement and a fixed, cylindrically bent sheet for AC voltage measurement.

[0006] EP 2 810 087 B1 discloses a measuring transformer arrangement for monitoring one or more phase conductors, comprising a voltage sensor and a current sensor. The voltage sensor has a measuring electrode for detecting an electrical voltage, the measuring electrode being ring-shaped and having a receptacle in which a probe of the current sensor is positioned. The receptacle is shaped as a recess in the measuring electrode and is arranged on the outer jacket side of the measuring electrode. The measuring electrode and the probe are embedded in an insulating body, which is a supporting insulator of the phase conductor or phase conductor. The insulating body is produced, for example, using a casting process, in which the measuring electrode and the probe are poured into a liquid insulating material which then hardens. One problem with this is that the insulating material shrinks when it cools.This can lead to partial detachment of the insulating material from the measuring electrode, resulting in the risk of partial discharges.

[0007] The invention is based on the object of providing an improved measuring transformer with a voltage sensor.

[0008] The object is achieved according to the invention by a measuring transducer having the features of claim 1.

[0009] Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] A measuring transducer according to the invention has an annular carrier element and a voltage sensor which has a mechanically flexible voltage measuring element arranged on the carrier element.

[0011] The annular support element stabilizes the mechanically flexible voltage measuring element and enables the voltage measuring element to be arranged in a ring around an electrical conductor in order to measure a voltage applied to the conductor. Due to the mechanical flexibility of the voltage measuring element, the voltage measuring element can be easily adapted to the dimensions of the support element, or voltage measuring elements of the same design can be used for support elements of different diameters by adapting the length of a voltage measuring element to the diameter of the respective support element. In contrast, a mechanically rigid annular voltage measuring element must have a diameter that is tailored to the respective requirements.Furthermore, the mechanical flexibility of the voltage measuring element enables improved encapsulation of the voltage measuring element in a plastic (insulating material), since its flexibility allows the voltage measuring element to adapt to the insulating material as it hardens. In one embodiment of the invention, the voltage measuring element comprises an electrically insulating film strip to which an electrically conductive coating is applied on at least one side. In particular, an electrically conductive coating can be applied to both sides of the film strip.

[0012] The electrical coating on one side of the foil strip and an electrical conductor around which the carrier element is arranged form a primary capacitor. The voltage across the conductor is then measured, for example, by measuring a displacement current through the primary capacitor, which is proportional to the first time derivative of the voltage across the primary capacitor.

[0013] If both sides of the foil strip have an electrically conductive coating, these coatings are electrically separated from one another by the foil strip. In this case, the two coatings form a secondary capacitor. The voltage applied to the conductor can then be measured alternatively via the secondary capacitor by measuring a voltage between the two coatings according to the voltage divider principle. The foil strip is as thin as possible, for example with a thickness of 50 pm, and is designed with a high relative permittivity. A high relative permittivity results in a high capacitance of the secondary capacitor, which leads to a high voltage divider ratio. This is particularly advantageous in high-voltage applications because it avoids high measuring voltages that are potentially life-threatening and difficult to insulate on the secondary side.

[0014] In a further embodiment of the invention, the coating on at least one side of the film strip comprises a plurality of coating strips spaced apart from one another and running parallel to one another along the film strip. By having a plurality of coating strips on at least one side of the film strip, the voltage measurement can advantageously be performed multiple times or redundantly.

[0015] In a further embodiment of the invention, the voltage measuring element has recesses. Recesses in the voltage measuring element advantageously allow the plastic to pass through these recesses when the measuring transducer is encapsulated in a plastic (insulating material).

[0016] In a further embodiment of the invention, the voltage measuring element is arranged in a ring shape on an inner side of the carrier element. This makes it possible, in particular, for a coating of the film strip to face an electrical conductor around which the carrier element is arranged.

[0017] In a further embodiment of the invention, the support element and the voltage measuring element are firmly bonded to one another by adhesive bonding. Alternatively or additionally, the voltage measuring element is firmly secured to the support element by at least one fastening element made of a dielectric material.

[0018] Such fastenings of the voltage measuring element to the support element enable, on the one hand, that the support element with the voltage measuring element can be embedded in a plastic

[0019] (insulating material) without the voltage measuring element becoming loose or displaced from its position. On the other hand, fastening the voltage measuring element to the carrier element by gluing or by fastening elements made of a dielectric material prevents the fastening from leading to increased electric field strengths, which could cause electrical breakdowns.

[0020] In a further embodiment of the invention, the carrier element is made of an electrically conductive material. For example, the carrier element is made of a plastic, e.g., a polyphenylene ether, in which carbon fibers are embedded.

[0021] Due to the electrically conductive design of the carrier element, the carrier element can provide a dielectric shielding property for the measuring transducer. In particular, the carrier element can electrically contact an outer coating (facing the carrier element) of the foil strip, so that the carrier element and the outer coating of the foil strip together provide dielectric shielding. In addition, the carrier element can also form a secondary capacitance with an inner coating (facing away from the carrier element) of the foil strip, which can be used to measure the voltage applied to a conductor around which the carrier element is arranged.

[0022] In a further embodiment of the invention, the support element consists of several, in particular two, annular components that are connected to one another in a force-fitting and / or form-fitting manner. This facilitates the assembly of the measuring transducer, particularly if a current sensor (see below) is arranged on the support element in addition to the voltage sensor.

[0023] In one embodiment of the invention, the measuring transducer, in addition to the voltage sensor, has a current sensor which is designed to measure an electric current and is arranged on the carrier element. For example, the current sensor has at least one Rogowski coil which runs around the carrier element. Each Rogowski coil is arranged on the carrier element, for example via at least one holding element, wherein the holding element has a recess in which the Rogowski coil is arranged and is connected to the carrier element in a force-fitting and / or form-fitting manner.

[0024] The above-mentioned embodiments of the invention advantageously make it possible to use the measuring transducer also for measuring an electric current through a conductor around which the carrier element is arranged.

[0025] In a further embodiment of the invention, the voltage sensor has at least one connection lug via which the voltage measuring element can be electrically contacted and which projects outwards from the carrier element.

[0026] This advantageously enables the electrical contacting of the voltage sensor via at least one connection lug protruding from the carrier element, so that no electrical contacts have to be led through or to the carrier element.

[0027] In a further embodiment of the invention, the carrier element and the voltage measuring element are cast in a plastic (insulating material), in particular in a casting resin.

[0028] By casting, the support element can be fixed in its position, for example in a switchgear.

[0029] Furthermore, the voltage measuring element can also be fixed to the support element by encapsulating it. If a current sensor is also arranged on the support element, the current sensor can also be fixed to the support element by encapsulating it.

[0030] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings.

[0031] FIG 1 is a sectional view of a gas-insulated switchgear, FIG 2 is a perspective sectional view of a

[0032] Section of an embodiment of a measuring transducer according to the invention,

[0033] FIG 3 is a sectional view of an embodiment of the voltage measuring element of a measuring transformer according to the invention,

[0034] FIG 4 is a side view of a portion of the voltage measuring element shown in Figure 3,

[0035] FIG 5 is a sectional view of a further embodiment of the voltage measuring element of a measuring transformer according to the invention,

[0036] FIG 6 is a sectional view of a further embodiment of the voltage measuring element of a measuring transformer according to the invention,

[0037] FIG 7 is a sectional view of a further embodiment of the voltage measuring element of a measuring transformer according to the invention,

[0038] FIG 8 is a sectional view of a further embodiment of the voltage measuring element of a measuring transformer according to the invention,

[0039] FIG 9 is a side view of a section of a further embodiment of the voltage measuring element of a measuring transformer according to the invention,

[0040] FIG 10 is a side view of a section of a further embodiment of the voltage measuring element of a measuring transformer according to the invention,

[0041] FIG 11 shows an exemplary embodiment of a connection between the carrier element and the voltage measuring element of a measuring transformer according to the invention in a sectional view, FIG 12 shows a further exemplary embodiment of a connection between the carrier element and the voltage measuring element of a measuring transformer according to the invention in a sectional view,

[0042] FIG 13 shows a further embodiment of a connection of the carrier element and the voltage measuring element of a measuring transformer according to the invention in a sectional view,

[0043] FIG 14 is a plan view of a fastening element of the embodiment shown in Figure 13,

[0044] FIG 15 is a side view of the fastening element shown in Figure 14,

[0045] FIG 16 shows a further embodiment of a connection of the carrier element and the voltage measuring element of a measuring transformer according to the invention in a sectional view,

[0046] FIG 17 shows a further embodiment of a connection of the carrier element and the voltage measuring element of a measuring transformer according to the invention in a sectional view,

[0047] FIG 18 shows a further embodiment of a connection of the carrier element and the voltage measuring element of a measuring transformer according to the invention in a sectional view,

[0048] FIG 19 shows an embodiment of a carrier element of a measuring transducer according to the invention in a perspective view,

[0049] FIG 20 a plan view of another

[0050] From an exemplary embodiment of a carrier element of a measuring transducer according to the invention,

[0051] FIG 21 a plan view of another

[0052] From an embodiment of a support element of a measuring transformer according to the invention, FIG. 22 is a plan view of a frame of a bushing in a switchgear with three support elements of a measuring transformer according to the invention fastened to the frame.

[0053] Corresponding parts in the figures are provided with the same reference symbols.

[0054] Figure 1 (FIG. 1) shows a sectional view of a gas-insulated switchgear 100. The switchgear 100 has two encapsulating housings 101, 102, through which a plurality of electrical conductors 103, 104 are guided. A bushing 105 is arranged between the encapsulating housings 101, 102. The bushing 105 has an annular frame 106, which is arranged between two mutually facing flanges 107, 108 of the encapsulating housings 101, 102. A measuring transformer 1 according to the invention is arranged on the frame 106 for each conductor 103, 104.

[0055] In Figure 1, only the measuring transformer 1 for the conductor 103 is visible. The measuring transformer 1 comprises a voltage sensor 3, which is designed to measure an electrical voltage applied to the conductor 103, and a current sensor 5, which is designed to measure an electrical current flowing in the conductor 102. Furthermore, the measuring transformer 1 comprises an annular carrier element 7, on which the voltage sensor 3 and the current sensor 5 are arranged. The carrier element 7 runs around the conductor 103. The voltage sensor 3 is arranged on an inner side of the carrier element 7 facing the conductor 103. The current sensor 5 is arranged on an outer side of the carrier element 7 facing away from the conductor 103. The carrier element 7 with the voltage sensor 3 and the current sensor 5 is cast in a plastic 9. The plastic 9 is, for example, a casting resin.The support element 7 is made of an electrically conductive material, in particular a plastic, for example, a polyphenylene ether, in which carbon fibers are embedded. The voltage sensor 3 has connecting lugs 11 that lead to a connector 109 arranged on the frame 106. The current sensor 5 is connected to the connector 109 by connecting lines 13.

[0056] Figure 2 (FIG 2) shows a perspective sectional view of a section of the measuring transformer 1. The voltage sensor 3 has a mechanically flexible voltage measuring element 15 which runs annularly on the inside of the carrier element 7 and is described in more detail below. The current sensor 5 comprises two Rogowski coils 17 which run annularly around the carrier element 7. The carrier element 7 consists of two annular components 7.1, 7.2 which are connected to one another in a force-fitting and / or form-fitting manner. The Rogowski coils 17 are arranged on the carrier element 7 by a plurality of clamp-like holding elements 19 which have a recess 21 for each Rogowski coil 17 and which also hold the components 7.1, 7.2 of the carrier element 7 together in a force-fitting and / or form-fitting manner, for example by a snap or latching connection. The holding elements 19 are made of an electrically non-conductive material and are mechanically deformable in order to be able to work with the components 7.1, 7.2 of the support element 7.

[0057] Figure 3 (FIG 3) and Figure 4 (FIG 4) show an embodiment of the voltage measuring element 15. The voltage measuring element 15 has an electrically insulating film strip 23, to which an electrically conductive coating 25 is applied on both sides. The coating 25 on each side of the film strip 23 has two spaced-apart coating strips 25.1, 25.2 running parallel to one another along the film strip 23. Figure 3 shows the course of the voltage measuring element 15 around the conductor 103 in a sectional view. The ends of the voltage measuring element 15 are not connected to one another, so that the voltage measuring element 15 forms an open ring around the conductor 103. The connection lugs 11 are arranged at one end of the voltage measuring element 15 and are cut or punched from the coated film strip 23.Figure 4 shows a section of the voltage measuring element 15 in the region of the terminal lugs 11 in a side view. The voltage measuring element 15 also has a plurality of slot-like recesses 27 that run in the film strip 23 in its longitudinal direction between the coating strips 25.1, 25.2 and allow the plastic 9 to pass through during its encapsulation. The film strip 23 is designed to be as thin as possible, for example, with a thickness of 50 μm, and with a high relative permittivity.

[0058] The conductor 103 and the inner coating 25 of the foil strip 23 facing the conductor 103 form a primary capacitor. The inner coating 25 facing the conductor 103 and the outer coating 25 of the foil strip 23 facing away from the conductor 103 form a secondary capacitor. The voltage measurement by means of the voltage measuring element 15 is carried out either by measuring a voltage between the inner coating 25 and the outer coating 25 of the foil strip 23 via the secondary capacitor according to the voltage divider principle or by measuring a displacement current through the primary capacitor, which is proportional to the first time derivative of the voltage applied to the primary capacitor.

[0059] Figure 5 (FIG. 5) shows a further embodiment of the voltage measuring element 15. This embodiment differs from the embodiment shown in Figures 3 and 4 only in that the terminal lugs 11 are each connected to one end of the coated foil strip 23 by crimping in a crimping area 29.

[0060] Figure 6 (FIG. 6) shows a further embodiment of the voltage measuring element 15. This embodiment differs from the embodiment shown in Figures 3 and 4 only in that the terminal lugs 11 are each connected to one end of the coated foil strip 23 by soldering in a soldering area 31.

[0061] Figure 7 (FIG 7) shows a further embodiment of the voltage measuring element 15. This embodiment differs from the embodiment shown in Figures 3 and 4 only in that the voltage measuring element 15 does not have any connection lugs 11.

[0062] Figure 8 (FIG 8) shows a further embodiment of the voltage measuring element 15. This embodiment differs from the embodiment shown in Figure 7 only in that the ends of the voltage measuring element 15 are electrically connected to one another in a connecting region 32, wherein each coating strip 25.1, 25.2 of both the inner coating 25 and the outer coating 25 of the voltage measuring element 15 is electrically closed.

[0063] Figure 9 (FIG 9) shows a section of another embodiment of the voltage measuring element 15. This embodiment differs from the embodiment shown in Figures 3 and 4 in that the coating 25 on each side of the film strip 23 has three spaced-apart coating strips 25.1, 25.2, 25.3 running parallel to one another along the film strip 23. Accordingly, the voltage measuring element 15 has three connection lugs 11 (not shown in Figure 9). Furthermore, the voltage measuring element 15 has slot-like recesses 27 that run in the film strip 23 in its longitudinal direction between each two adjacent coating strips 25.1, 25.2, 25.3.

[0064] Figure 10 (FIG 10) shows a section of another embodiment of the voltage measuring element 15. This embodiment differs from the embodiment shown in Figures 3 and 4 in that the coating 25 is continuous on each side of the film strip 23. Furthermore, the voltage measuring element 15 again has slot-like recesses 27 that run in the film strip 23 in its longitudinal direction, but in this case also include recesses in the coatings 25.

[0065] Figures 11 to 18 show exemplary embodiments of the measuring transducer 1 with different connections between the carrier element 7 and the voltage measuring element 15. Components of the measuring transducer 1 that are not essential for these connections are not shown in Figures 11 to 18. In each of these exemplary embodiments, the voltage measuring element 15 is arranged in a recess 33 in the carrier element 7, facing the conductor 103 and extending in a ring around the conductor 103. The exemplary embodiments differ from one another in the manner in which the voltage measuring element 15 is fixed in the recess 33.

[0066] Figure 11 (FIG 11) shows a schematic sectional view of the carrier element 7, the voltage measuring element 15 and the conductor 103. In this embodiment, the voltage measuring element 15 is integrally connected to the carrier element 7 in the recess 33 by adhesive bonding.

[0067] Figure 12 (FIG 12) shows a schematic sectional view of the support element 7, the voltage measuring element 15, and the conductor 103 according to another exemplary embodiment. In this exemplary embodiment, the voltage measuring element 15 is positively connected to the support element 7 by several plug-like fastening elements 35 made of a dielectric plastic. Each fastening element 35 has a head section 35.1 and a plug-in section 35.2 protruding from the head section 35.1. The head section 35.1 faces the conductor 103 and rests against the voltage measuring element 15. The plug-in section 35.2 is guided through the voltage measuring element 15 and the carrier element 7 and fixes the voltage measuring element 15 to the carrier element 7. Figure 13 (FIG 13) shows a schematic sectional view of the carrier element 7, the voltage measuring element 15 and the conductor 103 according to a further embodiment.In this embodiment, the voltage measuring element 15 is also connected to the carrier element 7 in a force-fitting manner by a plurality of fastening elements 35 made of a dielectric plastic.

[0068] Figure 14 (FIG 14) and Figure 15 (FIG 15) show a fastening element 35 of the embodiment shown in Figure 13. Figure 14 shows a top view of the fastening element 35, and Figure 15 shows a side view of the fastening element 35. The fastening element 35 has a bar section 35.3 and a plug-in section 35.2 protruding centrally from the bar section 35.3. The bar section 35.1 faces the conductor 103, rests against the voltage measuring element 15, and extends substantially across the width of the voltage measuring element 15. The plug-in section 35.2 is guided through the voltage measuring element 15 and the carrier element 7 and fixes the voltage measuring element 15 to the carrier element 7.

[0069] Figure 16 (FIG 16) shows a schematic sectional view of the support element 7, the voltage measuring element 15, and the conductor 103 according to another embodiment. This embodiment differs from the embodiment shown in Figures 13 to 15 only in that each fastening element 35 has two plug-in sections 35.2, which protrude from the beam section 35.3 at opposite end regions.

[0070] Figure 17 (FIG 17) shows a schematic sectional view of the support element 7, the voltage measuring element 15, and the conductor 103 according to another exemplary embodiment. This exemplary embodiment differs from the exemplary embodiment shown in Figures 13 to 15 only in that each fastening element 35 has three plug-in sections 35.2, with two plug-in sections 35.2 projecting from the beam section 35.3 at opposite end regions, and the third plug-in section 35.2 projecting centrally from the beam section 35.3.

[0071] Figure 18 (FIG 18) shows a schematic sectional view of the support element 7, the voltage measuring element 15, and the conductor 103 according to a further exemplary embodiment. In this exemplary embodiment, the voltage measuring element 15 is also force-fittingly connected to the support element 7 by several fastening elements 35 made of a dielectric plastic. Each fastening element 35 faces the conductor 103, extends across the entire width of the support element 7, and has curved end regions 35.4, each of which encompasses an edge region 7.3 of the support element 7, so that the fastening element 35 is clamped to the support element 7.

[0072] Figures 19 to 21 show embodiments of the carrier element 7 of a measuring transducer 1.

[0073] Figure 19 (FIG 19) shows an embodiment of the carrier element 7, in which the carrier element 7 has a lateral elongated hole 7.5 from which the connection lugs 11 of the voltage measuring element 15 are guided (in Figure 19 only one connection lug 11 is shown as an example).

[0074] Figure 20 (FIG 20) shows an embodiment of the support element 7, in which the support element 7 has a connecting element 37 which projects from an outer side of an annular region 7.6 of the support element 7. The connecting element 37 has webs 37.1 extending from the annular region 7.6 of the support element 7, the ends of which are connected to one another by a bridge 37.2. The connecting element 37 makes it possible to fasten the support element 7 to another component, for example to the frame 106. In this way, the support element 7 can be fixed for casting with the plastic 9. Figure 21 (FIG 21) shows an embodiment of the support element 7, in which the support element 7 has a plurality of connecting elements 37 which project from the outer side of the annular region 7.6 of the support element 7 in a manner distributed over its circumference. Unused connecting elements 37 can be removed if necessary, for example with side cutters.As a result, the support element 7 can be used for different installation positions without having to produce a support element 7 corresponding to the installation position for each installation position, thereby reducing the costs for producing the support elements 7.

[0075] Figure 22 (FIG 22) shows the frame 106 with three support elements 7 each fastened to the frame 106 by a connecting element 37.

[0076] Although the invention has been 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 therefrom by those skilled in the art without departing from the scope of the invention.

Claims

Patent claims 1. Measuring transducer (1) with an annular carrier element (7) and a voltage sensor (3) which has a mechanically flexible voltage measuring element (15) arranged on the carrier element (7).

2. Measuring transducer (1) according to claim 1, wherein the voltage measuring element (15) comprises an electrically insulating foil strip (23) to which an electrically conductive coating (25) is applied on at least one side.

3. Measuring transducer (1) according to claim 2, wherein an electrically conductive coating (25) is applied to both sides of the film strip (23).

4. Measuring transducer (1) according to claim 2 or 3, wherein the coating (25) on at least one side of the film strip (23) has a plurality of coating strips (25.1, 25.2, 25.3) spaced apart from one another and running parallel to one another along the film strip (23).

5. Measuring transducer (1) according to one of the preceding claims, wherein the voltage measuring element (15) has recesses (27).

6. Measuring transducer (1) according to one of the preceding claims, wherein the voltage measuring element (15) is arranged in a ring shape on an inner side of the carrier element (7).

7. Measuring transducer (1) according to one of the preceding claims, wherein the carrier element (7) and the voltage measuring element (15) are integrally connected to one another by adhesive bonding.

8. Measuring transducer (1) according to one of the preceding claims, wherein the voltage measuring element (15) is formed by at least one element made of a dielectric material Fastening element (35) is firmly attached to the support element (7).

9. Measuring transducer (1) according to one of the preceding claims, wherein the carrier element (7) is made of an electrically conductive material.

10. Measuring transducer (1) according to one of the preceding claims, wherein the carrier element (7) consists of several, in particular of two force-fitting and / or form-fitting connected annular components (7.1, 7.2).

11. Measuring transducer (1) according to one of the preceding claims with a current sensor (5) which is designed to measure an electrical current and is arranged on the carrier element (7).

12. Measuring transducer (1) according to claim 11, wherein the current sensor (5) has at least one Rogowski coil (17) which runs around the carrier element (7).

13. Measuring transducer (1) according to claim 12, wherein each Rogowski coil (17) is arranged on the carrier element (7) via at least one holding element (19), wherein the holding element (19) has a recess (21) in which the Rogowski coil (17) is arranged and is connected to the carrier element (7) in a force-fitting and / or form-fitting manner.

14. Measuring transducer (1) according to one of the preceding claims, wherein the voltage sensor (3) has at least one connection lug (11) via which the voltage measuring element (15) can be electrically contacted and which projects outwards from the carrier element (7).

15. Measuring transducer (1) according to one of the preceding claims, wherein the carrier element (7) and the voltage measuring element (15) are cast in a plastic (9), in particular in a casting resin.

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