Capacitive voltage transformer

Abstract

In a capacitive voltage transformer, a shield that holds the voltage divider electrodes in place restricts their elongation in the direction of the inner electrodes. Therefore, output voltage variations caused by thermal deformation of the voltage divider electrodes are less likely to occur, resulting in a more accurate output voltage and achieving high measurement precision or low specific error. Furthermore, the shield, which is attached to the frame, can also undergo thermal deformation, such as elongation in the direction of the inner electrodes. In this case, a force is applied from the shield to the voltage divider electrodes along the direction of the inner electrodes to further suppress elongation in this direction.

Description

Technical Field

[0001] This disclosure relates to a capacitive voltage transformer. Background Technology

[0002] As voltage transformers, capacitive transformers that utilize the principle of electrostatic capacitance voltage division are known. In a capacitive transformer, the voltage of the high-voltage conductor can be measured by measuring the output voltage from the voltage dividing electrode opposite to the high-voltage conductor.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-271924 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] When the voltage divider electrode of a capacitive transformer undergoes thermal deformation, a change in the output voltage may occur due to the thermal deformation. Therefore, suppressing thermal deformation can improve the measurement accuracy.

[0008] The purpose of this disclosure is to provide a capacitive voltage transformer that achieves improved measurement accuracy.

[0009] Technical means to solve the problem

[0010] A capacitive voltage transformer according to one aspect of this disclosure includes: a cylindrical frame extending in a first direction; a first electrode extending in the first direction within the frame; a second electrode extending coaxially relative to the first electrode within the frame and having a cylindrical shape surrounding the first electrode, and connected to a measuring device; a first shielding member joined to the frame and disposed at one end of the second electrode about the first direction; and a second shielding member joined to the frame and disposed at the other end of the second electrode about the first direction, the first shielding member and the second shielding member being held apart from the second electrode in the first direction.

[0011] The effects of the invention

[0012] Through various aspects of this disclosure, a capacitive voltage transformer that achieves improved measurement accuracy is provided. Attached Figure Description

[0013] [ Figure 1 A schematic cross-sectional view of a voltage transformer according to one embodiment is shown.

[0014] [ Figure 2 ] Figure 1 The diagram shows an enlarged view of the main parts of the voltage transformer.

[0015] [ Figure 3 [Showing] Figure 1 The diagram shows the equivalent circuit of the voltage transformer.

[0016] [ Figure 4 The diagram schematically illustrates the thermal deformation of the voltage divider electrode.

[0017] [ Figure 5 This shows a schematic cross-sectional view of voltage transformers of different shapes. Detailed Implementation

[0018] Hereinafter, embodiments of the capacitive voltage transformer of this disclosure will be described with reference to the accompanying drawings. The values, shapes, materials, etc., mentioned in the following description are merely examples, and various changes can be made as long as they do not create technical inconsistencies. Furthermore, the embodiments described below are also merely examples, and various combinations can be made as long as they do not create technical inconsistencies.

[0019] One embodiment of the voltage transformer 1 is a capacitive voltage transformer, which is a type of instrument transformer. For example... Figure 1 As shown, the voltage transformer 1 includes an internal electrode 10 (first electrode) extending in one direction (first direction). In this embodiment, the internal electrode 10 has a cylindrical shape and is made of a conductor such as metal. Normally, for example, a high AC voltage (three-phase AC) of 22 / √3 kV to 765 / √3 kV is applied to the internal electrode 10 at a frequency of 50 Hz or 60 Hz. The voltage transformer 1 is used to measure the voltage of the internal electrode 10.

[0020] like Figure 1 As shown, the voltage transformer 1 also includes a frame 20 that partially or entirely houses the internal electrode 10. The frame 20 has a cylindrical shape extending along the extending direction of the internal electrode 10, and defines a cavity within it for housing the internal electrode 10. The cavity of the frame 20 is kept airtight and filled with an insulating gas. In this embodiment, the frame 20 has a cylindrical shape and is coaxially arranged relative to the internal electrode 10. That is, the internal electrode 10 and the frame 20 share a common axis Z. Furthermore, in this embodiment, the frame 20 is made of a conductor such as metal.

[0021] like Figure 1As shown, the voltage transformer 1 also includes a voltage divider electrode 30 (second electrode) housed within the frame 20. The voltage divider electrode 30 has a cylindrical shape extending along the extending direction of the inner electrode 10, and is coaxially arranged relative to and surrounds the inner electrode 10. The voltage divider electrode 30 can be connected to a measuring device 35 disposed outside the voltage transformer 1. In this embodiment, the measuring device 35 is a voltage meter, which measures the voltage of the inner electrode 10 by measuring the voltage of the voltage divider electrode 30, utilizing the principle of electrostatic capacitance voltage division. The measuring device 35 is not limited to a voltage meter; for example, it can also be a protective relay or a signal converter.

[0022] In this embodiment, the voltage divider electrode 30 is composed of a cylindrical body portion 31 and a flange portion 32. In this embodiment, flange portions 32 are respectively provided at both ends of the body portion 31 with respect to the extending direction of the inner electrode 10. The flange portions 32 extend outward in a direction orthogonal to the extending direction of the inner electrode 10. The flange portions 32 may be formed around the entire circumference of the voltage divider electrode 30, in which case they are annular.

[0023] like Figure 1 As shown, the voltage transformer 1 also includes a shield 40 housed within the housing 20. The shield 40 is made of a conductor such as metal. The shield 40 is separate from and insulated from the voltage divider electrode 30. In this embodiment, the shield 40 has a mushroom-shaped cross-section extending inward in a direction orthogonal to the extending direction of the internal electrode 10. Specifically, as... Figure 2 As shown in the cross-section, the shield 40 has a handle 41 extending in a direction orthogonal to the extending direction of the inner electrode 10, and an umbrella portion 42 located at the inner end and wider than the handle 41. The shield 40 is arranged adjacent to the voltage divider electrode 30 with respect to the extending direction of the inner electrode 10, and the umbrella portion 42 is located in the extending direction of the handle 41 ( Figure 2 The upper portion of the shield 40 (in the left-right direction) covers the voltage divider electrode 30. More specifically, the shield 40 is adjacent to the voltage divider electrode 30 in a manner that relates to the extending direction of the inner electrode 10. When viewed from the extending direction of the inner electrode 10, the shield 40 can be disposed around the entire circumference of the inner electrode 10. When viewed from the extending direction of the inner electrode 10, the shield 40 can be composed of a single component surrounding the entire circumference of the inner electrode 10, or it can be composed of multiple components. The multiple components constituting the shield 40 can be arranged at equal angular intervals around the inner electrode 10. Figure 1 In the configuration shown, the shield 40 is composed of two components disposed on both sides of the internal electrode 10, but it may also be composed of three or more components.

[0024] In this embodiment, two shielding members 40A and 40B are provided adjacent to the voltage divider electrode 30 in the extending direction of the internal electrode 10. Shielding member 40A (first shielding member) is disposed on one end side of the voltage divider electrode 30 in the extending direction of the internal electrode 10 (in... Figure 1 In the configuration shown (top side), shield 40B (second shield) is disposed on the other end side of the voltage divider electrode 30 in the extending direction with respect to the inner electrode 10 (in Figure 1 (The lower side is shown in the configuration shown). Shielding member 40A and shielding member 40B are held apart by the voltage divider electrode 30 in the extending direction of the internal electrode 10.

[0025] In this embodiment, both shielding member 40A and shielding member 40B are fixed relative to the voltage divider electrode 30. Taking shielding member 40A as an example, then... Figure 1 , Figure 2 As shown, the shield 40A and the voltage divider electrode 30 can be fixed by bolts 51 and nuts 52 extending along the extending direction of the internal electrode 10. To insulate the shield 40A and the voltage divider electrode 30 from each other, an insulator 53 (first insulator) is provided between the shield 40A and the voltage divider electrode 30. Figure 2 In the configuration shown, a bolt 51 inserted from the shield 40A side passes through an insulating tube 54 that spans across the flange 32 of the voltage divider electrode 30 to reach the voltage divider electrode 30 side. The front end of the bolt 51 is separated by an insulating washer 55 for the nut 52 to screw into. Therefore, the bolt 51 is conductive to the shield 40A and insulated from the voltage divider electrode 30. The shield 40B is also fixed to the voltage divider electrode 30 using the same fixing configuration as the shield 40A.

[0026] In this embodiment, both shielding member 40A and shielding member 40B are joined to the frame 20 via the joint 56. As an example, the joint 56 is a mounting accessory and can be constructed entirely of a conductor such as metal, thus enabling electrical connection between the frame 20 and the shielding members 40A and 40B. The two shielding members 40A and 40B are electrically connected to each other via a specified wire, metal plate, metal foil, or the like.

[0027] In this embodiment, a grounding electrode 60 (third electrode) is provided on the outer peripheral surface 31a (i.e., the surface opposite to the inner electrode 10 side) of the main body 31 of the voltage divider electrode 30. An insulator 61 (second insulator) is provided between the grounding electrode 60 and the voltage divider electrode 30. The grounding electrode 60 is insulated from the voltage divider electrode 30. The grounding electrode 60 can be, for example, a metal foil, and the insulator 61 can be, for example, a resin film. In this case, the grounding electrode 60 and the insulator 61 are wound around the outer peripheral surface 31a of the main body 31 of the voltage divider electrode 30. The grounding electrode 60 and the insulator 61 can surround the voltage divider electrode 30 and be provided around its entire circumference.

[0028] The voltage transformer 1 in this embodiment can be made from, for example... Figure 3 The equivalent circuit is represented in that manner. In the voltage transformer 1, an electrostatic capacitor C1 is formed between the internal electrode 10 and the voltage divider electrode 30, and an electrostatic capacitor C2 is formed between the voltage divider electrode 30 and the ground electrode 60. The electrostatic capacitor C2 achieves a relatively large capacitance by using a thin insulator 61 such as a resin film, which allows the voltage divider electrode 30 to be close to the ground electrode 60.

[0029] Here, the thermal deformation of the voltage divider electrode 30 is explained. The voltage divider electrode 30 sometimes undergoes thermal deformation (expansion) as the temperature rises. In a cylindrical voltage divider electrode 30, as... Figure 4 As shown, thermal deformation such as elongation in the extending direction of the internal electrode 10 may occur. If such thermal deformation occurs, the area facing the internal electrode 10 increases, the electric field or electrostatic capacitance C1 changes, and as a result, the output voltage output from the voltage divider electrode 30 to the measuring device 35 changes.

[0030] In the voltage transformer 1 of this embodiment, the elongation of the voltage divider electrode 30 in the extending direction of the inner electrode 10 is limited by the shielding members 40A and 40B, which are held apart by the voltage divider electrode 30. As a result, the voltage transformer 1 is less prone to output voltage changes caused by thermal deformation of the voltage divider electrode 30, and by obtaining a more accurate output voltage, high measurement accuracy or low ratio error can be achieved.

[0031] In addition, shielding components 40A and 40B, which are joined to the frame 20, are also as follows: Figure 4 As shown, thermal deformation such as elongation in the extending direction of the inner electrode 10 may occur. In this case, a force is applied to the voltage divider electrode 30 from the shielding members 40A and 40B along the extending direction of the inner electrode 10, further suppressing the elongation of the voltage divider electrode 30 in the extending direction of the inner electrode 10. Thermal deformation such as elongation in the extending direction of the inner electrode 10 may also occur at the umbrella portion 42 located at the inner end of the shielding members 40A and 40B. In this case, the area of ​​the voltage divider electrode 30 exposed from the shielding members 40A and 40B relative to the inner electrode 10 is reduced, and the area of ​​the voltage divider electrode 30 that is electrostatically capacitively coupled to the inner electrode 10 is reduced. Due to the elongation of the umbrella portion 42 of the shielding members 40A and 40B, even when the voltage divider electrode 30 elongates in the extending direction of the inner electrode 10, the expansion of the area of ​​the voltage divider electrode 30 that is electrostatically capacitively coupled to the inner electrode 10 is suppressed.

[0032] Furthermore, in the voltage transformer 1, it is possible to suppress high-frequency surges of several MHz or higher from entering the circuit on the low-voltage side (e.g., the measuring device 35). This depends on the ground electrode 60 because, by forming a relatively large electrostatic capacitance C2 between the voltage divider electrode 30 and the ground electrode 60, the impedance Z2 of the electrostatic capacitance C2 is smaller than the impedance Z1 between the voltage divider electrode 30 and the measuring device 35 (Z2 < Z1), thus making it easier for high-frequency surges to flow to the ground electrode 60.

[0033] The voltage transformer 1 is not limited to the described form and can take various forms.

[0034] For example, the voltage divider electrode 30 can be as follows: Figure 5 As shown, it consists of multiple segments. Figure 5 In the configuration shown, the voltage divider electrode 30 is composed of two segments: a first voltage divider electrode 30A and a second voltage divider electrode 30B. By configuring the voltage divider electrode 30 into multiple segments, the output to the measuring device 35 can be multiplexed or redundant. The first voltage divider electrode 30A and the second voltage divider electrode 30B are arranged adjacent to each other along the extending direction of the internal electrode 10. The first voltage divider electrode 30A and the second voltage divider electrode 30B have substantially the same shape and the same size. When multiple voltage divider electrodes 30A and 30B are housed in the housing 20, all of the multiple voltage divider electrodes 30A and 30B are connected to the measuring device 35.

[0035] exist Figure 5 In the illustrated configuration, three shielding members 40A to 40C are provided adjacent to the two voltage divider electrodes 30 in the extending direction of the internal electrode 10. Shielding members 40A and 40C (first and second shielding members) are positioned across the two voltage divider electrodes 30 in the extending direction of the internal electrode 10, and shielding member 40B is positioned between the two voltage divider electrodes 30 in the extending direction of the internal electrode 10. Shielding members 40A and 40B are separated from the voltage divider electrode 30A in the extending direction of the internal electrode 10, and are connected to the voltage divider electrode 30A via... Figure 2 The same fixing configuration shown is used to fix the voltage divider electrode 30A. Shielding members 40B and 40C are spaced apart from the voltage divider electrode 30B in the extending direction of the internal electrode 10. Shielding members 40B and 40C are connected via... Figure 2 The same fixing configuration shown is used to fix the voltage divider electrode 30B.

[0036] In this embodiment, shielding members 40A and 40C are joined to the frame 20 via the joint 56. Shielding member 40B may or may not be joined to the frame 20. The three shielding members 40A to 40C are interconnected via specified wires, metal plates, metal foils, etc.

[0037] As can be understood from the description, the following contents are disclosed in this specification.

[0038] [Postscript 1]

[0039] A capacitive voltage transformer, comprising:

[0040] A cylindrical frame extending in the first direction;

[0041] A first electrode extends within the frame in the first direction;

[0042] The second electrode extends coaxially relative to the first electrode within the frame and has a cylindrical shape surrounding the first electrode, and is connected to the measuring device.

[0043] A first shielding member is joined to the frame and disposed on one end side of the second electrode with respect to the first direction; and

[0044] The second shielding member is joined to the frame and disposed on the other end side of the second electrode with respect to the first direction.

[0045] The first shield and the second shield are held together in the first direction, separated by the second electrode.

[0046] [Postscript 2]

[0047] According to Appendix 1, the capacitive voltage transformer, wherein the frame, the first shield and the second shield are made of conductors, and the first shield and the second shield are electrically connected to the frame.

[0048] [Postscript 3]

[0049] According to Appendix 2, the capacitive voltage transformer further includes a first insulator that separates the first shielding member and the second shielding member from the second electrode.

[0050] The first shield and the second shield are adjacent to the second electrode via the first insulator about the first direction.

[0051] [Postscript 4]

[0052] According to any one of Appendices 1 to 3, in a capacitive voltage transformer, when viewed from the first direction, both the first shield and the second shield surround the first electrode.

[0053] [Postscript 5]

[0054] According to the capacitive voltage transformer described in Appendix 4, when viewed from the first direction, both the first shield and the second shield are composed of one or more shields arranged at equal angular intervals surrounding the entire circumference of the first electrode.

[0055] [Postscript 6]

[0056] The capacitive voltage transformer according to any one of Appendices 1 to 5 includes a plurality of second electrodes arranged along the first direction.

[0057] [Postscript 7]

[0058] The capacitive voltage transformer according to any one of Appendices 1 to 6 further includes a third electrode disposed on the outer peripheral surface of the second electrode and grounded, with a second insulator as a barrier.

[0059] [Postscript 8]

[0060] According to Appendix 7, in the capacitive voltage transformer, the second insulator is a resin film wound around the outer peripheral surface of the second electrode.

[0061] Explanation of icon numbers

[0062] 1: Voltage transformer

[0063] 10: Internal electrodes

[0064] 20: Frame

[0065] 30, 30A, 30B: Voltage dividing electrodes

[0066] 40, 40A, 40B, 40C: Shielding components

[0067] 53: First Insulator

[0068] 60: Grounding electrode

[0069] 61: Second Insulator

Claims

1. A capacitive voltage transformer, comprising: A cylindrical frame extending in the first direction; A first electrode extends within the frame in the first direction; The second electrode extends coaxially relative to the first electrode within the frame and has a cylindrical shape surrounding the first electrode, and is connected to the measuring device. A first shielding member is joined to the frame and disposed on one end side of the second electrode with respect to the first direction; and The second shielding member is joined to the frame and disposed on the other end side of the second electrode with respect to the first direction. The first shield and the second shield are held together in the first direction, separated by the second electrode.

2. The capacitive voltage transformer according to claim 1, wherein, The frame, the first shield, and the second shield are made of conductors, and the first shield and the second shield are electrically connected to the frame.

3. The capacitive voltage transformer according to claim 2 further includes a first insulator separating the first shield and the second shield from the second electrode. The first shield and the second shield are adjacent to the second electrode via the first insulator about the first direction.

4. The capacitive voltage transformer according to claim 1, wherein, When viewed from the first direction, both the first shielding member and the second shielding member surround the first electrode.

5. The capacitive voltage transformer according to claim 4, wherein, When viewed from the first direction, both the first shield and the second shield are composed of one or more shields arranged at equal angular intervals surrounding the first electrode.

6. The capacitive voltage transformer according to claim 1, comprising a plurality of second electrodes arranged along the first direction.

7. The capacitive voltage transformer according to claim 1 further includes a third electrode disposed on the outer peripheral surface of the second electrode and grounded, separated by a second insulator.

8. The capacitive voltage transformer according to claim 7, wherein, The second insulator is a resin film wound around the outer peripheral surface of the second electrode.

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