Capacitive instrument transformer

Abstract

A capacitive instrument transformer (1) is provided with a current-carrying conductor (10), a cylindrical internal electrode (20), and an intermediate electrode (30). A primary voltage is applied to the current-carrying conductor (10), and a current flows through the current-carrying conductor (10). The internal electrode (20) is electrically connected to the current-carrying conductor (10) and is disposed so as to surround the current-carrying conductor (10). The intermediate electrode (30) faces the internal electrode (20) and is disposed radially outward of the internal electrode (20). The internal electrode (20) and the intermediate electrode (30) constitute a capacitor.

Description

Capacitor-type instrument transformer

[0001] This disclosure relates to a capacitor-type instrument transformer.

[0002] Patent Document 1 describes a capacitor voltage divider in which a busbar is placed inside a sealed conduit, a cylindrical intermediate electrode is placed outside the busbar, and voltage divider terminals are derived from the intermediate electrode. A conduit that serves as the ground electrode is connected to the sealed conduit via an insulator.

[0003] Japan National Office Publication No. 52-56412

[0004] In the capacitor voltage divider described in Patent Document 1, the busbar is formed from a single rod-shaped member, but sometimes the busbar is formed from multiple members. When the busbar is formed from multiple members, the connections between the members become complex, which hinders the improvement of the high performance of the output characteristics divided by the capacitor. Therefore, it is undesirable to place the intermediate electrode at the connection points between the members of the busbar. However, if the intermediate electrode is placed while avoiding the connection points between the members of the busbar, the axial length of the product becomes longer, which is a problem.

[0005] One aspect of this disclosure aims to realize a miniaturized capacitor-type instrument transformer.

[0006] To solve the above problems, a capacitor-type instrument transformer according to one aspect of the present disclosure comprises a current-carrying conductor to which a primary voltage is applied and through which current flows, a cylindrical internal electrode that is in electrical contact with the current-carrying conductor and is arranged to surround the current-carrying conductor, and an intermediate electrode that faces the internal electrode and is arranged radially outward from the internal electrode. The internal electrode and the intermediate electrode constitute a capacitor.

[0007] According to one aspect of this disclosure, capacitor-type instrument transformers can be miniaturized.

[0008] This is a cross-sectional view showing the schematic configuration of a capacitor-type instrument transformer according to Embodiment 1 of the present disclosure. This is an enlarged view of the area around the internal electrodes in Figure 1. This is a circuit diagram of the capacitor-type instrument transformer according to Embodiment 1. This is a cross-sectional view showing the schematic configuration of a capacitor-type instrument transformer according to Embodiment 2.

[0009] [Embodiment 1] Hereinafter, a capacitor-type instrument transformer 1 according to Embodiment 1 of the present disclosure will be described with reference to Figures 1 to 3.

[0010] Instrument transformers are used, for example, to monitor the bus voltage of a substation. Types of instrument transformers include capacitor type and electromagnetic induction type. Capacitor-type instrument transformer 1 is a voltage transformer with a capacitor as its main component, and is used, for example, incorporated into a gas-insulated switchgear (GIS) (not shown).

[0011] [Schematic Configuration of Capacitor-Type Instrument Transformer] Figure 1 is a cross-sectional view showing the schematic configuration of a capacitor-type instrument transformer 1. As shown in Figure 1, the capacitor-type instrument transformer 1 comprises a current-carrying conductor 10, a cylindrical internal electrode 20, an intermediate electrode 30, a container 40, a first insulating spacer 51, and a second insulating spacer 52.

[0012] The container 40 is made of, for example, metal. Inside the container 40 is dry air or SF ６ The container is filled with insulating gases such as [mention specific gases here]. The container 40 also contains the current-carrying conductor 10, the internal electrode 20, the intermediate electrode 30, the first insulating spacer 51, and the second insulating spacer 52, etc.

[0013] Note that the capacitor-type instrument transformer 1 shown in Figure 1 is a three-phase type, but only one phase of the three phases is shown in Figure 1, with the remaining two phases omitted. The remaining two phases are configured in the same way as in Figure 1. The capacitor-type instrument transformer 1 is also applicable to single-phase types and is not limited to three-phase types.

[0014] (Conducting element) As shown in Figure 1, the conducting element 10 is a rod-shaped conductive member that extends in the vertical direction of Figure 1, i.e., in the axial direction. Current flows through the conducting element 10 when the primary voltage from the gas-insulated switchgear described above is applied to it. The conducting element 10 is fixed to the container 40 via a first insulating spacer 51 and a second insulating spacer 52. The first insulating spacer 51 and the second insulating spacer 52 are insulators that interrupt the conduction of electricity between the inside and outside of the container 40.

[0015] The current-carrying conductor 10 is made of, for example, copper. In this case, the coefficient of linear expansion of the current-carrying conductor 10 is approximately 16.5 × 10⁻⁶. －６ The coefficient of thermal expansion of the current-carrying conductor 10 is different from that of the intermediate electrode 30. However, the coefficient of thermal expansion of the current-carrying conductor 10 may be the same as that of the intermediate electrode 30.

[0016] The current-carrying conductor 10 includes a first conductor 11, a second conductor 12, a third conductor 13, a first adapter conductor 14, and a second adapter conductor 15. The first conductor 11 is located between the first adapter conductor 14 and the second adapter conductor 15. The first conductor 11 is cylindrical, and its outer diameter is constant.

[0017] The second conductor 12 is located above the first adapter conductor 14 in Figure 1, i.e., above the axial direction of the current-carrying conductor 10, and is fixed by the first insulating spacer 51. The outer diameter of the second conductor 12 is constant. An AC power supply 80 (see Figure 3) is connected to the second conductor 12.

[0018] The third conductor 13 is located below the second adapter conductor 15 in Figure 1, that is, below the axial direction of the current-carrying conductor 10, and is fixed by the second insulating spacer 52. The outer diameter of the third conductor 13 is constant.

[0019] The first adapter conductor 14 connects the first conductor 11 to the second conductor 12, which has a larger outer diameter than the first conductor 11. The second adapter conductor 15 also connects the first conductor 11 to the third conductor 13, which has a larger outer diameter than the first conductor 11.

[0020] Figure 2 is an enlarged view of the area around the internal electrode 20 in Figure 1. As shown in Figures 1 and 2, the first adapter conductor 14 has a first adapter section 141, a second adapter section 142, a third adapter section 143, and a fourth adapter section 144.

[0021] The first adapter section 141 is positioned between the second conductor 12 and the second adapter section 142. In the first adapter section 141, the length of the diameter on the axial center side of the current-carrying conductor 10 is shorter than the length of the diameter on the axial end side.

[0022] The second adapter portion 142 is a rod-shaped member with a constant outer diameter and is positioned between the first adapter portion 141 and the third adapter portion 143. The diameter of the second adapter portion 142 is smaller than the diameter of the second conductor 12. The third adapter portion 143 is a rod-shaped member with a constant outer diameter and is positioned between the second adapter portion 142 and the fourth adapter portion 144.

[0023] The fourth adapter section 144 is positioned between the third adapter section 143 and the first conductor 11. In the fourth adapter section 144, the length of the axial lower diameter of the current-carrying conductor 10 is shorter than the length of the axial upper diameter.

[0024] The first adapter conductor 14 (for example, the fourth adapter portion 144) corresponds to the "part of the current-carrying conductor 10 whose outer diameter is not constant." Furthermore, the configuration of the first adapter conductor 14 is not limited to the above configuration, but can be changed as appropriate, as long as it connects the first conductor 11 and the second conductor 12 to each other.

[0025] (Internal Electrode) The internal electrode 20 is made of, for example, a cylindrical piece of aluminum. In this case, the coefficient of linear expansion of the internal electrode 20 is approximately 23.5 × 10⁻⁶. －６ It is [1 / K].

[0026] As shown in Figures 1 and 2, the internal electrode 20 is cylindrical in shape and is positioned to surround the third adapter portion 143, the fourth adapter portion 144, and the outer circumference of the first conductor 11 in the current-carrying conductor 10. In particular, the internal electrode 20 surrounds the portion of the current-carrying conductor 10 where the outer diameter is not constant, i.e., the periphery of the fourth adapter portion 144.

[0027] The internal electrode 20 has a connection portion 21 that contacts the current-carrying conductor 10. The internal electrode 20 is in electrical contact with the current-carrying conductor 10 via the connection portion 21. The connection portion 21 overlaps with the third adapter portion 143 and the fourth adapter portion 144 of the current-carrying conductor 10 in the axial direction of the internal electrode 20.

[0028] As shown in FIG. 2, the internal electrode 20 is fitted to the current-carrying conductor 10 at the connection portion 21 and is fixed to the current-carrying conductor 10 by being tightened in the axial direction of the internal electrode 20 from above in FIG. 2 by the fastening members 71 and 72. The fastening members 71 and 72 are, for example, screws.

[0029] It is preferable that the linear expansion coefficient of the internal electrode 20 is the same as that of the intermediate electrode 30. That is, it is preferable that the material of the internal electrode 20 is the same as that of the intermediate electrode 30.

[0030] (Intermediate electrode) As shown in FIG. 1, the intermediate electrode 30 faces the internal electrode 20 and is disposed on the outer side in the radial direction of the internal electrode 20. The intermediate electrode 30 has a first intermediate electrode 31 and a second intermediate electrode 32. The intermediate electrode 30 is made of, for example, cylindrical aluminum. Note that the intermediate electrode 30 does not have to be cylindrical.

[0031] The first intermediate electrode 31 and the second intermediate electrode 32 are arranged to be separated from each other in the vertical direction in FIG. 1, that is, in the axial direction of the current-carrying conductor 10. The first intermediate electrode 31 is disposed on the outer peripheral side of the upper portion of the internal electrode 20. The distance between the first intermediate electrode 31 and the internal electrode 20 is set to d [mm].

[0032] The second intermediate electrode 32 is disposed on the outer peripheral side of the lower portion of the internal electrode 20. The distance between the second intermediate electrode 32 and the internal electrode 20 is also set to d [mm]. The first intermediate electrode 31 and the internal electrode 20 constitute the main capacitor 91 (see FIG. 3). Although the second intermediate electrode 32 and the internal electrode 20 also constitute a capacitor, they are omitted in FIG. 3.

[0033] The first intermediate electrode 31 is disposed around the portions of the current-carrying conductor 10 where the outer diameter is not constant, that is, around the third adapter portion 143 and the fourth adapter portion 144, via the internal electrode 20. This makes it possible to keep the distance between the first intermediate electrode 31 and the internal electrode 20 that constitutes the main capacitor 91 constant.

[0034] [Electrical Configuration of Transformer for Capacitive Instrument] Next, the electrical configuration of the transformer 1 for capacitive instrument will be described with reference to FIG. 3. FIG. 3 is a circuit diagram of the transformer 1 for capacitive instrument. As shown in FIG. 3, the transformer 1 for capacitive instrument has a main capacitor 91, a voltage-dividing capacitor 92, and a fixed resistor 93. Note that the circuit diagram shown in FIG. 3 is an example and is not limited thereto.

[0035] The AC power supply 80 is an external power supply that outputs a primary voltage. One end of the AC power supply 80 is connected to the main capacitor 91, and the other end is grounded. The main capacitor 91 and the voltage-dividing capacitor 92 are connected in series with each other. The main capacitor 91 is composed of an internal electrode 20 and a first intermediate electrode 31 (see FIG. 1).

[0036] One end of the voltage-dividing capacitor 92 is connected to the main capacitor 91, and the other end is grounded. One end of the fixed resistor 93 is connected between the main capacitor 91 and the voltage-dividing capacitor 92. The other end of the fixed resistor 93 is grounded. Also, both ends of the fixed resistor 93 are connectable to the electrical device 100.

[0037] Here, let the voltage (primary voltage) of the AC power supply 80 be V １ [V], the divided output voltage be V ２ [V], the capacitance of the main capacitor 91 be C １ [F], the capacitance of the voltage-dividing capacitor 92 be C ２ [F], and the resistance value of the fixed resistor 93 be R [Ω].

[0038] Also, let the angular frequency be ω [rad / s], the frequency be f [Hz], and the reactance of the voltage-dividing capacitor 92 be XC ２ [Ω]. At this time, the following formula (1) holds. XC ２ = 1 / (ωC ２ ) = 1 / (2πfC ２ )... (1)

[0039] At this time, when XC ２ >> R, the following formula (2) holds. V ２ = 2πfC １ RV １ [V]... (2)

[0040] Output voltage V ２ The voltage is lower than that of the AC power supply 80, and the capacitance C of the main capacitor 91 １ It can be seen that it increases in proportion to V. Thus, the capacitor-type instrument transformer 1 controls the high voltage V of the AC power supply 80. １ Therefore, using the principle of capacitance voltage division, the low voltage V required for the electrical equipment 100 is used. ２ This is for extracting the output voltage V. The electrical device 100 (instrument) has an output voltage V. ２ By measuring the primary voltage V １ It is possible to monitor the fluctuations.

[0041] In the capacitor-type instrument transformer 1 of Embodiment 1 described above, a cylindrical internal electrode 20 is arranged to surround the current-carrying conductor 10, and an intermediate electrode 30 is arranged radially outside the internal electrode 20. The intermediate electrode 30 and the internal electrode 20 constitute a main capacitor 91. As a result, the shape of the current-carrying conductor 10 does not affect the capacitance of the main capacitor 91. Within the range of the inner diameter of the internal electrode 20, the material, shape, and diameter of the current-carrying conductor 10 can be freely changed. Therefore, the degree of design freedom can be increased.

[0042] In particular, in the current-carrying conductor 10, the intermediate electrode 30 can be placed in a portion where the outer diameter is not constant and there are steps or inclined surfaces, that is, at a position opposite the fourth adapter portion 144. Even in this case, the presence of the internal electrode 20 surrounding the fourth adapter portion 144 prevents any influence on the electrical characteristics of the main capacitor 91.

[0043] Thus, since the intermediate electrode 30 can be positioned opposite the portion of the current-carrying conductor 10 where the outer diameter is not constant, it is not necessary to ensure a long portion of the current-carrying conductor where the outer diameter is constant. This makes it possible to shorten the axial length of the capacitor-type instrument transformer 1.

[0044] Furthermore, since the internal electrode 20 is cylindrical, the distance d between the internal electrode 20 and the intermediate electrode 30 can be kept constant, and the capacitance of the main capacitor 91 can be set to a desired value.

[0045] Furthermore, since the current-carrying conductor 10 is positioned inside the internal electrode 20, the electrical characteristics of the main capacitor 91 are not affected by the current-carrying conductor 10. Therefore, the material, shape, and diameter of the current-carrying conductor 10 can be changed according to the magnitude of the current flowing through the current-carrying conductor 10, without affecting the main capacitor 91.

[0046] Furthermore, since the coefficient of linear expansion of the internal electrode 20 is the same as that of the intermediate electrode 30, the difference in the amount of expansion and contraction between the internal electrode 20 and the intermediate electrode 30 due to temperature changes can be reduced, thereby minimizing changes in the electrical characteristics of the main capacitor 91.

[0047] Furthermore, the capacitor is formed by an internal electrode 20 arranged to surround the current-carrying conductor 10 and an intermediate electrode 30 arranged radially outside the internal electrode 20. Therefore, the coefficient of thermal expansion of the current-carrying conductor 10 can be made different from that of the intermediate electrode 30. This allows the material of the current-carrying conductor 10 to be freely changed.

[0048] Furthermore, the internal electrode 20 is fixed to the third adapter portion 143 of the current-carrying conductor 10 by fastening members 71 and 72 at the connection portion 21. This improves the fixing strength between the internal electrode 20 and the current-carrying conductor 10.

[0049] Furthermore, the fastening members 71 and 72 fix the internal electrode 20 at the connection portion 21, which overlaps with the current-carrying conductor 10 in the axial direction of the internal electrode 20. Therefore, the fastening members 71 and 72 do not protrude from the side surface of the internal electrode 20 at the connection portion 21. This suppresses the influence of the fastening members 71 and 72 on the electric field distribution on the side surface of the internal electrode 20. Thus, by preventing the fastening members 71 and 72 from affecting the capacitance of the main capacitor 91, the desired output voltage V can be achieved. ２ It can be made possible to obtain it.

[0050] Furthermore, the intermediate electrode 30 has a first intermediate electrode 31 and a second intermediate electrode 32. By forming two capacitors, one with the first intermediate electrode 31 and the internal electrode 20, and the other with the second intermediate electrode 32 and the internal electrode 20, redundancy of the divided voltage extracted by the capacitor voltage division can be ensured.

[0051] [Embodiment 2] Next, a capacitor-type instrument transformer 1A according to Embodiment 2 of the present disclosure will be described with reference to Figure 4. For the sake of convenience of explanation, components having the same function as those described in Embodiment 1 will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0052] Figure 4 is a cross-sectional view showing the schematic configuration of a capacitor-type instrument transformer according to Embodiment 2. The capacitor-type instrument transformer 1A of Embodiment 2 differs from the capacitor-type instrument transformer 1 of Embodiment 1 in that it is provided with a dielectric 33 between the internal electrode 20 and the intermediate electrode 30.

[0053] Specifically, a dielectric 33 is placed between the first intermediate electrode 31 and the internal electrode 20, and a dielectric 33 is also placed between the second intermediate electrode 32 and the internal electrode 20.

[0054] As the dielectric 33, for example, an epoxy resin with a relatively high dielectric constant can be used among synthetic resins. By placing the dielectric 33 with a high dielectric constant between the internal electrode 20 and the intermediate electrode 30 in this way, the capacitance C of the main capacitor 91 in Figure 3 is increased. １ [F] can be increased.

[0055] This makes it possible to configure a main capacitor 91 and a voltage divider capacitor 92 suitable for voltage division without increasing the axial length of the capacitor-type instrument transformer 1A.

[0056] In Embodiment 2, epoxy resin was used as the dielectric 33, but the invention is not limited to this, and any other dielectric material such as acrylic resin, polyacetal resin, or polyurethane resin can be used.

[0057] [Other Embodiments] In embodiments 1 and 2 described above, the first intermediate electrode 31 and the second intermediate electrode 32 of the intermediate electrode 30 are arranged spaced apart in the axial direction of the current-carrying conductor 10, but the invention is not limited to this. For example, only one of the first intermediate electrode 31 or the second intermediate electrode 32 may be arranged facing the internal electrode 20, or three or more intermediate electrodes may be arranged facing the internal electrode 20.

[0058] Furthermore, in embodiments 1 and 2 described above, the fastening members 71 and 72 are shown to tighten the internal electrode 20 from the upper side in Figure 2, but the invention is not limited to this, and the fastening members may be shown to tighten the internal electrode 20 from the side. Also, the fastening members 71 and 72 are not required, and the internal electrode 20 may be fixed to the current-carrying conductor 10 simply by fitting the internal electrode 20 and the current-carrying conductor 10 together at the connection portion 21.

[0059] Furthermore, in embodiments 1 and 2 described above, the internal electrode 20 and the intermediate electrode 30 are made of the same material, but the invention is not limited to this, and the internal electrode 20 and the intermediate electrode 30 may be made of different materials.

[0060] Furthermore, in the embodiments 1 and 2 described above, the coefficient of linear expansion of the current-carrying conductor 10 is different from that of the intermediate electrode 30, that is, the material of the current-carrying conductor 10 and the material of the intermediate electrode 30 are different. However, the invention is not limited to this, and the materials of the current-carrying conductor 10 and the intermediate electrode 30 may be the same.

[0061] [Summary] A capacitor-type instrument transformer according to one aspect of the present disclosure comprises a current-carrying conductor to which a primary voltage is applied and through which current flows, a cylindrical internal electrode that is in electrical contact with the current-carrying conductor and is arranged to surround the current-carrying conductor, and an intermediate electrode that is opposite the internal electrode and is arranged radially outward from the internal electrode. The internal electrode and the intermediate electrode constitute a capacitor.

[0062] In the capacitor-type instrument transformer according to Embodiment 2 of this disclosure, the internal electrode may be cylindrical in shape in Embodiment 1 described above.

[0063] In the capacitor-type instrument transformer according to embodiment 3 of this disclosure, the configuration may include a dielectric material disposed between the internal electrode and the intermediate electrode, as in embodiment 1 or 2 described above.

[0064] In the capacitor-type instrument transformer according to embodiment 4 of the present disclosure, in any of embodiments 1 to 3 described above, the internal electrode surrounds the portion of the current-carrying conductor whose outer diameter is not constant. The intermediate electrode may be arranged around the portion via the internal electrode.

[0065] In the capacitor-type instrument transformer according to aspect 5 of the present disclosure, in aspect 4 described above, the energizing conductor has a first conductor and a second conductor. The portion may be an adapter conductor that connects the first conductor and the second conductor to each other.

[0066] In the capacitor-type instrument transformer according to embodiment 6 of the present disclosure, in any of embodiments 1 to 5 described above, the coefficient of linear expansion of the internal electrode may be the same as the coefficient of linear expansion of the intermediate electrode.

[0067] In the capacitor-type instrument transformer according to embodiment 7 of the present disclosure, in any of embodiments 1 to 6 described above, the coefficient of linear expansion of the current-carrying conductor may be different from the coefficient of linear expansion of the intermediate electrode.

[0068] In the capacitor-type instrument transformer according to embodiment 8 of the present disclosure, in any of embodiments 1 to 7 above, the internal electrode may have a connection portion that overlaps with the current-carrying conductor in the axial direction of the internal electrode, and the internal electrode may be fixed to the current-carrying conductor by a fastening member at the connection portion.

[0069] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0070] 1. 1A Capacitor-type instrument transformer 10 Conductor 11 First conductor 12 Second conductor 13 Third conductor 14 First adapter conductor 15 Second adapter conductor 20 Internal electrode 21 Connection part 30 Intermediate electrode 31 First intermediate electrode 32 Second intermediate electrode 33 Dielectric 71, 72 Fastening member 91 Main capacitor 100 Electrical equipment

Claims

1. A capacitor-type instrument transformer comprising: a current-carrying conductor to which a primary voltage is applied and current flows; a cylindrical internal electrode electrically in contact with the current-carrying conductor and arranged to surround the current-carrying conductor; and an intermediate electrode facing the internal electrode and arranged radially outside the internal electrode, wherein the internal electrode and the intermediate electrode constitute a capacitor.

2. The capacitor-type instrument transformer according to claim 1, wherein the internal electrode is cylindrical in shape.

3. The capacitor-type instrument transformer according to claim 1, further comprising a dielectric material disposed between the internal electrode and the intermediate electrode.

4. The capacitor-type instrument transformer according to claim 1, wherein the internal electrode surrounds the portion of the current-carrying conductor whose outer diameter is not constant, and the intermediate electrode is arranged around the portion via the internal electrode.

5. The capacitor-type instrument transformer according to claim 4, wherein the energizing conductor comprises a first conductor and a second conductor, and the portion is an adapter conductor connecting the first conductor and the second conductor to each other.

6. The capacitor-type instrument transformer according to claim 1, wherein the coefficient of linear expansion of the internal electrode is the same as the coefficient of linear expansion of the intermediate electrode.

7. The capacitor-type instrument transformer according to claim 6, wherein the coefficient of linear expansion of the current-carrying conductor is different from the coefficient of linear expansion of the intermediate electrode.

8. The capacitor-type instrument transformer according to any one of claims 1 to 7, wherein the internal electrode has a connection portion that overlaps with the current-carrying conductor in the axial direction of the internal electrode, and the internal electrode is fixed to the current-carrying conductor by a fastening member at the connection portion.

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