WO2012160625A1

WO2012160625A1 - Transformer for instruments

Info

Publication number: WO2012160625A1
Application number: PCT/JP2011/061659
Authority: WO
Inventors: 聖之平井; 羽馬　洋之
Original assignee: 三菱電機株式会社
Priority date: 2011-05-20
Filing date: 2011-05-20
Publication date: 2012-11-29
Also published as: JP4896280B1; CN103348425B; CN103348425A; JPWO2012160625A1

Abstract

Provided is a transformer for instruments, said transformer provided with: a metal adapter (3); cylindrically shaped intermediate electrodes (5a - 5c) that are attached to peripheral edge parts of hole parts (20a - 20c) in the metal adapter (3) via ring shaped insulator members (10) and that surround the periphery of center conductors (2a - 2c); substantially cylindrically shaped grounding shields (4a - 4c) each disposed so as to be adjacent to the respective intermediate electrode (5a - 5c) along the direction of an axial line; and an insulating sealed terminal mounted in a branching tube provided on the side surface of a metal container (1) and air tightly extracting lead wires connected to each of the intermediate electrodes (5a - 5c). The inside diameter of the intermediate electrodes (5a - 5c) is greater than the inside diameter of the respective grounding shields (4a - 4c).

Description

Instrument transformer

The present invention relates to an instrument transformer applied to a three-phase collective gas insulated switchgear.

In a three-phase collective gas insulated switchgear, three-phase conductors are collectively stored in a metal container filled with insulating gas. The instrument transformer measures the voltage of the conductor of each phase. An instrument transformer applied to a three-phase collective gas-insulated switchgear has a configuration using an annular intermediate electrode that coaxially surrounds a conductor of each phase (see, for example, FIG. 8 of Patent Document 1). . In such a configuration, in general, the intermediate electrode of the own phase is easily affected by the electric field due to the conductor of the other phase, the measurement error due to the voltage induction of the other phase becomes large, and the specification generally requires high measurement accuracy. May not be suitable.

Therefore, in the transformer for an instrument described in FIG. 1 of Patent Document 1, branch pipes as intermediate electrode storage chambers are provided at positions facing the conductors of the respective phases on the side wall portion of the metal container. An intermediate electrode for each phase is disposed in In such a configuration, the measurement accuracy of the voltage of each phase can be improved by reducing the influence of the electric field of the other phase.

Further, in Patent Document 2, a tubular ground shield is provided so as to surround each phase conductor, and a tubular intermediate electrode that wraps around the conductor is disposed inside each ground shield. Is disclosed.

Japanese Utility Model Publication No. 5-6376 Japanese Patent Laid-Open No. 2-115770

However, for example, in the instrument transformer shown in FIG. 8 of Patent Document 1, since the intermediate electrode of the own phase is affected by the electric field of the conductor of the other phase, the error due to the induced voltage of the other phase is large, and the voltage of each phase is There was a problem that it was difficult to measure accurately.

Further, in the instrument transformer of FIG. 1 of Patent Document 1, since the intermediate electrode of each phase is in a form only facing the conductor of the corresponding phase, for example, around the conductor as shown in FIG. 8 of Patent Document 1 In comparison with the configuration in which the intermediate electrode is coaxially arranged, the sensitivity of voltage detection is lowered, and there is a possibility that application to specifications requiring higher accuracy may be limited. Further, in this configuration, since it is necessary to provide a branch pipe for accommodating the intermediate electrode for each phase, three branch pipes must be provided in the metal container for the instrument transformer.

In the instrument transformer of Patent Document 2, since the intermediate electrode is disposed inside the ground shield and on the conductor side, it is necessary to secure an insulation distance between the intermediate electrode and the conductor. There was a problem that the dimension of a direction became large.

The present invention has been made in view of the above, and is an instrument transformer applied to a three-phase collective gas-insulated switchgear, which reduces the influence of an electric field caused by a conductor of another phase and is self-phased. It is an object of the present invention to provide an instrument transformer that can detect the voltage of the metal container with high accuracy and can reduce the radial dimension of the metal container.

In order to solve the above-described problems and achieve the object, the transformer for an instrument according to the present invention includes a three-phase center along the axial direction of the metal container in a cylindrical metal container filled with an insulating gas. A transformer for an instrument that is applied to a three-phase collective gas-insulated switchgear in which a conductor is housed and measures a voltage applied to each of the three-phase central conductors, attached to the metal container, and A metal adapter having three holes through which the center conductors of the phase pass, and each phase that is attached to the peripheral edge of each hole of the metal adapter via an annular insulating member and passes through each hole. A cylindrical intermediate electrode disposed so as to surround the outer periphery of the central conductor of each of the central conductors, and disposed adjacent to the intermediate electrode of each phase along the axial direction, the central conductor penetrating the intermediate electrode I'll surround the perimeter A substantially cylindrical ground shield disposed coaxially with the intermediate electrode, and a lead wire attached to the branch pipe provided on the side surface of the metal container and connected to the intermediate electrode of each phase. And an inner diameter of the intermediate electrode of each phase is larger than an inner diameter of the ground shield adjacent to the intermediate electrode in the axial direction.

According to the present invention, a transformer for an instrument applied to a three-phase collective gas insulated switchgear, which can detect the voltage of its own phase with high accuracy by alleviating the influence of the electric field due to the conductor of the other phase. In addition, there is an effect that the size of the metal container in the radial direction can be reduced.

FIG. 1 is a diagram illustrating a cross-sectional configuration of the instrument transformer according to the first embodiment. FIG. 2 is a vertical sectional view taken along line AA in FIG. FIG. 3 is a detailed view of part B of FIG. FIG. 4 is an enlarged view of a part of FIG. FIG. 5 is a diagram showing a pattern of the applied voltage. FIG. 6 is a diagram showing the relationship between the d dimension, the error due to other phase induction, and the capacitance α. FIG. 7 is a diagram showing a part of a longitudinal sectional configuration of the instrument transformer according to the second embodiment. FIG. 8 is a diagram showing the relationship between the dimension b, the error due to other phase induction, and the capacitance α. FIG. 9 is a diagram illustrating a part of a longitudinal cross-sectional configuration of the instrument transformer according to the third embodiment. FIG. 10 is a diagram showing an error due to other phase induction with respect to the length D in the axial direction of the ground shield 4a. FIG. 11 is another longitudinal sectional view taken along the line AA. FIG. 12 is a detailed view of part B of FIG.

Hereinafter, embodiments of an instrument transformer according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
1 is a diagram showing a cross-sectional configuration of an instrument transformer according to the present embodiment, FIG. 2 is a vertical cross-sectional configuration diagram taken along line AA of FIG. 1, and FIG. 3 is a detailed view of a portion B of FIG.

1 to 3 show a configuration of an instrument transformer applied to a three-phase collective gas insulated switchgear. For example, three-phase center conductors 2a to 2c are collectively stored in a cylindrical metal container 1 filled with an insulating gas such as SF ₆ gas. The metal container 1 has, for example, a cylindrical shape and is grounded. Central conductors 2a to 2c are extended in the direction of the central axis of the metal container 1, respectively. Since the central axis of the metal container 1 and the central axes of the central conductors 2a to 2c are parallel to each other, hereinafter, the direction of these central axes is simply referred to as “axial direction”. The center conductors 2a to 2c are main circuit conductors that are high-voltage charging parts. The center conductors 2a to 2c are arranged so as to form the vertices of an equilateral triangle, for example. For example, the center conductors 2a to 2c may be arranged to form vertices of an isosceles triangle. The center conductors 2a to 2c are supported by an insulating support (not shown) (for example, an insulating spacer). In FIG. 1, the cross sections of the central conductors 2a to 2c are shown densely, but they may be, for example, circular.

The instrument transformer according to the present embodiment is insulated from, for example, a substantially disk-shaped metal adapter 3 having holes 20a to 20c through which the central conductors 2a to 2c pass, respectively, and a peripheral portion of the hole 20a of the metal adapter 3. An intermediate electrode 5a that is attached via the member 10 and is disposed coaxially with the central conductor 2a so as to surround the outer periphery of the central conductor 2a, and a central conductor 2a that is disposed adjacent to the intermediate electrode 5a along the axial direction. Insulating the ground shield 4a coaxially with the central conductor 2a so as to surround the outer periphery of the metal wire, the signal wire 6a which is a lead wire connected to the intermediate electrode 5a, and the peripheral portion of the hole 20b of the metal adapter 3 An intermediate electrode 5b that is attached via the member 10 and is coaxially arranged with the central conductor 2b so as to surround the outer periphery of the central conductor 2b, and is arranged adjacent to the intermediate electrode 5b along the axial direction. A ground shield 4b coaxially arranged with the center conductor 2b so as to surround the outer periphery of the center conductor 2b, a signal line 6b which is a lead wire connected to the intermediate electrode 5b, and a hole 20c of the metal adapter 3 An intermediate electrode 5c that is attached to the peripheral edge via the insulating member 10 and is disposed coaxially with the central conductor 2c so as to surround the outer periphery of the central conductor 2c, and is disposed adjacent to the intermediate electrode 5c along the axial direction. A ground shield 4c arranged coaxially with the center conductor 2c so as to surround the outer periphery of the center conductor 2c, a signal line 6c which is a lead wire connected to the intermediate electrode 5c, and a side surface of the metal container 1. An insulating hermetic terminal 7 which is attached to the branch pipe 14 and leads out the signal lines 6a to 6c to the outside of the metal container 1 and is connected to the insulating hermetic terminal 7 and output via the signal lines 6a to 6c. Includes an AD converter 8 for converting them into digital signals from the voltage values of the intermediate electrode 5a ~ 5c after detecting the voltage values of the center conductor 2a ~ 2c, the.

The instrument transformer according to the present embodiment derives voltages induced in the intermediate electrodes 5a to 5c electrically insulated from the metal container 1 to the outside, and each of the central conductors 2a to 2c is derived from these induced voltages. This constitutes a so-called capacitor voltage divider for calculating the voltage. For example, the voltage of the center conductor 2a is determined as the voltage of the intermediate electrode 5a according to the capacitance between the center conductor 2a and the intermediate electrode 5a and the capacitance between the intermediate electrode 5a and the metal container 1. Divided pressure. Therefore, if the capacitance between the center conductor 2a and the intermediate electrode 5a is obtained in advance, the voltage of the center conductor 2a can be detected by detecting the voltage of the intermediate electrode 5a. Actually, in order to set the voltage induced in the intermediate voltage 5 a to an appropriate voltage value, for example, an adjustment capacitor (not shown) is provided between the insulating hermetic terminal 7 and the metal container 1. The same applies to the

center conductors

2b and 2c.

The metal adapter 3 has, for example, a disk shape slightly smaller than the inner diameter of the metal container 1, and is joined to the metal container 1 by the joint portion 9. The metal adapter 3 has three holes 20a to 20c formed according to the arrangement of the center conductors 2a to 2c, and the holes 20a to 20c have diameters larger than the outer diameters of the center conductors 2a to 2c, respectively. . The central conductors 2a to 2c are all arranged so as not to contact the metal adapter 3. The center conductors 2a to 2c penetrate the metal adapter 3 substantially vertically through the holes 20a to 20c, respectively.

A substantially annular insulating member 10 is attached to the peripheral edge portion of the hole 20a of the metal adapter 3, and the metal, for example, a cylindrical intermediate electrode 5a surrounds the outer periphery of the center conductor 2a via the insulating member 10. It is attached to the adapter 3. That is, the intermediate electrode 5 a is electrically insulated from the metal container 1 by the insulating member 10. The intermediate electrode 5a and the insulating member 10 are attached to the metal adapter 3 with, for example, bolts. Similarly, a substantially annular insulating member 10 is attached to the peripheral portion of the hole 20b of the metal adapter 3 so that, for example, a cylindrical intermediate electrode 5b surrounds the outer periphery of the center conductor 2b via the insulating member 10. And attached to the metal adapter 3. That is, the intermediate electrode 5 b is electrically insulated from the metal container 1 by the insulating member 10. The intermediate electrode 5b and the insulating member 10 are attached to the metal adapter 3 with, for example, bolts. Similarly, a substantially annular insulating member 10 is attached to the peripheral portion of the hole 20c of the metal adapter 3 so that, for example, a cylindrical intermediate electrode 5c surrounds the outer periphery of the center conductor 2c via the insulating member 10. And attached to the metal adapter 3. That is, the intermediate electrode 5 c is electrically insulated from the metal container 1 by the insulating member 10. The intermediate electrode 5c and the insulating member 10 are attached to the metal adapter 3 with, for example, bolts. Although the insulating members 10 are denoted by the same reference numerals, as is apparent from the above description and FIGS. 1 and 2, three insulating members 10 are provided according to the intermediate electrodes 5a to 5c.

The ground shield 4a has, for example, a substantially cylindrical shape and is arranged coaxially with the center conductor 2a so as to surround the outer periphery of the center conductor 2a. The ground shield 4a is disposed adjacent to the intermediate electrode 5a along the axial direction. The ground shield 4a has a flange portion 41 formed at one end thereof on the intermediate electrode 5a side, and the other end opposite to the intermediate electrode 5a has a curved shape that smoothly spreads toward the outer periphery with a predetermined curvature to alleviate electric field concentration. Part 42. In the illustrated example, a pair of ground shields 4a is provided, and these ground shields 4a are disposed on both sides of the intermediate electrode 5a so as to sandwich the intermediate electrode 5a in the axial direction. Here, in one of the pair of ground shields 4a, the flange portion 41 is arranged to face one end portion of the intermediate electrode 5a via the gap portion 13, and the other of the pair of ground shields 4a is The flange portion 41 is disposed on the surface of the metal adapter 3 opposite to the surface on which the insulating member 10 is disposed, and the pair of ground shields 4a are both attached to the metal adapter 3 with bolts or the like, for example. For example, the one ground shield 4a is attached to the metal adapter 3 with a bolt 11 that is longer than the axial length of the intermediate electrode 5a. The gap 13 is a gas gap that insulates the one ground shield 4a from the intermediate electrode 5a. The intermediate electrode 5 a is insulated from the metal container 1 by the insulating member 10 and the gap portion 13. In the three-phase collective gas-insulated switchgear, the self-phase intermediate electrode 5a is affected by the electric field of the

center conductors

2b and 2c of the other phases, but the ground shield 4a is the

center conductors

2b and 2c of the other phases. Can alleviate the influence of the electric field generated in Since the same applies to the ground shields 4b and 4c, description thereof will be omitted.

The inner diameter of the intermediate electrode 5a is larger than, for example, the inner diameter of the ground shield 4a. Similarly, the inner diameter of the intermediate electrode 5b is larger than the inner diameter of the ground shield 4b, for example, and the inner diameter of the intermediate electrode 5c is larger than the inner diameter of the ground shield 4c, for example. FIG. 4 is an enlarged view of a part of FIG. 3, in which the inner diameter of the intermediate electrode 5a is larger than the inner diameter of the ground shield 4a, and d = (the inner diameter of the intermediate electrode 5a−the inner diameter of the ground shield 4a) / 2> 0. It is.

Here, the effect of setting the inner diameters of the intermediate electrodes 5a to 5c to be larger than the inner diameters of the ground shields 4a to 4c will be described. FIG. 5 is a diagram showing a pattern of the applied voltage, and is a diagram for explaining that the capacitance between the intermediate electrode 5a and the center conductor 2a changes due to the influence of the voltages of the center conductors 2b and 2c. is there. The applied voltage (1) is when the voltage of the center conductor 2a is 100% and the voltages of the

center conductors

2b and 2c are 0%, respectively, and the capacitance between the intermediate electrode 5a and the center conductor 2a in this case is Let α (F). That is, α represents the capacitance when there is no influence of the electric field from the

center conductors

2b and 2c. On the other hand, the applied voltage (2) is when the voltage of the central conductor 2a is 100% and the voltages of the

central conductors

2b and 2c are -50%, respectively. In this case, the intermediate electrode 5a and the central conductor 2a The electrostatic capacity between them is β (F). That is, β represents the capacitance when the influence of the electric field from the

central conductors

2b and 2c which are other phases is the largest. Then, the error due to the other phase induction of the voltage measurement value of the center conductor 2a based on the voltage of the intermediate electrode 5a can be defined as follows:
Error due to other phase induction (%) = (α−β) / α × 100 (1)
That is, in the equation (1), by using the capacitance β when the influence of the electric field from the other phase is the greatest and the capacitance α when there is no influence of the electric field from the other phase, The error is evaluated. The definition by the expression (1) is the same for the

intermediate electrodes

5b and 5c. For example, the error due to the other phase induction of the voltage measurement value of the center conductor 2b based on the voltage of the intermediate electrode 5b is an electrostatic charge when the voltage of the center conductor 2b is 100% and the voltages of the

center conductors

2a and 2c are 0%. The capacitance α and the capacitance β when the voltage of the center conductor 2b is 100% and the voltages of the

center conductors

2a and 2c are −50% are defined by the equation (1).

FIG. 6 is a diagram showing the error due to other phase induction and the capacitance α with respect to d = (inner diameter of the intermediate electrode 5a−inner diameter of the ground shield 4a) / 2. The solid line represents the error due to other phase induction, and the dotted line represents the capacitance α. As shown in FIG. 6, it can be seen that as the d dimension increases, the capacitance α decreases, but the error due to the other phase induction also decreases. Therefore, by setting d> 0, it is possible to more accurately measure the voltage of the center conductor 2a of the own phase while suppressing errors due to other phase induction. It goes without saying that FIG. 6 also holds for the

intermediate electrodes

5b and 5c.

As described above, according to the present embodiment, the inner diameters of the intermediate electrodes 5a to 5c are made larger than the inner diameters of the ground shields 4a to 4c, respectively. And the voltage of the center conductor of the own phase can be measured with higher accuracy.

In addition, according to the present embodiment, the intermediate electrodes 5a to 5c are arranged in a cylindrical shape so as to circulate around the center conductors 2a to 2c, respectively, so that, for example, the area is larger than that of the intermediate electrode of FIG. Therefore, the sensitivity of voltage detection is increased. In FIG. 1 of Patent Document 1, it is necessary to provide three branch pipes for accommodating the intermediate electrode in the metal container. However, in the present embodiment, the number of branch pipes 14 may be one, so that the metal container 1 Is easy to process.

In the instrument transformer of Patent Document 2, since the intermediate electrode is disposed inside the ground shield and on the conductor side, it is necessary to secure an insulation distance between the intermediate electrode and the conductor. There was a problem that the dimension of a direction became large. On the other hand, in the present embodiment, the inner diameters of the intermediate electrodes 5a to 5c are made larger than the inner diameters of the ground shields 4a to 4c, respectively. It can be made smaller compared to the transformer for use.

Further, according to the present embodiment, the intermediate electrode 5a and the ground shield 4a are disposed so as to be adjacent to each other along the axial direction, and the intermediate electrode 5b and the ground shield 4b are disposed so as to be adjacent to each other along the axial direction. Since the intermediate electrode 5c and the ground shield 4c are arranged so as to be adjacent to each other along the axial direction, the intermediate electrode is arranged inside the ground shield like the instrument transformer of Patent Document 2. Compared with the configuration, the insulation distance can be ensured, and the radial dimension of the metal container 1 can be reduced.

Further, according to the present embodiment, for example, the gap 13 as a gas gap is provided between one of the pair of ground shields 4a and the intermediate electrode 5a, so that the other of the pair of ground shields 4a and the intermediate electrode There is no need to provide the insulating member 10 between the intermediate electrode 5a and the insulating member on one side of the intermediate electrode 5a can be omitted to simplify the structure. A configuration in which an insulating member is disposed between both the pair of ground shields 4a and the intermediate electrode 5a without providing the gap portion 13 is also possible. FIG. 11 is another vertical cross-sectional view taken along the line AA, and FIG. 12 is a detailed view of a portion B in FIG. As shown in FIGS. 11 and 12, for example, an annular insulating member 10 is disposed between the intermediate electrode 5a and the metal adapter 3, and for example, an annular member is disposed between one of the pair of ground shields 4a and the intermediate electrode 5a. The insulating member 12 is disposed. The configuration of FIGS. 11 and 12 has the same effect as the present embodiment except for the simplification of the above structure. The same applies to the

intermediate electrodes

5b and 5c.

Further, according to the present embodiment, since the ground shield 4a is disposed on both sides in the axial direction across the intermediate electrode 5a, the influence of the electric field generated in the

center conductors

2b and 2c of the other phases is suppressed, and the self-phase The voltage of the center conductor 2a can be measured with high accuracy. The ground shield 4a is preferably arranged on both sides of the intermediate electrode 5a, but can be arranged only on one side of the intermediate electrode 5a. The same applies to the

intermediate electrodes

5b and 5c.

When the ground shield 4a is not provided, the electric field around the metal adapter 3 needs to be relaxed. By providing the ground shield 4a as in the present embodiment, both the electric field relaxation around the metal adapter 3 and the influence of the electric field generated in the

center conductors

2b, 2c of the other phases can be realized. . The same applies to the

intermediate electrodes

5b and 5c.

Embodiment 2. FIG.
FIG. 7 is a diagram showing a part of a longitudinal cross-sectional configuration of the instrument transformer according to the present embodiment, and should be compared with FIG. 4. In the present embodiment, the relationship between the inner diameters of the intermediate electrodes 5a to 5c and the inner diameter of the insulating member 10 is further defined under the configuration of the first embodiment. That is, as shown in FIG. 7, the inner diameter of the annular insulating member 10 interposed between the metal adapter 3 and the intermediate electrode 5a is smaller than the inner diameter of the intermediate electrode 5a (see P region), and b = (intermediate The inner diameter of the electrode 5a−the inner diameter of the insulating member 10) / 2> 0. The same relationship holds true for the intermediate electrode 5b and the insulating member 10 in contact therewith, and the intermediate electrode 5c and the insulating member 10 in contact therewith. On the other hand, in Embodiment 1, the inner diameter of the insulating member 10 is substantially equal to the inner diameter of the intermediate electrode 5a. Other configurations of the present embodiment are the same as those of the first embodiment.

FIG. 8 is a diagram showing an error due to other phase induction and a capacitance α with respect to b = (inner diameter of intermediate electrode 5a−inner diameter of insulating member 10) / 2> 0. The solid line represents the error due to other phase induction, and the dotted line represents the capacitance α. As shown in FIG. 8, it can be seen that as the dimension b increases, the capacitance α decreases, but the error due to other phase induction also decreases. Therefore, by setting b> 0, it is possible to more accurately measure the voltage of the center conductor 2a of the own phase while suppressing errors due to other phase induction. It goes without saying that FIG. 8 also holds for the

intermediate electrodes

5b and 5c.

According to the present embodiment, since the inner diameters of the intermediate electrodes 5a to 5c are larger than the inner diameter of the insulating member 10, the influence of the electric field generated in the center conductor of the other phase is suppressed, and the voltage of the center conductor of the own phase is suppressed. Can be measured with high accuracy. Other effects of the present embodiment are the same as those of the first embodiment.

Embodiment 3 FIG.
FIG. 9 is a diagram showing a part of the longitudinal cross-sectional configuration of the instrument transformer according to the present embodiment, and should be compared with FIG. 4. In the present embodiment, the relationship between the length of the intermediate electrode 5a in the axial direction and the length of the ground shield 4a in the axial direction is further defined based on the configuration of the first embodiment. That is, as shown in FIG. 9, when the length of the intermediate electrode 5a in the axial direction is C and the length of the ground shield 4a in the axial direction is D, in this embodiment, D ≧ C. The same relationship holds true for the intermediate electrode 5b and the ground shield 4b, and the intermediate electrode 5c and the ground shield 4c.

FIG. 10 is a diagram showing an error due to other phase induction with respect to the axial length D of the ground shield 4a. FIG. 10 shows the relationship between the D dimension and the error due to the other phase induction for the three cases of the small, medium, and large C dimensions. Further, the target value of error due to other phase induction is represented by Q. The target value Q is a value such that the voltage measurement accuracy falls within the required specifications when the error is less than or equal to this value. As shown in FIG. 10, it can be seen that as the D dimension increases, the error due to the other phase induction also decreases. In the comparison between the three cases of small, medium and large C dimensions, the larger the C dimension, the smaller the error. Thus, if the length of the ground shield 4a in the axial direction is increased, errors due to other phase induction can be suppressed. From the comparison with the length of the intermediate electrode 5a in the axial direction, for example, D ≧ C. It is effective to do.

Further, in the region indicated by R in FIG. 10, the error due to the other phase induction is substantially equal to the target value Q regardless of three patterns of large, medium, and small C dimensions. Needless to say, the above description also holds true for the relationship between the ground shield 4b and the intermediate electrode 5b and the relationship between the ground shield 4c and the intermediate electrode 5c.

According to the present embodiment, since the length of the ground shield 4a in the axial direction is equal to or longer than the length of the intermediate electrode 5a in the axial direction, the influence of the electric field generated in the center conductor of the other phase is suppressed, and the self-phase The voltage of the center conductor can be measured with high accuracy.

In addition, as shown in FIG. 9, the length in the radial direction of the ground shield 4a (the length in the radial direction of the flange portion) is larger than the length in the radial direction of the intermediate electrode 5a, for example.

Other effects of this embodiment are the same as those of the first and second embodiments. Moreover, this Embodiment and Embodiment 2 can also be combined.

As described above, the present invention is useful as an instrument transformer applied to a three-phase collective gas insulated switchgear.

DESCRIPTION OF SYMBOLS 1 Metal container 2a-2c Center conductor 3 Metal adapter 4a-4c Ground shield 5a-5c Intermediate electrode 6a-6c Signal line 7 Insulation airtight terminal 8 AD conversion part 9

Junction part

10, 12 Insulation member 11 Bolt 13 Gap part 14 Branch pipe 20a to 20c Hole 41 Flange 42 Bent

Claims

The three-phase central conductor is applied to a three-phase collective gas insulated switchgear in which a three-phase central conductor is accommodated along the axial direction of the metal container in a cylindrical metal container filled with an insulating gas. An instrument transformer for measuring the voltage applied to each of
A metal adapter attached to the metal container and having three holes formed through the three-phase central conductors;
Cylindrical intermediate electrodes that are attached to the periphery of each hole of the metal adapter via an annular insulating member, and are arranged so as to surround the outer periphery of the center conductor of each phase that passes through each of the holes. ,
A substantially cylindrical shape that is arranged so as to be adjacent to the intermediate electrode of each phase along the axial direction, and is arranged coaxially with the intermediate electrode so as to surround the outer periphery of the central conductor that penetrates the intermediate electrode. A ground shield,
An insulating hermetically sealed terminal that is attached to a branch pipe provided on a side surface of the metal container and that air-tightly draws out lead wires connected to the intermediate electrodes of the respective phases;
An inner diameter of the intermediate electrode of each phase is larger than an inner diameter of the ground shield adjacent to the intermediate electrode in the axial direction.
The instrument transformer according to claim 1, wherein the ground shield is disposed on both sides in the axial direction across the intermediate electrode.
The instrument transformer according to claim 2, wherein a gas gap is provided between the ground shield disposed on one side of the intermediate electrode and the intermediate electrode.
2. The instrument transformer according to claim 1, wherein an inner diameter of the intermediate electrode is larger than an inner diameter of the insulating member.
The instrument transformer according to claim 1, wherein a length of the ground shield in the axial direction is equal to or longer than a length of the intermediate electrode adjacent to the ground shield in the axial direction.