JP2000147024A - Installation method of current transformer and current transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an installation method for current transformer by which high measurement accuracy can be obtained. SOLUTION: A current transformer 1 composed of an annular coil is constituted, in such a way that one 4a of two parallel buses 4a and 4c, through which electric currents flows in the opposite directions in used as an object to be measured and wingings 3, are wound spirally around almost the whole peripheral surface of an annular core 2 coaxially arranged with the bus 4a and made of an insulating material, and then a lead-out section 31 which is not wound with the windings 3 and from which both ends of the winding 3 are led out is provided at part of the core 2 in the peripheral direction. Measurement errors caused by the presence of the lead-out section 31, which is a no-winding section, is reduced as compared with the conventional example by setting the position of the section 31 at a central angle θc in the large of 30 deg.-80 deg. of the winding 3 from the plane formed of the buses 4a and 4c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current transformer used for measuring a current flowing through a bus using an induced voltage of a coil.

[0002]

2. Description of the Related Art As one means for measuring a current flowing through a bus to be measured, the magnetic field generated by the current is induced in a winding of an annular coil coaxially arranged with the bus. There is a current measuring device using a through-type current transformer that uses voltage as a medium. FIG. 7 is a front view of this type of current transformer, and FIG. 8 is a longitudinal sectional view taken along line VIII-VIII in FIG.

[0003] In the drawing, reference numeral 2 denotes an insulative winding core having a rectangular cross section, which is attached coaxially to a bar-shaped bus bar 4. The winding 3 is wound around the center axis of the rectangular cross section over the entire circumference of the winding core 2, and the current transformer 1 is configured. In this state, when a current flows through the bus 4, a magnetic field is generated in the circumferential direction of the current transformer 1. A voltage is induced in the current transformer 1 by the magnetic field, and the value of the current flowing through the bus 4 can be detected by measuring the voltage.

[0004] Due to the current flowing through the bus 4, not only the above-described circumferential magnetic field but also an axial magnetic field is generated around the current transformer 1. As a result, the magnetic field in the axial direction
Therefore, an error occurs in the obtained current value. Therefore, in the conventional current transformer, the return wire 30 connected to one end of the winding 3 is caused to make a round along the one surface of the winding core 2 in a direction opposite to the direction in which the winding proceeds, and the winding 3 and the return wire 30 Are the output terminals ka and la, respectively, and the current value of the bus 4 is measured using the induced voltage obtained between the output terminals ka and la.

[0005] In this case, the voltage induced in the winding 3 by the magnetic field in the axial direction and the voltage induced in the pull-back line 30 are canceled out, and a measurement error due to the influence of the magnetic field in the axial direction. Can be eliminated. In FIG. 7, the case where the winding 3 is wound in a single layer is described. However, when the winding 3 is formed as a multilayer winding of two layers or more, the number of unwinding turns of the return wire 30 is also equal to the number of layers. It is necessary to

[0006]

The main circuit is often arranged in a U-shape inside a switch or the like, and the current value of such a main circuit is determined by using the above-described conventional current transformer. In the case of performing measurement by the method, the return portion of the bus is arranged in parallel near the bus to be measured, and there is a problem that an induced voltage due to this causes an error in the measured value for the following reason.

FIG. 9 is an explanatory diagram showing a circumferential distribution of a voltage induced in a current transformer arranged on a U-shaped bus bar. FIG.
As shown in a, the penetrating portion 4a and the return portion 4c are opposite portions of the same bus, and currents in opposite directions are flowing. In order to measure the value of the current flowing through the penetrating portion 4a, the current transformer 1 is arranged around the penetrating portion 4a. A non-winding part is provided for fixing the. The current transformer 1 is arranged such that the non-winding portion is located between the through portion 4a and the return portion 4c. As shown in FIG. 9B, a voltage having the same polarity as that of the induced voltage due to the current of the through portion 4a is induced in the portion of the winding 3 on the side of the return portion 4c, and a voltage is generated in the portion of the winding 3 opposite to the return portion 4c. A voltage having a polarity opposite to that of the voltage induced by the current of the portion 4a is induced. When the winding density and the cross-sectional area of the current transformer 1 are constant in the circumferential direction, the return portion 4
The sum of the induced voltages due to c is zero. However, since the winding density becomes non-uniform due to the presence of the non-winding portion, the total induced voltage due to the return portion 4c is not zero,
An error will occur in the measured value.

[0008] Further, in order to reduce the size of a switch, which is an installation space, there has been a problem in miniaturizing a current transformer. The present invention has been made in view of such circumstances,
An object of the present invention is to provide a current transformer that effectively eliminates a measurement error caused by a magnetic field from a bus arranged in parallel with a bus to be measured. It is another object of the present invention to provide a current transformer that is smaller than before.

[0009]

According to a first aspect of the present invention, there is provided a method for installing a current transformer, comprising the steps of: providing a current transformer having a winding core made of an annular insulator; and a winding wound around the winding core. A winding is arranged so that a bus penetrates through the winding core, and with respect to a plane defined by the bus and a bus arranged outside the winding core and parallel to the bus, The position is set within the range of the central angle of the core of 30 to 80 °.

When a current transformer having an annular winding core and a winding wound on the winding core is used as a current measuring device, the magnitude of the measurement error is determined by the winding with respect to the plane defined by the two buses. It depends on the position of the wire drawing part in the core circumferential direction,
It has been experimentally found that there is a position of the lead portion of the winding where the measurement error becomes zero when the center angle of the winding core is in the range of 30 to 80 °.

According to the method for installing a current transformer according to the first aspect of the present invention, the lead-out portion of the winding is set so that the center angle of the winding core with respect to the plane defined by the two buses is within the range of 30 to 80 °. To reduce the measurement error. Further, the measurement error can be reduced to zero by arranging the lead portion of the winding at the optimum position.

A current transformer according to a second aspect of the present invention includes a winding core formed of an annular laminate in which a magnetic material and an insulating material are stacked in the axial direction thereof, and a winding wound on the winding core. It is characterized by being.

According to the current transformer of the second aspect, since the relative permeability of the core and the cross-sectional area of the core are inversely proportional when the output voltage is equal, the magnetic material and the insulating material A core is formed by an annular laminated body obtained by laminating the core and the core is made of a low magnetic permeability material having a slightly higher relative magnetic permeability than that of the insulator, thereby providing a small current transformer.

Further, since the magnetic flux entering from both end surfaces of the core has a greater effect on the measured value than the magnetic flux entering from the outer peripheral surface of the core, the laminating direction is defined as the axial direction of the core. The outermost magnetic material of the core obtains a magnetic shielding effect against magnetic flux entering from both end surfaces, and does not affect the circumferential magnetic flux passing through the internal magnetic material by preventing the magnetic flux from reaching the inside of the core. In this way, practically sufficient measurement accuracy is ensured.

A current transformer according to a third aspect of the present invention includes an annular core formed of a conductive material and having a cutout in a part in the circumferential direction, and a winding wound around the core. It is characterized by having.

According to the current transformer according to the third aspect of the present invention, the notch is provided in a part of the core in the circumferential direction to prevent a current from flowing in the core in the circumferential direction, thereby preventing the output voltage from being lost. . This makes it possible to configure the current transformer not only with an insulating material but also with a core using a conductive material.

A current transformer according to a fourth invention is characterized in that the lead-out portion of the winding and the missing portion are arranged at the same location.

According to the current transformer according to the fourth aspect of the present invention, since the relative permeability is different from that of the other parts of the core, the missing part causing the measurement error and the winding density are different from the other parts. The lead portion of the winding causing the measurement error is arranged at the same location, the length of the portion where the relative permeability and the winding density are not uniform is suppressed, and the measurement error is reduced.

According to a fifth aspect of the present invention, in the method for installing a current transformer, a bus is arranged so as to penetrate the core, and the bus and a bus arranged outside the core in parallel with the bus. The current transformer according to any one of the second to fourth aspects of the present invention is provided in which the position of the lead-out portion of the winding is set within a central angle range of the core of 30 to 80 ° with respect to a defined plane. I do.

According to the method for installing a current transformer according to the fifth aspect of the present invention, the winding lead-out portion is set such that the center angle of the winding core with respect to the plane formed by the two buses is within the range of 30 to 80 °. To reduce the measurement error as compared with the prior art. Furthermore,
The measurement error can be reduced to zero by arranging the lead of the winding at the optimum position.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 The present invention will be described below in detail with reference to the drawings showing an embodiment. FIG. 1 is a front view showing a configuration of a main part of a current transformer installation method according to a first embodiment of the present invention, and FIG.
FIG. 2 is an enlarged vertical sectional view taken along line II. In the figure, reference numeral 4 denotes a bus. A winding core 2 made of an insulating material and having an annular shape with a rectangular cross section is arranged coaxially with the bus bar 4. The winding core 2 is wound around a central axis of the rectangular cross section in a single-layer helical shape over substantially the entire circumference, thereby forming an annular coil current transformer 1. A return wire 30 is wound around the winding core 3 once around the end surface of the winding core 2 inside the spiral of the winding 3. One end of the winding 3 and one end of the return wire 30 are connected,
The respective other ends are drawn out from the annular coil and serve as output terminals ka and la. The lead portion 31 from which the output terminals ka and la are drawn is a portion where the winding 3 is not wound by the angle θg at the center angle of the core 2.

After passing through the current transformer 1, the bus 4
It is bent in a U-shape, and is configured in the order of a penetrating portion 4a penetrating the current transformer 1, an intermediate portion 4b, and a return portion 4c. The penetrating part 4a and the return part 4c are separated by a distance L. The position of the lead-out portion 31 with respect to the plane defined by the bus bar 4 is set such that the central angle θc of the core 2 is 30.
The current transformer 1 is installed so as to have an angle of 80 °.

With the above-described configuration, a magnetic field is generated in the circumferential direction of the winding core 2 by the current flowing through the through portion 4a, and a voltage is induced in the winding 3 by the magnetic field, so that the output terminals ka,
By measuring the voltage from la, the value of the current flowing through the bus 4 can be known. In addition, the penetration portion 4a
The voltage is also induced by the magnetic field generated in the axial direction of the drawing, but this voltage is offset by the voltage caused by the same magnetic field induced in the return line 30. In addition, since the drawer 31 exists, the winding density in the circumferential direction is not uniform, and an error occurs in the measured value.

FIG. 3 is a graph showing the relationship between the position of the lead portion of the winding and the measurement error. In the figure, the vertical axis represents the measurement error ε, and the horizontal axis represents the angle θc. The outer diameter of the core 2 is 420 mm, the inner diameter is 380 mm, and the thickness in the axial direction is 2 mm.
0 mm and the angle θg is 4 °, the curve L1 shows the relationship between the angle θc and the measurement error ε when the distance L is 230 mm, and similarly, the curve L2 is the curve L3 when the distance L is 300 mm. When L is 400 mm, curve L4 is when distance L is 800 mm, and curve L5 is when distance L is 2
The relationship at the time of 000 mm is shown. Both curves are monotonically increasing functions. When the distance L is 230 mm, the error ε is less than or equal to −1% when the angle θc is near 0 °, the error ε increases rapidly as the angle θc increases, and when the angle θc is 30 °. ε is 0%. When the angle θc further increases, the error ε continues to increase while weakening the increase, and finally converges at around 0.5%. The other curves L2, L3, L4, and L5 also show the same tendency as the curve L1 and increase. However, as the distance L increases, the error ε with respect to the change in the angle θc increases.
The rate of increase is smaller. And the distance L is 3
When the distance θ is 00 mm, the angle θc is around 45 °, and when the distance L is 400 mm, the angle θc is around 55 °, and the distance L
Is 800 mm, the angle? C is around 70 degrees, and when the distance L is 2000 mm, the angle? C is around 80 degrees and the error? Is 0%.

As described above, there is a position of the lead portion of the winding where the measurement error becomes zero with respect to the distance between the buses, and the plane formed by the bus 4 is within a practical range of the distance between the buses. , The central angle of the lead portion of the winding with respect to the central axis of the winding core is in the range of 30 to 80 °. Note that when the distance L between the buses is 230 mm, the bus 4 is in contact with the current transformer 1, so it cannot be said that it is an appropriate installation position and is outside the installation range.

For such a reason, an angle corresponding to the distance L and having a measurement error of zero exists at 30 to 80 °, and by setting the angle θc within this range, the measurement error can be suppressed to a low level. it can. Further, by setting the angle θc at an angle where the measurement error is zero based on the actual results, the measurement error can be almost eliminated. In the first embodiment, the angle θc is set to an angle that makes the measurement error zero based on the actual results.

There is a relationship that the measurement error is halved when the angle θg is halved, but the angle at which the measurement error at which the measurement error becomes zero becomes zero does not change. Core 2
When the radius L and the distance L are changed at the same magnification, the angle at which the measurement error is zero does not change. In addition, the winding 3 has a multilayer structure having the number of layers L0, and the outermost layer has no lead-out portion 31 and is wound with a uniform winding density over the entire circumference of the core 2. The number of rewind turns of 30 may be L0. At this time, the measurement error is 1 /
Although it becomes L0 times, the angle at which the measurement error is zero does not change.

Embodiment 2 FIG. 4 is a vertical sectional view showing a method of installing a current transformer according to the present invention and a configuration of a main part of a current transformer according to Embodiment 2 of the present invention.
The cross-sectional view taken along line -I is the same as FIG. In the figure, reference numeral 4 denotes a bus. A winding core 2 having an annular shape with a rectangular cross section is arranged coaxially with the bus bar 4. The winding core 2 is made by mixing magnetic powder into an insulating material 2a made of an insulating material such as glass cloth and a synthetic resin. The magnetic material 2b having a relatively low relative magnetic permeability is formed in a thin annular plate shape by alternately laminating them in the axial direction and solidifying them. Embodiment 1
Similarly to the above, the winding core 2 is wound around the center axis of the rectangular cross section in a single-layer spiral shape over substantially the entire circumference,
An annular coil current transformer 1 is configured. A lead-back line 30 is provided between the spiral 3 and the end face of the core 2 inside the spiral.
Is wound once in the circumferential direction. One end of the winding 3 and one end of the return wire 30 are connected, and the other end is drawn out from the annular coil and serves as output terminals ka and la. The lead portion 31 from which the output terminals ka and la are drawn is a portion where the winding 3 is not wound by the angle θg at the center angle of the core 2.

After passing through the current transformer 1, the bus 4
It is bent in a U-shape, and is configured in the order of a penetrating portion 4a penetrating the current transformer 1, an intermediate portion 4b, and a return portion 4c. The penetrating part 4a and the return part 4c are separated by a distance L. The position of the lead-out portion 31 with respect to the plane defined by the bus bar 4 is set such that the central angle θc of the core 2 is 30.
The current transformer 1 is installed so as to have an angle of 80 °.

With the above configuration, the average relative permeability of the core 2 can be made slightly larger than that of the core. When a current flows through the through portion 4a to be measured, a magnetic field is generated in the circumferential direction of the current transformer 1 which is an annular coil. When the magnetic field generated at this time is H and the magnetic flux density inside the annular coil is B, the current I flowing through the through portion 4a is represented by the following equation. In this equation, μ0 is the magnetic permeability in vacuum, μs is the relative magnetic permeability, and x is the circumferential length of the annular coil. I = ∫H · dx = ∫ ｛B / (μ0 · μs)｝ dx (1)

When the current I flowing through the penetrating portion 4a is a sine wave alternating current having an angular frequency ω, the cross-sectional area of the annular coil interlinking with the magnetic field H is S, and the magnetic flux in this intersecting cross section is Φ, An equation (2) for obtaining the current I is obtained from the equation (1). I = {Φ · Δx / (μ0 · μs · S)} (2)

Further, a minute length Δx in the circumferential direction of the annular coil
Assuming that the number of windings per winding is N and the induced voltage induced by the magnetic field H in the windings between Δx is e, the above equation (2) can be transformed into the following equation (3). | I | = Δx · {e / (N · μ0 · μs · S · ω)} (3)

N / Δx in the equation (3) is the winding density n in the circumferential direction of the annular coil.
Is constant in the circumferential direction of the annular coil, the current I flowing through the penetrating portion 4a is the induced voltage E of the entire annular coil.
Is obtained by the following equation. | I | = E / (n · μ0 · μs · S · ω) (4)

That is, by measuring the induced voltage E induced in the annular coil and applying the measured value to the equation (4),
The current I flowing through the through portion 4a can be known.

In general, the relative permeability μs of the insulator is around 1. From the equation (4), by forming the core 2 with a magnetic permeability μs higher than this, the same output voltage E can be generated by reducing the interlinkage cross-sectional area S of the annular coil.

That is, when the average relative magnetic permeability is μ1, a cross-sectional area of about 1 / μ1 is possible to generate the same output voltage as compared with the case of a core made of an insulating material, and the size is reduced. be able to. The relative permeability of the core 2 is 10
Good degree.

Further, in order to improve the linearity of the induced voltage with respect to the current, it is necessary to avoid the concentration of the magnetic flux on the core 2 due to the portion other than the through portion 4a. The magnetic flux B1 from the return portion 4c entering from the outer peripheral surface of the core 2 and the return portion 4 entering from both end surfaces of the core 2 are provided at the portion of the core 2 on the side of the return portion 4c.
and a magnetic flux B3 from the intermediate portion 4b. Since the composite of the magnetic flux B2 and the magnetic flux B3 is larger than the magnetic flux B1, the lamination direction of the core 2 is set to the axial direction of the through portion 4a. As a result, the concentration of the magnetic flux in the substantially axial direction of the core 2 inside the core 2 can be favorably prevented.

As in the first embodiment, the measurement error can be reduced to zero by the presence of the angle θc corresponding to the distance L and the arrangement of the drawer 31 at this position depending on the actual results.

Third Embodiment FIG. 5 is a cross-sectional view showing a method for installing a current transformer according to the present invention and a configuration of a main part of a current transformer according to a third embodiment. FIG. FIG. 6 is a vertical sectional view taken along line VI. In the figure, reference numeral 4 denotes a bus. A winding core 2 having an annular shape with a rectangular cross section is arranged coaxially with the bus bar 4, and the winding core 2 is a magnetic material having a relatively low relative magnetic permeability, and is made of stainless steel which is also a conductor. , A cutout portion 2c that is partially cut in the circumferential direction is provided. Further, an insulator (not shown) is inserted into the missing portion 2c. As in the first embodiment, a winding 3 is wound around the center axis of a rectangular cross section of the winding core 2 in a single-layer helical shape over substantially the entire circumference, and a current transformer of an annular coil is formed. 1 is configured. A return wire 30 is wound around the winding core 3 once around the end surface of the winding core 2 inside the spiral of the winding 3. One end of winding 3 and return wire 3
0 is connected to one end, and the other end is pulled out from the annular coil and serves as output terminals ka and la. The lead portion 31 from which the output terminals ka and la are drawn is a portion where the winding 3 is not wound by the angle θg at the center angle of the core 2. The missing part 2c and the drawer 31 are arranged at the same location.

After passing through the current transformer 1, the bus 4
It is bent in a U-shape, and is configured in the order of a penetrating portion 4a penetrating the current transformer 1, an intermediate portion 4b, and a return portion 4c. The penetrating part 4a and the return part 4c are separated by a distance L. The position of the lead-out portion 31 with respect to the plane defined by the bus bar 4 is set such that the central angle θc of the core 2 is 30.
The current transformer 1 is installed so as to have an angle of 80 °.

In the case where the winding core 2 is a conductor and has a complicated arrangement such that the bus circuit has a three-phase arrangement, a current flows in the circumferential direction of the winding core 2, and a magnetic flux caused by the current flows to the winding 3. Interlinking,
Although a change in the output voltage has occurred, in the configuration of the third embodiment, since the missing portion 2c is provided, the induced current is
Can be prevented from flowing in the circumferential direction, and the occurrence of the change can be favorably prevented.

When the winding 3 is wound around the missing portion 2c of the winding core 2, this portion becomes an air-core coil and has a relative permeability of 1
About. When the relative permeability in the circumferential direction of the winding core is not constant, a measurement error occurs. A measurement error also occurs from the drawer. For this reason, when these positions are different, both are affected, and the measurement error is further increased.

By arranging the missing portion 2c and the lead-out portion 31 at the same place, it is possible to prevent the occurrence of measurement errors from both, and to reduce the case where the missing portion 2c and the lead-out portion 31 are located at different positions. , The measurement error can be reduced.

Since stainless steel is both a conductor and a low magnetic permeability material, a small current transformer can be formed. Further, since the core is made of a single material, the manufacturing cost can be reduced as compared with the case where the core of the laminate is used.

Also, as in the first embodiment, the measurement error can be reduced to zero by the presence of the angle θc corresponding to the distance L and the arrangement of the drawer 31 at this position depending on the actual results.

[0046]

As described above in detail, according to the current transformer installation method of the first invention, the lead-out portion of the winding is defined by the bus to be measured and the bus arranged parallel thereto. The center angle of the center axis of the winding core with respect to the plane is 30 to 8
By arranging at a position within the range of 0 °, it is possible to reduce the measurement error as compared with the related art. Further, the measurement error can be reduced to zero by arranging it at an optimum position.

According to the current transformer according to the second aspect of the present invention, since the winding core is constituted by a laminated body of the magnetic material and the insulating material, the current transformer has a lower relative permeability than the insulating core. The current transformer can be a core, and thus the current transformer can be reduced in size as compared with the related art.

Further, since the lamination direction of the laminated body is set to the axial direction of the core, the magnetic shield effect is high against magnetic flux entering from both end surfaces of the core, and the magnetic flux is applied in the circumferential direction of the bus passing through the inside of the core. There is no influence on the magnetic flux, so that the output voltage with respect to the measured current can secure sufficient linearity for practical use.

According to the current transformer according to the third aspect of the present invention, the core is made of a conductive material, and the core is provided with a cutout in a part of the core in the circumferential direction. Since the induced current does not flow, it is possible to prevent a change in the output voltage from occurring.

Further, compared with the case of a core using an insulator,
It can be a core with a low permeability, a little higher in relative permeability,
As a result, the same output voltage can be obtained by reducing the cross-sectional area of the core, so that the size can be reduced as compared with the related art.

Further, by reducing the cross-sectional area of the core, the cross-sectional dimension can be reduced as compared with the skin thickness through which the induced current penetrates. The value of the current flowing per volume is sufficiently small and can be neglected.

On the other hand, since the surge has a high frequency, the skin thickness through which the induced current penetrates is sufficiently thin.
The skin thickness becomes very small with respect to the cross-sectional dimensions, and as a result, the induced current flows only in the surface of the core, so that the current value flowing through the unit volume becomes sufficiently large, thereby reducing the induced voltage and reducing the winding voltage. Can be suppressed.

According to the current transformer according to the fourth aspect of the present invention, since the cutout portion of the winding core in the circumferential direction and the lead-out portion of the winding are arranged at the same location, compared to the case where these are arranged at different positions. Since the relative permeability and the winding density of the winding core are different from the others, the total length of the portion causing the measurement error can be shortened, and thus the measurement error can be reduced.

According to the method for installing a current transformer according to the fifth aspect of the present invention, the lead-out portion of the winding is wound around the plane defined by the bus to be measured and the bus arranged parallel thereto. By arranging the center angle of the center axis within a range of 30 to 80 °, it is possible to reduce the measurement error as compared with the related art. Further, the present invention has an excellent effect such that the measurement error can be reduced to zero by arranging it at an optimum position.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a main part of a method for installing a current transformer according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view taken along line II-II of FIG.

FIG. 3 is a graph showing a relationship between a position of a lead portion of a winding and a measurement error.

FIG. 4 is a longitudinal sectional view showing a method of installing a current transformer according to the present invention and a configuration of a main part of a second embodiment of the current transformer.

FIG. 5 is a cross-sectional view showing a method of installing a current transformer according to the present invention and a configuration of a main part of a third embodiment of the current transformer.

6 is a longitudinal sectional view taken along line VI-VI of FIG.

FIG. 7 is a front view of a conventional current transformer.

8 is a longitudinal sectional view taken along line VIII-VIII in FIG.

FIG. 9 is an explanatory diagram illustrating a circumferential distribution of a voltage induced in a current transformer arranged on a U-shaped bus bar.

[Explanation of symbols]

2 core, 2c missing part, 3 windings, 31 lead-out part (winding lead-out part), 4 busbars.

Claims (5)

[Claims] 1. A current transformer having a winding core made of an annular insulator and a winding wound around the winding core is arranged so that a bus passes through the winding core. The position of the lead-out portion of the winding is set within a central angle range of the core of 30 to 80 ° with respect to a plane defined by the generatrix and a generatrix arranged outside and parallel to the core. A method for installing a current transformer, characterized in that: 2. A current transformer comprising: a winding core formed of an annular laminate in which a magnetic material and an insulating material are stacked in an axial direction thereof; and a winding wound on the winding core. vessel. 3. A variation comprising: an annular core made of a conductive material and provided with a cutout in a part in a circumferential direction; and a winding wound on the core. Sink. 4. The current transformer according to claim 3, wherein the lead portion of the winding and the missing portion are arranged at the same position. 5. A winding disposed on a plane defined by the bus and a bus disposed outside of the core and parallel to the bus. 5. The method for installing a current transformer according to claim 2, wherein the position of the drawer is set within a range of the central angle of the core of 30 to 80 [deg.].