JPH09127158A - Direct current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct current sensor, in which a magnetic field generated by two detected conductors are cancelled with high accuracy to be effective for a use as an earth current detector or the like. SOLUTION: The position of conductor for detection piercing and disposed inside a detecting core part for forming the direct current sensor is changeable. In order to dispose the conductor for detection and a detecting coil wound round the detecting ore part in specified positions, a pair of plate-like conductors 1a, 1b for detection formed by a Cu plate are fixed with an insulating resin so as to be disposed in symmetrical positions about an imaginary line connecting between the respective centers of a pair of detecting coils 3a, 3b inside an inside shield part 8a and integrally fixed with a sensor part 10 to a terminal block 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a DC current sensor provided in equipment using various DC currents, and is particularly effective for applications such as a ground fault current detector and the like. -A high-sensitivity DC current sensor having a configuration that can be easily incorporated and arranged in a DC switchboard used for control equipment of a substation.

[0002]

2. Description of the Related Art Conventionally, as a direct current sensor, a shunt resistance type, a mag-amp type, a magnetic multi-vibrator type, a hall element type and the like are known. But,
These DC current sensors are not only complicated in structure, but it is difficult to say that they are structures that can cope with minute current changes, and at present, they have not been put into practical use as highly sensitive DC current sensors.

In view of such a situation, the inventor of the present application has previously proposed a conventional high-sensitivity direct current sensor having a relatively simple structure and having an excellent detection ability even for a minute current change. A direct current sensor having a structure completely different from that of the method has been proposed (EP0 579 462 A, JP-A-6-74978, JP-A-6-194389, JP-A-6-281674, Japanese Patent Application No. 5-297542,
Japanese Patent Application No. 5-352405).

That is, a detection core portion made of a soft magnetic material forming an annulus, a detection coil wound around the detection core portion in a toroidal shape, and periodically arranged in at least a part of the detection core portion in the circumferential direction. A direct current sensor having a basic configuration including a means for forming a magnetic gap, in which a detected conducting wire penetrates inside a detection core part constituting the direct current sensor and flows to the detected conducting wire. This made it possible to measure DC current with high sensitivity.

As an example of the above DC current sensor, there is a DC current sensor having a structure as shown in FIG. That is, the detection core portion 2 made of a soft magnetic material forming an annulus, the pair of detection coils 3a and 3b wound around the detection core portion in a toroidal shape, and further at least in the circumferential direction of the detection core portion 2. As a means for periodically forming a magnetic gap in a part, a pair of excitation core portions 4a, 4b made of a soft magnetic material that are connected in a direction orthogonal to the circumferential direction of the detection core portion 2 and form an annular shape, An exciting coil 5 that is wound around the detection core portion 2 and that periodically excites the detection core portion 2 in a direction orthogonal to the circumferential direction at an orthogonal portion 6 between the detection core portion 2 and the excitation core portions 4a and 4b. It has a configuration having. In the figure, reference numeral 1 denotes a conductor to be detected which is arranged to pass through the void portion of the detection core portion 2.

In such a structure, when a direct current I flows in the conductor 1 to be detected, a magnetic field clockwise in the direction of the direct current I is generated in the detection core portion 2 and a magnetic flux is generated in the detection core portion 2. Φ ₀ is generated. At this time, a predetermined alternating current is passed through the exciting coil 5 to generate a magnetic flux that periodically changes in the α direction in the figure in the pair of exciting core portions 4a and 4b.
When a and 4b are magnetically saturated periodically, the core crossing portion 6 which is a part of the detection core portion 2 in the circumferential direction becomes a so-called substantial magnetic gap in which the relative permeability μ is extremely close to 1, The magnetic flux Φ ₀ in the detection core unit 2 is reduced to Φ ₁ (Φ ₁ approximation 0).

Here, if the alternating current passing through the exciting coil 5 is set to frequency f ₀ and the exciting core portions 4a and 4b are saturated near the peak value of the current, the exciting core portion is excited twice in one cycle of the exciting current. 4a and 4b will be saturated. That is, the core intersection portion 6, which is a part of the detection core portion 2 in the circumferential direction, is saturated, and the magnetic flux Φ ₀ generated in the detection core portion 2 by the direct current I flowing through the detected conductor 1 is 2
It is modulated by f ₀ and the frequency 2f changes with the change of the magnetic flux Φ _0.
A voltage V _{DET of 0} will be generated in the detection coils 3a and 3b.

Regardless of the direction of the direct current I flowing through the conductor 1 to be detected, in any case, the voltage V _DET ∝ DC current I is obtained from the relationship between the magnetic flux Φ ₀ ∝ DC current I and the voltage V _DET ∝ magnetic flux Φ _0.
Therefore, it becomes possible to detect the electromotive force proportional to the direct current I flowing through the conductor 1 to be detected by the detection coils 3a and 3b.

As described above, the DC current sensor shown in FIG. 7 has a relatively simple structure and has an electromagnetically well-balanced structure. Therefore, the DC current sensor is excellent in detecting even a minute current change. It has the ability to realize stable and highly sensitive measurement.

Also, in the DC current sensor having the structure shown in FIG. 8, the DC coil shown in FIG. 7 is different from that shown in FIG. 7 except that the exciting coil is composed of a pair of 5a and 5b and wound around the pair of exciting core portions 4a and 4b. The configuration is similar to that of the current sensor, and the DC current I flowing through the conductor 1 to be detected can be stably and highly sensitively measured by the same operation as described above.

In the DC current sensor having the structure shown in FIG. 9, it is difficult to clearly separate the constituent parts of the detection core part and the excitation core part, and an annular ring which forms a hollow part communicating with the inside in the circumferential direction is formed. The detection core portion 2 and the excitation core portion 4 each having the configuration shown in FIGS.
It is configured so that the functions of a and 4b are both expressed.

That is, the detection core portion 2 made of an annular soft magnetic material forming a hollow portion 7 which communicates with the inside in the circumferential direction.
An exciting coil 5 which is wound around the hollow portion 7 in the circumferential direction to periodically excite the detection core portion 2 in a direction orthogonal to the circumferential direction; and a toroidal shape on the outer peripheral portion of the detection core portion 2. Although it is composed of a pair of detection coils 3a and 3b wound around, the operation is basically the same as that of the DC current sensor having the structure shown in FIGS. I can be measured stably with high sensitivity.

[0013]

The DC current sensor shown in FIG. 7, FIG. 8 and FIG. 9 described above has a simple structure and is capable of highly sensitive measurement as compared with various DC current sensors known in the related art. As a result, the range of applications for DC current sensors has been expanded.

In the above description, the case in which the number of detected conductors penetrating the inside of the detection core portion is one has been described, but the same effect can be obtained in the case of a plurality of conductors. However, when it is used as a ground fault current detector or the like, two detected conductors are arranged inside the detection core section to detect the difference in their round-trip currents. It is necessary to cancel the magnetic field generated by the conductor with high accuracy.

For example, when the operating current (reciprocal current) is 50 A and the ground fault current (differential current) is 1 mA, the ground fault current (differential current) is 1 / 50,000 of the operating current (reciprocal current), which is extremely high. High-precision detection is required, but if an imbalance occurs in the cancellation of the magnetic field generated by the two detected conductors, it becomes difficult to detect the ground fault current (difference current) with high accuracy, and the error output Will occur.

The present invention is proposed in view of the above-mentioned current situation, and in particular, it is possible to cancel a magnetic field generated by two conductors to be detected with high accuracy and is effective as an application of a ground fault current detector or the like. It is intended to provide a DC current sensor having a configuration. Another object of the present invention is to provide a DC current sensor having a configuration that can be easily incorporated and arranged in a DC switchboard used for control equipment of a power generation / substation.

[0017]

As a result of various studies on the configuration for achieving the above-mentioned object, the inventor of the present application found that the position of a conductor to be detected penetratingly arranged inside a detection core portion constituting a direct current sensor was changed. , It is confirmed that the canceling of the magnetic field generated by the detected conductor becomes unbalanced, and further, the detected conductor and the detection coil wound around the detection core portion are arranged at specific positions. The inventors have completed the present invention by finding that the above can be achieved.

That is, according to the present invention, a detection core portion made of a soft magnetic material forming an annulus, a pair of detection coils wound around the detection core portion in a toroidal shape, and at least in the circumferential direction of the detection core portion. In a direct current sensor having a pair of detected conductors penetratingly arranged inside a sensor section having a part for periodically forming a magnetic gap, the pair of detected conductors is connected to a pair of detection coils. The direct current sensor is characterized in that the direct current sensors are arranged symmetrically with respect to an imaginary line connecting the center points.

Further, in the above structure, the pair of lead wires to be detected are each made of a Cu plate, and are integrally fixed to the terminal block together with the sensor portion. Further, these DC current sensors are We also propose a DC current sensor, which is characterized in that a plurality of DC current sensors are arranged in parallel.

As a preferred form of the sensor portion constituting the above DC current sensor, a detection core portion made of a soft magnetic material forming an annular shape, and a pair of detection coils wound around the detection core portion in a toroidal shape, A pair of exciting core portions made of a soft magnetic material that are connected to each other in a direction orthogonal to the circumferential direction of the detecting core portion and form an annular shape; and a detecting core portion wound around each exciting core portion or the detecting core portion. A structure composed of an exciting coil that periodically excites the detection core portion in a direction orthogonal to the circumferential direction at a portion orthogonal to the exciting core portion, and an annular soft material that forms a hollow portion that communicates in the circumferential direction inside. A detection core portion made of a magnetic material, an exciting coil which is wound around the hollow portion in the circumferential direction, and which periodically excites the detection core portion in a direction orthogonal to the circumferential direction, and an outer peripheral portion of the detection core portion. Toroidal We propose a structure comprising a pair of detection coils arranged wound.

In the direct current sensor of the present invention, the fact that the detection core and the excitation core are made of a soft magnetic material forming an annulus is not limited to the so-called ring-shaped structure of the soft magnetic material, but soft magnetic material. It suffices that the materials are connected so as to form an electromagnetic closed circuit. In addition to the rectangular frame shape as shown in FIG. 7, FIG. 8 and FIG. Can be adopted.

As the material of the detection core and the excitation core, permalloy is usually preferable from the viewpoint of magnetic properties and workability, but other known soft magnetic materials such as silicon steel plate, amorphous, electromagnetic soft iron, soft ferrite, etc. It can be used.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the DC current sensor of the present invention will be described based on an embodiment shown in FIGS.
FIG. 1 is a perspective explanatory view of a direct current sensor, FIG. 2 is a plan explanatory view thereof, FIG. 3 is a vertical sectional explanatory view, and FIG. 4 is an operating principle explanatory view.

In the figure, 10 is a sensor section,
As shown in FIG. 7, the DC current sensor having the above-described configuration of FIG. 7 is arranged in the shield case 8 (however, 8a is an inner shield part and 8b is an outer shield part). That is, in FIG. 3, reference numeral 2 is a rectangular frame-shaped detection core portion, and 3a and 3b are a pair of detection coils wound in a toroidal shape at positions facing each other in the circumferential direction of the detection core portion 2,
Reference numerals 4a and 4b denote exciting core portions that are connected to each other in the circumferential direction of the detection core portion 2 in orthogonal directions to form an annular shape, and an excitation coil 5 is wound around the outer circumference of the detection core portion 2.

Reference numerals 1a and 1b are a pair of plate-shaped detected conductors made of a Cu plate, and as shown in FIG.
As described later in detail, the insulating resin 14 is fixed so as to be arranged at a symmetrical position with respect to an imaginary line connecting the center points of the pair of detection coils 3a and 3b. It is integrally fixed to the terminal block 12 together with the sensor unit 10.

Further, a pair of plate-shaped detected conductors 1a, 1b
Are connected on the terminal block 12 by the bolts 13 and the vinyl-coated detection lead wires 11a and 11b connected to the load side and the switchboard side as shown in the figure. 15 is a terminal block 12
And is used when the terminal block 12 is arranged and fixed in the switchboard or the like with bolts or the like (not shown).

The positional relationship between the pair of plate-shaped detected conductors 1a and 1b and the pair of detection coils 3a and 3b in the DC current sensor having the above structure will be described in detail with reference to FIG. When an operating current (reciprocating current) flows through the pair of plate-shaped detected conductors 1a and 1b, a magnetic field is generated around the plate-shaped detected conductors 1a and 1b by the plate-shaped detected conductors 1a and 1b. Here, since the operating currents (reciprocating currents) flowing through the plate-shaped detected conductors 1a and 1b flow in opposite directions, when the magnitudes are equal, the pair of plate-shaped detected conductors 1a, 1b The strength of the magnetic field at the point P on the vertical bisector AA between 1b becomes zero (H = 0). That is, at the point P on the vertical bisector A-A, the magnetic fields generated by the operating currents (reciprocating currents) flowing through the pair of plate-shaped detected conductors 1a and 1b completely cancel each other and become zero. Becomes

Therefore, if the central points 3a-C and 3b-C of the pair of detection coils 3a and 3b are arranged at the position of this point P so as to coincide with each other, the arrangement balance of the pair of plate-shaped detected conductors 1a and 1b is arranged. It is possible to prevent the generation of error output due to. In other words, the pair of plate-shaped detected conductors 1
a and 1b are the center points 3 of the pair of detection coils 3a and 3b, respectively.
By arranging in a symmetrical position with respect to an imaginary line AA connecting aC and 3b-C, the pair of plate-shaped detected conductors 1
The center points 3a-C and 3b-C of the detection coils 3a and 3b can be arranged at positions where the magnetic field generated by the reciprocating current flowing through a and 1b is zero. That is, the action on the detection coils 3a and 3b by the magnetic field generated by the reciprocating current flowing through the pair of plate-shaped detected conductors 1a and 1b is balanced, and as a result, the error output can be prevented.

In the DC current sensor having such a structure, when an operating current (reciprocating current) flows through the pair of plate-shaped detected conductors 1a and 1b, the plate-shaped detected conductors 1a and 1b are detected.
A magnetic field is generated around the plate-shaped conductors 1a and 1b to be detected by 1b. However, since the directions of the currents flow in opposite directions and the magnitudes of the currents are equal, the magnetic fields completely cancel each other out, and the detection coils 3a, 1b No output voltage is generated at 3b.

In such a state, when a ground fault current (differential current) is generated, a difference occurs between the currents flowing through the pair of plate-shaped detected conductors 1a and 1b, and the respective plate-shaped detected conductors 1a and 1b.
There will be a difference in the magnetic field generated around b. As a result, a magnetic flux in a predetermined direction is generated in the detection core portion 2 based on the difference between the magnetic fields generated around the plate-shaped detected conductors 1a and 1b. At this time, when a predetermined alternating current is applied to the exciting coil 5, an output voltage corresponding to the ground fault current (differential current) is generated in the detection coils 3a and 3b based on the operating principle described above.

In the above description, the configuration of the sensor section has been described based on the configuration of FIG. 7, but in the configurations of FIGS. 8 and 9 as well, the positions of the pair of lead wires to be detected and the pair of detection coils are as described above. Similar effects can be obtained by arranging them. Further, the shape of the detection core portion is not limited to that shown in the figure, and means for periodically forming a magnetic gap in at least a part of the circumferential direction of the detection core portion made of a soft magnetic material forming an annulus is provided. Various configurations can be adopted as long as the configurations are provided.

Further, in the above description, the case of the plate-shaped detected conductors made of a Cu plate as the pair of detected conductors has been described, but the present invention is not limited to such a shape and material, and is conventionally used. It is also possible to use a vinyl-coated conductive wire, etc., which is, for example, arranged at the above predetermined position,
A supporting member made of an insulating resin or the like having a through hole for arranging the vinyl-coated conductor is previously arranged inside the sensor part, and the vinyl-coated conductor is inserted into the through-hole of the supporting member when the vinyl-coated conductor is arranged. The configuration of can also be adopted.

Further, in the above description, the pair of detected wires and the sensor portion are integrally fixed to the terminal block, but the presence or absence of the terminal block does not impair the original effect of the present invention. Absent. That is, even if the terminal block is not used, the same effect can be obtained by arranging the positions of the pair of detected conductors and the pair of detection coils in the relationship as described above.

However, with the structure in which the pair of conductors to be detected and the sensor section are integrally fixed to the terminal block as shown in the figure, the state in which the error output due to the reciprocating current is minimized can be maintained most effectively. In addition, it is possible to avoid characteristic changes due to mounting conditions and the like, and it is not necessary to adjust the balance at the time of installation, and it is possible to greatly improve the reliability of the DC current sensor.

In particular, if the terminal block as shown in the figure is used, the installation space is almost the same as that of the conventional terminal block without newly installing wiring as the ground fault current detector or securing a new installation site. It can be easily installed in the switchboard. The other embodiment shown in FIG. 5 comprises a plurality (4 in the figure) of the DC current sensors shown in FIG. 1 arranged in parallel, which is a particularly desirable arrangement in the switchboard.

[0036]

EXAMPLE In order to confirm the effect of the present invention, a direct current sensor having the structure shown in FIG. 1 was prepared and its characteristics were measured. The sensor unit has the configuration shown in FIG. That is, 0.3 mm permalloy (78% Ni-5% M
o-4% Cu-bal. The Fe) thin plate was punched into a predetermined shape and subjected to bending to obtain a core assembly. In addition,
The dimensions of each core part are L = 30 mm, H = 10 mm, W ₁ =
30 mm, W ₂ = 5 mm, and this core assembly was completed by magnetic annealing in a hydrogen gas atmosphere at 1100 ° C. for 3 hours.

As shown in the figure, a silk winding wire having an outer diameter of 0.3 mm is wound around the outer circumference of the detection core portion as an exciting coil for 20 turns, and as a pair of detection coils, the outer diameter of each of the detection core portions is 0. 60 mm 2 formal wire
They were arranged in a turn winding, and further, these were made of 0.3 mm permalloy (78% Ni-5% Mo-4% Cu-bal.
Fe) Surrounded by a shield case made of a thin plate, it was used as a sensor portion constituting the DC current sensor of the present invention.

As the pair of lead wires to be detected, a Cu plate having a cross-sectional dimension of a portion arranged inside the detection core portion having a width of 10 mm and a thickness of 3 mm is used, and virtual points connecting the central points of the pair of detection coils are used. Set the dimension between the facing surfaces to 2mm so that they are symmetrical with respect to the line, and fix them to the terminal block.
The direct current sensor of this invention was completed.

As a comparative example, the structure of the above-mentioned sensor is the same, and a vinyl-coated conductor having an outer diameter of 3 mm is used as a pair of detected conductors on a virtual line connecting the center points of the pair of detection coils. A direct current sensor arranged so as to be in contact with the inside was created.

In each DC current sensor, the output voltage of the detection coil (total value of the pair of detection coils), that is, the error output, when a round trip current of equal magnitude is passed through the pair of detected wires, The measured value of the direct current sensor of the present invention is shown by a broken line, and the measured value of the direct current sensor of the comparative example is shown by a solid line in FIG. The output voltage was previously set to 1 V when the ground fault current was 1 mA.

As is apparent from the figure, in the direct current sensor of the comparative example, the reciprocating current is about ±± 50 A.
Although an error output of about 0.5 V occurred, the value was almost negligible with the DC current sensor of the present invention. Therefore, even if the ground fault current has a very small value (for example, about 1 mA or less) with respect to the value of the round-trip current, it is possible to stably realize highly accurate measurement without being affected by the error output. .

[0042]

The DC current sensor of the present invention is generated by a pair of detected conductors by arranging a pair of detected conductors and a pair of detection coils wound around the detection core portion at specific positions. Since it is possible to cancel the magnetic field with high accuracy without generating imbalance, the error output is prevented from occurring, and the ground fault current (differential current) consisting of a very small value relative to the round-trip current value is also high. It can be detected accurately. Therefore, it is possible to stably provide a configuration that is extremely effective for applications such as a ground fault current detector.

In particular, in a structure in which both the pair of detected wires and the sensor section in which a pair of detection coils are wound and arranged are fixed to the terminal block, characteristic changes due to mounting conditions can be avoided, and balance adjustment during installation is unnecessary. As a result, the reliability is improved, and it is possible to easily incorporate and arrange in the DC switchboard used for the control equipment of the power generation / substation, etc., which is an industrially effective configuration.

[Brief description of the drawings]

FIG. 1 is a perspective explanatory view showing an embodiment of a direct current sensor of the present invention.

FIG. 2 is a plan view of the DC current sensor of the present invention shown in FIG.

FIG. 3 is a vertical cross-sectional explanatory view of the DC current sensor of the present invention shown in FIG.

FIG. 4 is an explanatory view of the operating principle of the DC current sensor of the present invention shown in FIG.

FIG. 5 is a plan view showing another embodiment of the DC current sensor of the present invention.

FIG. 6 is a measurement result of an error output for explaining the effect of the DC current sensor of the present invention, and is a graph showing the relationship between the reciprocating current flowing through the pair of detection target wires and the output power (error output) of the detection coil. .

FIG. 7 is a perspective view showing a conventional DC current sensor.

FIG. 8 is a perspective explanatory view showing a conventional DC current sensor.

FIG. 9 is a perspective view showing a conventional DC current sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detected conducting wire 1a, 1b Plate-shaped detected conducting wire 2 Detecting core part 3a, 3b Detecting coil 3a-C, 3b-C Center point 4a, 4b Exciting core part 5, 5a, 5b Exciting coil 6 Orthogonal part 7 Hollow part 8 Shield case 8a Inner shield part 8b Outer shield part 10 Sensor part 11a, 11b Detection lead wire 12 Terminal block 13 Bolt 14 Insulating resin 15 Through hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Yamaguchi 2-19-1 Minami Suita, Suita City, Osaka Prefecture Sumitomo Special Metals Co., Ltd., Suita Works (72) Inventor Hiroshi Hayashida 3-chome, Wakaoji, Amagasaki City, Hyogo Prefecture Kansai Electric Power Co., Inc. Incorporated Research Institute of Technology (72) Inventor Kiyoshi Moriguchi, 3-chome, Wakaoji, Amagasaki City, Hyogo Kansai Electric Power Co., Inc. Incorporated Research Institute of Technology (72) Isao Otoze 1-6-10, Oyodokita, Kita-ku, Osaka-shi, Osaka Kansai Keiki Industry Co., Ltd.

Claims (5)

[Claims] 1. A detection core portion made of a soft magnetic material forming an annulus, a pair of detection coils wound around the detection core portion in a toroidal shape, and a cycle in at least a part of a circumferential direction of the detection core portion. In a direct current sensor having a pair of detected conductors penetratingly arranged inside a sensor portion having means for forming a magnetic gap, the pair of detected conductors are connected to the center points of a pair of detection coils. A DC current sensor characterized by being placed symmetrically with respect to the connecting virtual line. 2. The direct current sensor according to claim 1, wherein each of the pair of lead wires to be detected is made of a Cu plate and is integrally fixed to the terminal block together with the sensor portion. 3. A direct current sensor comprising a plurality of the direct current sensors according to claim 2 arranged in parallel. 4. A sensor section, a detection core section made of a soft magnetic material forming an annular shape, a pair of detection coils wound around the detection core section in a toroidal shape, and a circumferential direction of the detection core section. A pair of exciting core portions made of a soft magnetic material that are connected in the orthogonal direction to form an annulus, and the exciting core portions or the detecting core portions that are wound around the exciting core portions and are orthogonal to the exciting core portions and the exciting core portions. 2. The DC current sensor according to claim 1, further comprising an exciting coil that periodically excites the detection core portion in a direction orthogonal to the circumferential direction. 5. A detection core part made of an annular soft magnetic material forming a hollow part communicating with the sensor part in the circumferential direction inside the sensor part, and a detection core part wound around the hollow part in the circumferential direction and arranged therewith. 2. The direct current according to claim 1, comprising an exciting coil that is periodically excited in a direction orthogonal to the circumferential direction, and a pair of detecting coils wound around the outer peripheral portion of the detecting core portion in a toroidal shape. sensor.