JP2015052457A - Detector and detection method of magnetic metal foreign-matter in insulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a magnetic metal foreign matter from an insulator at a high sensitivity, when a non-magnetic metal part is included in the insulator such as a connection part of a transformer lead wire.SOLUTION: A detector of a magnetic metal foreign matter in an insulator of an embodiment includes: a coil that is disposed so as to cover a part to be inspected of an inspecting object formed of an insulator including a magnetic metal foreign matter and a non-magnetic metal part, and applies a predetermined DC magnetic field to the part to be inspected; a magnetic field detector that is disposed between the part to be inspected and the coil, and detects a distribution state of the DC magnetic field varied by including of the magnetic metal foreign matter in the part to be inspected; and a DC power supply for supplying DC current to the coil.

Description

  Embodiments described herein relate generally to a magnetic metal foreign object detection device and a detection method inside an insulator.

  Such magnetic metal foreign matter inspection is important because magnetic metal foreign matter such as tool fragments mixed in an insulator used in electrical equipment such as a transformer may cause a reduction in breakdown voltage. As a typical inspection method for such magnetic metal foreign matter, there are a method using an X-ray foreign matter detector and a method using a metal detector for detecting a metal foreign matter using magnetism. In particular, in the transformer lead wire connection part, the insulation paper wound around the lead core wire is peeled off once, the core wire is fastened with bolts, and then the insulation paper is manually rewound again, resulting from bolts and tools. There is a high risk of involving magnetic metal foreign matter, and there is a high need for magnetic foreign matter inspection.

  A metal detector magnetizes an inspection object made of magnetic metal foreign matter or an inspection object containing magnetic metal foreign matter with an electromagnet or a permanent magnet, and captures changes in the magnetic field caused by the presence of the magnetic metal foreign matter in the inspection object. It detects the presence or absence of magnetic metal foreign matter, and has the merit that the apparatus price and maintenance cost can be reduced compared with the X-ray foreign matter detector. As a magnetization method, a method in which an AC magnetic field is generated with a large coil and an object to be inspected is passed therethrough, and a method in which a permanent magnet or the like is scanned with respect to the object to be inspected.

  However, when using a method of detecting a metal foreign object by magnetism, for example, in the inspection of the insulation coating portion of the transformer lead wire, there is a nonmagnetic metal part such as a copper wire in the insulator as the object to be inspected. An eddy current is generated in the non-magnetic metal part, the applied magnetic field is weakened, the detection sensitivity for the magnetic metal foreign substance contained in the insulator is lowered, and it is difficult to detect the magnetic metal foreign substance. There was a problem of becoming.

  Moreover, since there is a magnetic bolt or the like in the central portion of the connection portion of the transformer lead wire, using a magnetization method in which magnetic flux penetrates deep into the connection portion, the bolt is magnetized, There was a problem that it was difficult to detect magnetic metal foreign matter.

  As a means for solving the above-described problems, a method has been proposed in which the entire object to be inspected including the non-magnetic metal part is magnetized and the residual magnetization of the magnetic metal foreign matter in the object to be detected is detected by a magnetic sensor ( For example, see Patent Document 1).

  However, the technique proposed in Patent Document 1 needs to magnetize the inspection object to a magnetic metal foreign object to a level at which residual magnetization can be detected. When such a method is applied to, for example, inspection of a magnetic metal foreign object at the connection portion of a transformer lead wire, the bolt located near the center of the connection portion is magnetized, and not only the residual magnetization of the magnetic metal foreign material. Since the residual magnetization of the bolt is also detected, it is difficult to detect the magnetic metal foreign matter.

JP-A-11-72479

  An object of the present invention is to detect magnetic metal foreign matter from an insulator with high sensitivity when the insulator includes a non-magnetic metal part, such as a connection portion of a transformer lead wire. .

  The magnetic metal foreign object detection device inside the insulator according to the embodiment is disposed so as to cover an inspection site of an inspection object made of an insulator including a magnetic metal foreign material and a nonmagnetic metal site, A coil for applying a predetermined DC magnetic field, and the DC magnetic field that is disposed between the inspection site and the coil and changes due to the magnetic metal foreign matter being contained in the inspection site A magnetic field detection device for detecting a distribution state of the current and a DC power source for supplying a DC current to the coil.

It is a perspective view which shows schematic structure of the magnetic metal foreign material detection apparatus inside the magnetic body in 1st Embodiment. FIG. 2 is a transparent perspective view of the magnetic metal foreign object detection device shown in FIG. 1. It is a figure for demonstrating the detection method of the magnetic metal foreign material by the magnetic metal foreign material detection apparatus shown in FIG.1 and FIG.2. It is a figure for demonstrating the detection method of the magnetic metal foreign material by the magnetic metal foreign material detection apparatus shown in FIG.1 and FIG.2. It is a figure for demonstrating the detection method of the magnetic metal foreign material by the magnetic metal foreign material detection apparatus shown in FIG.1 and FIG.2. It is a permeation | transmission perspective view which shows schematic structure of the magnetic metal foreign material detection apparatus inside the magnetic body in 2nd Embodiment. It is a permeation | transmission perspective view which shows schematic structure of the magnetic metal foreign material detection apparatus inside the magnetic body in 2nd Embodiment.

(First embodiment)
FIG. 1 is a perspective view showing a schematic configuration of a magnetic metal foreign object detection device inside a magnetic body in the present embodiment, and FIG. 2 is a transparent perspective view of the magnetic metal foreign object detection device shown in FIG. 3 to 5 are diagrams for explaining a magnetic metal foreign object detection method by the magnetic metal foreign object detection device shown in FIGS. 1 and 2.

  As shown in FIGS. 1 and 2, the magnetic metal foreign object detection device 10 in the magnetic body according to the present embodiment is provided with a coil (covering the inspection site ST of the inspection object S made of an insulator). (Hereinafter referred to as “transmission coil”) 11 and an additional coil (hereinafter referred to as “reception coil”) 12 as magnetic field detection means disposed between the region to be inspected ST and the coil 11. . A direct current power source 13 is connected to the transmission coil 11, and by applying a predetermined direct current from the direct current power source 13 to the transmission coil 11, a predetermined direct current magnetic field is generated from the transmission coil 11 to the inspection site ST. It is to be applied.

  The “DC magnetic field” in this embodiment and the following embodiments means a magnetic field generated by applying a direct current to the transmission coil 11.

  The receiving coil 12 detects a distribution state (disturbance of distribution) of a direct-current magnetic field generated when the magnetic metal foreign object is included in the inspection site ST of the inspection object S in the magnetic metal foreign object detection method described below. Thereafter, it is connected via a lead 15 to a current measuring device or voltage measuring device 14 for measuring a current or voltage signal corresponding to the detected DC magnetic field.

  The transmission coil 11 is required to cover the entire inspection site ST of the inspection object S, and detects magnetic metal foreign matter in the inspection object S in the detection method described below for the inspection region ST. Since it is required to apply a sufficiently large DC magnetic field, the coil diameter and the number of windings are appropriately determined to satisfy these requirements.

  The receiving coil 12 scans over the entire length direction (Y direction in the figure) of the inspection site ST of the inspection object S in the magnetic metal foreign matter detection method described below, and the above-described direct current. Since it is required to detect the distribution state (distribution disorder) of the magnetic field, the coil diameter is required to be small enough to detect the distribution state, and the number of windings is sufficient to detect the distribution state. The number is such that it can be detected.

  Next, a magnetic metal foreign object detection method using the magnetic metal foreign object detection device 10 shown in FIGS. 1 and 2 will be described with reference to FIGS. In the present embodiment, the inspection object S (inspection site ST) includes a magnetic metal foreign substance D at a substantially central portion in consideration of the structure of the connection portion of the transformer lead wire, and an aluminum foil or the like below Consider a case where a non-magnetic metal portion NM exists.

  First, a direct current is supplied from the direct current power source 13 to the transmission coil 11, and a direct current magnetic field B is generated from the transmission coil 11 as shown in FIG. At this time, if the magnetic metal foreign matter D does not exist in the inspection site ST of the inspection object S, the DC magnetic field B detected by the receiving coil 12 is DC in the width direction (X direction in the figure) of the inspection site ST. As shown in FIG. 4, the distribution state of the magnetic field component Bx has a substantially constant value from one end side to the other end side in the length direction (Y direction in the drawing) of the inspected site ST.

  Therefore, even if the receiving coil 12 is scanned over the entire length direction (Y direction in the figure) of the inspection site ST of the inspection object S, the component Bx of the direct current magnetic field B in the width direction of the inspection site ST. Since the distribution state is constant, no current flows through the receiving coil 12.

  On the other hand, when the magnetic metal foreign material D is included in the substantially central portion of the inspection object S (that is, the inspection site ST) as in this embodiment, the DC magnetic field B is attracted to the magnetic metal foreign material D (Z in the figure). Therefore, as shown in FIG. 5, the component Bx in the width direction of the DC magnetic field at the substantially central portion where the magnetic metal foreign matter D of the site to be inspected ST is locally reduced.

  Therefore, when the receiving coil 12 is scanned over the entire length direction (Y direction in the drawing) of the inspection site ST of the inspection object S, the length direction (Y direction in the drawing) of the inspection site ST. Since the distribution state of the width direction component Bx of the direct current magnetic field B in FIG. 3 changes locally at the substantially central portion thereof, when the receiving coil 12 reaches the substantially central portion of the region to be inspected ST, As the component Bx changes, a current flows through the receiving coil 12. As a result, by measuring this current with the current measuring device 14 or the voltage measuring device 14, the magnetic metal foreign matter D in the inspection object S can be detected.

  In the present embodiment, since the magnetic metal foreign matter D in the inspection object S is detected using the DC magnetic field B (change) generated from the transmission coil 11, aluminum is provided below the magnetic metal foreign matter D. Even if a nonmagnetic metal part NM such as a foil is present, eddy current does not occur in the nonmagnetic metal part NM. Accordingly, an excessive decrease in the DC magnetic field B can be suppressed, and thereby the width direction component Bx of the DC magnetic field B can be held to a certain level. For this reason, since the magnetic field intensity (Bx) relating to the detection of the magnetic metal foreign matter D can be sufficiently maintained, the magnetic metal foreign matter D can be detected with sufficiently high detection sensitivity.

  Further, since no eddy current is generated in the nonmagnetic metal part NM, the magnetic field intensity (Bx) relating to the detection of the magnetic metal foreign substance D even when the magnetic metal foreign substance D exists close to the nonmagnetic metal part NM. Since the magnetic metal foreign matter D can be detected with sufficiently high detection sensitivity.

  Furthermore, in the present embodiment, when detecting the magnetic metal foreign matter D, the DC magnetic field B uses the distribution state of Bx in the width direction (X direction in the drawing) of the site ST to be inspected. Like a connection part etc., the influence of magnetic metal bodies, such as a bolt which exists deep inside, can be disregarded. Therefore, it is possible to detect the metallic magnetic foreign substance D in the inspection object S without being affected by the magnetic metal body essential in the inspection object S.

  In the present embodiment, the single receiving coil 12 is scanned along the length direction (Y direction in the figure) of the inspection site ST of the inspection object S. However, a plurality of receiving coils are prepared, At the same time, scanning in the length direction can be performed. Further, a plurality of receiving coils may be arranged and scanned in the circulation direction of the region to be inspected ST. Furthermore, a magnetic body may be disposed in the core of the transmission coil 11 in order to increase the DC magnetic field.

(Second Embodiment)
FIG. 6 is a transparent perspective view showing a schematic configuration of the magnetic metal foreign object detection device inside the magnetic body in the present embodiment.

  As shown in FIG. 6, the magnetic metal foreign object detection device 20 of the present embodiment is replaced with a single receiving coil 12 in the magnetic metal foreign object detection device 10 of the first embodiment shown in FIGS. A first additional coil (hereinafter referred to as “first reception coil”) 22-1 and a second additional coil (hereinafter referred to as “second reception coil”) 22-2 are disposed, The difference is that scanning is performed in the opposite directions along the length direction (Y direction in the drawing) of the inspection site ST from the substantially central portion of the inspection site ST of the inspection object S.

  In the magnetic metal foreign object detection device 10 of the first embodiment, when the width direction (X direction) component Bx of the DC magnetic field B is not uniform in the width direction (X direction), the receiving coil 12 is scanned. Based on the above-described non-uniformity of the DC magnetic field component Bx in the width direction, even when the magnetic metal foreign matter D does not exist, current flows in the receiving coil 12 and the magnetic metal foreign matter D is accurately detected. May not be possible.

  However, in the present embodiment, the first receiving coil 22-1 and the second receiving coil 22-2 are prepared, and these receiving coils are inspected from the substantially central portion of the inspection site ST of the inspection object S. Since scanning is performed in opposite directions along the length direction of the portion ST (Y direction in the figure), the first receiving coil 22-based on the non-uniformity of the DC magnetic field component Bx in the width direction described above. The currents flowing through the first and second receiving coils 22-2 are substantially equal, and by taking the difference between these currents, the non-uniformity of the DC magnetic field component Bx can be canceled. Therefore, the first receiving coil 22-1 and / or the second receiving coil 22-2 detects a change in the DC magnetic field component Bx in the width direction caused by the magnetic metal foreign matter D, and detects the magnetic metal foreign matter D. Can be performed accurately.

  Since other features and operational effects are the same as in the first embodiment, description thereof is omitted in this embodiment.

(Third embodiment)
FIG. 7 is a transparent perspective view showing a schematic configuration of the magnetic metal foreign object detection device inside the magnetic body in the present embodiment.

  As shown in FIG. 7, the magnetic metal foreign object detection device 30 of the present embodiment is replaced with a single reception coil 12 in the magnetic metal foreign object detection device 10 of the first embodiment shown in FIGS. The difference is that a magnetic sensor 32 including a plurality of magnetic sensor elements 32A is disposed over the entire inspection site ST of the inspection object S.

  In the magnetic metal foreign object detection device 10 of the first embodiment, when the width direction (X direction) component Bx of the DC magnetic field B is not uniform in the width direction (X direction), the receiving coil 12 is scanned. Based on the above-described non-uniformity of the DC magnetic field component Bx in the width direction, even when the magnetic metal foreign matter D does not exist, current flows in the receiving coil 12 and the magnetic metal foreign matter D is accurately detected. May not be possible.

  However, in this embodiment, since the magnetic sensor 32 including the plurality of magnetic sensor elements 32A is disposed over the entire inspection site ST of the inspection object S, the above-described DC magnetic field component Bx in the width direction described above is provided. Based on the non-uniformity, the currents flowing through the magnetic sensor elements 32A of the magnetic sensor 32 become substantially equal, and the non-uniformity of the DC magnetic field component Bx can be canceled by taking the difference between these currents. Therefore, the magnetic sensor 32 can detect a change in the DC magnetic field component Bx in the width direction caused by the magnetic metal foreign matter D and accurately detect the magnetic metal foreign matter D.

  Further, since the magnetic sensor 32 itself has higher sensitivity than the above-described receiving coil 12, in addition to the improvement in detection sensitivity due to the above-described difference, the detection sensitivity by the magnetic sensor 32 itself can be improved.

  Further, since the magnetic sensor 32 itself has a high detection sensitivity, for example, the magnetic sensor 32 is constituted by a single magnetic sensor element 32A, and the length direction of the inspected site ST (Y in the figure), as in the first embodiment. Even in the case of scanning in the direction), it is possible to detect a change in the DC magnetic field component Bx in the width direction with high sensitivity compared to the receiving coil 12 in the first embodiment, and to detect the magnetic metal foreign matter D. It will be possible to do accurately.

  Since other features and operational effects are the same as in the first embodiment, description thereof is omitted in this embodiment.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10, 20, 30 Magnetic metal foreign object detection device inside insulator 11 Coil (transmitting coil)
12 Additional coil (receiver coil)
13 DC power supply 14 Current measuring instrument or voltage measuring instrument 15 Conductor S Inspected object ST Inspected part B DC magnetic field D Metallic foreign material NM Nonmagnetic metal part 22-1 First additional coil (first receiving coil)
22-2 Second additional coil (second receiving coil)
32 Magnetic sensor 32A Magnetic sensor element

Claims (11)

A coil for applying a predetermined direct-current magnetic field to the inspected part, which is disposed so as to cover the inspected part of the inspected object including an insulator including a magnetic metal foreign matter and a nonmagnetic metal part;
A magnetic field detection device that is disposed between the inspection site and the coil and detects a distribution state of the DC magnetic field that changes due to the magnetic metal foreign matter included in the inspection site;
A direct current power source for supplying direct current to the coil;
A magnetic metal foreign matter detection device inside an insulator, comprising:   2. The magnetic metal inside an insulator according to claim 1, wherein the magnetic field detection means is an additional coil and is configured to scan over the entire length of the region to be inspected. Foreign object detection device.   The additional coil includes a first coil and a second coil having the same shape, and the first coil and the second coil are opposite to each other in the length direction of the region to be examined from the central portion thereof. The apparatus for detecting a magnetic metal foreign substance inside an insulator according to claim 2, wherein the apparatus is configured to scan over the entire length direction.   2. The magnetic metal foreign matter inside an insulator according to claim 1, wherein the magnetic field detection means is a magnetic sensor and is configured to scan over the entire length direction of the inspection site. Detection device.   2. The magnetic metal foreign object detection in an insulator according to claim 1, wherein the magnetic field detection means is a plurality of magnetic sensors and is arranged over the entire length direction of the part to be inspected. apparatus. A coil is disposed so as to cover a portion to be inspected of an inspection object made of an insulator including a magnetic metal foreign matter and a non-magnetic metal portion, and a DC current is supplied to the coil from a DC power source, whereby the coil Generating a predetermined DC magnetic field from and applying the DC magnetic field to the site to be inspected;
Disposing a magnetic field detection device between the inspected part and the coil, and detecting a distribution state of the DC magnetic field that changes due to the magnetic metal foreign matter being included in the inspected part;
A magnetic metal foreign object detection method inside an insulator, comprising:   7. The magnetic metal foreign matter detection method in an insulator according to claim 6, wherein the magnetic field detection means is an additional coil, and scans the entire length of the region to be inspected.   The additional coil includes a first coil and a second coil having the same shape, and the first coil and the second coil are opposite to each other in the length direction of the region to be examined from the central portion thereof. The method according to claim 6, wherein scanning is performed over the entire length direction.   7. The magnetic metal foreign matter detection method in an insulator according to claim 6, wherein the magnetic field detection means is a magnetic sensor, and scans the entire length of the region to be inspected.   7. The magnetic metal foreign object detection method in an insulator according to claim 6, wherein the magnetic field detection means is a plurality of magnetic sensors and is disposed over the entire length direction of the inspected part. .   The magnetic metal foreign object is detected by detecting a distribution state of a magnetic field component of the DC magnetic field in a width direction of the site to be inspected, according to claim 6. Metal foreign matter detection method.

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