JP2005257594A - Fault region detecting method for conductor of wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently accurately detect a fault region in a wire easily with a small magnetic sensor by utilizing a magnetic field component in a longitudinal direction of the wire caused by current perturbation in the fault region of the conductor of the wire. <P>SOLUTION: In the fault region of conductor in the wire, a local sudden variation magnetic field occurs due to the current perturbation and a large circumferential circuit magnetic field due to a conductor electric current works. When the angle between the sensing direction of the magnetic sensor and the longitudinal direction of the wire is set to θ, the magnetic sensing quantity of the magnetic sensor to the circumferential circuit magnetic field and the sudden variation magnetic field changes with the angle θ. As the angle θ is controlled so as to contain the magnetic sensing quantity within the measurement rage of the magnetic sensor and local sudden variation magnetic field due to current perturbation is sensed even with a little movement of the magnetic sensor, the fault region of the conductor can be exactly found. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for detecting a conductor defect portion of an electric wire, and is useful for detecting defects (defects) such as wire conductor breakage, scratches, non-conductor formation, and deterioration such as stress corrosion cracking.

One of the methods to detect defects and defects such as wire breakage, scratches, non-conductivity, and deterioration due to stress corrosion cracking, etc., the load current that is actually flowing is disturbed in the defective part, and the change in the magnetic field generated thereby is detected. A method of detecting is known.
When the defect occurs, the contour of the conductor cross section at that location becomes non-circular, the center of the current path of the cross section shifts, and the distribution of the peripheral circuit magnetic field based on the conductor current changes. It has been proposed to detect a defective part by paying attention to this fact. (Patent Document 1, Non-Patent Document 1)

Japanese Patent Laid-Open No. 10-73631 Takashi Nonaka and two others, “Fundamental study on non-destructive magnetic flaw detection of electric wires” T, IEEEjapan, Vol, 121-A, No. 3,2001, p282-287

In Patent Document 1, as shown in FIG. 9, search coils 1o and 1o ′ are arranged around the electric wire at a position equidistant from the center of the electric wire in a plurality of pairs separated by 180 °, and the core direction of the search coil and the electric wire The tangential direction of the concentric circles is matched, and the difference between the outputs of both search coils of each pair is used as the sensor output.
In FIG. 9, when the displacement of the center of the current path cross section of the stranded wire conductor is zero, that is, there is no change in the circumferential circuit magnetic field distribution, the outputs of both coils are equal and the sensor output is 0, indicating no defect. When the peripheral circuit magnetic field distribution change occurs, the outputs of both coils are not equal and a sensor output is generated, and it is determined that there is a defect.

任意座標点ｐ1(x1,y1)における磁束密度(Ｂｘ1，Ｂy1)及びｐ2(x2,y2)における磁束密度(Ｂｘ2，Ｂy2)をサーチコイルにより測定し、これらの測定値から電流路断面の中心座標Ｃ1(Cx1,Cy1)を計算し、この中心座標の変位から撚線導体の欠陥箇所を評価している。 In Non-Patent Document 1, as shown in FIG. 10, the center C1 (Cx1, Cy1) of the current path cross section has arbitrary coordinate points p1 (x1, y1) and p2 (x2, y2) and these arbitrary coordinate points p1 (x1, y1). ) And magnetic flux density (Bx1, By1) and (Bx2, By2) at p2 (x2, y2)

The magnetic flux density (Bx1, By1) at the arbitrary coordinate point p1 (x1, y1) and the magnetic flux density (Bx2, By2) at p2 (x2, y2) are measured by the search coil, and the center coordinates of the current path cross section are obtained from these measured values. C1 (Cx1, Cy1) is calculated, and the defective portion of the stranded conductor is evaluated from the displacement of the center coordinates.

  However, in the above conventional example, during the movement of the magnetic sensor along the electric wire, the shake of the magnetic sensor with respect to the axis of the electric wire is unavoidable, and this shake causes a relative shift of the center of the current path cross section of the stranded conductor. Therefore, it is difficult to accurately detect a defective portion of the conductor.

When the conductor current is I, the magnetic field strength H at a distance r from the conductor center is
H = I / (2πr)
Given in.
A current of several tens of A to several hundreds of A is passed through the wired wire, and the magnetic flux density on the outer periphery of the wire is extremely high. For example, if the current value is 150 A and the wire radius is 15 mm, the magnetic flux density on the wire surface is as high as 1600 A / m. The magnetic field sensor has a measurement limit, and it is difficult to measure a high magnetic field of 1600 A / m.
However, in the above-described conventional example, the search coil is arranged with its magnetic sensing direction directed to the direction of the circumferential circuit magnetic field of the electric wire. It is necessary to arrange them at positions that are considerably separated, and an increase in the size of the sensor is inevitable.
Furthermore, in the conventional example described in Patent Document 1, two search coils are arranged around the electric wire at positions spaced equidistant from the center of the electric wire in pairs separated by 180 °, and the current center of the conductor path cross section of the stranded wire conductor is arranged. The sensor output is the difference between the outputs of the two search coils at the time of deviation, but the change ΔH in the ambient magnetic field strength H with respect to the deviation ΔL is given by ΔH = HΔL / r, and the search coil is located far away from the center of the wire. If r is increased by arranging it, the output difference between the two search coils is reduced accordingly, the sensor output ΔH is lowered, and it is difficult to ensure sufficient detection sensitivity.

  Recently, magneto-impedance effect elements have been developed as magnetic field sensor elements with high magnetic field detection resolution and micro dimensions.

  The object of the present invention is to easily detect a defective portion in a wire with sufficiently high accuracy with a small magnetic sensor using a magnetic field component in the longitudinal direction of the wire caused by current disturbance at the defective portion of the conductor of the wire. Makes it possible to do.

  The conductor defect location detection method for an electric wire according to claim 1 is configured such that the magnetic sensor is moved along the electric wire with the direction of magnetic sensing of the magnetic sensor in the middle direction between the parallel direction and the perpendicular direction with respect to the longitudinal direction of the electric wire, It is characterized in that a conductor defect portion of an electric wire is detected from an output change of the magnetic sensor.

  According to a second aspect of the present invention, there is provided a method for detecting a defective conductor portion of an electric wire according to the first aspect of the present invention, wherein the magnetic impedance effect type magnetic sensor having a magnetic impedance effect element as a sensor element is used as a magnetic sensor. Features.

A local steeply changing magnetic field based on current disturbance is generated and a large peripheral circuit magnetic field based on a conductor conduction current acts on a defective portion of a conductor in an electric wire. Assuming that the angle between the magnetic sensing direction of the magnetic sensor and the longitudinal direction of the electric wire is θ, the magnetic sensitivity of the magnetic sensor with respect to the circumferential circuit magnetic field and the steeply changing magnetic field changes according to the angle θ.
In the present invention, the angle θ is adjusted so that the amount of magnetic sensitivity falls within the measurement range of the magnetic sensor, and even if the magnetic sensor is slightly deviated, the local steeply changing magnetic field based on the current disturbance can be detected. It is possible to reliably detect a defective portion of the conductor.
In addition, a magnetic sensor in which the magneto-impedance effect element is oriented at an angle θ with respect to the longitudinal direction of the electric wire and the magneto-impedance effect element is close to the surface of the electric wire can be used. Therefore, the detection operation can be easily performed with high sensitivity.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a basic configuration of a magnetic sensor used in the present invention.
In FIG. 1, reference numeral 1 denotes a magneto-impedance effect element, which has a zero magnetostriction or a negative magnetostriction having an outer shell portion in which magnetic domains whose spontaneous magnetization directions are opposite to each other in the circumferential direction of the wire are alternately separated by domain walls. An amorphous alloy wire is used. The inductance voltage component in the output voltage between both ends of the wire generated when a high-frequency excitation current is passed through an amorphous magnetic wire having zero magnetostriction or negative magnetostriction is obtained by the circumferential magnetic flux generated in the cross section of the wire. This occurs due to the magnetization of the easily magnetizable outer shell in the circumferential direction. Therefore, the circumferential magnetic permeability mu _theta depends on the circumferential direction of magnetization of Dosotokara portion. Therefore, when a detected magnetic field is applied in the axial direction (maximum magnetosensitive direction) of the energized amorphous wire, the circumferential direction magnetic flux and the detected magnetic field magnetic flux generated by the energization are combined in the circumferential direction. The direction of the magnetic flux acting on the easily magnetized outer shell part is deviated from the circumferential direction, and the magnetization in the circumferential direction is less likely to occur, the circumferential permeability μ _θ changes, and the inductance voltage changes. Will do. This fluctuation phenomenon is called a magnetic inductance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a detected wave (signal wave). Further, when the frequency of the energization current is in the order of MHz, a high-frequency skin effect appears greatly, and the skin depth δ = (2ρ / wμ _θ ) ^1/2 (μ _θ is the circumferential permeability, ρ as described above. electrical resistivity, w is shows the angular frequency, respectively) is changed by mu _theta, as the mu _theta is the so changed by the detected magnetic field, the resistance voltage division also be detected magnetic field in the wire between both ends output voltage It will fluctuate with. This fluctuation phenomenon is called a magneto-impedance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a detected wave (signal wave).

  In FIG. 1, 2 is a high-frequency power source for applying a high-frequency excitation current to the magneto-impedance effect element, and 3 is a modulation of the high-frequency excitation current (carrier wave) by a detected magnetic field (signal wave) acting in the axial direction of the magneto-impedance effect element. Demodulation circuit for demodulating the modulated wave thus generated, 4 an amplification circuit for amplifying the demodulated wave, 5 an output terminal, 6 a negative feedback coil, and 7 a bias magnetic field coil. For the magneto-impedance effect element 1, an amorphous ribbon, an amorphous sputtered film, or the like can be used in addition to zero magnetostrictive or negative magnetostrictive amorphous wires.

In the magneto-impedance effect element, as described above, the direction of the magnetic flux acting on the outer shell portion that is easily magnetized in the circumferential direction is obtained by combining the circumferential magnetic flux based on the excitation current and the axial magnetic flux due to the detected magnetic field. Due to the deviation from the circumferential direction, the circumferential magnetic permeability μ _θ changes, the inductance is changed, and the impedance is changed by the change of the skin depth of the high frequency skin effect of the circumferential magnetic permeability μ _θ . Accordingly, although even the circumferential direction positional shift phi by the synthesized magnetic field by ± of the detected magnetic field becomes ± phi, the circumferential direction of the magnetic field reduction ratio cos (± phi) is unchanged, the degree of reduction in thus mu _theta is of the detected magnetic field It does not change depending on the direction. Accordingly, the detected magnetic field-output characteristics are substantially bilaterally symmetrical with respect to the y axis when the detected magnetic field is taken on the x axis and the output is taken on the y axis as shown in FIG. This detected magnetic field-output characteristic is non-linear. With non-linear characteristics, it is difficult to measure with high sensitivity. Therefore, negative feedback is applied by the negative feedback coil 6 to linearize the characteristics as shown in FIG. In FIG. 2B, Δw is a linear range where the gain without negative feedback is very large and the gain is determined only by the feedback rate β. However, since the polarity of the detected magnetic field cannot be determined with this output characteristic, the bias magnetic field is applied by the bias coil 7 so that the polarity can be determined as shown in FIG. That is, the characteristic of (b) in FIG. 2 is moved in the negative direction of the x-axis by the bias magnetic field, and the maximum range −Hmax to + Hmax of the detected magnetic field is within the range of the single oblique line region. Further, as shown in FIG. 2 (d), a linear characteristic passing through the origin is obtained by adjusting the zero point. Therefore, in FIG. 2D, when the detected magnetic field is + He, the output is + Eo, and when the detected magnetic field is -He, the output is -Eo, and the detected magnetic field can be accurately measured based on polarity discrimination. .

As shown in FIG. 3, an operational amplifier Q (negative feedback path insertion impedance Z ₂ , input side insertion impedance Z ₁ ) that applies negative feedback from the output to the inverting input terminal is used to obtain the linear output characteristics capable of discriminating the polarity. It can also be used. In this case, if the resistance inserted in the negative feedback coil is R, the number of turns of the coil is n, the length is L, the gain of the demodulation amplifier 34 is A, the detected magnetic field is Hex, and the output is Eout,

A >> Z ₁ RL / (Z ₂ n)

Under

Eout = RLZ ₁ Hex / (nZ ₂ ) + VccZ ₁ R / [Z ₂ (Z ₂ + R)]

Is established, and the output characteristics can be shifted in the ± direction of the x-axis by adjusting various constants (Z ₁ , Z ₂ , resistance R, coil turns n, etc.), and the diagonal straight line portion whose polarity can be discriminated by the adjustment 2 can be positioned within the range of the maximum detected magnetic field ± Hmax, and the linearity output characteristics capable of discriminating the polarity as shown in FIG. 2 (d) can be obtained by adjusting the zero point in the y-axis direction. it can.

FIG. 4 (a) is a drawing showing an example of a magnetic sensor used in the present invention, in which Se is a sensor, Ca is an electric wire, and M is a ground measuring instrument. An electric wire holding wheel is attached to the sensor, and the sensor is moved by pulling the wire, but these configurations are not shown.
FIG. 4B is a circuit diagram of the sensor.
In FIG. 4, p is a substrate. Reference numeral 1 denotes a magneto-impedance effect element, which is provided with a negative feedback coil for making the output characteristics linear and a bias coil for making it possible to determine the polarity of the output characteristics.

5A is a side view showing an example of the magneto-impedance effect element with a coil, FIG. 5B is a bottom view, and FIG. 5C is a cross-sectional view of FIG. FIG.
In FIG. 5, reference numeral 100 denotes a substrate chip, and for example, a ceramic plate can be used. Reference numeral 101 denotes an electrode provided on one surface of the substrate piece, and includes an element connecting projection 102. This electrode can be provided by printing and baking a conductive paste, for example, a silver paste. 1x is a magneto-impedance effect element connected between the protrusions 102 and 102 of the electrodes 101 and 101 by soldering or welding. As described above, an amorphous wire, amorphous ribbon, sputtered film or the like having zero or negative magnetostriction can be used. 103 is a C-type iron core, 6x is a negative feedback coil wound around the C-type iron core, 7x is also a bias magnetic field coil, and the magneto-impedance effect element 1x and the C-type iron core 103 constitute a loop magnetic circuit. Thus, both ends of the C-shaped iron core 103 are fixed to the other surface of the substrate piece 100 with an adhesive or the like. The iron core material may be a magnetic material having a small residual magnetic flux density. Examples thereof include permalloy, ferrite, iron, amorphous magnetic alloy, magnetic powder mixed plastic, and the like. 104 and 104 are lead conductors joined to the electrodes 102 and 102 by welding or the like.

In FIG. 4, u is a magneto-impedance effect element with a coil. p is a substrate, and the magneto-impedance effect element u with coil is supported by the lead conductor 104, and the lead conductor is set so that the magnetosensitive direction (axial direction) of the magneto-impedance effect element 1 is an angle θ with respect to the longitudinal direction of the electric wire Ca. 104 is bent.
Reference numeral 2 denotes a high-frequency current source for exciting the magneto-impedance effect element. The magnetic field to be detected (wire longitudinal component of the magnetic field generated based on the current disturbance at the defective portion of the conductor) is used as a signal wave, and the high-frequency excitation current is a carrier wave. The modulated wave as shown above appears at the output end of the magneto-impedance effect element. Reference numeral 3 denotes a demodulation circuit, which demodulates the modulated wave and outputs the signal wave. Reference numeral 4 denotes an amplifier. The output is negatively fed back to the magneto-impedance effect element 1 through the negative feedback coil 6 and the output is linearized. In addition, a bias magnetic field is applied to the magneto-impedance effect element 1 through the bias coil 7 with the + Vcc power source, and the polarity of the output characteristics can be discriminated.
The high-frequency current source, the demodulation circuit, and the amplifier are mounted on the substrate.

  According to the present invention, in order to detect a defective portion of a conductor of an electric wire, the magnetic sensor is attached to the electric wire so that the magnetic sensing direction of the magnetic sensor is at an angle θ between the parallel direction and the perpendicular direction with respect to the longitudinal direction of the electric wire. The position where the change in the output of the magnetic sensor occurs is determined as a defective portion of the conductor of the electric wire.

When a defect occurs in the conductor of the electric wire, the conductor cross section at the occurrence location is reduced and the current is reduced as shown in FIG. 6 (a), so that a pair is formed as shown in FIG. 6 (b). Reverse polarity current poles p and p 'can be assumed, and a magnetic field is generated by the current holes.
Considering the distribution pattern of the perpendicular component Hy along the longitudinal direction of the electric field of the magnetic field, high-density magnetic flux is condensed between the current poles p and p ′ having a narrow interval, and the magnetic flux is canceled and coarsened outside the current pole. Because of the density, as shown in FIG. 6C, the pattern has a steep change near the defect location e and a high peak value.
When the magnetic sensor is moved in the longitudinal direction of the electric wire by setting the angle between the longitudinal direction of the electric wire and the magnetic sensor to θ, the magnetic sensitivity of the magnetic sensor with respect to the perpendicular component Hy becomes Hy · cos θ. Further, since the magnetic sensitivity of the magnetic sensor with respect to the circumferential circuit magnetic field Hc caused by the current flowing through the conductor is Hc · cos θ, the total magnetic sensitivity is given by (Hy · cos θ + Hc · cos θ).
Hy · cos θ is a magnetic field that is suddenly sensed when the magnetic sensor passes through a defective conductor. On the other hand, Hc · cos θ is a magnetic field that is constantly sensed during the movement of the magnetic sensor, and the total magnetosensitive amount ( If Hy · cos θ + Hc · cos θ) is written together with the magnetosensitive amount-output characteristics of the magnetic sensor, it is as shown in FIG.
In the present invention, by adjusting the angle θ of the magnetic sensor with respect to the longitudinal direction of the electric wire, the total amount of magnetic sensitivity (Hy · cos θ + Hc · cos θ) is within the limit that can be accommodated within the measurement range −Hmax to + Hmax. The magnetic field sensor is moved as much as possible in the longitudinal direction of the electric wire at this inclination angle θ, a steeply changing magnetic field is detected, and the magnetic field sensor position at the time of detection is determined as a defective portion of the conductor.

  In the above embodiment, the number of magneto-impedance elements to be used is one, but two magneto-impedance effect elements are arranged with the electric wire in the center, and as shown in FIG. The magnetic field generated on the basis of, for example, one magneto-impedance effect element 1a in the wire longitudinal direction path aa ', and the other magneto-impedance effect element 1b in the distance about the half circumference of the wire with respect to the wire longitudinal direction path a-a'. If the wire is moved along the wire longitudinal direction path bb ′ separated by w / 2, one of the paths can be sufficiently close to the defective portion e of the conductor, and the magnetic sensor moving along the path is sensitive. Since the magnetosensitive amount Hy · cos θ of Hy can be increased, it is possible to well reduce the influence of the detection sensitivity on the path.

It is drawing which shows the magneto-impedance effect type sensor used in this invention. It is drawing which shows the output characteristic of the magneto-impedance effect type sensor used in this invention. It is drawing which shows another example of the magneto-impedance effect type sensor used in this invention. It is drawing which shows an example of the sensor for a conductor defect location detection used in this invention. It is drawing which shows the magneto-impedance effect element with a coil in the sensor of FIG. It is drawing which shows the magnetic field detected with the conductor defect location detection method of the electric wire which concerns on this invention. It is drawing which shows the relationship between angle (theta) with respect to the electric wire of the magnetic sensing direction of a magnetic sensor in the conductor defect location detection method of the electric wire which concerns on this invention, and the output characteristic of a sensor. It is drawing which shows another Example of the conductor defect location detection method of the electric wire which concerns on this invention. It is drawing which shows a prior art example. It is drawing which shows the prior art example different from the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magneto-impedance effect element 2 Current source for high frequency excitation 3 Demodulation circuit 4 Amplifier Ca Electric wire e Defect location of conductor

Claims (2)

Move the magnetic sensor along the electric wire with the magnetic sensing direction of the magnetic sensor in the middle direction between the parallel direction and the perpendicular direction to the longitudinal direction of the electric wire, and detect the conductor defect location of the electric wire from the change in output of the magnetic sensor A method for detecting a conductor defect portion of an electric wire. The method for detecting a conductor defect portion of an electric wire according to claim 1, wherein a magnetic impedance effect type magnetic sensor using the magnetoimpedance effect element as a sensor element is used as the magnetic sensor.

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