JPH1096756A - Detecting method for defect of insulated wire and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the defective part of a conductor in a hot-line state to be detected, reduce generation of dislocation of a sensor and detection error due to unblanced insulator thickness, and improve detecting sensitivity of the defective part such as breaking of element wire. SOLUTION: A magnetic field sensor 2 and a distance sensor 7 are arranged in parallel in the lengthwise direction of an insulated wire 1, a distance up to the surface of a conductor 1a is measured, the induced voltage of the magnetic field sensor 2 based on the magnetic field generated at letting flow alternating current is computed from the distance data of the distance sensor 7, this computed result is compared with the induced voltage actually detected by the magnetic field sensor 2, and hence existence of abnormality of the concuctor 1a is discriminated, by whether difference is generated between both or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a defect in an insulated wire, and more particularly, to a method for detecting a defective portion of an insulated wire such as an overhead distribution line due to stress corrosion cracking or broken wire of a conductor. The present invention relates to a technique for detecting with high accuracy.

[0002]

2. Description of the Related Art As a technique for detecting whether or not a defective portion due to stress corrosion cracking or broken wire has occurred in a conductor portion of an insulated wire such as an overhead distribution wire, as shown in FIG. For example, two magnetic field sensors (search coils) 2 are arranged at 180 ° intervals around 1 to detect a magnetic field generated by a load current flowing through the insulated wire 1 and
A method is known in which the output of the magnetic field sensor 2 is sent to a differential amplifier 5 via a low-pass filter 3 and a preamplifier 4, and the difference voltage is output to a voltmeter or the like via another low-pass filter 6 for measurement. Have been.

[0003]

However, when the magnetic field of the insulated wire 1 is detected by the two magnetic field sensors 2, as shown in FIG. 5, the two magnetic field sensors 2 are positioned at the center of the conductor 1 a. If the magnetic field sensors 2 are arranged at a distance, the abnormality of the conductor 1a can be accurately detected. However, as shown in FIG. As shown in FIG. 7, the insulating coating 1b of the insulated wire 1
Is uneven, or when a protrusion is formed on the surface of the insulating coating 1b, the difference voltage (V ₂ −V) between the two magnetic field sensors 2 regardless of the presence or absence of a defect in the conductor 1a. ₁ )
Is output, the accuracy of determining the presence or absence of an abnormality is impaired.

[0004] The present invention has been made in view of the above circumstances, and achieves the following objects. To enable detection of defective conductors in the live state. To reduce detection errors caused by sensor displacement and uneven thickness. Improving the detection sensitivity of defective parts such as broken wires. To improve the measurement accuracy of the distance to the conductor surface.

[0005]

Means for Solving the Problems When a magnetic field sensor and a distance sensor are arranged in parallel in the longitudinal direction of an insulated wire, the distance to the conductor surface of the insulated wire is measured, and an alternating current is applied to the insulated wire. Calculate the induced voltage of the magnetic field sensor based on the magnetic field generated by the distance data of the distance sensor, compare the calculation result with the induced voltage actually detected by the magnetic field sensor, and determine whether there is a difference. The presence or absence of abnormality is determined. A magnetic field sensor and a distance sensor that are in parallel with each other are arranged facing each other at a position 180 degrees apart in the circumferential direction of the insulated wire, and two pieces of detection data are compared. The magnetic field sensor and the distance sensor are arranged side by side in an inward state on the inner wall of the wire insertion hole opened in the support, the insulated wire is inserted into the wire insertion hole, and the magnetic field sensor and the distance sensor are arranged along the longitudinal direction of the insulated wire. While shifting the position, a defective portion of the conductor is detected.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method and an apparatus for detecting a defect of an insulated wire according to the present invention will be described below with reference to FIG.
This will be described with reference to FIG. 1 to 3, reference numeral 2 denotes a magnetic field sensor, 7 denotes a distance sensor, 10 denotes a support, 11 denotes a housing, and 12 denotes a pressing plate.

The distance sensor 7 is, for example, an eddy current displacement sensor. When an electric current flows through a coil, the distance sensor 7 changes its impedance based on the occurrence of eddy current in a conductor present in the vicinity of the coil. What detects the distance to the conductor 1a is adopted.

The support 10 includes a housing 11 in which two sets of a magnetic field sensor 2 and a distance sensor 7 arranged in parallel with each other are arranged in a facing state, and a holding plate 12 combined with the housing 11. 11 and the holding plate 12 are integrated by a fastener such as a bolt.

FIG. 1 shows a central portion of the housing 11.
As shown in FIG. 3, an electric wire insertion hole 11a for inserting the insulated electric wire 1 is formed, and an inner wall on one side of the electric wire insertion hole 11a is formed into a shape deleted by forming a slit 11b, and a holding plate 12 is formed. Is closed by the attachment of

The magnetic field sensor 2 and the distance sensor 7 which are in parallel with each other are connected to the wire insertion hole 1 in the support 10.
As shown in FIG. 1, two sets of the two sets are arranged facing each other at a position 180 degrees apart in the circumferential direction of the insulated wire 1 inserted into the wire insertion hole 11 a. I have.

The above-described detection circuit and method shown in FIG. 4 are applied to the magnetic field sensor 2. When detecting the difference voltage, the magnetic field sensor 2 detects the magnetic field based on the distance to the surface of the conductor 1a by the distance sensor 7. The induced voltage generated in the sensor 2 is calculated and compared with the actually measured value.

As shown in FIG. 2, when the magnetic field sensor 2 is disposed at a position 180 degrees apart in the circumferential direction of the insulated wire 1, an alternating current I such as a load current flows through the conductor 1a. A magnetic field is generated based on the alternating current I, but when the center of the current distribution coincides with the center of the conductor 1a and the distance from the surface of the conductor 1a to the pair of magnetic field sensors 2 is the same. , The detection voltages of the two magnetic field sensors 2 become equal.

However, as shown in FIG. 3, when a deviation Δd occurs between the center of the current distribution and the center of the conductor 1a, two magnetic fields are calculated as shown in the following equations (1) and (2). A difference occurs in the detection voltage of the sensor 2. V ¹ = 2πfn (μ ₀ LI / 2π) · ln [{(d−Δd) + a + b} / (d−Δd + b)] (1) V ² = 2πfn (μ ⁰ LI / 2π) Ln [{(d + Δd) + a + b} / (d + Δd + b)] (2) where f: frequency, n: number of coil turns, μ ₀ : permeability, L: coil circumference Direction length, I: current, ln: natural logarithm,
d: conductor radius, Δd: current center displacement, a: coil width, b: distance to coil. In the example of FIG. 3,
It is assumed that the magnetic field sensor 2 is wound in a rectangular shape.

In addition to the detection of the differential voltage by the pair of magnetic field sensors 2 shown in FIG.
The distance to the surface a is measured, and the induced voltage of the magnetic field sensor 2 based on the magnetic field corresponding to the alternating current I is calculated from the distance data of the distance sensor 7. By comparing this calculation result with the induced voltage actually detected by the magnetic field sensor 2, it is determined whether there is a significant difference between the conductor 1a and the presence or absence of a defective portion such as stress corrosion cracking or broken wire in the conductor 1a. . According to such a method of determining the presence or absence of a defective portion, the voltage difference between the pair of magnetic field sensors 2 is caused by an abnormality in the conductor 1a, the two magnetic field sensors 2 are offset, or the insulating coating 1b of the insulated wire 1 is provided. It is possible to identify whether or not the uneven thickness occurs.

When the conductor 1a is a single wire, it is effective to rotate the insulated wire 1 or the support 10 to change the circumferential position and detect the presence or absence of a defect. In the case of a stranded wire, since the element wire repeatedly appears at the same position in a spiral shape, the position of the magnetic field sensor 2 and the distance sensor 7 are shifted along the longitudinal direction of the insulated wire 1 to determine the presence or absence of a defect. You may make it detect.

[0016]

According to the method and the apparatus for detecting a defect of an insulated wire according to the present invention, a magnetic field sensor and a distance sensor are arranged in parallel in the longitudinal direction of the insulated wire, and the distance to the conductor surface of the insulated wire is changed. Is measured, and the presence / absence of a conductor abnormality is determined by comparing the calculated induced voltage based on the distance data with the actually measured induced voltage. Therefore, the following effects are obtained. (1) By operating the magnetic field sensor using the load current flowing through the insulated wire, even if the insulated wire is in a live state, it is possible to easily detect a defective portion of the conductor. (2) By measuring the distance to the conductor surface using a distance sensor in parallel with the magnetic field sensor, it is possible to reduce the occurrence of detection errors due to displacement or uneven thickness of the sensor. (3) By comparing the induced voltage based on the calculation and the actual measurement and performing the correction, it is possible to improve the determination accuracy and the detection sensitivity of the presence / absence of the conductor abnormality. (4) By arranging the magnetic field sensor and the distance sensor in parallel on the inner wall of the wire insertion hole formed in the support in an inward state, the insulated property of the insulated wire is secured, and the detection of a defective portion of the conductor is efficiently performed. Can do it.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a method and an apparatus for detecting a defect of an insulated wire according to the present invention.

FIG. 2 is a cross-sectional plan view showing how the magnetic field sensor and the distance sensor shown in FIG.

FIG. 3 is a schematic diagram of a displacement between a magnetic field sensor and an insulated wire in FIG. 1;

FIG. 4 is a connection diagram showing a conventional technique for detecting a defective portion of an insulated wire.

FIG. 5 is a front view showing the arrangement of the magnetic field sensor and the insulated wires of FIG. 4;

FIG. 6 is a front view showing a detection state when the magnetic field sensor of FIG. 5 is offset.

FIG. 7 is a front view showing a detection state when the insulated wire of FIG. 5 is uneven in thickness.

[Description of Signs] 1 Insulated wire 1a Conductor 1b Insulating coating 2 Magnetic field sensor (search coil) 3 Low pass filter 4 Preamplifier 5 Differential amplifier 6 Low pass filter 7 Distance sensor 10 Support 11 Housing 11a Wire insertion hole 11b Slit 12 Pressing plate

Claims (5)

[Claims] 1. A magnetic field sensor (2) and a distance sensor (7) are arranged in parallel in the longitudinal direction of an insulated wire (1), and the distance sensor measures the distance to the surface of the conductor (1a) of the insulated wire. Then, the induced voltage of the magnetic field sensor based on the magnetic field generated when an alternating current flows through the insulated wire is calculated based on the distance data of the distance sensor, and the calculated result is compared with the induced voltage actually detected by the magnetic field sensor. And determining whether there is any abnormality in the conductor based on whether or not there is a difference. 2. A magnetic field sensor (2) and a distance sensor (7) in parallel with each other are connected to each other in a circumferential direction of an insulated wire (1).
2. The method according to claim 1, further comprising the steps of: disposing the detection data at positions separated by 0 degrees, and comparing the detection data at two locations. 3. A magnetic field sensor (2) for converting a magnetic field generated when an alternating current flows through a conductor (1a) into a voltage and detecting the voltage.
And a distance sensor (7) for measuring the distance to the conductor surface are arranged in parallel in the longitudinal direction of the insulated wire (1), and are calculated based on the induced voltage detected by the magnetic field sensor and the distance data of the distance sensor. An insulated wire defect detecting device, which compares the obtained induced voltage of a magnetic field sensor with the detected value. 4. A magnetic field sensor (2) and a distance sensor (7) are arranged in parallel on an inner wall of an electric wire insertion hole (11a) opened in a support (10), and the insulated electric wire (1) is an electric wire. The defect detecting device for an insulated wire according to claim 3, wherein the device is inserted into an insertion hole. 5. A magnetic field sensor (2) and a distance sensor (7) in parallel with each other are connected to each other in a circumferential direction of the insulated wire (1).
The insulated wire defect detecting device according to claim 3 or 4, wherein the devices are arranged opposite to each other at positions separated by 0 degrees.