JPH10123194A - Detecting method for defect of insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detecting method in which the abnormality of a conductor part can be detected by a method wherein outputs of one pair of conductor electric-field sensors which are installed in symmetric position in the circumferential direction of an insulated wire are corrected by outputs of one pair of external magnetic-field sensors which are installed on their symmetric line and the outputs are compared with each other. SOLUTION: Two conductor magnetic field sensors 11 of an identical type are installed in separated symmetric positions in the circunferential direction of an insulated wire 1, and a magnetic field ϕa which is generated at a time when an alternating current is made to flow to the insulated wire 1 is detected. In addition, two external magnetic-field sensors 12 of an identical type are installed on the symmetric line C of the conductor magnetic-field sensors 11 in such a way that a detecting axial line is matched with the symmetric line C, and an external magnetic field ϕb is detected. Detection values of the conductor magnetic- field sensors 11 are corrected by detection values of the external magnetic-field sensors 12, and the existence of an abnormality such as a strand disconnection or the like in a conductor part 2 is discriminated on the basis of whether a difference is generated between the detection values of the two conductor magnetic-field sensors or not. By this method, it is possible to obtain a detecting method whose detecting range is expanded and whose detecting efficiency can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a defect in an insulated wire, and more particularly to a method for detecting a defect in an insulated wire such as an overhead distribution wire such as a broken wire of a conductor while reducing the influence of an external magnetic field. The present invention relates to a detection technique.

[0002]

2. Description of the Related Art The following methods (1) and (2) are known as techniques for detecting whether or not a defective portion such as a broken wire has occurred in a conductor portion of an insulated wire such as an overhead distribution wire. . (1) A method in which an AC magnetic field intersects a conductor portion and a phenomenon in which eddy current loss fluctuates at a defect occurrence location such as a broken wire is detected as a change in impedance of a detection coil (eddy current flaw detection method). (2) A method of arranging a magnetic field sensor around an insulated wire and detecting whether or not a magnetic field generated when an alternating current flows through the insulated wire varies depending on the circumferential position of the insulated wire.

[0003]

However, in the method (1), the detection range tends to be locally small. Since sensitivity is affected by the distance between the coil and the conductor, the sensitivity is likely to be reduced due to the thickness of the insulating coating. It is easy to pick up errors due to the twist of the stranded conductor. And other issues remain. In the method (2), the magnetic field sensor detects an external magnetic field around the insulated wire, so that the detection accuracy tends to be reduced. In particular, as shown in FIG. 4, when a magnetic field sensor b is arranged on a T-phase insulated wire a and a magnetic field φt is detected under a situation where a load current such as a three-phase alternating current flows, R Since the magnetic fields φr and φs based on the phase and S-phase load currents are detected, errors increase. And other issues remain.

[0004] The present invention has been made in view of the above circumstances, and achieves the following objects. 1) To enable the detection range to be expanded. 2) To reduce the occurrence of errors due to the thickness of the insulating coating and the twist of the stranded conductor. 3) To prevent a decrease in detection accuracy due to the influence of an external magnetic field. 4) To enable detection of a defective portion of a conductor in a live state. 5) To reduce the influence of load current such as three-phase alternating current.

[0005]

Means for Solving the Problems Two conductor magnetic field sensors of the same type are arranged at symmetrical positions spaced apart in the circumferential direction of an insulated wire,
Detects the magnetic field generated when an alternating current flows through the insulated wire, and arranges two external magnetic field sensors of the same type on the symmetry line of the two conductor magnetic field sensors with the detection axes aligned with the symmetry line. To detect the external magnetic field, correct the value detected by the conductor magnetic field sensor with the value detected by the external magnetic field sensor, and determine whether there is an abnormality in the conductor part based on whether there is a difference between the values detected by the two conductor magnetic field sensors. By doing so, the defect detection of the insulated wire is performed. The two external magnetic field sensors are arranged to be superimposed on the symmetry line and compared with each other in detection value, or arranged separately on both sides of the insulated wire to compare the detection values. It is desirable that the two external magnetic field sensors detect the external magnetic field by aligning the detection axis with the symmetry line of the two conductive magnetic field sensors. A technology of detecting a magnetic field generated when an alternating current is applied to an insulated wire, which is arranged at a remote position, is adopted. When two conductor magnetic field sensors are arranged at a position 180 degrees apart, a technique of arranging two external magnetic field sensors at a position of 90 degrees is adopted. Magnetic fields detected by the conductor magnetic field sensor and the external magnetic field sensor are compared in a state converted into an electric signal. The load current flowing through the insulated wire is used as an alternating current for generating a magnetic field. 3 arranged in a line
When a three-phase alternating current is supplied by more than one insulated wire, two conductor magnetic field sensors of the same type are symmetrically positioned at 180 degrees apart in the circumferential direction on the insulated wire, and The magnetic field generated when an alternating current flows is detected by the two conductor magnetic field sensors, and the presence or absence of abnormality in the conductor part is determined by whether or not the detected value has a difference. Is employed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a method for detecting a defect of an insulated wire according to the present invention will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes an insulated wire such as an overhead distribution wire, 2 denotes a conductor portion, 3 denotes an insulating coating portion, 11 denotes a conductor magnetic field sensor, 12 denotes an external magnetic field sensor, 13 denotes a connection line, 14 denotes a lead wire, 15 is a connection terminal, C is a symmetric line, φa
Indicates a conductor magnetic field, and φb indicates an external magnetic field.

In the first embodiment, two conductor magnetic field sensors 11 of the same type are arranged symmetrically at circumferentially separated positions on the insulated wire 1 and are generated when an alternating current flows through the insulated wire 1. A magnetic field (conductor magnetic field) φa to be detected is detected, and two external magnetic field sensors 12 of the same type are arranged on the symmetry line C of the two conductor magnetic field sensors 11 with the detection axes aligned with the symmetry line C. Detecting the external magnetic field φb,
The value detected by the conductor magnetic field sensor 11 is applied to the external magnetic field sensor 12.
In this case, the presence or absence of an abnormality such as a broken wire of the conductor portion 2 is determined based on whether or not there is a difference between the detection values of the two conductor magnetic field sensors 11.

The conductor magnetic field sensor 11 is, for example, a bobbin in which a fine wire is densely wound, and two sensors (of the same type) having the same characteristics such as the number of turns, the winding diameter, and the size are used in combination. The conductor magnetic field sensor 11 detects a magnetic flux generated when an alternating current flows through the conductor portion 2 and its fluctuation by converting the magnetic flux into a voltage, and detects two types of the same type.
For example, the detection axis is arranged at a position 180 degrees apart in the circumferential direction of the insulated wire 1 so that the detection axis is parallel to the tangential direction of the circumference.

The external magnetic field sensor 12 has the same structure and the same specifications as the conductor magnetic field sensor 11, and is used in combination of two. The two are superimposed on the symmetry line C, and the detection axis is Are arranged in a direction coinciding with the symmetry line C.

As shown in FIG. 1, the two conductor magnetic field sensors 11 and the external magnetic field sensor 12 are connected in series by a connection line 13 and are drawn out by a lead line 14. Note that, as shown in FIG. 1, when an external magnetic field φb exists, an induced voltage based on the magnetic flux of the external magnetic field φb is generated in the conductive magnetic field sensor 11 and the external magnetic field sensor 12, respectively. The external magnetic field sensors 12 are connected so as to cancel the induced voltage due to the external magnetic field φb.

As shown in FIG. 1, when the detection axis of the conductor magnetic field sensor 11 is set parallel to the symmetry line C, the conductor magnetic field sensor 11 and the external magnetic field sensor 12 are connected to the same type. By setting such a value, the induced voltages of the two magnetic field sensors 11 and 12 can be made equal to enhance the canceling performance.

The detection axis of the conductor magnetic field sensor 11 is
In the case where the external magnetic field sensor 12 is inclined with respect to the symmetry line C, the setting is made so that the external magnetic field sensor 12 is reduced or the induced voltage is divided so that the induced voltage of the external magnetic field sensor 12 is reduced by the sine value of the angle. Is made.

When a load current flows through the insulated wire 1, this load current is used as an alternating current. The conductor magnetic field φa generated based on the load current is converted into a voltage by the external magnetic field sensor 12 and the voltage V
_1, is taken as V _2, the comparison and the difference between the voltages V _1, V ₂ are detected. Therefore, the voltages V ₁ and V ₂ are compared in a state where the induced voltage due to the external magnetic field φb is removed. The conductor magnetic field φa generated when an alternating current flows through the conductor portion 2 is uniformly distributed when the center of the current distribution coincides with the center of the conductor portion 2. When it is off center, it becomes non-uniform and a difference in magnetic flux density occurs depending on the outer peripheral position of the insulated wire 1.
The presence or absence of a defective portion such as a broken wire in the conductor portion 2 is determined based on whether a significant difference has occurred.

When the conductor portion 2 is a single wire,
It is effective to detect the presence or absence of a defect by rotating the insulated wire 1 or each of the magnetic field sensors 11 and 12 to change the position in the circumferential direction, but when the conductor portion 2 is a stranded wire, the strand is Because it appears repeatedly at the same position in a spiral, the insulated wire 1
The presence or absence of a defective portion can be detected while shifting the position of each of the magnetic field sensors 11 and 12 along the longitudinal direction.

FIG. 2 shows a second embodiment of the method for detecting a defect of an insulated wire according to the present invention, in which two external magnetic field sensors 12 of the same type sandwich both sides of the insulated wire 1 on a symmetry line C. In this case as well, it is possible to offset the induced voltage due to the external magnetic field φb to reduce the occurrence of errors.

FIG. 3 shows a third embodiment of the insulated wire defect detecting method according to the present invention, in which three or multiple insulated wires 1 are arranged in a line and a three-phase alternating current is applied. As in the case, when the direction of the external magnetic field φb is preset (predetermined direction), the two conductor magnetic field sensors 11 of the same type are symmetrically arranged on the insulated wire 1 at positions 180 degrees apart in the circumferential direction. In addition, the symmetric line C and the detection axis are set in parallel with the arrangement direction of the plurality of insulated wires 1 and the direction of the magnetic field generation source, and the conductor magnetic field φa generated when an alternating current flows through the insulated wires 1 Is detected, the presence or absence of an abnormality such as a broken wire of the conductor portion 2 can be determined without being affected by the external magnetic field φb and omitting the installation of the external magnetic field sensor 12.

[0017]

According to the method for detecting a defect of an insulated wire according to the present invention, two conductor magnetic field sensors are arranged at symmetrical positions spaced apart in the circumferential direction of the insulated wire, and when an alternating current flows through the insulated wire. In addition to detecting fluctuations in the generated magnetic field and determining whether there is an abnormality such as a broken wire in the conductor portion while canceling out the influence of the external magnetic field, the following effects are obtained. (1) By performing defect detection based on a magnetic field generated when an alternating current is applied to an insulated wire, the detection range can be expanded and the detection efficiency can be improved. (2) By detecting the difference in magnetic flux based on the deviation of the center of the current distribution of the conductor, the influence of the thickness of the insulating coating and the twist of the stranded conductor can be reduced, and the occurrence of errors can be reduced. (3) By detecting the external magnetic field and correcting the detection value, it is possible to suppress a decrease in the accuracy of detecting a defective portion in an environment where the external magnetic field is present. (4) By using the magnetic field generated by the load current of the insulated wire, even if the insulated wire is in a live state, it is possible to detect whether or not the conductor has a defect. (5) In an insulated wire energized with three-phase alternating current, the influence of the load current of another phase can be reduced and the defect detection accuracy can be improved. (6) When three-phase alternating current is supplied by insulated wires arranged in a line, the arrangement of the conductor magnetic field sensors can be simplified, and the detection workability can be improved.

[Brief description of the drawings]

FIG. 1 shows a first method of detecting a defect of an insulated wire according to the present invention.
It is a connection diagram showing an embodiment.

FIG. 2 shows a second method of detecting a defect of an insulated wire according to the present invention.
It is a connection diagram showing an embodiment.

FIG. 3 shows a third method of detecting a defect of an insulated wire according to the present invention.
It is a mimetic diagram of a magnetic field detection situation showing an embodiment.

FIG. 4 is a front view showing a magnetic field detection state when a current flows through a three-phase AC insulated wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulated wire 2 Conductor part 3 Insulation coating part 11 Conductive magnetic field sensor 12 External magnetic field sensor 13 Connection line 14 Lead wire 15 Connection terminal C Symmetry line φa Conductive magnetic field (magnetic field) φb External magnetic field (magnetic field)

Claims (6)

[Claims] 1. An insulated wire (1) having two conductor magnetic field sensors (11) of the same type arranged at symmetrical positions spaced apart in the circumferential direction.
Magnetic field (φa) generated when alternating current is passed through insulated wires
And the two external magnetic field sensors (12) of the same type are arranged on the symmetry line (C) of the two conductor magnetic field sensors with the detection axis aligned with the symmetry line, and the external magnetic field (φb) is detected. Is detected, the value detected by the conductor magnetic field sensor is corrected by the value detected by the external magnetic field sensor, and the presence or absence of an abnormality in the conductor portion (2) is determined based on whether or not there is a difference between the values detected by the two conductor magnetic field sensors. A method for detecting defects in an insulated wire. 2. The defect detection of an insulated wire according to claim 1, wherein two external magnetic field sensors (12) are arranged on the symmetry line (C) in a superimposed state and the detected values are compared. Method. 3. The detection values are compared by arranging two external magnetic field sensors (12) on both sides of the insulated wire (1) on the symmetry line (C). The method for detecting a defect of an insulated wire as described above. 4. A magnetic field generated when an alternating current flows through an insulated wire (1) by disposing two conductor magnetic field sensors (11) at positions 180 degrees apart in a circumferential direction on the insulated wire (1). (Φa) is detected.
Or the method of detecting a defect of an insulated wire according to 3. 5. The method according to claim 1, wherein a load current flowing through the insulated wire is used as an alternating current.
Or the method for detecting a defect of an insulated wire according to 4. 6. When three or more insulated wires (1) arranged in a row are energized with three-phase alternating current, two conductor magnetic field sensors (11) of the same type are connected to each other by 180 degrees in the circumferential direction of the insulated wires. A magnetic field (φa) generated when an alternating current is applied to the insulated wire by symmetrically arranging the detection axes in a symmetrical state at a distance from the arrangement direction of the insulated wires, and using two conductor magnetic field sensors (12) A method for detecting a defect in an insulated wire, comprising: determining whether there is an abnormality in the conductor portion (2) based on whether there is a difference between the detected values.