JPH02306161A - Apparatus for flaw detection of electric wire - Google Patents

Abstract

PURPOSE:To effectively remove noise from the output of a flaw detection coil and to prevent the erroneous operation of a camera in photographing by processing the difference signal between the output of a flaw detection signal detecting circuit and that of a noise level setting device a s a flaw detection signal. CONSTITUTION:The output signal 15a of a flaw detection signal detecting circuit 125 receiving the output signal S1 of a flaw detection coil 5 is smoothed by a noise level setting device 21 to obtain a noise level signal 21a. A limiter circuit 22 subtracts the signal 21a from the signal 15a to set off noise Sn and takes out only a flaw detection signal S1' is recorded on a data recorder 31 and a shutter driving circuit 32 triggers the signal S1' to operate a camera 11.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric wire flaw detection device for inspecting flaws, etc. on the outer surface of electric wires and strands.

(Prior Art) For example, overhead lines such as AC3R are often installed through mountainous areas, and are frequently damaged by lightning. The degree of damage varies widely, from slight damage to damage such as partial wire breakage, which cannot be left untreated. Breakage of the strands causes corona discharge and reduces the tensile strength of the overhead wire, which may lead to major accidents such as breakage. Therefore, electric wire flaw detection devices have been developed that automatically detect flaws over the entire length of electric wires such as overhead lines.

FIG. 3 shows a schematic configuration diagram of a conventional electric wire flaw detection device.

In the figure, this device has a pair of drive wheels 3 so that it can run on electric wires 1, and these drive wheels 3 are
It is driven by a drive unit 4 such as a motor to run on the electric wire 1 in the direction of an arrow 10a.

Moreover, several flaw detection coils 5 are provided inside this device, and are positioned by guide wheels 6 that maintain a predetermined distance from the electric wire 1. This guide wheel 6 is provided so as to trace the outer peripheral surface of the electric wire 1. The coil holder 7 that supports each flaw detection coil 5 is attached to the frame 2 of the apparatus using a hanging metal fitting 8, as indicated by the arrow 10b.
It is suspended so that it can move in any direction. This hanging fitting 8 is
It absorbs the vertical vibration of the coil holder 7 and acts together with the guide wheel 6 to maintain the distance between the flaw detection coil 5 and the electric wire 1 at a predetermined distance.

A control section 9 is provided to process the output signal of the flaw detection coil 5 or to output a predetermined drive signal to the drive section 4. On the other hand, a camera 11 and a mirror 12 are arranged on the rear side surface of the frame 2 so as to sandwich the electric wire 1 therebetween.

The above device operates as follows.

First, the drive unit 4 rotates the drive wheels 3 and causes the frame 2 to travel along the electric wire 1 at a constant speed in the direction of the arrow 10a in the figure. While the frame 2 is running, the flaw detection coil 5
While maintaining a predetermined distance from the electric wire 1,
Perform flaw detection on the outer surface. If a flaw exceeding a certain level is detected on the surface of the electric wire 1, the control section 9 records the detection signal and operates the camera 11 to take a photograph of the outer surface of the electric wire 1. The mirror 12 is provided for photographing the back side of the electric wire 1 which cannot be directly photographed by the camera 11.

(Problem to be Solved by the Invention) By the way, if the distance between the flaw detection coil 5 and the electric wire 1 is always kept constant as described above, it is theoretically possible to detect even extremely minute flaws. Become. However, the surface of the electric wire usually has regular irregularities due to the twisted strands. Therefore, this causes the induced voltage in the flaw detection coil 5 to change regularly, which appears as noise in the output signal.

FIG. 4 shows a graph of the output signal waveform of the flaw detection coil.

This graph represents changes in the output of the flaw detection coil, with the vertical axis representing the signal level [V] and the horizontal axis representing time [sec].

In the output of this flaw detection coil, in addition to the flaw detection signal S1 that is originally to be detected, the above-mentioned noise Sn is mixed.

The output signal of such a flaw detection coil is recorded by a tape recorder or the like.

Furthermore, each time the flaw detection signal S1 is detected, the camera 11 described above with reference to FIG. 3 is operated to take a photograph of the outer surface of the wire. Shooting level Vs for this camera operation
is set to a predetermined level higher than the level Vn of the noise Sn. That is, when the flaw detection signal S1 exceeding the imaging level Vs is input, the camera is activated. Such setting of the imaging level Vs has been performed with reference to a predetermined manual, taking into account experimental data and inspection results of actually removed electric wires, etc.

However, the noise level Vn varies due to roughness of the surface of the wire due to aging, adhesion of dust, etc. Therefore,
There also arises a problem that the level of the flaw detection signal S1 becomes lower than the photographing level Vs, and necessary photographing is not performed. On the other hand, if the imaging level Vs is set too low, there is a problem in that unnecessary imaging is performed due to noise.

The present invention has been made with attention to the above points, and an object of the present invention is to provide a wire flaw detection device that effectively removes noise from the output of a flaw detection coil and prevents malfunctions of a camera for photographing. It is something to do.

(Means for Solving the Problems) The electric wire flaw detection apparatus of the present invention includes a flaw detection signal detection circuit, a noise level setting device that smoothes the output of the flaw detection signal detection circuit and outputs a noise level signal, and a flaw detection signal detection circuit. A limiter circuit that compares the output of the circuit and the output of the noise level setting device to obtain a difference signal between the two, and a flaw detection signal processing circuit that processes the difference signal outputted from the limiter circuit as a flaw detection signal. It is characterized by:

(Function) The above electric wire flaw detection device obtains a noise level signal corresponding to a noise envelope by smoothing the output of the flaw detection signal detection circuit that receives the output signal of the flaw detection coil. By subtracting this noise level signal from the output signal of the flaw detection coil, the noise is canceled out and only the flaw detection signal can be extracted. This process is performed by a limiter circuit. Since the difference signal output from the limiter circuit includes only the flaw detection signal, this signal is used to operate a camera or the like. Furthermore, if it is desired to measure the actual level of the flaw detection signal, a noise level signal may be added to the output of the smitter circuit.

(Example) Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of the electric wire flaw detection apparatus of the present invention.

The illustrated device includes a flaw detection coil 5, a flaw detection signal detection circuit 15, an auto-tuning circuit 2o, and a flaw detection signal processing circuit 3.
0 and a camera 11. These circuits are mounted on the main body case 2 of the electric wire flaw detection apparatus shown in FIG.

Note that, in FIG. 1, illustrations of circuits etc. that are unnecessary for the detailed explanation of the present invention are omitted.

Here, the flaw detection coil 5 has the configuration already explained in FIG. 3, and is configured to detect minute changes in induced voltage using a bridge or the like.

The flaw detection signal detection circuit 15 is a circuit that receives the output signal of the flaw detection coil 5 and performs amplification and the like.

The auto-tuning circuit 20 includes a noise level setter 21
and a limiter circuit 22.

The noise level setter 21 includes a rectifier (not shown) that receives the output of the flaw detection signal detection circuit 15, rectifies it, and smooths it.
Consists of smoothing capacitor, smoothing coil, etc. this is,
It is composed of a well-known low-pass filter and the like. The limiter circuit 22 includes a noise level signal 21a output from the noise level setter 21 and an output signal 15a from the flaw detection signal detection circuit 15.
This is a circuit that accepts the following signals and outputs a difference signal Sl' between the two. This limiter circuit 22 is composed of a known comparison amplifier circuit and the like.

The flaw detection signal processing circuit 30 includes a data recorder 31 and a shutter drive circuit 32.

The data recorder 31 consists of a tape recorder or the like, and is a device that receives the difference signal SL' outputted from the limiter circuit 22 and magnetically records it. The shutter drive circuit 32 receives a difference signal Sl output from the limiter circuit 22.
This is a circuit that operates the camera 11 using ' as a trigger, and is composed of a known circuit that shapes the waveform of the difference signal Sl' and operates a relay or the like.

The above device operates as follows.

First, the output signal 15a of the flaw detection signal detection circuit 15 is
As shown in the figure, the noise Sn and the flaw detection signal S1 are mixed. On the other hand, the noise level setter 21 smoothes the output signal 15a of the flaw detection signal detection circuit 15 and outputs a noise level signal 21a. Normally, the probability that the flaw detection signal S1 is included in the output signal 15a of the flaw detection signal detection circuit 15 is extremely low, and if this signal 15a is smoothed, the noise level, which is a signal that substantially corresponds to the envelope of the noise Sn. signal 2
1a is obtained.

When this noise level signal 21a and the output signal 15a of the flaw detection signal detection circuit 15 are input to the limiter circuit 22 and a difference signal SL' between the two is taken, only the upper part of the flaw detection signal S1 is extracted from the limiter circuit 22. is output. That is,
An output signal with the noise Sn masked is obtained. The data recorder 31 records this. Further, the shutter drive circuit 32 uses this difference signal SL' as a trigger to drive the camera 11.
Activate.

FIG. 2 shows a block diagram of another embodiment of the device of the invention.

The device shown in the figure differs from the device shown in FIG. 1 in that a limiter level return circuit 23 is added to the auto-tuning circuit 20.

This limiter level recovery circuit 23 receives the noise level signal 21a output from the noise level setter 21, while
Accepting the difference signal SL' output from the limiter circuit 22,
This circuit adds both of them and outputs the result to the flaw detection signal processing circuit 30. The limiter level recovery circuit 23 includes an analog signal addition circuit composed of an operational amplifier, etc., and a difference signal S
It consists of a gate circuit etc. that blocks the noise Sn in the part where l' does not exist.

The apparatus of FIG. 2 operates as follows.

First, the difference signal Sl' output from the limiter circuit 22 is obtained by subtracting the noise level signal 21a from the output signal 15a of the flaw detection signal detection circuit 15, as described above. Therefore, the difference signal SL' has the same level as the flaw detection signal S1. Therefore, the limiter level recovery circuit 23
At this point, the level of the flaw detection signal S1 is returned to its original level.

In this case, simply adding the output of the limiter circuit 22 and the output of the noise level setter 21 returns the original output signal 15a of the flaw detection signal detection circuit 15. Therefore,
It is preferable that the limiter level recovery circuit 23 performs processing using a so-called AND gate, etc., which operates to add the noise level signal 21a to the difference signal Sl' output from the limiter circuit 22 only when that signal is input. .

In this way, only the true flaw detection signal is taken out from the limiter level recovery circuit 23.

The present invention is not limited to the above embodiments.

The configuration of the flaw detection signal detection circuit 15, noise level setter 21, limiter circuit 22, limiter level recovery circuit 23, etc. is as follows.
Various known circuits having equivalent functions may be substituted. Furthermore, the flaw detection signal processing circuit 30 does not necessarily need to be provided with the data recorder 31 or the shutter drive circuit 32, and may be used as a known various data recording or analysis circuit for processing the flaw detection signal output from the auto-tuning circuit 20. No problem.

(Effects of the Invention) The wire flaw detection device of the present invention described above can clearly distinguish and extract true flaw detection signals from among the signals output from the flaw detection signal detection circuit, thereby preventing malfunctions of cameras, etc. can. Further, if the difference signal output from the limiter circuit is recorded in a flaw detection signal processing circuit, data analysis becomes extremely easy because noise is removed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the electric wire flaw detection device of the present invention, FIG. 2 is a block diagram showing a modification thereof, FIG. 3 is a schematic configuration diagram showing an example of a conventional general electric wire flaw detection device, and FIG. The figure is a graph showing the output signal waveform of the flaw detection coil. 5-----1-----Flaw detection coil, 11------1 Camera, 15-----1----Flaw detection signal detection circuit, 20-----
-----Auto tuning circuit, 21-11---
- Noise level setter, 21 a - - Noise level signal, 22 ------- Limiter circuit, 30 - - - 11 - Flaw detection signal processing circuit, 31 ----
---Data recorder, 32-----Shutter drive circuit. (1 other person)

Claims (1)

[Claims] a flaw detection signal detection circuit; a noise level setter that smoothes the output of the flaw detection signal detection circuit and outputs a noise level signal;
a limiter circuit that compares the output of the flaw detection signal detection circuit and the output of the noise level setter to obtain a difference signal between the two;
An electric wire flaw detection apparatus comprising: a flaw detection signal processing circuit that processes the difference signal output from the limiter circuit as a flaw detection signal.