JPH02309267A - Apparatus for detecting trouble section of underground transmission line - Google Patents

Abstract

PURPOSE:To miniaturize the title apparatus by giving the stress corresponding to the detection value of a sheath current to an optical fiber and measuring the propagation constant of said optical fiber. CONSTITUTION:The secondary output of the current transformer 2 arranged to a cross-bond line 1 is connected to the coil 9 provided to one inner end of the outside pipe 14 of a stress generator 20 and a flange 13a is supported by the limiter pipe 17 provided to the flange 13b at the other end in the pipe 14. Further, an optical fiber 6 is spirally wound around the coil spring 12 provided between the flanges 13a, 13b and both ends of the fiber 6 are taken out of the stress generator 20 to connect not only one end thereof to a light source 7 but also the other end thereof to a photodetector 8. The flange 13a is moved by the magnetic field generated from the coil 19 by the trouble current of the cross-bond line 1 and the fiber 6 extends and contracts so as to follow the extention and contraction of the spring 12. The change of the transmission loss of light due to the pitch change of the fiber 6 is detected by the photodetector 8 and subjected to computer processing to detect the direction and magnitude of the trouble current flowing through the cross-bond line 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for detecting a faulty section of an underground power transmission line, and in particular, the present invention relates to a device for detecting a faulty section of an underground power transmission line, which is designed to reduce the size of the device and simplify the configuration. Regarding a detection device.

[Background technology]

BACKGROUND OF THE INVENTION As the demand for electrical energy increases, a stable supply of power becomes necessary, and technologies related to the reliability of underground power transmission lines such as cables are being developed. Similarly, in the event of a sudden accident, it is necessary to quickly locate the failure location and carry out appropriate restoration work. A typical accident on underground power transmission lines is a ground fault where the conductor and sheath are short-circuited due to insulation breakdown, and when this ground fault occurs, it is necessary to identify the ground fault section immediately. .

Figure 5 shows a circuit diagram of a fault section detection device for detecting a fault current in a long-distance underground power transmission line device having a cross-bond connection.
The optical conversion circuit 4 is arranged on the secondary side of the . The optical conversion circuit 4 includes a load resistor 4a, diodes 4b, 4c, 4d, and 4'e (among them, 4C is a Zener diode exhibiting constant voltage characteristics against reverse voltage) arranged in parallel with the load resistor 4a, and its diagonal. It has a configuration in which a limiting resistor 4f and an LED (light emitting diode) 4g are connected in series on the top, and the LED 4g emits light in proportion to the magnitude of the current flowing through the cross bond line 1, thereby performing electrical/optical conversion.

The optical signal output by the LED 4g is transmitted via the fiber optic cable 5 to a central computer (not shown), where it is regenerated together with the signals from each section, and the absolute value of the current flowing through the sheath circuit in the event of a ground fault, and phase by 2
Ground fault sections are detected by comparing between the two. this is,
The principle is the same as the accident section detection device that is put into practical use on overhead power transmission lines using OPCW (overhead ground wire).

In order to more accurately determine the phase and absolute value of the signal from current transformer 2, it is full-wave rectified as shown in Figure 6, and half of it is used as a measurement signal, and the remaining half is used for calibration. used as a traffic signal. The calibration signal is Zener diode 4
The level of the signal for measurement is always constant due to the effect of c, and the level of the signal for measurement can be accurately determined by the ratio of the signal for calibration and the signal for measurement. Further, the phase can also be easily detected by detecting the position of the calibration signal.

[Problems to be Solved by the Invention] However, conventional fault section detection devices for underground power transmission lines do not use various semiconductor elements such as diodes to rectify signals output from current transformers. Therefore, there is a problem that the entire device becomes larger. In addition, due to differences in the electrical characteristics of each element, level differences occur in the measurement signals and calibration signals output from each detection device.
When waveforms are compared using a central computer, it is necessary to store the light level characteristics of each detection device in advance in this computer, which causes the disadvantage that the determination logic becomes complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fault section detection device for an underground power transmission line, which allows the detection device to be miniaturized.

Another object of the present invention is to provide a faulty section detection device for an underground power transmission line that can eliminate the difference in level of signals output from each detection device and simplify the determination logic of a computer.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention includes a detection means for detecting conductor current or sheath current of an underground power transmission line;
The present invention provides a failure section detection device for an underground power transmission line, which includes stress generating means for applying stress to an optical fiber according to the detection output of the detection means, and measuring means for measuring the propagation constant of the optical fiber.

That is, the underground power transmission line failure section detection device of the present invention includes the following means.

(1) Detection means Detects the conductor current or sheath current of underground power transmission lines. This can be done by placing .

(2) Stress generating means A device that applies stress to the optical fiber according to the conductor current or sheath current detected by the above-mentioned detection means, for example, a coil that generates a magnetic field according to the conductor current or sheath current. , a magnetic body that moves under repulsion and attraction based on the magnetic field generated by the coil, and a coil spring that expands and contracts due to the movement of the magnetic body, and the optical fiber is spirally connected along the coil spring. By winding the optical fiber or integrating the optical fiber by passing it inside the coil spring, the optical fiber can be made to follow the expansion and contraction of the coil spring, thereby making it possible to change the helical pitch, etc. of the optical fiber.

(3) Measuring means Measuring the propagation constant of an optical fiber, for example,
It can be configured with a light source connected to one end of an optical fiber and a light receiver connected to the other end of the optical fiber. In other words, by transmitting light with a predetermined intensity from a light source to a light receiver via an optical fiber, it is possible to detect the propagation constant (change in loss) of the optical fiber based on the light level received by the light receiver. can.

[Function] In the above configuration, the stress applied to the optical fiber changes depending on the conductor current or sheath current of the underground power transmission line.
The level of light emitted from the light source at the light receiving section changes. By detecting this change in light level at multiple points and processing it with a computer, the direction and magnitude of the fault current can be detected, and thereby the fault section of the cable can be located. Calculations in the computer are performed based on the light level of the light receiving section or the ratio of the light levels of the received and emitted light, but the latter provides higher calculation accuracy.

〔Example〕

Hereinafter, the underground power transmission line failure section detection device of the present invention will be described in detail.

FIG. 1 shows a first embodiment of the present invention, in which a current transformer 2 for detecting the current flowing through the cross bond line l is arranged on the cross bond line l, and the secondary output of the current transformer 2 is is connected to the coil 9 disposed in the stress generator 20. The coil 9 is provided inside one side of the outer pipe 14 and is surrounded by flanges 10a, 10b made of a material with high magnetic permeability and a side plate 11.
A flange 13a made of a magnetic material and a limiter pipe 17 that slides inside the outer pipe 14 and supports the flange 13a are provided at the other end of the outer pipe 14. flange 13 provided on
A coil spring work 2 is provided between b and flange 13a. An optical fiber 6 is spirally wound around the coil spring 12 along the coil spring 12, and both ends of the optical fiber 6 are taken out from a W20 made by Kogyo Kogyo Co., Ltd., and a light source 7 is attached to one end and a light receiving device is attached to the other end. 8 are connected to each other. 1
Reference numerals 7a and 17b are large diameter portions that restrict the amount of movement of the limiter pipe 17, and are designed to prevent the optical fiber 6 from being damaged due to excessive extension or contraction of the coil spring 12. Note that the stress generating device 20 is installed in a place where conditions such as temperature and humidity are stable.

FIG. 2(a) shows the relationship between the coil spring 12 and the optical fiber 6. As shown in FIG. 1, the optical fiber 6 is spirally wound along the coil spring 12.

Furthermore, as shown in (+), the optical fiber 6 may be integrated into the coil spring 12 by passing it through the interior of the coil spring 12. By doing so, there is no need to protect the optical fiber 6, and the structure is further simplified. be done.

The present invention will be explained in detail below.

When a fault current flows through the cross-bond wire 1 due to a ground fault, etc., the current transformer 2 outputs a secondary current to the coil 9 according to the turns ratio, thereby forming a magnetic field in the coil 9, and increasing the secondary current. Depending on the direction and size, an attractive force or a repulsive force is generated between the flange 10a and the flange 13a. When the flange 13a moves due to this force, the coil spring 12 expands and contracts, and the optical fiber 6 spirally wound along this also follows the expansion and contraction of the coil spring 12.
The helical pitch of changes. That is, when an attractive force is generated between the flange 10a and the flange 13a and the coil spring 12 is expanded, the pitch of the optical fiber 6 is increased, and a repulsive force is generated between the flange 10a and the flange 13a, and the coil spring 12 is expanded. When compressed, the pitch of the optical fiber 6 becomes smaller. On the other hand, a light source 7 connected to one end of the optical fiber 6 always emits light having a predetermined intensity, and a light receiver 8 connected to the other end receives the light. Therefore, when the coil spring 12 is expanded and the pitch of the optical fiber 6 is large, the transmission loss of the light emitted from the light source 7 is reduced, and when the coil spring 12 is compressed and the pitch of the optical fiber 6 is small, the transmission loss of the light emitted from the light source 7 is reduced. In this case, the transmission loss of the light emitted from the light source 7 increases. That is, as shown in FIG. 3, the light level received by the light receiver 8 is constant during normal operation, but when a failure occurs, the light level changes depending on the propagation constant of the optical fiber 6.

Therefore, since the winding direction of the coil 90 and the magnetic field polarity of the flange 13a are determined in advance, it is possible to detect the direction and magnitude of the fault current flowing through the cross bond wire l based on the light level received by the light receiver 8. This allows the fault section of the cable to be located by the computer processing described above.

FIG. 4 shows a second embodiment of the present invention, in which the coil 9 of FIG. 1 is omitted and the secondary output of the current transformer 2 is directly connected to the coil spring 12. Flanges 15a and 15b with high magnetic permeability are fixed to both ends of the coil spring 12, and a coil shaft 18a is installed inside the coil spring 12 to increase the magnetic flux density generated when a current flows through the coil spring 12. ,
18b is provided.

The coil shafts 18a and 18b have a male and female structure in sliding contact, and also serve as a stopper when the coil spring 12 expands and contracts. Further, the coil spring 12 is fixed to the outer vibrator 4 at one location so as to be located at the center. At both ends of the outer pipe 140, magnetic parts 16a, 16 having different polarities with respect to the coil spring 12 are provided.
b is provided. Even in such a configuration, when a fault current flows through the cross bond wire 1, a waveform having a light level as shown in FIG. 3 is obtained from the light receiver 8, and the fault section of the cable can be similarly located. .

〔Effect of the invention〕

As explained above, according to the underground power transmission line failure section detection device of the present invention, the following effects can be achieved.

(1) Since a rectifying semiconductor element and a power source for driving the sensor are not required, the device can be made smaller.

(2) Since the level fluctuation of the optical signal is determined by the characteristics of the coil spring, there is no need to consider the characteristics of each detection device, and the computer's determination logic can be simplified.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the first embodiment of the present invention, and FIG. 2 (
a) and ra) are explanatory diagrams showing the relationship between the coil spring and the optical fiber, and Fig. 3 is a graph showing the light level received by the light receiver.
FIG. 4 is an explanatory diagram showing a second embodiment of the present invention, FIG. 5 is an explanatory diagram showing a conventional fault section detection device for underground power transmission lines,
FIG. 6 is an explanatory diagram showing an output waveform in conventional failure section detection. Explanation of symbols

Claims (4)

[Claims] (1) detection means for detecting conductor current or sheath current of an underground power transmission line; stress generation means for applying stress to an optical fiber according to the detected conductor current or sheath current; and propagation of the optical fiber. 1. A failure section detection device for an underground power transmission line, comprising: a measuring means for measuring a constant. (2) The failure section detection device for an underground power transmission line according to claim 1, wherein the detection means is a current transformer arranged in a cross bond line of the underground power transmission line. (3) A coil that generates a magnetic field according to the stress generating means, the conductor current or sheath current, a magnetic body that moves by repulsion or attraction based on the magnetic field generated from the coil, and movement of the magnetic body. and a coil spring that expands and contracts, and the optical fiber is spirally wound along the coil spring, or is integrated by being passed through the inside of the coil spring. A fault section detection device for an underground power transmission line according to item 1. (4) The underground power transmission line according to claim 1, wherein the measuring means is constituted by a light source connected to one end of the optical fiber and a light receiver connected to the other end of the optical fiber. Failure section detection device.