JPH0748073B2 - Optical fiber laying structure for detection in power cable line fault point detection system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed temperature sensor, and more particularly to a system for detecting an accident occurrence point in a power cable line by using a Raman scattering type optical fiber type distributed temperature sensor, and more particularly to its distribution. The present invention relates to a structure in which an optical fiber, which is a temperature detection unit of a mold temperature sensor, is laid on a power cable line.

2. Description of the Related Art Recently, as a system for detecting an accident occurrence point such as a ground fault in a power cable line, for example, as disclosed in Japanese Patent Laid-Open No. 1-267428, Raman scattering type optical fiber type distributed type Systems using temperature sensors have been developed. That is, the Raman scattering type optical fiber type distributed temperature sensor can measure the temperature distribution in the length direction of the optical fiber which is the temperature detecting portion, and therefore, if the optical fiber is arranged along the power cable line. The position where the temperature rises due to an accident such as a ground fault in the power cable line (the temperature rise peak position) can be detected, and the location of the accident can be known.

The principle of temperature distribution measurement by the Raman scattering type optical fiber type distributed temperature sensor as described above is as follows. That is, when light is incident on the optical fiber, slight fluctuations in the refractive index in the optical fiber and light scattering due to absorption and re-emission of molecules and atoms forming the optical fiber occur. The scattered light includes Rayleigh scattered light having the same wavelength as the incident light and Raman scattered light having the wavelength different from the incident light. The latter Raman scattered light is scattered light generated by thermal vibrations of molecules and atoms forming an optical fiber, and its intensity largely depends on temperature. Therefore, pulsed light of a specific wavelength (usually a laser pulse) is used as the incident light, and the delay of the time until the light returns due to the scattered light and the intensity of the Raman backscattered light are detected to determine the length of the optical fiber. The temperature at each position in the vertical direction can be measured.

By the way, generally when laying power cable lines,
It is practiced to connect power cables (unit cables) of a certain length one after another, and therefore a power cable line always has a connecting portion. On the other hand, regarding maintenance of power cable lines, it is rare for the same department or person to perform maintenance and management over the entire length of a long-distance power cable line. It is usually divided and each department is in charge of a different department or maintenance manager. In this case, the boundary of the maintenance section (maintenance demarcation point) is usually placed at the connection portion of the power cable.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, in the maintenance of power cable lines,
Since each maintenance section has different departments and persons in charge of maintenance management, it is necessary to know in which maintenance section the accident occurred, especially in the vicinity of the boundary of the maintenance section. It is necessary to accurately detect whether or not has occurred. On the other hand, the boundary of the maintenance section is generally the connection part of the unit cable, but this connection part has a much higher frequency of occurrence of ground fault accidents, etc. than the normal part of the power cable. It is strongly desired to improve the detection accuracy of the accident occurrence position.

By the way, the Raman scattering type optical fiber type distributed temperature sensor can detect the temperature rise peak position fairly accurately due to its characteristics, and therefore the power cable line accident detection system using the temperature sensor also has considerable accuracy. Although it is possible to detect the location of a ground fault accident, etc., it is still insufficient to accurately detect which side the fault occurrence location belongs to near the boundary position of each maintenance section as described above. Moreover, it is still insufficient from the viewpoint of accurate detection of the accident occurrence position at the connection part where the accident occurrence frequency is high.

The present invention has been made in view of the above circumstances, and it is necessary to accurately detect an accident occurrence point such as a ground fault accident near a boundary position of a maintenance section in a power cable line or at a connection portion between unit cables. The purpose is to be able to.

Means for Solving the Problems The optical fiber laying structure for detection of the invention according to claim 1 is
In the power cable line fault point detection system, the optical fiber, which is the temperature detection part of the Raman scattering type optical fiber type distributed temperature sensor, is placed along the power cable line and the temperature rise position in the power cable line is detected to detect the accident occurrence point. The power cable line is divided into a plurality of sections, and in the vicinity of the section boundaries, two or more portions of the same optical fiber in different length directions are overlapped and run.

Further, in the optical fiber laying structure for detection of the invention described in claim 2, the optical fiber which is the temperature detecting portion of the Raman scattering type optical fiber type distributed temperature sensor is arranged along the power cable line in the same manner as described above. In the power cable line fault point detection system that detects the temperature rise position and detects the accident occurrence point, the power cable line is configured by connecting a plurality of unit cables in series, and at the connection part of each unit cable, In the same optical fiber, two or more portions in different length directions are overlapped with each other.

In the optical fiber laying structure of the invention according to claim 1, in the area near the section boundary in the power cable line (hereinafter, referred to as section boundary area), the same optical fiber for detection has different length directions. More than one part is duplicated. Therefore, when a temperature rise occurs due to an accident such as a ground fault within the section boundary area, the temperature rise peak position, that is, the accident occurrence position is detected by two or more portions of the same optical fiber. . If the accident occurrence position is detected by two or more portions of the same optical fiber in this way, the detection accuracy is significantly higher than that in the case where the accident position is detected by only one portion of the optical fiber. For example, even if the temperature rise peak position in the section boundary region obtained by the optical fiber does not necessarily appear clearly, it is clarified by superimposing each information from two or more portions of the optical fiber corresponding to the section boundary region. be able to. Specifically, when a position-temperature curve obtained by detecting one portion of the optical fiber in a certain boundary area is obtained, for example, as shown in FIG. It is difficult to determine the temperature peak position from the curve of A). In such a case, for example, if a position-temperature curve as shown in FIG. 8B is obtained from another portion of the optical fiber for the same section boundary region, FIG. 8A is obtained.
By superimposing the curve of FIG. 8 and the curve of FIG. 8B to obtain a curve as shown in FIG.
The PO can be easily determined and the accident location can be clearly determined. Alternatively, even if the temperature peak position information obtained from the optical fiber deviates from the true position, the error can be reduced by averaging the position information obtained in two or more portions of the optical fiber. it can.
Specifically, when a position-temperature curve obtained by detecting one portion of the optical fiber in a certain section region, for example, a curve as shown in FIG. Although the position PA is clearly shown, it is assumed that the peak position PA deviates from the true accident occurrence position PP and that a position error LA exists. In this case, position-temperature curves as shown in FIG. 9B and FIG. 9C are obtained from one or more other locations (two locations in the example of the figure) in the same section boundary region. However, if the peak positions on those curves are PB and PC, respectively,
By averaging the peak positions PA, PB, and PC, the average peak position PD as shown in FIG. 9D can be obtained. By doing so, the position error LB between the average peak position PD and the true accident occurrence position PP becomes extremely small. That is, it is possible to determine the accident occurrence position with a small error. Therefore, from the above, it is possible to accurately detect the accident occurrence position in the section boundary region and accurately determine which section the accident occurrence position belongs to.

In the optical fiber laying structure of the invention described in claim 2,
In each connection portion of the power cable line in which a plurality of unit cables are connected in series via the connection portion, two different portions in the length direction of the same optical fiber for detection are overlapped. Therefore, when a temperature rise occurs due to an accident such as a ground fault in the connection portion, the peak temperature rise position, that is, the accident occurrence position is detected by two or more different portions of the same optical fiber. Similarly to the above, the accident occurrence position in the connection portion can be detected with high accuracy.

In the actual power cable line, the connection portion of the unit cable is often the boundary of the maintenance section as described above. Therefore, in this case, in the invention of claim 1, the accident in the section boundary area is caused. The fact that the occurrence position is detected by two or more portions of the same optical fiber is the same as the fact that the accident occurrence position in the connecting portion is detected by two or more portions of the same optical fiber in the invention of claim 2. It will be. That is, in this case, it is possible to accurately detect the accident occurrence position such as the ground fault in the section that is the section boundary area and the connection section at the same time.

Embodiment FIG. 1 schematically shows the overall configuration of an embodiment that combines the embodiment of the invention described in claim 1 and the embodiment of the invention described in claim 2.

In FIG. 1, the electric power cable line 1 has connecting portions 2A and 2B.
A plurality of unit cables 3A to 3C are connected in series via the power cable line 1, and this power cable line 1 has a plurality of maintenance sections with the center of the connecting sections 2A and 2B as section boundaries 7A and 7B.
It is divided into 4A-4C. Therefore, the connecting portions 2A and 2B are section boundary regions 8A and 8B, respectively. An optical fiber 5 runs along the entire power cable line 1. The optical fiber 5 is connected to a distributed temperature sensor measurement unit 6, and the distributed temperature sensor measurement unit 6 is connected to a host computer 9. Here, in the connection part 2A (that is, the section boundary area 8A),
The optical fiber 5 is provided with two portions 51 and 52 which are arranged at predetermined intervals in the length direction. That is, the optical fiber 5
Is the extra length after being routed along the connecting portion 2A at the portion 51.
53 is returned in a state of being separated from the connecting portion 2A, and is routed again to the connecting portion 2A at the portion 52. Similarly, in the connecting portion 2B (that is, the section boundary region 8B), the optical fiber 5 is also provided with two portions 54 and 55 at predetermined intervals in the lengthwise direction, and between the portions 54 and 55, the same as above. The extra length portion 56 is separated from the connecting portion 2B.

The specific configuration of the distributed temperature sensor measurement unit 6 to which the optical fiber 5 is connected may be the same as a general configuration,
Usually, it is constructed as shown in FIG. That is, the measuring unit 6 is for giving laser pulse light as incident light to the optical fiber, separating the Raman backscattered light returning from the optical fiber, receiving it, amplifying and averaging it. As shown in FIG. 2, a laser light source 10 for oscillating a laser pulsed light as incident light, a drive circuit 11 for driving the laser light source 10, and Raman from reflected scattered light returning from the optical fiber 5 Separation demultiplexer 12 for separating scattered light, and cutting demultiplexer 13 for cutting light components other than Raman light in Raman scattered light
And a light receiving element 14 for converting the Raman scattered light output from the cutting demultiplexer 13 into an electric signal, and a light receiving element 14
And an averaging circuit 16 for improving the S / N ratio of the electric signal. The output signal of the measuring unit 6 (the output signal of the averaging circuit 16) is given to the host computer 9, and the signal for control from the host computer 9 is given to the measuring unit 6. In the host computer 9, the temperature distribution in the length direction of the optical fiber 5 is obtained by calculating the electric signal from the measuring section 6, and the temperature rise peak position, that is, the accident occurrence point such as the ground fault accident is detected. Desired. At this time, as described above, the connecting portions 2A, 2B
In the (section boundary areas 8A, 8B), the two portions 51, 52; 54, 55 of different lengths of the optical fiber are overlapped, so that the signal from the optical fiber is The information obtained by the above can be processed in the host computer 9 to accurately determine the temperature rise peak position, that is, the accident occurrence position such as the ground fault. For example, when a temperature rise peak occurs at the connection portion 2A (section boundary region 8A) due to a ground fault accident or the like, as shown in FIG.
_{Since 1} and P ₂ occur, the length of the extra length 53 and the
If the overlapping length of 2 is stored in the host computer 9, the temperature rise peak position at the connecting portion 2A can be obtained.

In addition, the concrete mode of arranging the optical fiber 5 along each of the unit cables 3A to 3C and the connecting portions 2A and 2B is arbitrary, but for example, as shown in FIG. It may be supported by an appropriate supporting means (not shown) along the line, or spirally wound as shown in FIG. In addition, here, in the connection parts 2A and 2B, overlapping two parts of the optical fiber along the connection part means
It is not limited to the case of arranging them on the same side of 2A, 2B in a double overlapping or adjacent manner, but includes the case of arranging on the opposite side of the connecting portions 2A, 2B as shown in FIG. 6, for example.

Furthermore, in the above embodiments, two portions 51, 5 of the optical fiber 5 are provided in each of the connecting portions 2A, 2B (section boundary regions 8A, 8B).
2; 54, 55 are configured to overlap each other, but in some cases, each connection part 2A, 2B (section boundary region 8A, 8B) overlaps three or more parts in different length directions of the optical fiber. You may follow along. For example, FIG. 7 shows an example in which three portions 51, 52, 57 of the optical fiber 5 are arranged along the connecting portion 2A (section boundary region 8A) in an overlapping manner. In the example of FIG. 7, each part 55
There is no extra length between 1,52 and 57.

Further, in the embodiment of FIG. 1 described above, the section boundaries 7A.7B are shown as being at the center of the connecting portions 2A, 2B, but when the section boundaries 7A, 7B are at the ends of the connecting portions 2A, 2B. Also, in such a case, the section boundary regions 8A and 8B are usually defined as the same regions as the connecting portions 2A and 2B as in the above example, but in some cases, the end portions of the connecting portions 2A and 2B are A region including both side portions sandwiching the section boundaries 7A and 7B, that is, a region including both the connection portion and the end portion of the subsequent unit cable may be defined as the section region.

In addition to this, the section boundaries 7A, 7B may be set at positions separate from and independent of the connecting portions 2A, 2B. In such a case, the section boundary areas 8A, 8B are also located at positions away from the connecting portions 2A, 2B. Therefore, the embodiment of the invention of claim 1 and the embodiment of the invention of claim 2 are different.

Advantageous Effects of Invention According to the detection optical fiber laying structure in the power cable line fault point detection system according to the invention of claim 1, the same detection optical fiber has different length directions in the region near the section boundary in the power cable line. Since more than one part is overlapped, the temperature rise peak position, that is, the accident occurrence position such as a ground fault, is detected in two or more parts of the optical fiber in that region, and therefore the position can be detected with high accuracy. Therefore, it is possible to easily detect in which of the adjacent sections the accident occurrence position has occurred.

Further, according to the optical fiber laying structure for detection in the power cable line fault point detection system of the invention of claim 2, at the connecting portion of each unit cable in the power cable line, two or more locations in the same optical fiber in different length directions are provided. Since the parts overlap each other, the temperature rise peak position, that is, the accident occurrence position such as the ground fault accident is detected by the two or more parts of the optical fiber at the connection part, and therefore the accident occurrence frequency such as the ground fault accident occurs. It is possible to detect an accident occurrence signal in a connection part with high accuracy with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of an example of an optical fiber laying structure for detection in a power cable line accident occurrence point detection system of the present invention, and FIG. 2 is used in the power cable line accident occurrence point detection system of the present invention. Fig. 3 is a block diagram showing an example of a measuring unit according to Fig. 3, Fig. 3 is a diagram showing the relationship between the position in the lengthwise direction of the optical fiber and the detected temperature according to the configuration of Fig. 1, and Figs. Are front views showing examples of main parts of the detection optical fiber laying structure shown in FIG. 1,
FIG. 7 is a schematic diagram showing another example of the main part of the optical fiber laying structure for detection of the present invention, and FIG. 8 is for detecting the accident occurrence point of the power cable line by the optical fiber laying structure for detection of the present invention. Diagram for explaining an example of the action of
FIG. 9 is a diagram for explaining another example of the action for detecting the accident occurrence point of the power cable line by the optical fiber laying structure for detection of the present invention. 1 ... Power cable line, 2A, 2B ... Connection part, 3A, 3B, 3C
...... Unit cable, 4A, 4B, 4C …… Maintenance section, 5 …… Optical fiber, 51,52,54,55 …… Part of optical fiber, 7A, 7B ……
Section boundaries, 8A, 8B, 8C ... Section boundary areas.

Claims (2)

[Claims] 1. A power cable for detecting an accident occurrence point by detecting a temperature rise position in the power cable line by placing an optical fiber, which is a temperature detecting portion of a Raman scattering type optical fiber type distributed temperature sensor, along the power cable line. In the line fault point detection system, the power cable line is divided into a plurality of sections, and in the vicinity of the section boundary, two or more portions of the same optical fiber in different length directions are overlapped. An optical fiber laying structure for detection in a power cable line fault point detection system characterized by the above. 2. A power cable for detecting an accident occurrence point by detecting a temperature rising position in the power cable line by placing an optical fiber, which is a temperature detecting portion of a Raman scattering type optical fiber type distributed temperature sensor, along the power cable line. In the line fault point detection system, the power cable line has a configuration in which a plurality of unit cables are connected in series, and at the connection portion of each unit cable, there are two or more locations in the same optical fiber in different length directions. An optical fiber laying structure for detection in a power cable line fault point detection system, which is characterized by overlapping portions.