JPH0748327B2 - Power cable and its temperature distribution measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention utilizes the fact that the intensity of Raman scattered light is a function of temperature, and the electric power capable of measuring a continuous temperature distribution in the longitudinal direction of a cable conductor. The present invention relates to a cable and its temperature distribution measuring method.

[Conventional technology]

Generally, in order to manage the allowable current of the power cable,
One example is measuring the temperature distribution in the longitudinal direction of the cable conductor. As a means for measuring this temperature distribution, it is conceivable to attach a large number of thermocouples at a predetermined interval along the longitudinal direction of the cable conductor, but since the thermocouple is a conductor in this means, the thermocouple is attached to the cable conductor. When they are directly contacted with each other, the thermocouple becomes the same potential as the cable conductor, and the measurement work is extremely dangerous. Therefore, conventionally, the temperature distribution has not been measured directly on the cable conductor. However, in order to measure the temperature distribution of the cable conductor, the temperature in the longitudinal direction of the cable conductor can be indirectly measured by attaching a large number of thermocouples at predetermined intervals along the longitudinal direction of the insulator provided around the cable conductor. It is possible to measure the distribution.

[Problems to be Solved by the Invention]

However, in the conventional technique in which a large number of thermocouples are mounted at a predetermined interval along the longitudinal direction of the insulator in the power cable as described above, a large number of measurement points are required, and therefore a large number of thermocouples are required. It takes a lot of man-hours, there is a problem that the temperature distribution measuring means becomes enormous price, and there is a problem that the insulation performance is impaired. Moreover, since the temperature distribution in the longitudinal direction of the cable conductor is indirectly and partially measured, there is a problem that the measurement temperature accuracy is low.

Therefore, the present invention has been made in consideration of the above circumstances,
An object of the present invention is to provide a power cable and a temperature distribution measuring method thereof, which can continuously and safely measure temperature distribution in the longitudinal direction of a cable conductor with high accuracy without impairing electrical insulation performance. And

[Means for Solving the Problems]

The power cable according to the present invention is a power cable in which a cable conductor is insulated with an insulator, and a sheath is provided on the outer periphery of the insulator, wherein Raman scattered light having electrical insulation is provided along the longitudinal direction of the cable conductor. It is characterized in that a fiber core wire is provided.

Further, the temperature distribution measuring method of the power cable according to the present invention is such that Raman scattering is introduced into the optical fiber core by causing pulsed light to enter from the end of the Raman scattering optical fiber core provided along the axial direction of the cable conductor. Is generated, the Raman scattered light intensity is detected, and the temperature distribution is continuously measured in the longitudinal direction of the cable conductor based on the Raman scattered light intensity.

[Action]

Since the present invention is configured as described above, by providing a Raman scattering optical fiber core wire having an electrically insulating property along the longitudinal direction of the cable conductor, a pulse is provided at the end of the optical fiber core wire. When light is incident, Raman scattering occurs in the optical fiber core, and the intensity of this Raman scattered light is expressed by a function that depends on temperature, so the Raman scattered light intensity does not impair the insulation performance of the power cable. The temperature distribution in the longitudinal direction of the cable conductor can be obtained. Therefore, the temperature distribution continuous in the longitudinal direction of the power cable can be measured with one Raman scattering optical fiber core wire, which is inexpensive, and since the optical fiber core wire is an insulator, the measurement work is extremely safe.

〔Example〕

Hereinafter, the present invention will be described based on illustrated embodiments. FIG. 1 shows a power cable according to an embodiment of the present invention. As shown in FIG. 1, a power cable 1 comprises a cable conductor 2 in which a plurality of copper strands are twisted together to form each divided conductor 2a, and an inner semiconductive layer 3, a polyethylene insulating layer 4, and an outer semiconductive layer 5 are sequentially arranged. The inner semiconductive layer 3, the polyethylene insulating layer 4 and the outer semiconductive layer 5 are usually formed by a coextrusion method,
The inner semiconductive layer 3 and the polyethylene insulating layer 4 as well as the insulating layer 4 and the outer semiconductive layer 5 are integrated.
The outer semiconductive layer 5 is covered with a cable sheath 6 made of plastic, metal or the like.

Further, a Raman scattering optical fiber core wire 7 having an electrically insulating property is provided along the longitudinal direction at the central portion of the cable conductor 2, and this optical fiber core wire 7 is as shown in FIG. The optical fiber element wire 7a is covered with a ceramic layer 7b of alumina (Al ₂ O ₃ ) or the like, and a metal layer 7c of copper, aluminum, stainless steel or the like is provided on the outer periphery of the ceramic layer 7b. Therefore, by providing the Raman scattering optical fiber core wire 7 in the central portion of the cable conductor 2, it becomes easy to incorporate the optical fiber core wire 7 into the power cable 1 in manufacturing.
Then, when a pulse is made incident from the end portion of the optical fiber core wire 7, Raman scattering occurs in the optical fiber core wire 7, and a continuous temperature distribution in the longitudinal direction of the cable conductor 2 is obtained from the intensity of the Raman scattered light. It will be.

Next, using the temperature distribution measuring device 10 as shown in FIG. 3 to measure continuous temperature distribution in the longitudinal direction of the cable conductor 2 of the power cable 1 will be described. In the figure, the power cable 1 including the Raman scattering optical fiber core wire 7 is arranged in a power transmission system in which the temperature distribution is to be measured. The temperature distribution measuring device 10 has an optical branching device 15, a light source 14 is provided at one port of the optical branching device 15, and a detection system is provided at the other port. The light source driving device 13, the pulse delay circuit 12, and the pulse generator 11 are connected to the light source 14, and the signal output from the pulse generator 11 is directly input to the data processing circuit 19 while the pulse delay circuit 2 is used. The pulse signal delayed by a predetermined time is input to the light source driving device 13. The light source driving device 13 drives the light source 14 according to the input pulse signal, and the light source 14 emits pulsed light of frequency ω ₀ . The pulsed light from the light source 14 passes through the optical branching device 15 and enters the end portion of the Raman scattering optical fiber core wire 7 in the power cable 1. Other Rayleigh scattered light of the frequency omega ₀ is in the optical fiber 7, the Raman scattered light is generated consisting of two components of the frequency ω ₀ -ω _{f (Stokes} light) and ω _{0 +} ω _{f (anti-Stokes} light).

A part of the Rayleigh scattered light and Raman scattered light generated in the Raman scattering optical fiber core wire 7 returns through the optical fiber core wire 7, is emitted from the end portion thereof, is branched by the optical branching device 15, and is further Stokes by the optical branching device 16. Divided into light and anti-Stokes,
The intensities of these lights are detected by the photo detectors 17 and 18, respectively, and the output signals are sent to the data processing circuit 19. In the data processing circuit 19, the temperature of the optical fiber core wire 7 is obtained, and the distance is determined based on the time difference between the pulse signal from the pulse generator 11 and the Raman scattered light detection signals from the light receivers 17 and 18. Then, by continuously scanning the display 20, the temperature distribution of the Raman scattering optical fiber core wire 7 can be continuously obtained in the longitudinal direction of the cable conductor 2. Here, the measurement temperature range of the Raman scattering optical fiber core wire 7 in the present embodiment is −20 to + 150 ° C.,
Measurement temperature accuracy is ± 1 ℃, and measurement distance is 2km (resolution:
1m).

As described above, according to this embodiment, since the two-wavelength measurement method is adopted, there is no influence of disturbance. Also,
Since a continuous temperature distribution in the longitudinal direction of the cable conductor 2 of the power cable 1 can be measured with a single Raman scattering optical fiber core wire, it is possible to provide a power cable for temperature distribution measurement that is easy to measure and inexpensive. You can

FIG. 4 shows a power cable according to another embodiment of the present invention. When the same parts as those in the above embodiment are designated by the same reference numerals, the divided conductors 2a constituting the cable conductor 2 in this embodiment will be described. Raman-scattering optical fiber core wires 7 are laid vertically or twisted along the longitudinal direction of the cable conductor 2 between the shoulders of the optical conductors. According to this embodiment, the optical fiber core wires are arranged in the circumferential direction of the cable conductor 2. Since 6 can be arranged,
The measurement temperature accuracy will be further improved. In this case, the temperature distribution can be measured by providing at least one optical fiber core wire 7. The other structure and operation are the same as those of the above-mentioned embodiment, and therefore the explanation thereof is omitted.

〔The invention's effect〕

As described above, according to the power cable of the present invention, the electrically insulating Raman scattering optical fiber core wire is provided along the longitudinal direction of the cable conductor, so that the longitudinal direction can be achieved without impairing the insulation performance. The continuous temperature distribution can be measured with high accuracy, and the temperature control of the cable conductor becomes easy.

Further, according to the temperature distribution measuring method of the power cable according to the present invention, since the Raman scattering optical fiber core wire is used, the measurement work becomes easier and cheaper than the method of measuring the temperature distribution with the thermocouple. It becomes possible to measure. In addition, since the Raman scattering optical fiber core wire is an insulator, the measurement work is extremely safe.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a power cable according to an embodiment of the present invention, FIG. 2 is a schematic sectional view showing a Raman scattering optical fiber core wire of FIG. 1, and FIG. 3 is a cable conductor in the same embodiment. FIG. 4 is a block diagram showing a temperature distribution measuring device, and FIG. 4 is a schematic sectional view showing a power cable according to another embodiment of the present invention. 1 ... Power cable, 2 ... Cable conductor, 2a ... Split conductor,
4 ... Polyethylene insulating layer, 6 ... Cable sheath, 7 ... Raman scattering optical fiber core wire, 10 ... Temperature distribution measuring device.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Isao Kaji 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Hajime Takehana 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Isao Miura 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (56) References: Mitsuihei 2-134173 (JP, U)

Claims (4)

[Claims] 1. A power cable in which a cable conductor is insulated with an insulator and a sheath is provided on the outer periphery of the insulator, and a Raman scattering optical fiber core having electrical insulation along the longitudinal direction of the cable conductor. A power cable characterized by having a wire. 2. The power cable according to claim 1, wherein the Raman scattering optical fiber core wire is provided in a central portion of the cable conductor. 3. The power cable according to claim 1, wherein the Raman scattering optical fiber core wire is provided between shoulder portions of divided conductors which constitute the cable conductor. 4. Raman scattering is generated in the optical fiber core by injecting pulsed light from the end portion of the Raman scattering optical fiber core provided along the axial direction of the cable conductor. Is detected and the temperature distribution is continuously measured in the longitudinal direction of the cable conductor based on the Raman scattered light intensity.