JP2642841B2 - Optical fiber composite power cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber composite power cable in which an optical fiber for measuring a temperature distribution of a cable is composited.

[0002]

2. Description of the Related Art In recent years, overhead cables in urban areas have become
Regardless of the power cable or communication cable, undergrounding is being promoted from the viewpoint of traffic and aesthetics. In particular, overhead power cables may hinder fire fighting activities in building areas, and there is a strong demand for underground power cables. For this reason, the undergrounding of power cables in major cities has been progressing remarkably recently. However, if a power cable goes underground, it takes a lot of time to recover from a cable accident in the event of a cable accident.Therefore, safety measures such as monitoring the power cable and detecting abnormalities at an early stage to prevent damage to other attached cables, etc. The need for countermeasures is increasing. It is also important to locate cable fault points after an accident in a short time.

In general, power cables are often designed and laid with a margin for the current capacity. In response to the recent rapid increase in power demand, the permissible temperature is monitored while monitoring the temperature of the actual cable operating state. It is important to manage the current that can be transmitted below. From the above background, an optical fiber composite power cable in which an optical fiber cable having a temperature distribution detecting function is combined with a power cable to manage the allowable current of the power cable and to search for an abnormal point of the cable may be used. It has become.

An OTDR (optical time domain) is used for temperature distribution measurement using this optical fiber.
Reflectometry) method is used,
The principle of the temperature distribution measurement will be described with reference to FIG.

The frequency of a light pulse incident on an optical fiber is ωo, and the frequency of light corresponding to the difference ΔE between the ground level of the energy level of the fiber constituent material (for example, SiO ₂ ) and the excitation level is ωf (ωf = ΔE / H, h; Planck constant). When a strong light pulse is incident on the optical fiber, energy is transferred between the incident photon and the constituent material of the optical fiber, and is mixed with Rayleigh scattered light having the same frequency as the incident light (ωo) and is called Raman scattered light. Higher frequency (ωo + ωf) and lower frequency (ωo-
ωf) is observed.

This is because a photon (ω
o) is absorbed by the fiber constituent material in the ground state, and the Stokes light (ωo−ω) when the material is in an excited state having a higher energy level than the original ground state when photons are emitted.
f) is emitted, and vice versa.
+ Ωf) is released.

The frequency deviation ωf of the Raman scattered light is a value inherent to the substance and is proportional to the difference ΔE between the thermal energy levels as described above.
0 ¹² ) Hz.

The intensity of the Stokes light and the anti-Stokes light has a temperature dependence shown in FIG. 7, and the temperature dependence of the anti-Stokes light is relatively large. The distributed optical fiber temperature sensor measures the light by observing the temporal change in the intensity ratio of the Stokes light and the anti-Stokes light of the backward Raman scattered light scattered in the optical fiber and transmitted in the direction opposite to the traveling direction of the incident light. Is converted to the distance from the incident point to the reflection point, and the temperature distribution in the longitudinal direction of the cable is measured.

Next, the configuration of the temperature measurement system will be described. FIG. 5 is a block diagram of a distributed temperature measurement system using an optical fiber. The measuring system is roughly divided into an optical fiber core 7, a measuring unit 20, a digital averaging unit 29, and a computer 30 including a display unit.
Consists of

[0010] The optical fiber core has a function of temperature detection based on the above-described principle and a transmission path of the temperature detection information. The measurement unit 20 includes an optical unit 21 and a photoelectric conversion unit 24. The optical unit 21 receives a trigger signal from the digital averaging unit 29 and causes the pulse light source 22 (for example, a laser diode or the like) of monochromatic light to emit light. Optical fiber core wire 7 through spectral device 23
Incident on. Further, the optical unit 21 separates the reflected light from the optical fiber core wire 7 into Stokes light and anti-Stokes light by the spectral device 23. The photoelectric conversion unit 24 converts the separated Stokes light and anti-Stokes light into electric signals by light receiving elements 25 and 26 (for example, silicon avalanche photodiodes; Si-APDs).
The signal is amplified by the amplifiers 27 and 28 and sent to the digital averaging unit 29.

[0011] Digital averaging unit 29, a number of times above the measurement at a high speed is performed (e.g., 10 ⁹ times), is designed to remove noises by averaging process converts the measurement signal into a digital signal. The computer 30 controls the entire measurement and also controls the digital averaging unit 2.
The data is downloaded from 9 and converted into a temperature and a distance and displayed on a display screen or printed out.

From the pulse light source 22 to the optical fiber core 7
Is t = 2Lo / v (where Lo is the optical fiber cord from the incident end of the pulsed light to the point where backscattering occurs). 7 and v are the speed of light in the optical fiber.) Since the digital averaging unit 29 triggers the pulse light source 22 to emit pulse light, the light receiving elements 25 and 26 By measuring the time t until the detection signal is output, the position where the backscattered light is generated can be located, and as a result, the position where the temperature abnormality of the power cable 1 occurs can be obtained.

The optical fiber distribution type temperature measuring system described above has already been commercialized and sold by the applicant of the present invention as "optical fiber distribution type temperature sensor DFS-1000 type". An example of the measurement performance of this system is shown below. Temperature measurement accuracy ± 1 ° C Temperature measurement range -20 to + 150 ° C Measurable distance 2km Distance resolution 1m Measurement required time about 10 seconds Also, Fig. 8 shows an example of Raman backscattering measurement of the system, and Fig. 9 shows the measurement of Fig. 8 The example which converted the data of the example into the temperature is shown.

Further, an optical fiber composite power cable in which an optical fiber and a power cable, which are adapted to the above-described optical fiber distribution type temperature measuring system, are combined, has already been applied for a patent by the applicant of the present invention (Japanese Patent Application No. Sho 63). -28669
8 and Japanese Patent Application No. 63-296101; "Method of measuring power cable and its temperature distribution").

[0015]

However, such a conventional technique is satisfactory as a temperature distribution measurement for the purpose of controlling the allowable current of a cable.
Has sufficient detection capability for local temperature rises (hot spots) that occur in relatively short sections of cables such as cable ground faults and that occur in a non-rotationally symmetric manner about the cable axis. There was a problem that not.
Also, when providing optical fiber cores,
Consider bending strain of optical fiber core when bending
To protect the fiber optic cable from damage.
There has been no technology that takes such consideration into consideration in the past. In view of the above points, the present invention can detect a ground fault accident early and reliably, and the optical fiber core wire is damaged by bending strain.
It is an object of the present invention to provide an optical fiber composite power cable which does not have a risk of being damaged .

[0016]

SUMMARY OF THE INVENTION An optical fiber composite power cable according to the present invention includes an internal semiconductive cable around a cable center conductor.
An insulator is provided through a layer, and an outer semiconductive
In a power cable provided with a shielding layer including an external conductor through a layer and a jacket provided on the outer periphery of the shielding layer, an optical fiber core is provided along a longitudinal direction on a part of the shielding layer, The optical fiber core is set to 2.5 to 20 of the outer diameter of the shielding layer.
An object of the present invention is to solve the above problem by wrapping the outer circumference of the insulator at twice the pitch and detecting an accident in the power cable based on the Raman scattered light intensity of the optical fiber.

Further, the present invention relates to a power cable in which a cable center conductor is insulated by an insulator, and a jacket is provided on the outer periphery of the insulator. A core fiber is provided, and the optical fiber core is wound around the outer periphery of the insulator at a pitch of 2.5 to 20 times the outer diameter of the insulator, and a power cable accident is detected based on the Raman scattered light intensity of the optical fiber core. Can be detected.

[0018]

The present inventor has developed a method for simulating a ground fault in a power cable as shown in FIG. Development of Cable Fault Point Evaluation Method by Temperature Detection ”, Amano et al.). In this method, a test power cable in which a defect (0.1 mmφ conductor) is buried in an insulator during the power cable manufacturing process is created, and a high voltage is applied to the test power cable to reduce the power in the event of a ground fault. It measures the temperature distribution of the cable. According to this temperature distribution measurement, if the optical fiber core is wound around the outer periphery of the insulator at a pitch of 2.5 to 20 times the outer diameter of the insulating layer or the insulator, precise accuracy can be obtained in accordance with various voltage classes and various nominal cross-sectional areas. It was discovered that cable temperature distribution can be measured.

Further , the optical fiber core is placed outside the shielding layer.
Insulator at a pitch of 2.5 to 50 times the diameter or insulator outer diameter
Wrapping around the outer periphery is based on the following reasons. Optical fiber core wire more than the winding pitch of the shielding layer conductor
Of the optical fiber core
When the wires cross, the optical fiber core will have a large size.
There is a possibility that breakage may occur due to application of an excessive strain stress. This
In order to avoid crossover, the minimum winding pin
Make the minimum winding pitch of the optical fiber core larger than
Need to be done. Minimum winding pitch of shield layer conductor
Is 2.5 times the outer diameter of the shielding layer or the insulator. There
Therefore, in the present invention, the outer diameter of the optical fiber core is adjusted to the outer diameter of the shielding layer.
Or 2.5 times or more the outer diameter of the insulator and the optical fiber
This is to prevent the conductor from crossing. To reduce the cost of optical fiber composite power cables
Need to increase the winding pitch as much as possible
is there. However, the winding pitch is too large
If the power cable is bent too much,
The bending strain of the optical fiber increases, and the optical fiber
May be damaged. No such damage occurs
Maximum winding pitch is the outer diameter of the shielding layer or outer diameter of the insulator
20 times that of Therefore, in the present invention, an optical fiber
The maximum winding pitch of the shielding layer outer diameter or insulator outer diameter.
20 times. In the present invention, an optical fiber core wire provided on a shield layer or a jacket of a power cable is wound around the outer periphery of the insulator at a pitch of 2.5 to 20 times the outer diameter of the shield layer or the outer diameter of the insulator, and pulsed around the optical fiber. By measuring the time change of the intensity ratio between Stokes light and anti-Stokes light of backward Raman scattered light when light is incident, a local temperature rise that is asymmetric with respect to the cable central axis in a short section of the cable is detected. In addition to detecting the ground fault accident of the power cable at an early stage, the distance from the cable terminal to the accident point can be calculated, and the accident point can be located. Also, for the above reason, the winding of the optical fiber
The pitch is 2.5 to 20 times the outer diameter of the shielding layer or the outer diameter of the insulator.
To prevent excessive bending strain of the optical fiber
Therefore, breakage of the optical fiber can be prevented.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of an optical fiber composite power cable according to the first embodiment of the present invention. As shown in the figure, an optical fiber composite power cable 1 has an inner semiconductive layer 3 and a cross-linked polyethylene insulating layer (insulator) on the outer periphery of a cable center conductor 2 in which a plurality of copper strands are twisted to form a divided conductor.
4, an outer semiconductive layer 5 is provided in order, and usually, the inner semiconductive layer 3, the polyethylene insulating layer 4 and the outer semiconductive layer 5 are formed by a co-extrusion method, and a gap between the inner semiconductive layer 3 and the polyethylene insulating layer 4 is formed. And the crosslinked polyethylene insulating layer 4 and the outer semiconductive layer 5 are integrated.

A shield layer 8 is provided on the outer periphery of the outer semiconductive layer 5 by spirally winding a large number of copper wires, and a cable sheath (outer jacket) 9 made of plastic, metal or the like is coated thereon. ing.

Further, four optical fiber cores 7 are provided in a part of the shielding layer 8 in the circumferential direction along the longitudinal direction, and the optical fiber cores 7 are optical fibers as shown in FIG. The element wire 7a is covered with a metal layer 7c of copper, aluminum, stainless steel or the like, and a gap between the metal layer 7c and the optical fiber element wire 7a is lubricated with a ceramic powder such as alumina (Al ₂ O ₃ ) or a powder lubrication such as talc powder. The agent 7b is enclosed.

In the first embodiment, the optical fiber core 7
Are provided on the outer periphery of the insulating layer 4, but the invention is not limited to this, and at least one or more may be provided.

FIG. 1 is a partially exploded view showing the spirally wound shape of the shielding layer 8 with the cable sheath 9 of the optical fiber composite power cable 1 of the first embodiment removed. In this embodiment, the pitch of the spiral winding of the optical fiber core wire 7 which is a part of the shielding layer 8 is eight times the outer diameter of the shielding layer 8, but is not limited to this.

The optical fiber combined with the power cable as described above is connected to the distributed temperature measurement system shown in FIG. 5 described in the prior art, and the pulse light is made incident on the optical fiber to reduce the intensity of the Raman scattered light. By measuring the time change, a continuous temperature distribution in the longitudinal direction of the cable can be measured, and a temperature rise in a cable ground fault can be detected. Also, without distortion bending the optical fiber 7 is caused to excessive breakage of the optical fiber 7 can be prevented.

Next, FIG. 4 shows a sectional view of an optical fiber composite power cable 1A according to a second embodiment of the present invention, and the same parts as those in the first embodiment are described with the same reference numerals.
In the second embodiment, the insulating layer 4 of the power cable 1 shown in FIG.
The optical fiber core wire 7 shown in FIG. 3 is provided on the outer circumference of the insulating layer 4, and the optical fiber core wire 7 is spirally wound around the outer circumference of the insulating layer 4.
An optical fiber composite power cable 1A is configured by providing a jacket 9 on the outer periphery. The winding pitch of the optical fiber core wire 7 may be any value between 2.5 and 20 times the outer diameter of the insulating layer 4. This optical fiber composite power cable 1A
5 can be connected to the distributed temperature measurement system of FIG. 5 similarly to the first embodiment to measure a continuous temperature distribution in the longitudinal direction of the cable, and detect a temperature rise due to a cable ground fault. In addition, winding the optical fiber 7
The pitch of the optical fiber is set to 2.5 to 20 times the outer diameter of the insulating layer 4.
The bending distortion of the fiber core wire 7 can be prevented from being excessively generated.
Therefore, breakage of the optical fiber 7 can be prevented. The preferred embodiment has been described above, but this does not limit the scope of the invention. The scope of the invention should be limited only by the appended claims. From the above description, many modifications within the spirit and scope of the invention will be apparent to those skilled in the art.

[0027]

As described above, in the present invention, the optical fiber core of the optical fiber composite power cable is
Stokes of backward Raman scattered light when pulsed light is incident on an optical fiber by helically winding the outer circumference of the shielding layer or insulating layer at a pitch of 2.5 to 20 times the outer diameter of the shielding layer or insulating layer Measuring the temporal change of the intensity ratio of light to anti-Stokes light to detect a local temperature rise that is asymmetric with respect to the cable center axis in a short section of the cable, and to detect a ground fault in the power cable at an early stage. And the distance from the cable terminal to the accident location can be calculated, and the location of the accident location can be located. Also shields the winding pitch of the optical fiber
Make the optical fiber 2.5 to 20 times the outer diameter of the layer or insulator.
Optical fiber core when the composite power cable is bent
Since optical bending distortion does not occur excessively, optical fiber
The breakage of the core wire can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially exploded view of an optical fiber composite power cable according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the optical fiber composite power cable according to the first embodiment of the present invention.

FIG. 3 is an enlarged sectional view of an optical fiber cable;

FIG. 4 is a sectional view of an optical fiber composite power cable according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a distributed temperature measurement system.

FIG. 6 is an explanatory diagram of the Raman scattering principle.

FIG. 7 is a diagram showing the temperature dependence of Raman scattered light intensity.

FIG. 8 is a measurement example of Raman scattered light intensity.

FIG. 9 is an example of temperature measurement by measuring the intensity of Raman scattered light.

FIG. 10 is a diagram illustrating an outline of a cable ground fault pseudo fault test method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical fiber composite power cable (first embodiment) 1A optical fiber composite power cable (second embodiment) 2 cable center conductor 3 inner semiconductive layer 4 crosslinked polyethylene insulating layer 5 outer semiconductive layer 7 optical fiber core 7a Optical fiber strand 7b Powder lubricant 7c Metal layer 8 Shielding layer 9 Cable sheath (jacket) 20 Measurement unit 21 Optical unit 22 Pulse light source 23 Spectral device 24 Photoelectric conversion unit 25, 26 Light receiving element 27, 28 Amp (amplifier) 29 Digital averaging unit 30 Computer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01B 11/22 H01B 11/22

Claims (2)

(57) [Claims] 1. An inner semiconductive layer around a cable center conductor.
Via an insulating member, outer semiconductive layer on the outer periphery of the insulator
A shield layer including an external conductor is provided via the above, and in a power cable having a jacket provided on the outer periphery of the shield layer, an optical fiber core is provided along a longitudinal direction on a part of the shield layer,
The optical fiber core wire is wound around the outer periphery of the insulator at a pitch of 2.5 to 20 times the outer diameter of the shielding layer, and it is possible to detect a power cable accident based on the Raman scattered light intensity of the optical fiber core wire. An optical fiber composite power cable, characterized in that: 2. A power cable in which a cable center conductor is insulated by an insulator, and a jacket is provided on an outer periphery of the insulator, wherein a part of the jacket is provided with an optical fiber core along a longitudinal direction thereof. And the optical fiber core wire having the outer diameter of the insulator.
An optical fiber composite power cable, which is wound around the insulator at a pitch of 5 to 20 times, and is capable of detecting an accident of the power cable based on Raman scattered light intensity of the optical fiber core.