Temperature measurement method

Abstract

To provide a temperature measurement method for a power cable capable of measuring the temperature of a cable conductor across the entire length with good responsiveness.SOLUTION: When measuring a temperature of a cable conductor, a magnetic body is arranged in the periphery of the cable conductor of a power cable, the temperature of the magnetic body is measured by using an optical fiber arranged along the power cable, and the temperature of the cable conductor is calculated based on the measured temperature of the magnetic body.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for measuring the temperature of a power cable. [Background technology]

[0002] Conventionally, evaluation of the soundness of laid power cables has been performed using optical fiber sensors (see, for example, Patent Document 1). Patent Document 1 discloses detection of partial discharge occurring in a power cable by using an optical fiber combined with the power cable over its entire length.

[0003] Also known is an optical fiber sensor that arranges an optical fiber along an object to be measured and detects continuous distribution information (temperature, strain, vibration, etc.) along the optical fiber from changes in the transmission characteristics (intensity, phase, frequency, wavelength, etc.) of the light propagating through the optical fiber. This type of optical fiber sensor is called a "distributed type." A distributed optical fiber sensor measures the temperature of the cable conductor over the entire length of the power cable, and the current flow and therefore the amount of power consumption can be determined based on the measured temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-297154 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, an optical fiber is disposed inside a power cable, specifically between the cable shielding layer and the cable insulator. When this optical fiber is used as a distributed optical fiber sensor to detect the temperature of the cable conductor, the temperature of the cable conductor is transmitted to the optical fiber via the insulator. Therefore, the response of the optical fiber to the temperature change of the cable conductor is delayed, making it difficult to grasp the temperature change in real time. In particular, it is considered that the response of the optical fiber sensor becomes worse for high-voltage cables with thicker cable insulators.

[0006] An object of the present invention is to provide a method for measuring the temperature of a power cable, which is capable of measuring the temperature of the cable conductor over its entire length with good responsiveness. [Means for solving the problem]

[0007] The temperature measuring method according to the present invention comprises: A magnetic material is disposed around the cable conductor of the power cable, measuring the temperature of the magnetic body using an optical fiber arranged along the power cable; The temperature of the cable conductor is calculated based on the measured temperature of the magnetic body. Effect of the Invention

[0008] According to the present invention, the temperature of a cable conductor can be measured with good responsiveness. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a method for measuring the temperature of a cable conductor according to an embodiment. [Diagram 2] 2A and 2B are diagrams illustrating an example of a composite optical fiber. [Diagram 3] FIG. 3 is a diagram showing a configuration of a power cable. [Figure 4] 4A and 4B are diagrams showing an example of an arrangement mode of the composite optical fiber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0011] FIG. 1 is a conceptual diagram showing a method for measuring the temperature of a cable conductor according to one embodiment of the present invention.

[0012] As shown in FIG. 1, in this embodiment, a distributed optical fiber sensor consisting of an optical fiber composite wire 10, a light source 31, and a detector 32 is used to measure the temperature of a cable conductor 21 (see FIG. 3) over the entire length of a power cable 20.

[0013] Specifically, light is emitted from a light source 31 to the optical fiber 11 of the composite optical fiber wire 10. The emitted light propagates through the optical fiber 11, and generates scattered light during the propagation process. By detecting this scattered light with a detector 32, it is possible to measure the temperature around the optical fiber 11 and the deformation (strain) of the optical fiber 11. The principle of the distributed optical fiber sensor is well known, so a detailed description thereof will be omitted.

[0014] 1, the composite optical fiber 10 is arranged to be spirally wound along the outer circumferential surface of the power cable 20 over the entire length. Also, for example, the composite optical fiber 10 may be incorporated inside the power cable 20.

[0015] The optical fiber composite wire 10 is composed of an optical fiber 11 and a magnetic wire 12. The magnetic wire 12 may be a solid linear member (see FIG. 2A) or a hollow tubular member (see FIG. 2B).

[0016] The magnetic wire 12 is made of a magnetic material (magnetic body) such as iron, nickel, or cobalt, or an alloy thereof. The magnetic wire 12 generates heat by induction heating caused by current flow through the cable conductor 21.

[0017] The optical fiber 11 is disposed in the vicinity of the magnetic wire 12. "In the vicinity of the magnetic wire 12" means a position close enough that the temperature of the magnetic wire 12 can be detected by the transmission characteristics of the optical fiber 11.

[0018] In this embodiment, the temperature of the cable conductor 21 is not measured directly, but rather the temperature of the magnetic wire 12 is measured by the optical fiber 11 by utilizing the fact that a temperature change of the cable conductor 21 is reflected in a temperature change of the magnetic wire 12, and the temperature of the cable conductor 21 is indirectly measured based on the temperature of the magnetic wire 12.

[0019] 2A and 2B are diagrams illustrating an example of the composite optical fiber 10. FIG.

[0020] 2A and 2B, a known configuration can be applied in which a linear member or a tubular member is disposed as a reinforcing wire around the optical fiber 11. However, in conventional optical fiber composite wires, the reinforcing wire is not made of a magnetic material.

[0021] In Fig. 2A, the composite optical fiber wire 10 is composed of a composite optical fiber strand in which an optical fiber 11 and a solid magnetic wire 12 are stranded together. In Fig. 2A, the composite optical fiber wire 10 has two optical fibers 11 and 17 magnetic wires 12.

[0022] The optical fiber 11 is preferably arranged in the outermost layer of the stranded wire. In the case of a stranded optical fiber, if the optical fiber 11 is arranged in the center, heat is trapped and the temperature of the magnetic wire 12 is not easily reflected in the optical fiber 11, which may result in a decrease in responsiveness. In contrast, if the optical fiber 11 is arranged in the outermost layer of the stranded wire, heat dissipation is improved, so that the temperature of the magnetic wire 12 is quickly reflected in the optical fiber 11, improving responsiveness.

[0023] 2B, the optical fiber composite wire 10 has a configuration in which an optical fiber 11 is disposed in the hollow portion of a tubular magnetic wire 12. In FIG. 2B, one optical fiber 11 is disposed in the hollow portion of the magnetic wire 12.

[0024] 2A and 2B, the optical fibers 11 are disposed near the magnetic wire 12. In the optical fiber composite wire 10, the positional relationship between the optical fibers 11 and the magnetic wire 12 is substantially fixed, so that the optical fibers 11 are reliably disposed near the magnetic wire 12. Note that, in the optical fiber composite wire 10, the number of optical fibers 11 disposed is not particularly limited.

[0025] FIG. 3 is a diagram showing a configuration of a power cable.

[0026] 3, the power cable 20 has, in order from the center, a cable conductor 21, a cable insulator 22, a cable shielding layer 23, and a cable sheath 24. Although not shown in the figure, an inner semiconductive layer may be interposed between the cable conductor 21 and the cable insulator 22, and an outer semiconductive layer may be interposed between the cable insulator 22 and the cable shielding layer 23.

[0027] 4A and 4B are diagrams showing an example of an arrangement of the composite optical fiber 10 relative to the power cable 20. Fig. 4A shows an example in which the composite optical fiber 10 is arranged outside the power cable 20 along the power cable 20, and Fig. 4B shows an example in which the composite optical fiber 10 is arranged inside the power cable 20 along the power cable 20.

[0028] 4A shows a case where the composite optical fiber 10 is arranged in a triplex type power cable in which three power cables 20 are twisted together. As shown in FIG. 4A, the composite optical fiber 10 is arranged, for example, near the contact portion of the two power cables 20.

[0029] The optical fiber composite wire 10 may be arranged, for example, so as to be in contact with the power cable 20, or may be arranged apart from the power cable 20. In either case, the optical fiber composite wire 10 is arranged along the axial direction of the power cable 20. When the optical fiber composite wire 10 is arranged apart from the power cable 20, the effect of a temperature rise in the magnetic wire 12 on the cable sheath 24 can be reduced, and damage to the power cable 20 can be prevented.

[0030] In addition, the optical fiber composite wire 10 may be placed at a position where a temperature change of the cable conductor 21 is reflected in a temperature change of the magnetic wire 12, that is, at a position where an induced current flows in the magnetic wire 12 when a current is applied to the cable conductor 21, thereby causing a rise in temperature.

[0031] Fig. 4B shows a case where the composite optical fiber 10 is disposed inside the power cable 20. As shown in Fig. 4B, the composite optical fiber 10 is disposed, for example, in the cable shielding layer 23. In Fig. 4B, a part of the shield wire (wire shield) forming the cable shielding layer 23 is replaced with the composite optical fiber 10.

[0032] When the optical fiber composite wire 10 is disposed inside the power cable 20, the insulating performance of the power cable 20 may be impaired due to heat generation from the magnetic wire 12, so it is preferable to dispose the optical fiber composite wire 10 away from the cable insulator 22. For example, the optical fiber composite wire 10 may be disposed between the cable shielding layer 23 and the cable sheath 24. The optical fiber composite wire 10 may also be disposed by being embedded in the cable sheath 24. In particular, when the cable shielding layer 23 is formed of a copper tape instead of a wire shield as shown in FIG. 4B, the optical fiber composite wire 10 may be disposed on the outer periphery of the copper tape (between the cable shielding layer 23 and the cable sheath 24). Alternatively, if it is disposed outside the copper tape (cable shielding layer 23), it is preferable to dispose the optical fiber composite wire 10 inside the cable sheath 24 or outside the power cable 20 (outside the cable sheath 24) as shown in FIG. 4A.

[0033] In FIG. 4A and FIG. 4B, the number of the composite optical fiber 10 arranged is not particularly limited.

[0034] When a current is applied to the cable conductor 21 of the power cable 20, the cable conductor 21 generates heat and its temperature rises, and a magnetic field is generated around the cable conductor 21, causing an induced current (eddy current) to flow through the magnetic wire 12 placed in this magnetic field. The induced current causes the magnetic wire 12 to generate heat and its temperature rises (induction heating). That is, a change in temperature of the cable conductor 21 is reflected in a change in temperature of the magnetic wire 12.

[0035] By detecting the transmission characteristics of the optical fiber 11, the temperature of the magnetic wire 12 can be measured, and the temperature of the cable conductor 21 can be calculated based on the temperature of the magnetic wire 12. For example, the relationship between the temperature of the magnetic wire 12 and the temperature of the cable conductor 21 may be experimentally obtained in advance.

[0036] As described above, the power cable temperature measuring method according to the embodiment has the following features either alone or in any suitable combination.

[0037] That is, in the power cable temperature measurement method according to the embodiment, a magnetic wire 12 (magnetic material) is arranged around a cable conductor 21 of a power cable 20, the temperature of the magnetic wire 12 is measured using an optical fiber 11 arranged along the power cable 20, and the temperature of the cable conductor 21 is calculated based on the measured temperature of the magnetic wire 12.

[0038] According to the temperature measuring method of this embodiment, the temperature distribution of the cable conductor 21 can be measured over its entire length by using a distributed optical fiber sensor. Furthermore, since the temperature of the cable conductor 21 is reflected in the magnetic wire 12 in a short time, the response is improved compared to the case where the temperature of the cable conductor 21 is directly measured by an optical fiber. Therefore, the temperature of the cable conductor 21 can be measured over its entire length with good response. Furthermore, since the current flowing through the cable conductor 21 can be estimated from the temperature distribution of the cable conductor 21 and the amount of power consumption can be monitored, this is suitable for demand control.

[0039] In addition, since the temperature of the magnetic wire 12 is measured by the optical fiber 11, it is sufficient to arrange the magnetic wire 12 and the optical fiber 11 so that the temperature change of the cable conductor 21 is reflected in the temperature change of the magnetic wire 12, and the temperature measurement equipment can be constructed relatively freely.

[0040] In the present embodiment, the magnetic wire 12 (magnetic body) is configured as a long member arranged along the power cable 20. This makes it possible to continuously measure the temperature distribution of the cable conductor 21 over the entire length of the power cable 20.

[0041] In this embodiment, an optical fiber composite wire 10 is used that has a magnetic wire 12 and an optical fiber 11. This allows the optical fiber 11 to be reliably positioned in the vicinity of the magnetic wire 12, improving measurement accuracy.

[0042] In this embodiment, the composite optical fiber 10 is arranged along the outer circumferential surface of the cable sheath 24 of the power cable 20 (see FIG. 4A). This makes it possible to easily install a temperature measuring device for the cable conductor 21 even in an existing cable facility.

[0043] In the present embodiment, the composite optical fiber 10 is disposed in the cable shielding layer 23 of the power cable 20. This allows a temperature measuring means for the cable conductor 21 to be built into the power cable 20 by utilizing a known cable manufacturing technique, and the temperature measuring equipment can be simplified.

[0044] The invention made by the inventor has been specifically described above based on an embodiment, but the present invention is not limited to the above embodiment and can be modified within the scope of the gist of the invention.

[0045] For example, in the embodiment, the optical fiber composite wire 10 in which the optical fiber 11 and the magnetic wire 12 are integrated is used, but the optical fiber 11 and the magnetic wire 12 may be arranged separately for the power cable 20. In this case, a plurality of magnetic bodies may be discretely arranged along the longitudinal direction of the power cable 20, and the optical fiber 11 may be arranged so as to pass near each of the magnetic bodies.

[0046] In the embodiment, the temperature distribution of the cable conductor 21 is measured by the distributed optical fiber sensor, but in addition to the temperature distribution of the cable conductor 21, the distortion of the power cable 20 and vibrations in the surrounding environment can be detected and used for the maintenance and inspection of the cable facility. For example, the optical fiber 11 arranged along the power cable 20 can be used to monitor the deformation of the power cable 20 due to thermal expansion and contraction after installation, the movement of the power cable 20 due to slipping, and abnormal axial force. In this way, when detecting the distortion and deformation of the power cable 20 using the optical fiber 11, it is preferable to arrange a plurality of optical fiber composite wires 10. Also, for example, the optical fiber 11 arranged along the power cable 20 can be used to detect discharge sounds to detect failures of the cable facility in advance, or to detect vibrations associated with excavation for underground burial and issue a warning.

[0047] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0048] 10 Optical fiber composite wire 11 Optical Fiber 12 Magnetic wire (magnetic material) 20 Power Cable 21 Cable conductor 22 Cable insulation 23 Cable shielding layer 24 Cable sheath

Claims

1. A magnetic material is disposed around the cable conductor of the power cable, measuring the temperature of the magnetic body using an optical fiber arranged along the power cable; calculating a temperature of the cable conductor based on the measured temperature of the magnetic body; Temperature measurement method.

2. The magnetic body is a long member arranged along the power cable. The temperature measuring method according to claim 1 .

3. An optical fiber composite wire having the magnetic material and the optical fiber is used. The temperature measuring method according to claim 2 .

4. The optical fiber composite wire is arranged along an outer peripheral surface of a cable sheath of the power cable. The temperature measuring method according to claim 3.

5. The composite optical fiber is embedded in a cable sheath of the power cable. The temperature measuring method according to claim 3.

6. The power cable has a cable shielding layer formed of a wire shield, The composite optical fiber is disposed on the cable shielding layer. The temperature measuring method according to claim 3.

7. The power cable has a cable shielding layer made of copper tape; The composite optical fiber is disposed on an outer periphery of the cable shielding layer. The temperature measuring method according to claim 3.

Images