JPH03183925A - Distribution type pressure/sound pressure sensor - Google Patents

Abstract

PURPOSE:To detect pressure and sound pressure with high sensitivity by forming a reinforced transmission layer of a hard material on the surface of an exposed part of a sensor fiber and constituting a sensor part. CONSTITUTION:A sensor cable 1 has sensor parts 3... formed at specific sensor parts 3... formed at specific intervals. In each sensor part 3, the sheath 5 of a sensor cable and the jacket 6 of the sensor fiber 2 are removed, the reinforced transmission layer 7 is formed of the hard material on the surface of the exposed sensor fiber 2, and a 2nd coating layer 8 is formed of resin on the reinforced transmission layer 7. Then when the generation of the pressure and sound pressure in the laying section of the cable 10 is detected, a pressure and sound pressure measuring instrument is connected to the cable 10, Brillouin- scattered light is generated in the sensor fiber 2, and probe pulse light matching the Brillouin frequency is made incident in the opposite direction; and variation in the intensity of its projection light with is measured and the loss distribution of the sensor fiber 2 is detected.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a distributed pressure and sound pressure sensor using optical fiber, and is particularly suitable for detecting ground faults in electrical cables buried underground. Regarding.

"Prior Art and its Problems" Conventionally, as this type of pressure and sound pressure sensor, an electric type sensor in which a sensor element such as a piezoelectric body is attached to a predetermined location of a conductive wire has been known.

However, a sensor using a conductive wire made of a metal conductor cannot be used in a section where electromagnetic induction occurs, and is not suitable as a sensor for detecting strain in a power cable that generates electromagnetic induction.

On the other hand, pressure and sound pressure sensors using optical fibers can detect pressure and sound pressure with high sensitivity using optical fibers.
It is also currently being widely researched because it can be used in sections with electromagnetic induction.

However, when actually applied to underground cables,
A sensor that can detect the pressure and sound pressure generated in the cable with high sensitivity has not yet been developed. This was a major problem in terms of preserving socially important systems such as ground faults in power cables buried underground.

In particular, when a cable ground fault occurs, strong pressure is applied to the cable in a short period of about a few seconds. Sound waves are also generated by the discharge. Immediacy is required when detecting these. When using a distributed sensor to measure the entire length of an underground power cable, etc., the structure of the sensor itself is limited and becomes similar to a normal optical fiber cable, reducing the sensitivity of the sensor. For this reason, it was necessary to develop a detection form suitable for underground cables and a pressure and sound pressure sensor section that can detect pressure and sound pressure with high sensitivity.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a distributed pressure and sound pressure sensor suitable for detecting the occurrence of a ground fault in an underground cable.

"Means for Solving the Problems" The distributed pressure and sound pressure sensor of the present invention includes one or more sensor sections that modulate the transmitted light by applying external pressure or sound pressure to the transmitted light transmitted to the sensor fiber. In the pressure and sound pressure sensor having the present invention, the above-mentioned problem has been solved by configuring the sensor portion by exposing the sensor fiber and forming a reinforcing transmission layer made of a hard material on the exposed portion.

"Function" The distributed pressure and sound pressure sensor of the present invention has high sensitivity because pressure or sound pressure from the outside is efficiently transmitted to the sensor fiber by the reinforcing transmission layer made of a hard material. Also,
The exposed sensor fiber is mechanically reinforced by this reinforcing transmission layer.

"Embodiment" FIGS. 1 and 2 are diagrams showing an embodiment of the pressure and sound pressure sensor according to the present invention, in which reference numeral 1 indicates a sensor cable, 2 indicates a sensor fiber, and 3 indicates a sensor section. It is.

The sensor cable 1 includes a sensor fiber 2 and a tensile strength member 4.
and a sheath 5 that covers these. As the tensile strength member 4, an FRP tear tension member, a wire tension member, or the like is used. Further, as the material for the sheath 5, ordinary vinyl chloride, polyethylene, etc. are used.

The sensor fiber 2 is a quartz-based single mode optical fiber having a primary coat of silicon, epoxy acrylate, urethane resin, etc., or an optical fiber having a secondary coating such as a nylon coating on the primary coat. Fiber cores are preferably used.

The sensor cable l has sensor sections 3 and 3 at predetermined intervals.
...is being formed. As shown in FIG. 2, in these sensor parts 3, the sheath 5 of the sensor cable 1 and the coating 6 of the sensor fiber 2 are removed, and a reinforcing transmission layer 7 made of a hard material is formed on the exposed surface of the sensor fiber 2. , furthermore, a second coating layer 8 made of resin is provided on the reinforcing transmission layer 7.
The structure is such that

This reinforcing transmission layer 7 is for transmitting external pressure and sound pressure to the sensor fiber 2, causing distortion in that portion of the sensor fiber 2, and reinforcing the exposed portion of the sensor fiber 2. Further, as the material for the reinforcing transmission layer 7, metal, glass, low melting point ceramics, etc. are used. Methods for forming these hard materials onto the surface of the sensor fiber 2 include covering the exposed portion of the sensor fiber 2 with a low-melting-point glass or metal sleeve and fusing this sleeve with heat, or using the DTP method or sputtering method. Using the metal coated fiber thus produced, a method of inserting the metal coat fiber into the connection point of the sensor fiber 2 and fusion splicing both ends can be applied.

A second coating layer 8 made of resin formed on the reinforcing transmission layer 7 is formed for the purpose of imparting insulation to the reinforcing transmission layer 7 or reinforcing the exposed portion of the sensor fiber 2 including the reinforcing transmission layer 7. Synthetic resin materials with excellent insulation properties and mechanical strength, such as polyimide, polyimide amide, polyamide, and polyester, are used. Moreover, this second covering layer 8 can also be formed using a fitting part made of resin.

As shown in FIG. 1, the sensor cable l configured in this manner is attached in contact with a cable 10 such as an electric cable laid in a conduit 9 buried underground. Manholes 11, . ing. This manhole 11.
The interval between ... is usually about 100 to 200 m. Inside the manhole 11, the sound pressure detection position of the sensor unit 3 is preferable because the sounds generated in the vicinity are concentrated 11.1. .

Then, the sensor cable 1 is placed in the conduit 9 together with the cable 10, and in order to detect the generation of pressure and sound pressure in the nodoful 100it installation section, a pressure and sound pressure measuring device is attached to the sensor cable l. The loss distribution of the sensor fiber 2 is determined by connecting the sensor fiber 2 to generate a brilliant scattered light in the sensor fiber, making the probe pulse light incident from the opposite direction in accordance with this brilliant frequency, and measuring the temporal intensity change of the emitted light. This is done by sensing.

FIG. 3 shows an example of a pressure and sound pressure measuring device suitably used in the distributed pressure and sound pressure sensor of the present invention. , an optical fiber coupler 14, a light receiver 15, and a calculation display device 16.

The pump laser light emitted from the pump laser device 12 passes through the optical fiber coupler 14 and enters into the second fiber from one end of the sensor fiber 2, and the probe laser light from the laser device 13 passes through the sensor fiber coupler 14. The amplified signal of the Brilliant scattered light, which is generated when the probe laser light is amplified by the pump laser light, passes through the optical fiber coupler 14, enters the light receiver 15, is photoelectrically converted, and is further converted. The electrical signal is sent to the arithmetic display device 16, and is observed as a waveform of temporal loss change of the amplified signal of the Brilliant scattered light.

The amplified signal of the Brilliant scattered light obtained in above) shows a waveform similar to that of a normal OT D R signal. Then, a ground fault or the like occurs in the cable 10, and the pressure
When sound pressure or the like is transmitted as distortion from the sensor section 3 to the sensor fiber 2, the frequency of the Brilliant scattered light changes due to the distortion in the sensor fiber 3, and the waveform of the amplified signal of the Brilliant scattered light changes. The resulting distortion is detected.

(Experimental Example) A single mode fiber (core diameter IO μm1, Clarad outer diameter 125I1 m) was used as a sensor fiber.

This sensor fiber has a normal nylon jacket and Kevlar-reinforced PVC core, and 1? R.I.
) The cable has a tenonyonmenha. As shown in FIG. 4, the sensor section has a sensor fiber connection point secured with a sealing glass 17, and a metal sheath 18 on the outside thereof.
It has a structure in which the outside is coated with a thin layer of polyimide amide resin 19 for insulation.

A pressure/sound pressure measuring device configured similarly to that shown in FIG. 3 was connected to this sensor fiber, and the strain/pressure distribution of the sensor fiber was measured. A semiconductor pumped YAG laser was used as the pump laser light of the light source. The fiber input of this pump laser light was 800 mW. In addition, a BR single mode laser was used as the probe laser beam (because wavelength tuning is possible).

The brilliant scattered light was photoelectrically converted by a light receiver, amplified by an arithmetic display device, and its waveform was observed. As a result, the pressure resolution was 5 kg/cm', and it was possible to detect strain over a working length of 10 to 20 km.

Effects of the Invention j As explained above, in the distributed pressure and sound pressure sensor according to the present invention, the sensor portion is configured by forming a reinforcing transmission layer made of a hard material on the surface of the exposed portion of the sensor fiber.
Sound pressure and pressure rising to this sensor section are transmitted to the sensor fiber as distortion with high sensitivity, allowing pressure and sound pressure to be detected with high sensitivity.

[Brief explanation of drawings]

1 and 2 are views showing one embodiment of the present invention, in which FIG. 1 is a schematic side view of a sensor cable, FIG. 2 is a side sectional view of the sensor section, and FIG. 3 is a pressure A schematic configuration diagram showing an example of a sound pressure measuring device, and FIG. 4 is a side sectional view of a sensor section for explaining an experimental example. 2...Sensor fiber, 3...Sensor section, 7.1.7.18...Reinforcement transmission layer.

Claims (1)

[Scope of Claims] A pressure and sound pressure sensor having one or more sensor sections that modulate the transmitted light by applying external pressure or sound pressure to the transmitted light transmitted to the sensor fiber, wherein the sensor section is connected to the sensor fiber. A distributed pressure and sound pressure sensor characterized in that a reinforcing transmission layer made of a hard material is formed on the exposed portion.