CN111341490A - Optical fiber composite high-voltage cable with built-in humidity sensor - Google Patents

Abstract

The invention discloses an optical fiber composite high-voltage cable with a built-in humidity sensor, comprising a cable body, wherein the cable body includes a water blocking layer and at least one humidity sensor optical fiber, and the water blocking layer is arranged in the cable body; at least one humidity sensor The sensor optical fiber is arranged outside the water blocking layer along the axial direction of the cable body, and the humidity sensor optical fiber is used to detect the humidity inside the cable body. The invention has good electrical and mechanical properties and sensitive sensing characteristics through the built-in humidity sensor optical fiber, and the humidity sensor optical fiber is arranged on the metal shielding layer so as not to distort the electric field distribution inside the cable. In the long-term operation, the humidity of the water-blocking belt layer can be monitored in real time through the humidity sensor fiber optic device, and the humidity factors affecting the normal and stable operation of the cable can be monitored, so as to improve the operation reliability and provide strong support for the construction of the power Internet of Things perception layer.

Description

A fiber optic composite high-voltage cable with built-in humidity sensor

technical field

The invention relates to a cable in the research field of power transmission equipment, in particular to an optical fiber composite high-voltage cable with a built-in humidity sensor.

Background technique

At present, with the continuous development of economy and society, compared with overhead transmission lines, cross-linked polyethylene cables are widely used in urban network transformation due to their advantages of being beneficial to urban beautification and low failure rate. Power cables are laid underground and are easily damaged by external forces such as municipal engineering, causing moisture intrusion. In order to prevent water branches from being damped by insulation, high-voltage cables often use cable buffer layers as longitudinal water-blocking structures. However, recent studies have found that after long-term operation of cables in the south coast and other places, buffer layer defects are prone to occur, unknown white powder appears on the surface of the semiconducting resistance water belt, the insulating shielding layer is ablated, and in severe cases, the insulating layer is even ablated to cause failure. The defect is related to the degree of moisture in the cable. The surface resistance and volume resistivity of the semi-conductive buffer water-blocking tape of the defective cable increase, which is not conducive to the good electrical connection between the inner sheath of the cable and the insulating shielding layer, and affects the normal and stable operation of the cable. On-line monitoring of the humidity parameters of the power cable buffer layer is beneficial to reflect the cable operating environment in real time, and formulate differentiated operation and maintenance strategies according to the degree of humidity.

The current common humidity sensors are divided into traditional, electrolyte, ceramic and polymer humidity sensors. Among the first three kinds of sensors, the traditional humidity sensor has poor measurement accuracy, the electrolyte-type humidity sensor has poor stability and hysteresis, and the ceramic-type humidity sensor has low sensitivity and large size, all of which are not suitable for online monitoring of power cable humidity. Polymer sensors can be divided into electrical and optical sensors according to different parameters. Among them, the electrical polymer sensors are easily affected by environmental factors and have poor stability. The polymer-based sensors with optical characteristics are generally used in aerospace and shipbuilding, biomedicine, engineering structure safety detection and other fields, but they are not used in power cables.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide an optical fiber composite high-voltage cable with a built-in humidity sensor, which can monitor the operating humidity inside the cable in real time through the humidity sensor optical fiber, and provide a theory for differentiated operation and maintenance management. in accordance with.

According to an embodiment of the first aspect of the present invention, an optical fiber composite high-voltage cable with a built-in humidity sensor is provided, including a cable body, wherein the cable body includes:

The water blocking tape layer is arranged in the cable body;

At least one humidity sensor optical fiber is arranged outside the water blocking layer along the axial direction of the cable body, and the humidity sensor optical fiber is used to detect the humidity inside the cable body.

The optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention further includes a temperature sensor optical fiber arranged beside the humidity sensor optical fiber, and the temperature sensor optical fiber is arranged in parallel with the humidity sensor optical fiber.

According to the optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention, the outer surface of the water blocking layer is provided with a metal shielding layer, and the humidity sensor optical fiber and the temperature sensor optical fiber are arranged in the metal shielding layer.

According to the optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention, the metal shielding layer has a plurality of metal wires arranged at intervals along the circumferential direction, and at least one of the metal wires is arranged on the humidity sensor optical fiber. and the temperature sensor fiber.

According to the optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention, the metal shielding layer further includes a metal tape wound on the outer surface of the metal wire, and the metal tape is used for connecting the metal wire and the humidity sensor optical fiber. And the temperature sensor fiber fixed.

According to the optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention, the metal wire may be one or more of copper wire, aluminum wire, lead wire and low carbon steel wire.

According to the optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention, the temperature sensor optical fiber comprises a temperature sensor optical fiber core, a temperature sensor optical fiber cladding, and a temperature sensor optical fiber protective layer arranged in sequence from the inside to the outside, The temperature sensor fiber core is provided with a plurality of temperature fiber grating regions.

According to the optical fiber composite high-voltage cable with a built-in humidity sensor according to the embodiment of the first aspect of the present invention, the humidity sensor optical fiber includes a humidity sensor optical fiber core, a humidity sensor optical fiber cladding, and a humidity sensor optical fiber protective layer sequentially arranged from the inside to the outside, The humidity sensor fiber core is provided with a plurality of humidity fiber grating regions, and the outer surface of the humidity sensor fiber core with the humidity fiber grating regions is coated with a humidity-sensitive coating.

According to the optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention, the humidity-sensitive coating is one or more of a polyimide layer, an epoxy-phenolic resin layer and a carbon fiber composite material layer kind.

According to the optical fiber composite high-voltage cable with built-in humidity sensor according to the embodiment of the first aspect of the present invention, the water blocking tape layer is formed by adding polymer water blocking powder between two layers of non-woven fabrics.

The beneficial effects of the invention are: the invention has good electrical and mechanical properties and sensitive sensing characteristics through the built-in humidity sensor optical fiber, and the humidity sensor optical fiber is arranged on the metal shielding layer so as not to distort the electric field distribution inside the cable. During long-term operation, the humidity of the water-blocking belt layer can be monitored in real time through the humidity sensor optical fiber, and the humidity factors that affect the normal and stable operation of the cable can be monitored, so as to improve the operation reliability and provide strong support for the construction of the perception layer of the power Internet of things.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly describes the accompanying drawings that are used in the description of the embodiments. Obviously, the described drawings are only a part of the embodiments of the present invention, but not all of the embodiments, and those skilled in the art can obtain other design solutions and drawings according to these drawings without creative work.

1 is a cross-sectional view of an embodiment of the present invention;

Fig. 2 is the schematic diagram of the humidity sensor optical fiber in the embodiment of the present invention;

3 is a schematic diagram of a temperature sensor optical fiber in an embodiment of the present invention;

FIG. 4 is a flow chart of the fabrication of the humidity sensor optical fiber in the embodiment of the present invention.

Detailed ways

This part will describe the specific embodiments of the present invention in detail, and the preferred embodiments of the present invention are shown in the accompanying drawings. Each technical feature and overall technical solution of the invention should not be construed as limiting the protection scope of the invention.

In the description of the present invention, it should be understood that the azimuth description, such as the azimuth or position relationship indicated by up, down, front, rear, left, right, etc., is based on the azimuth or position relationship shown in the drawings, only In order to facilitate the description of the present invention and simplify the description, it is not indicated or implied that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.

In the description of the present invention, the meaning of several is one or more, the meaning of multiple is two or more, greater than, less than, exceeding, etc. are understood as not including this number, above, below, within, etc. are understood as including this number. If it is described that the first and the second are only for the purpose of distinguishing technical features, it cannot be understood as indicating or implying relative importance, or indicating the number of the indicated technical features or the order of the indicated technical features. relation.

In the description of the present invention, unless otherwise clearly defined, words such as setting, installation, connection should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

1 to 2, an optical fiber composite high-voltage cable with a built-in humidity sensor includes a cable body, wherein the cable body includes a conductor 1 located in the center of the cable, and a semiconductive shielding layer is extruded outside the conductor 1 in a three-layer co-extrusion manner 2. After the insulating layer 3 and the insulating shielding layer 4, the conductor 1, the semiconducting conductor shielding layer 2, the insulating layer 3 and the insulating shielding layer 4 together form the cable insulating core; the water blocking layer 5 is wrapped around the insulating core; A metal wire is laid at a certain interval along the circumferential direction outside the water blocking layer 5 as a metal shielding layer 6, and at least one humidity sensor optical fiber 71 is placed in the metal shielding layer 6, and the humidity sensor optical fiber 71 is axially arranged in the cable body. The metal shielding layer 6 is covered with an inner sheath 8 , and the inner sheath 8 is coated with an anti-corrosion layer 9 , and the anti-corrosion layer 9 is extruded with an outer sheath 10 . The humidity sensor optical fiber 71 is used to detect the humidity inside the cable body. Specifically, the inner sheath 8 adopts a smooth lead sheath. The anti-corrosion layer 9 is asphalt, the outer sheath 10 is polyethylene, and the water-blocking tape layer is a semi-conductive buffer water-blocking tape layer formed by adding polymer water-blocking powder between two layers of non-woven fabrics.

As shown in FIG. 2 , the humidity sensor optical fiber 71 includes a humidity sensor optical fiber core 711 , a humidity sensor optical fiber cladding 712 and a humidity sensor optical fiber protective layer 713 arranged in sequence from the inside to the outside. The humidity sensor optical fiber core 711 is provided with multiple A humidity fiber grating region 710 is provided, and the outer surface of the humidity sensor fiber core 711 having the humidity fiber grating region 710 is coated with a humidity-sensitive coating 714 .

After the cable is damaged by external force, water seeps longitudinally by making joints or other means, moisture penetrates into the water blocking tape layer 5, causing the humidity sensitive coating 714 to expand, and the humidity sensor optical fiber 71 undergoes axial strain stretching. As the grating spacing Λ in the humidity fiber grating region 710 increases, the wavelength λ of the optical fiber transmission light changes accordingly. Due to the linear relationship between the Bragg wavelength drift and the humidity change, the humidity change of the water-blocking zone layer 5 can be obtained to realize the online humidity monitoring of the water-blocking zone layer 5 and provide a theoretical basis for differentiated operation and maintenance management in time. The present invention monitors the internal humidity of the cable through the humidity sensor optical fiber 71, which can prevent the cable from running for a long time after being seriously damped, causing the surface resistance and volume resistivity of the water-blocking tape layer 5 to be too large, and finally lead to electrical leakage between the insulating shielding layer 4 and the inner sheath 8. Poor contact will affect the stable operation of the cable.

Specifically, one of the fabrication methods of the humidity sensor optical fiber 71 is as follows:

Ultraviolet light is used to pass through the mask, and the oxygen-carrying single-mode optical fiber is etched to obtain a fiber Bragg grating. The fiber Bragg grating is a humidity fiber grating region 710, and the length of the humidity fiber grating region 710 is 6-10 mm. The period is Λ. The single-mode optical fiber is placed on the production platform as shown in Figure 4, and both ends of the single-mode optical fiber are connected to the traction motor 16 of the platform. The single-mode optical fiber is slowly pulled, and passes through the pretreatment zone 11, the coating zone 12, the curing zone 14, and the cooling zone 15 in sequence, and a moisture-sensitive coating is formed on the surface of the pre-etched humidity fiber grating zone 710 after adding a moisture-sensitive material 714, the coated humidity sensitive material is polyimide, and the humidity sensor optical fiber 71 is made.

It should be noted that, in the pretreatment area 11, a special hydrogen fluoride solution is used to corrode the humidity sensor fiber cladding 712 and the humidity sensor fiber protection layer 713 of the humidity fiber grating region 710, and the humidity sensor fiber core 711 is exposed and cleaned with alcohol, and then with silane. The coupling agent solution pretreats the surface. A polyimide solution is provided in the coating area 12 , and the humidity fiber grating area 710 is precisely coated by controlling the pulling device 13 , so that the polyimide solution is uniformly distributed on the surface of the humidity fiber grating area 710 . There are three high-temperature drying boxes in the curing zone 14, and the temperatures of the three high-temperature drying boxes are 100° C., 166° C. and 280° C. respectively. Different temperatures are used to volatilize impurities and thin the optical fibers that have completed the coating process in the coating zone 12 at different temperatures. Curing treatment and thickness control. The ideal thickness of the moisture sensitive coating 714 is 30 μm. The pulling device is composed of a traction motor, a telescopic lifting device, a rotating mechanism, a clamp handle and other components. It is equipped with an electronic control circuit and can operate the azimuthal movement of the optical fiber and periodic rotation at a uniform speed.

In some embodiments, a temperature sensor optical fiber 72 arranged beside the humidity sensor optical fiber 71 is further included, and the temperature sensor optical fiber 72 is arranged in parallel with the humidity sensor optical fiber 71 . The temperature sensor fiber 72 is used for compensating the wavelength change of the humidity sensor fiber 71 caused by the extrusion change of temperature and external stress.

In some embodiments, as shown in FIG. 3 , the temperature sensor optical fiber 72 includes a temperature sensor optical fiber core 721 , a temperature sensor optical fiber cladding 722 and a temperature sensor optical fiber protective layer 723 arranged in sequence from the inside to the outside. A plurality of temperature fiber grating regions 720 are provided in the optical fiber core 721 .

One of the fabrication methods of the temperature sensor fiber 72 is as follows:

Ultraviolet light is used to pass through the mask, and the oxygen-carrying single-mode fiber is etched to obtain a fiber Bragg grating. The fiber Bragg grating is a temperature fiber grating region 720, and the temperature fiber grating region 720 has a length of 6-10 mm. The period is Λ.

In order to reduce errors, in the production process of the temperature sensor fiber 72 and the humidity sensor fiber 71, when etching the grating regions on the two fibers, ensure that the distance between the grating regions is the same, and the gratings on the humidity sensor fiber 71 and the temperature sensor fiber 72 are Area positions are aligned one by one.

The specific principles are as follows:

The fiber Bragg grating reflects the wavelengths that satisfy the Bragg condition. According to the coupled mode theory, the characteristic equation of FBG is:

λ _B = 2n _eff Λ (1)

Among them, λ _B is the center wavelength of the FBG, n _eff is the effective refractive index of the grating; Λ is the period of the grating. Changes in physical quantity stress and temperature will cause changes in n _eff and Λ, resulting in the shift of the central wavelength λ _B . By measuring the center wavelength offset Δλ _B , the physical quantity to be measured can be obtained.

The fiber Bragg grating is laid in the cable and is affected by stress and temperature at the same time. From the elastic mechanics, the center wavelength offset Δλ _B can be expressed as:

Δλ _B =λ _B K _ε ·Δε+λ _B K _T ·ΔT (2)

K _ε =1-(1/2)·n _eff ² [P ₁₂ -μ(P ₁₁ +P ₁₂ )] (3)

K _T = (α+β) (4)

Among them, K _ε is the strain sensitivity; K _T is the temperature sensitivity; Δε is the stress change; ΔT is the temperature change; P ₁₁ and P ₁₂ are the elastic-optic coefficients of the material; μ is the Poisson’s ratio of the fiber material itself; P _e is the strain Sensitivity coefficient, P _e =(1/2)·n _eff ² [P ₁₂ -μ(P ₁₁ +P ₁₂ )]; α is the thermo-optic coefficient; β is the thermal expansion coefficient. The optical fiber used in the patent is an ordinary single-mode silica optical fiber, the thermal optical coefficient α≈6.17×10 ^-6 /℃, and the thermal expansion coefficient β≈5×10 ^-7 /℃.

The humidity sensor fiber 71 is coated with a humidity-sensitive material on the surface of the grid region, and the humidity-sensitive material expands to cause strain after being damp, and the center wavelength shifts. The wavelength change of the humidity sensor fiber 71 and the temperature sensor fiber 72 can be expressed as:

Δλ _B71 /λ _B71 =K _ε71 ·Δε+K _T71 ·ΔT+K _M71 ·ΔY (5)

Δλ _B72 /λ _B72 =K _ε72 ·Δε+K _T72 ·ΔT (6)

Among them, K _M71 is the humidity sensitivity, K _M71 =(1-P _e )ξ _M C ₁ , ξ _M is the humidity expansion coefficient of the humidity sensitive material, and C ₁ is related to the adhesion coefficient between the humidity sensitive material and the optical fiber; ΔY is the humidity change quantity.

Since both the humidity sensor fiber 71 and the temperature sensor fiber 72 have the same core material at the grid regions, they have the same temperature response. And because the two are laid in parallel and next to each other, the two gate areas have the same force and the same amount of stress change, which can be obtained from equations (5)-(6):

(Δλ _B71 /λ _B71 )-(Δλ _B72 /λ _B72 )=K _M71 ·ΔY (8)

After the wavelength change of the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 is measured, the humidity change amount ΔY can be obtained.

In some embodiments, a metal shielding layer 6 is disposed on the outer surface of the water blocking tape layer, and the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 are disposed in the metal shielding layer 6 . The temperature sensor optical fiber 72 and the humidity sensor optical fiber 71 are arranged on the metal shielding layer 6 so as not to distort the electric field distribution inside the cable, to ensure good mechanical performance of the cable, and not to be disturbed by magnetic fields, thus greatly improving the service life of the cable.

In some embodiments, the metal shielding layer 6 has a plurality of metal wires arranged at intervals in the circumferential direction, and at least one of the metal wires is arranged between the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 . Specifically, as shown in FIG. 1 , the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 are laid at the bottom of the cable after a metal wire is spaced therebetween. The humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 need to be laid close to each other, and because the distance between the two metal wires in the metal shielding layer 6 is limited, a metal wire between the two optical fibers can ensure that the two optical fibers have sufficient space and not squeeze each other. pressure.

Specifically, on the premise of ensuring the normal operation of the cable, and according to actual production requirements, the metal wire may be one or more of copper wire, aluminum wire, lead wire, low carbon steel wire, and the like.

Specifically, on the premise of ensuring the normal operation of the cable, according to actual production needs, the moisture-sensitive coating 714 is one or more of a polyimide layer, an epoxy-phenolic resin layer and a carbon fiber composite material layer. .

In some embodiments, the metal shielding layer 6 further includes a metal tape wound on the outer surface of the metal wire, and the metal tape is used to fix the metal wire, the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 . The metal wire, humidity sensor optical fiber 71 and temperature sensor optical fiber 72 are located on the same layer, the winding direction of the metal wire, humidity sensor optical fiber 71 and temperature sensor optical fiber 72 is the same, and the winding direction of the metal tape is different from that of the metal wire. Specifically, if the metal wire is wound in the right direction, the metal belt is wound in the left direction, and the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 are fixed while the metal belt fastens the metal wire.

Preferably, the metal shielding layer 6 is composed of concentrically sparsely wound soft copper wires, the surfaces of the copper wires are reversely fastened with copper tapes, and the average gap between two adjacent copper wires is not greater than 4 mm. If the copper wire in the metal shielding layer 6 is wound in the right direction, the copper tape is wound in the left direction, and the thickness of the copper tape is 0.5 mm and the width is 8 mm. The outer diameter of the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 is the same as that of the copper wire. When the copper wire is fastened with the copper tape, the humidity sensor optical fiber 71 and the temperature sensor optical fiber 72 are fixed together.

The preferred embodiments of the present invention have been specifically described above, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. , these equivalent modifications or substitutions are all included within the scope defined by the claims of the present application.

Claims (10)

1. An optical fiber composite high-voltage cable with a built-in humidity sensor, characterized in that it comprises a cable body, wherein the cable body comprises: The water blocking tape layer is arranged in the cable body; At least one humidity sensor optical fiber is arranged outside the water blocking layer along the axial direction of the cable body, and the humidity sensor optical fiber is used to detect the humidity inside the cable body. 2 . The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 1 , further comprising a temperature sensor optical fiber arranged beside the humidity sensor optical fiber, and the temperature sensor optical fiber is arranged in parallel with the humidity sensor optical fiber. 3 . 3. The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 2, wherein: the outer surface of the water blocking layer is provided with a metal shielding layer, and the humidity sensor optical fiber and the temperature sensor optical fiber are arranged on the metal shielding layer Inside. 4 . The fiber optic composite high-voltage cable with built-in humidity sensor according to claim 3 , wherein the metal shielding layer has a plurality of metal wires arranged at intervals along the circumferential direction, and at least one of the metal wires is arranged in the humidity. 5 . between the sensor fiber and the temperature sensor fiber. 5 . The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 4 , wherein the metal shielding layer further comprises a metal tape wound on the outer surface of the metal wire, and the metal tape is used to connect the metal wire, humidity, etc. The sensor fiber and the temperature sensor fiber are fixed. 6 . The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 4 , wherein the metal wire can be one or more of copper wire, aluminum wire, lead wire and low carbon steel wire. 7 . 7. The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 2, wherein the temperature sensor optical fiber comprises a temperature sensor optical fiber core, a temperature sensor optical fiber cladding and a temperature sensor optical fiber protection sequentially arranged from the inside to the outside layer, the temperature sensor fiber core is provided with a plurality of temperature fiber grating regions. 8. The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 1, wherein the humidity sensor optical fiber comprises a humidity sensor optical fiber core, a humidity sensor optical fiber cladding and a humidity sensor optical fiber protection sequentially arranged from inside to outside The humidity sensor fiber core is provided with a plurality of humidity fiber grating regions, and the outer surface of the humidity sensor fiber core with the humidity fiber grating regions is coated with a humidity-sensitive coating. 9 . The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 1 , wherein the humidity-sensitive coating is one of a polyimide layer, an epoxy-phenolic resin layer and a carbon fiber composite material layer. 10 . or more. 10 . The optical fiber composite high-voltage cable with built-in humidity sensor according to claim 1 , wherein the water-blocking tape layer is formed by adding polymer water-blocking powder between two layers of non-woven fabrics. 11 .

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