阅读说明：本技术 一种环形结构的光纤电流传感器 (Optical fiber current sensor with annular structure ) 是由 张家洪 张建鑫 郁聪 赵振刚 于 2021-01-18 设计创作，主要内容包括：本发明公开了一种环形结构的光纤电流传感器,所述传感器主要由环形硅钢片、超磁致伸缩棒、光纤布拉格光栅、连接条和支撑条制成,当导线通电,环形硅钢片会聚集导线周围的磁场,形成聚磁回路；在环形硅钢片上切割出一定长度的缺口,圆柱形超磁致伸缩棒上端与环形硅钢片缺口一端粘贴在一起,连接条左端上表面与圆柱形超磁致伸缩棒下端粘贴在一起,连接条右端下表面与支撑条上端粘贴在一起,支撑条下端与环形硅钢片粘贴在一起。本发明提供的光纤电流传感器测量结果不受温度影响,解决了光纤光栅电流传感器受外界温度干扰而不稳定的问题。本发明还具有体积小、结构简单、成本低、性能稳定、灵敏度高、电绝缘性好、耐腐蚀的优点。(The invention discloses an optical fiber current sensor with an annular structure, which is mainly made of an annular silicon steel sheet, a giant magnetostrictive rod, an optical fiber Bragg grating, a connecting strip and a supporting strip, wherein when a lead is electrified, the annular silicon steel sheet can gather a magnetic field around the lead to form a magnetism gathering loop; the upper surface of the left end of the connecting bar is adhered to the lower end of the cylindrical giant magnetostrictive rod, the lower surface of the right end of the connecting bar is adhered to the upper end of the supporting bar, and the lower end of the supporting bar is adhered to the annular silicon steel sheet. The measurement result of the optical fiber current sensor provided by the invention is not influenced by temperature, and the problem that the optical fiber grating current sensor is unstable due to the interference of external temperature is solved. The invention also has the advantages of small volume, simple structure, low cost, stable performance, high sensitivity, good electrical insulation and corrosion resistance.)

1. The optical fiber current sensor with the annular structure is characterized by comprising an annular silicon steel sheet (1), a connecting strip (2), a giant magnetostrictive rod (3), a supporting strip (4), a coil (5), a lead (6) and an optical fiber Bragg grating (7), wherein the coil (5) is wound on one side of the annular silicon steel sheet (1), and the lead (6) is arranged below the coil; the novel ultra-high-precision connection structure is characterized in that a gap is formed in the annular silicon steel sheet (1), the upper end of the ultra-magnetostrictive rod (3) is fixed with one end of the gap of the annular silicon steel sheet (1), the upper surface of the left end of the connection strip (2) is fixed with the lower end of the ultra-magnetostrictive rod (3), the lower surface of the right end of the connection strip (2) is fixed with the upper end of the support strip (4), the lower end of the support strip (4) is fixed with the annular silicon steel sheet (1), and two optical fiber Bragg gratings (7) with the same parameters are respectively adhered to the upper surface and the lower surface of the connection strip (2) and are symmetrically distributed.

2. The fiber optic current sensor according to claim 1, characterized in that two fiber bragg gratings (7) are connected to the demodulator (9) by a grating pigtail (8).

3. The optical fiber current sensor according to claim 1, wherein the length of the gap on the annular silicon steel sheet (1) is 25-35mm, the outer radius of the annular silicon steel sheet is 40-50mm, and the inner radius of the annular silicon steel sheet is 20-25 mm.

4. The current sensor according to claim 1, characterized in that the number of the connecting strips (2) is one, the material is stainless steel, the shape is a cuboid, the length is 30-35mm, the width is 3-8mm, and the thickness is 1-2 mm.

5. The current sensor according to claim 1, wherein the number of the giant magnetostrictive rod (3) is one, and the giant magnetostrictive rod is cylindrical in shape, and has a bottom diameter of 3-8mm and a length of 20-30 mm.

6. The current sensor according to claim 1, wherein the number of the support bars (4) is one, the material is stainless steel, the shape is a cuboid, the length is 10-15mm, the width is 2-4mm, and the thickness is 1-2 mm.

7. The current sensor according to claim 1, wherein the coil (5) is powered by a constant current source, and the number of turns of the coil is 400 and 600 turns.

Technical Field

The invention relates to the field of optical current sensors, in particular to an optical fiber current sensor with an annular structure.

Background

With the development of the electric power industry in China, the electric power industry puts higher requirements on the current sensor, and the traditional current sensor has a series of problems of magnetic saturation, ferromagnetic resonance, flammability, explosiveness and the like. The optical current sensor enters eyes of scholars at home and abroad due to the self anti-magnetic interference capability. The optical current sensor is mainly divided into: faraday effect, hybrid opto-electric and magnetostrictive.

The working principle of the Faraday effect type current sensor is to adopt the Faraday effect, and the problems of linear birefringence and temperature are always a big problem of the Faraday effect type current sensor. The photoelectric hybrid sensor utilizes the traditional electromagnetic induction principle, and the optical fiber is only used for signal transmission and does not solve the influence of factors such as magnetic saturation, environmental magnetic field and the like. The magnetostrictive fiber Bragg grating current sensor mainly utilizes the combination of a giant magnetostrictive material and a fiber Bragg grating as a sensitive unit, the giant magnetostrictive material can be axially stretched under the action of a magnetic field, the fiber Bragg grating adhered on the giant magnetostrictive material generates strain, a grating tail fiber transmits an optical signal to a demodulator, and the demodulator demodulates the central wavelength of the fiber Bragg grating. The transmission mode can realize distributed measurement and has better industrial prospect.

Magnetostrictive fiber bragg grating current sensors have become one of the research hotspots of optical current sensors. Since the fiber grating is susceptible to temperature, temperature compensation is required. In the existing method, a sensor is designed by adopting a giant magnetostrictive material with a cross-shaped structure and temperature compensation is carried out. Two pieces of giant magnetostrictive material are needed to be arranged in a cross shape, and two fiber Bragg gratings are respectively stuck on the two pieces of giant magnetostrictive material. The structure needs two pieces of giant magnetostrictive material, and has the disadvantages of complex structure, high cost and inconvenient operation.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the optical fiber current sensor with the annular structure, which can avoid the influence of temperature on the measurement result while measuring the current.

In order to solve the technical problems, the technical scheme of the invention is as follows: an optical fiber current sensor with an annular structure comprises an annular silicon steel sheet, a connecting strip, a giant magnetostrictive rod, a supporting strip, a coil, a conducting wire and an optical fiber Bragg grating, wherein the coil is wound on one side of the annular silicon steel sheet, and the conducting wire is arranged below the coil; the upper end of the giant magnetostrictive rod is fixed with one end of the annular silicon steel sheet gap, the upper surface of the left end of the connecting strip is fixed with the lower end of the giant magnetostrictive rod, the lower surface of the right end of the connecting strip is fixed with the upper end of the supporting strip, the lower end of the supporting strip is fixed with the annular silicon steel sheet, and two optical fiber Bragg gratings with the same parameters are respectively adhered to the upper surface and the lower surface of the connecting strip and are symmetrically distributed.

As a further description of the above technical solution, two fiber bragg gratings are connected to the demodulator through a grating pigtail.

Preferably, the length of the notch on the annular silicon steel sheet is 25-35mm, the outer radius of the annular silicon steel sheet is 40-50mm, and the inner radius of the annular silicon steel sheet is 20-25 mm.

Preferably, the connecting strips are made of stainless steel, are rectangular solids, and have the length of 30-35mm, the width of 3-8mm and the thickness of 1-2 mm.

Preferably, the number of the giant magnetostrictive rods is one, the giant magnetostrictive rods are cylindrical, the diameter of the bottom of the giant magnetostrictive rods is 3-8mm, and the length of the giant magnetostrictive rods is 20-30 mm.

Preferably, the number of the supporting bars is one, the supporting bars are made of stainless steel and are cuboid in shape, the length of the supporting bars is 10-15mm, the width of the supporting bars is 2-4mm, and the thickness of the supporting bars is 1-2 mm.

Preferably, the coil is powered by a constant current source, and the number of turns of the coil is 400 and 600 turns.

The working principle of the invention is as follows: when the current sensor provided by the invention is used for measuring current, light enters from one end of the optical fiber Bragg grating, the grating in the optical fiber is equivalent to a wavelength band reflector, partial light wave can be reflected, and the central wavelength lambda of the light wave is reflected_BIs composed of

λ_B＝2n_effΛ (1)

In the formula, n_effIs effective for the coreRefractive index, Λ being the grating period, n_effAnd Λ are both functions of temperature and strain. When the fiber Bragg grating is simultaneously under the action of axial stress and temperature, the fiber Bragg grating can generate axial strain, and the relationship between the axial strain epsilon of the fiber Bragg grating and the change of the central wavelength of the fiber Bragg grating is

Δλ_B＝λ_B(1-P_e)ε+λ_B(α_Λ+α_n)ΔT (2)

In the formula, P_eFor an effective photoelastic coefficient, it is about 0.22 for a silicon fiber medium. Δ T represents a temperature change; alpha is alpha_ΛAnd alpha_nRespectively, the thermal expansion coefficient and the thermo-optic coefficient of the optical fiber are respectively 0.55 multiplied by 10 for the germanium-doped optical fiber^-6And 8.6X 10^-6。

When the current I is introduced into the lead, the annular silicon steel sheet gathers the magnetic field around the lead to form a magnetic gathering loop, and the magnetic field intensity on the silicon steel sheet is H₁According to the electromagnetic induction principle, the magnetic field intensity H on the annular silicon steel sheet₁Is composed of

In the formula, I represents the measured current, and r is the radius of the silicon steel sheet. When the coil is electrified with current i, the bias magnetic field H on the silicon steel sheet₂Is composed of

H₂＝Ni (4)

In the formula, N represents the number of coil turns, and i represents the current on the coil. The giant magnetostrictive material is arranged at the notch of the silicon steel sheet, and because the relative permeability of the giant magnetostrictive material is smaller than that of the silicon steel sheet, the magnetic field on the giant magnetostrictive material is smaller than that on the silicon steel sheet, and the magnetic field H on the giant magnetostrictive material₃Is composed of

H₃＝β₁(H₂+H₁) (5)

In the formula, beta₁Is the magnetic flux leakage coefficient of the magnetic circuit. The giant magnetostrictive material is magnetized and stretched axially under the action of magnetic fieldDisplacement amount delta l₁And a magnetic field H₃Has a corresponding relationship of

Δl₁＝k₁H₃h₁ (6)

In the formula, k₁Is the magnetostriction coefficient, h, of the giant magnetostrictive material (giant magnetostrictive rod)₁Is the height of the giant magnetostrictive material. The deformation of the stainless steel strip (connecting strip) is caused by the axial stretching of the giant magnetostrictive material, and the stress F of the stainless steel strip is

F＝k₂·Δl₁ (7)

In the formula, k₂Is the elastic coefficient of the stainless steel strip. The strain amount of the fiber Bragg grating is

Wherein L is the length of the stainless steel strip, E is the modulus of elasticity, b₀Is the width of the fixed end of the stainless steel strip, h₂Is the thickness of the stainless steel strip.

Substituting the formula (3) to the formula (8) into the formula (2) to obtain the variation relation between the measured current I and the variation of the central wavelength of the fiber Bragg grating

Two fiber Bragg gratings with the same parameters are adhered to two surfaces of a stainless steel bar (connecting bar), under the same temperature environment, the wavelength variation of the two fiber Bragg gratings caused by temperature is equal, but the current generates a magnetic field to further enable the upper and lower fiber Bragg gratings to generate tensile and compressive strain. Optical fiber Bragg grating wavelength variation delta lambda for generating tensile strain_B1And the variation delta lambda of the wavelength of the optical fiber Bragg grating generating the compressive strain_B2Are respectively as

Therefore, the wavelength variation of the two fiber Bragg gratings is subtracted, so that the influence of temperature can be removed, and the wavelength variation of the fiber Bragg gratings after the subtraction is obtained as

δλ＝Δλ_B1-Δλ_B2＝2λ_B(1-P_e)(KI+b) (12)

Wherein

The formula (12) shows that the measured current I can be obtained by obtaining the variation of the two fiber Bragg grating wavelengths through the demodulator, and the measurement is not influenced by the temperature.

Compared with the prior art, the invention has the following beneficial effects: the invention provides the optical fiber current sensor with a novel structure, which ensures that the measuring result is not influenced by temperature, solves the problem that the optical fiber grating current sensor is unstable due to the interference of external temperature, has high precision and stable performance, has the advantages of small volume, simple structure, low cost, high sensitivity, good electrical insulation and corrosion resistance, and can work under severe conditions.

Drawings

FIG. 1 is a schematic front view of a fiber optic current sensor of the present invention in an annular configuration;

FIG. 2 is a schematic side view of a fiber optic current sensor of the present invention in an annular configuration;

the labels in the figure are: 1-annular silicon steel sheet, 2-connecting bar, 3-giant magnetostrictive rod, 4-supporting bar, 5-coil, 6-lead, 7-fiber Bragg grating, 8-grating tail fiber and 9-demodulator.

Detailed Description

The technical solutions of the present invention will be described in further detail with reference to the drawings and specific examples, but the present invention is not limited to the following technical solutions.

Example 1

As shown in fig. 1 and 2, an optical fiber current sensor with an annular structure includes an annular silicon steel sheet 1, a connecting bar 2, a cylindrical giant magnetostrictive rod 3, a supporting bar 4, a coil 5, a conducting wire 6, two fiber bragg gratings 7, two grating pigtails 8, and a demodulator 9.

The specification and the size of each component in the embodiment are as follows: the length of the gap on the annular silicon steel sheet 1 is 28mm, the outer radius of the annular silicon steel sheet is 45mm, the inner radius of the annular silicon steel sheet is 25mm, and the annular silicon steel sheet is made into an annular magnetic field which is easier to gather.

The connecting strip 2 is made of stainless steel and is shaped like a cuboid, the length is 32mm, the width is 5mm, and the thickness is 1.5 mm. The connecting strip needs to be pasted with the fiber Bragg grating, so that the connecting strip is made into a cuboid and is convenient to paste.

The giant magnetostrictive rod 3 is a cylinder, the diameter of the bottom of the cylinder is 5mm, and the length of the cylinder is 25 mm.

The quantity of support bar 4 is one, and the material is the stainless steel, and the shape is the cuboid, and convenient processing is length for 11.5mm, and the width is 3mm, and thickness is 1.5 mm.

The coil 5 is powered by a constant current source, and the number of turns of the coil is 500.

A coil 5 is wound on the annular silicon steel sheet 1, a constant current source is used for supplying power to provide a bias magnetic field, and a lead 6 is arranged between the coil 5 and the fiber Bragg grating 7. Cutting a gap with a certain length on the annular silicon steel sheet, respectively coating a layer of epoxy resin adhesive on the upper end of the cylindrical giant magnetostrictive rod 3 and one end of the gap of the annular silicon steel sheet 1, sticking the two parts, and waiting for about 24 hours to solidify the two parts. The upper surface of the left end of the connecting bar 2 and the lower end of the cylindrical giant magnetostrictive rod 3 are adhered together by epoxy resin adhesive, the lower surface of the right end of the connecting bar 2 and the upper end of the supporting bar 4 are adhered together by epoxy resin adhesive, and the lower end of the supporting material 4 and the annular silicon steel sheet 1 are adhered together by epoxy resin adhesive.

The two fiber bragg gratings 7 with the same parameters are respectively adhered to the upper surface and the lower surface of the stainless steel strip 2 by using epoxy resin glue, one point is respectively taken at two ends of a grating area of the fiber bragg grating and is adhered to the upper surface of the stainless steel strip 2, the fiber bragg grating is adhered to the point corresponding to the upper surface and the lower surface of the stainless steel strip 2, the upper fiber bragg grating and the lower fiber bragg grating are symmetrically distributed, and the two fiber bragg gratings 7 are connected to a demodulator 9 through two grating tail fibers 8.

When the magnetic field collecting device is used, the lead 6 is electrified, and the annular silicon steel sheet 1 collects a magnetic field around the lead 6 to form a magnetic field collecting loop. The cylindrical giant magnetostrictive rod 3 at the notch of the annular silicon steel sheet 1 is subjected to the action of a magnetic field to generate axial downward stretching, so that the left end of the connecting strip 2 is driven to deform downwards, the optical fiber Bragg grating 7 adhered to the upper surface of the connecting strip 2 is stretched, and the optical fiber Bragg grating 7 adhered to the lower surface of the connecting strip 2 is contracted. The two fiber bragg gratings 7 are connected to a demodulator 9 through a grating tail fiber 8. The influence of the temperature on the two fiber bragg gratings 7 is the same, the central wavelengths of the two fiber bragg gratings 7 measured by the demodulator 9 are subtracted, the influence of the temperature on the central wavelength variation of the fiber bragg gratings 7 is removed, and the magnitude of the measured current can be obtained through the relation between the central wavelength variation of the fiber bragg gratings 7 and the measured current.

The specific measurement process is as follows: light is incident from one end of the fiber Bragg grating, the grating in the fiber is equivalent to a wavelength band reflector, partial light waves can be reflected, and the central wavelength lambda of the reflected light waves_BIs composed of

λ_B＝2n_effΛ (1)

In the formula, n_effIs the effective refractive index of the fiber core, Λ is the grating period, n_effAnd Λ are both functions of temperature and strain. When the fiber Bragg grating is simultaneously under the action of axial stress and temperature, the fiber Bragg grating can generate axial strain, and the relationship between the axial strain epsilon of the fiber Bragg grating and the change of the central wavelength of the fiber Bragg grating is

Δλ_B＝λ_B(1-P_e)ε+λ_B(α_Λ+α_n)ΔT (2)

In the formula, P_eFor an effective photoelastic coefficient, Δ T represents the temperature change for a silicon fiber medium of about 0.22; alpha is alpha_ΛAnd alpha_nRespectively representing thermal expansion of optical fibersThe coefficient of expansion and the thermo-optic coefficient are respectively 0.55X 10 for the germanium-doped fiber^-6And 8.6X 10^-6。

When the current I is introduced into the lead, the annular silicon steel sheet gathers the magnetic field around the lead to form a magnetic gathering loop, and the magnetic field intensity on the silicon steel sheet is H₁Magnetic field intensity H on silicon steel sheet according to electromagnetic induction principle₁Is composed of

In the formula, I represents the measured current, and r is the radius of the silicon steel sheet. When the coil is electrified with current i, the bias magnetic field H on the silicon steel sheet₂Is composed of

H₂＝Ni (4)

In the formula, N represents the number of coil turns, and i represents the current on the coil. The giant magnetostrictive material is arranged at the notch of the silicon steel sheet, and because the relative permeability of the giant magnetostrictive material is smaller than that of the silicon steel sheet, the magnetic field on the giant magnetostrictive material is smaller than that on the silicon steel sheet, and the magnetic field H on the giant magnetostrictive rod (material)₃Is composed of

H₃＝β₁(H₂+H₁) (5)

In the formula, beta₁Is the magnetic flux leakage coefficient of the magnetic circuit. The giant magnetostrictive material is magnetized and stretched axially under the action of magnetic field, and the displacement delta l of the giant magnetostrictive material₁And a magnetic field H₃Has a corresponding relationship of

Δl₁＝k₁H₃h₁ (6)

In the formula, k₁Is the magnetostriction coefficient, h, of the giant magnetostrictive material₁Is the height of the giant magnetostrictive material. The deformation of the stainless steel strip is caused by the axial stretching of the giant magnetostrictive material, and the stress F of the stainless steel strip is

F＝k₂·Δl₁ (7)

In the formula, k₂Is the elastic coefficient of the stainless steel strip. The strain amount of the fiber Bragg grating is

Wherein L is the length of the stainless steel strip, E is the modulus of elasticity, b₀Is the width of the fixed end of the stainless steel strip, h₂Is the thickness of the stainless steel strip.

Substituting the formula (3) to the formula (8) into the formula (2) to obtain the variation relation between the measured current I and the variation of the central wavelength of the fiber Bragg grating

Two fiber Bragg gratings with the same parameters are adhered to two surfaces of the stainless steel strip, under the same temperature environment, the wavelength variation of the two fiber Bragg gratings caused by temperature is equal, but the current generates a magnetic field to further enable the upper and lower fiber Bragg gratings to generate tensile and compressive strain. Optical fiber Bragg grating wavelength variation delta lambda for generating tensile strain_B1And the variation delta lambda of the wavelength of the optical fiber Bragg grating generating the compressive strain_B2Are respectively as

Therefore, the wavelength variation of the two fiber Bragg gratings is subtracted, so that the influence of temperature can be removed, and the wavelength variation of the fiber Bragg gratings after the subtraction is obtained as

δλ＝Δλ_B1-Δλ_B2＝2λ_B(1-P_e)(KI+b) (12)

Wherein

The formula (12) shows that the measured current I can be obtained by obtaining the variation of the two fiber Bragg grating wavelengths through the demodulator, and the measurement is not influenced by the temperature.

In conclusion, the optical fiber current sensor with the annular structure can eliminate the influence of temperature on the measurement result and obtain an accurate measurement result.

It should be noted that the above description is given for a specific implementation, but this is not to be construed as limiting the invention, and various known variations and modifications based on the above disclosure are within the scope of the invention for those skilled in the art.