Stator winding interlayer optical fiber temperature and strain dual parameter monitoring device and its use method

Abstract

A stator winding interlayer optical fiber temperature and strain dual-parameter monitoring device comprises multiple interlayer insulating strips, a protective housing, a temperature sensing grating, a strain sensing grating, sensing optical fibers, and a protective sleeve. Each interlayer insulating strip is positioned between an upper layer of wire rods and a lower layer of wire rods. Multiple groups of staggered upper and lower layer wire rods form the stator winding. The middle section of each interlayer insulating strip is provided with a T-shaped protective housing. The lower end of the protective housing is sleeved onto the outer side of the upper end of the protective housing, and the upper end of the protective housing extends beyond the outer side of the interlayer insulating strips. A longitudinally arranged sensing optical fiber is disposed within the protective housing. The upper ends of all sensing optical fibers pass through the protective housing and are then assembled into an optical cable assembly within an optical fiber terminal box. The optical cable assembly is separated by an optical fiber distribution frame and connected to a fiber optic Bragg grating (FBG) demodulator. The FBG demodulator is then connected to a terminal device for signal communication. The present invention allows for simultaneous temperature and strain monitoring, simplifying monitoring.

Description

Technical Field

[0001] The present invention relates to an improvement of a temperature-strain dual-parameter monitoring technology, belongs to the field of hydro-generators, and in particular to a stator winding interlayer optical fiber temperature-strain dual-parameter monitoring device and a use method thereof. Background Art

[0002] The temperature and strain between the stator winding layers of large hydro-turbine generators affect the operating life of the generators. Controlling the temperature and strain of the stator windings is the key to the safe and reliable operation of the generators. Therefore, accurate, real-time, and reliable monitoring of the stator winding temperature and strain is of great significance. Currently, the temperature between the stator winding layers of large hydro-turbine generators is mostly measured using platinum resistance or thermocouples, and the strain is mostly measured using electronic strain gauges. Both are measured and transmitted through electrical signals. The transmission medium wire is metal, which is easily interfered with by strong electric and magnetic fields, making it impossible to measure correctly. Metal materials are also prone to arcing, corona, heating, and other problems under strong electric and magnetic fields, causing great harm. In existing solutions, only the temperature parameter can be monitored, and temperature and strain cannot be monitored simultaneously.

[0003] A Chinese patent application with application number CN202311083542.5, filed on August 25, 2023, discloses a method and device for measuring the stator winding temperature of a direct-drive permanent magnet wind turbine. This method relates to the field of wind power measurement technology and includes: installing a temperature acquisition module in the air gap on the outer wall of the rotor; using the temperature acquisition module to acquire the temperature of the stator winding during operation of the wind turbine to obtain a temperature signal; converting the temperature signal into an optical signal and transmitting it to a control terminal; and determining the fault mode of the wind turbine based on the temperature signal, a reference temperature curve, and / or auxiliary parameters. Infrared temperature sensors are characterized by high sensitivity and non-contact temperature data acquisition. The infrared temperature sensor is installed on the outer wall of the rotor near the air gap. As the rotor rotates, the temperature of the stator winding is measured, requiring fewer infrared temperature sensors and reducing magnetic field distortion. This solution only provides real-time online monitoring of temperature changes but does not address the problem of simultaneous monitoring of temperature and strain.

[0004] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of this patent application, and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that temperature and strain cannot be monitored simultaneously, and to provide a stator winding interlayer optical fiber temperature and strain dual parameter monitoring device and its use method that can monitor temperature and strain simultaneously.

[0006] To achieve the above objectives, the technical solution of the present invention is: a stator winding interlayer optical fiber temperature and strain dual parameter monitoring device, the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device comprising a plurality of interlayer insulating strips, a protective housing, a temperature sensing grating, a strain sensing grating, a sensing optical fiber, and a protective sleeve;

[0007] Each interlayer insulating gasket is arranged between the upper wire rod and the lower wire rod, and multiple groups of upper wire rods and lower wire rods are staggered to form a stator winding. The middle section of each interlayer insulating gasket is provided with a protective shell with a T-shaped cross-section. The lower end of the protective sleeve is sleeved on the outer side of the upper end of the protective shell, and the upper end of the protective sleeve extends to the outer side of the interlayer insulating gasket. A longitudinally arranged sensing optical fiber is provided in the protective shell. The upper ends of all sensing optical fibers pass through the protective sleeve and are then gathered into an optical cable set in the optical fiber terminal box. The optical cable set is separated by the optical fiber distribution frame and connected to the optical fiber Bragg grating demodulator. The optical fiber Bragg grating demodulator is connected to the terminal equipment signal.

[0008] A temperature measuring cavity is provided at the lower end of the protective shell, and a temperature sensing grating for measuring temperature changes is provided on the sensing optical fiber in the temperature measuring cavity. The lower end of the temperature sensing grating is a free end, and the upper end of the temperature sensing grating is a fixed end, which is connected to the inner wall of the protective shell. A strain sensing grating for measuring stress changes is provided on the sensing optical fiber at the upper end of the temperature sensing grating.

[0009] The protective shell includes a front shell and a rear shell, the upper end of the front shell is connected to the lower end of the rear shell, and the upper end of the rear shell is connected to the lower end of the protective sleeve;

[0010] The temperature measuring cavity is arranged in the front end housing, and the strain sensing grating is arranged in the rear end housing.

[0011] The temperature measuring cavity and the rear end shell are both filled with thermal conductive grease, and the free end of the sensing optical fiber is suspended in the temperature measuring cavity.

[0012] A layer of aerospace optical glue is provided on the bottom of the inner wall of the rear end shell, and the aerospace optical glue is bonded to the sensing optical fiber located in the rear end shell.

[0013] The aerospace optical adhesive forms a guide groove, and the sensing optical fiber is arranged longitudinally along the guide groove formed by the aerospace optical adhesive.

[0014] The protective sleeve comprises an outermost rubber layer, a middle tensile buffer layer, and an innermost flame retardant sleeve layer. The rubber layer, the tensile buffer layer and the flame retardant sleeve layer are connected in sequence.

[0015] A method for using a stator winding interlayer optical fiber temperature and strain dual-parameter monitoring device, the method comprising the following steps:

[0016] First, one end of the sensing optical fiber is inserted into the temperature measuring cavity along the protective sleeve and protective shell of the interlayer insulation gasket. The other end of the sensing optical fiber passes through the protective sleeve and is then assembled into an optical cable set in the optical fiber terminal box. The optical cable set is separated by the optical fiber distribution frame and connected to the optical fiber Bragg grating demodulator. The optical fiber Bragg grating demodulator is connected to the terminal device signal. Then, the free end of the temperature sensing grating is suspended in the temperature measuring cavity, and the fixed end is fixed to the bottom of the inner wall of the protective shell. Then, the strain sensing grating is fixed to the area at the upper end of the temperature measuring cavity in the protective shell. Then, the entire interlayer insulation gasket is placed between the corresponding upper wire rod and the lower wire rod. Then, the generator is started, and the temperature data of the temperature sensing grating and the strain data of the strain sensing grating are measured after running for a preset time.

[0017] The temperature data of the temperature sensing grating is measured as follows: since one end of the temperature sensing grating is free and the other end is fixed, the temperature sensing grating is not affected by external stress but only by the ambient temperature, and temperature changes will cause the center wavelength of the grating to drift;

[0018] The influence of the ambient temperature includes the thermal expansion and contraction effect which will affect the change of the grating period Λ, the thermo-optical effect which will cause the core refractive index n eff changes;

[0019] The formula for the change of the grating period caused by thermal expansion and contraction is as follows:

[0020]

[0021] The formula for the change in the core refractive index caused by the thermo-optical effect is as follows:

[0022]

[0023] Where: a is the thermal expansion coefficient of the optical fiber material, ξ is the thermo-optical coefficient of the optical fiber, and V is the normalized frequency of the optical fiber;

[0024] In a certain temperature range, the temperature change ΔTding is related to the grating period change ΔΛ and the core refractive index change Δn eff proportional to;

[0025] The influence of temperature change on FBG reflection wavelength drift is as follows:

[0026] Δλ1=λ1(α+ξ)ΔT=K T ΔT;

[0027] Among them, after the material of the sensing optical fiber is determined, the thermal expansion coefficient α and the thermo-optical coefficient ξ are constants, so there is a linear relationship between Δλ1 and ΔT. By measuring the wavelength change Δλ1 of the temperature sensing grating, the temperature of the measuring point in the stator winding is measured.

[0028] The strain sensing grating is fixed in a protective housing, which causes it to be affected by both temperature and external stress. Changes in temperature and strain will cause the center wavelength of the grating to drift.

[0029] The influence of the external stress includes: mechanical stretching causing the change of the grating period Λ, the elastic effect causing the core refractive index n eff changes;

[0030] The mechanical stretching causes the grating period to change as follows:

[0031]

[0032] The formula for the change in the core refractive index caused by the elastic-optic effect is:

[0033]

[0034] Where ε is the fiber Bragg grating strain, P 11 、P 12 is the elastic-optical coefficient of the optical fiber, o is the Poisson's ratio, P ε is the effective elastic-optical coefficient;

[0035] The influence formula of the stress on the FBG reflection wavelength drift is:

[0036] Δλ B =λ B (1-P ε )ε=K ε ε.

[0037] The effects of temperature and strain on its wavelength drift are completely independent of each other and are linearly additive. The wavelength change is:

[0038] Δλ2=K T ΔT+K ε ε;

[0039] Because the strain sensing grating and the temperature sensing grating are subject to the same stator winding interlayer temperature, the wavelength drift caused by temperature is equal. Therefore, the difference in the wavelength drift of the two gratings is related to the strain, that is, the strain between the winding layers is obtained as follows:

[0040] Δλ2-Δλ1=K ε ε.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. In the present invention, a stator winding interlayer optical fiber temperature and strain dual parameter monitoring device and its use method, the interlayer insulating pad is arranged between the upper layer wire rod and the lower layer wire rod, and multiple groups of upper layer wire rods and lower layer wire rods are staggered to form the stator winding. The middle section of each interlayer insulating pad is provided with a protective shell with a T-shaped cross section. The lower end of the protective sleeve is sleeved on the outer side of the upper end of the protective shell. The upper end of the protective sleeve extends to the outer side of the interlayer insulating pad. A longitudinally arranged sensing optical fiber is provided in the protective shell. The upper ends of all sensing optical fibers pass through the protective sleeve and are then gathered into an optical cable set in the optical fiber terminal box. The optical cable set is separated by the optical fiber distribution frame and then connected to the optical fiber terminal box. The fiber Bragg grating (FBG) demodulator is connected to the terminal device signal. When used, temperature sensing gratings and strain sensing gratings are inscribed on the sensing optical fiber in the monitoring area. The temperature sensing grating is not affected by stress and is only affected by the ambient temperature. By monitoring the wavelength drift, stress-free temperature measurement can be achieved. The strain sensing grating is affected by both stress and temperature, but by performing temperature compensation on it with the temperature sensing grating, the strain condition of the measurement area can be calculated. This achieves the simultaneous monitoring of temperature and strain parameters using two gratings on a single optical fiber, while better avoiding the mutual influence of temperature and strain, making the monitoring results more accurate. Therefore, the present invention can monitor temperature and strain simultaneously, making monitoring simple.

[0043] 2. In the present invention, a stator winding interlayer optical fiber temperature and strain dual-parameter monitoring device and its use method, the protective sheath includes an outermost rubber layer, a middle tensile buffer layer, and an innermost flame-retardant sleeve layer. The rubber layer, tensile buffer layer, and flame-retardant sleeve layer are sequentially connected. When used, the protective outer shell is made of a rigid polymer stress-sensitive material with an insulation strength of Class F or above. This can not only transmit stress and strain, but also ensure that the optical fiber is not damaged during installation and generator operation, thereby improving the survival rate of the sensor. The rubber layer is made of a rubber material with an insulation strength of Class F, the tensile buffer layer is an aramid tensile buffer material, and the flame-retardant sleeve layer is made of a high-temperature resistant flame-retardant sleeve material. The layered protection structure further ensures the safety of the optical fiber, reduces the bending loss of the optical fiber lead-out pad, and has a good protective structure and moisture-proof performance. Therefore, the present invention has good protection effect and is safe to use.

[0044] 3. In a stator winding interlayer optical fiber temperature and strain dual-parameter monitoring device and its use method, the present invention comprises a temperature measurement cavity disposed within a front housing, a strain sensing grating disposed within a rear housing, and a layer of aerospace optical adhesive disposed on the bottom of the inner wall of the rear housing, which is bonded to the sensing optical fiber within the rear housing. During use, the temperature measurement cavity and the inner wall of the rear housing are filled with thermal conductive grease, and the free end of the sensing optical fiber is suspended above the thermal conductive grease. The thermal conductive grease not only improves thermal conductivity sensitivity but also eliminates the influence of generator stator winding vibration on measurement. Therefore, the present invention improves thermal conductivity sensitivity and eliminates the influence of generator stator winding vibration on measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a structural schematic diagram of the present invention.

[0046] Figure 2 It is a structural schematic diagram of the interlayer insulating pads in the present invention.

[0047] Figure 3 It is a distribution diagram of the optical cables in the present invention.

[0048] Figure 4 This is a schematic diagram of the arrangement position of the interlayer insulating pads in the present invention.

[0049] Figure 5 It is a structural schematic diagram of the upper wire rod and the lower wire rod in the present invention.

[0050] Figure 6 It is a structural schematic diagram of the protective shell in the present invention.

[0051] Figure 7 It is a top view of the protective shell in the present invention.

[0052] Figure 8 It is a structural schematic diagram of the protective sleeve in the present invention.

[0053] In the figure: interlayer insulating gasket 1, temperature measuring cavity 2, protective shell 3, front shell 31, rear shell 32, aerospace optical adhesive 33, temperature sensing grating 4, strain sensing grating 5, free end 6, fixed end 7, sensing optical fiber 8, protective sleeve 9, rubber layer 91, tensile buffer layer 92, flame retardant sleeve layer 93, upper wire rod 11, lower wire rod 12, optical fiber terminal box 13, optical fiber distribution frame 14, optical fiber Bragg grating demodulator 15, terminal equipment 16. DETAILED DESCRIPTION

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] See also Figures 1 to 8 A stator winding interlayer optical fiber temperature and strain dual parameter monitoring device, the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device includes a plurality of interlayer insulating strips 1, a protective shell 3, a temperature sensing grating 4, a strain sensing grating 5, a sensing optical fiber 8, and a protective sleeve 9;

[0056] Each of the interlayer insulating gaskets 1 is arranged between the upper wire rods 11 and the lower wire rods 12, and multiple groups of upper wire rods 11 and lower wire rods 12 are staggered to form a stator winding. The middle section of each interlayer insulating gasket 1 is provided with a protective shell 3 with a T-shaped cross-section. The lower end of the protective sleeve 9 is sleeved on the outer side of the upper end of the protective shell 3, and the upper end of the protective sleeve 9 extends to the outer side of the interlayer insulating gasket 1. A longitudinally arranged sensing optical fiber 8 is provided in the protective shell 3. The upper ends of all sensing optical fibers 8 pass through the protective sleeve 9 and are then gathered into an optical cable set in the optical fiber terminal box 13. The optical cable set is separated by the optical fiber distribution frame 14 and connected to the optical fiber Bragg grating demodulator 15. The optical fiber Bragg grating demodulator 15 is connected to the terminal equipment 16 for signal connection;

[0057] A temperature measuring cavity 2 is provided at the lower end of the protective shell 3, and a temperature sensing grating 4 for measuring temperature changes is provided on the sensing optical fiber 8 in the temperature measuring cavity 2. The lower end of the temperature sensing grating 4 is a free end 6, and the upper end of the temperature sensing grating 4 is a fixed end 7. The fixed end 7 is connected to the inner wall of the protective shell 3, and a strain sensing grating 5 for measuring stress changes is provided on the sensing optical fiber 8 at the upper end of the temperature sensing grating 4.

[0058] The protective shell 3 includes a front shell 31 and a rear shell 32. The upper end of the front shell 31 is connected to the lower end of the rear shell 32, and the upper end of the rear shell 32 is connected to the lower end of the protective sleeve 9.

[0059] The temperature measuring cavity 2 is arranged in the front end housing 31 , and the strain sensing grating 5 is arranged in the rear end housing 32 .

[0060] The temperature measuring cavity 2 and the rear end housing 32 are filled with thermal conductive grease, and the free end 6 of the sensing optical fiber 8 is suspended in the temperature measuring cavity 2 .

[0061] A layer of aerospace optical adhesive 33 is provided on the bottom of the inner wall of the rear end shell 32 , and the aerospace optical adhesive 33 is bonded to the sensing optical fiber 8 located in the rear end shell 32 .

[0062] The aerospace optical adhesive 33 forms a guide groove, and the sensing optical fiber 8 is longitudinally arranged along the guide groove formed by the aerospace optical adhesive 33 .

[0063] The protective sleeve 9 includes an outermost rubber layer 91, a middle tensile buffer layer 92, and an innermost flame retardant sleeve layer 93. The rubber layer 91, the tensile buffer layer 92 and the flame retardant sleeve layer 93 are connected in sequence.

[0064] A method for using a stator winding interlayer optical fiber temperature and strain dual-parameter monitoring device, the method comprising the following steps:

[0065] First, one end of the sensing optical fiber 8 is inserted into the temperature measuring cavity 2 along the protective sleeve 9 and the protective shell 3 of the interlayer insulating gasket 1. The other end of the sensing optical fiber 8 passes through the protective sleeve 9 and is then gathered into an optical cable set in the optical fiber terminal box 13. The optical cable set is separated by the optical fiber distribution frame 14 and connected to the optical fiber Bragg grating demodulator 15. The optical fiber Bragg grating demodulator 15 is connected to the terminal device 16 signal. Then, the free end 6 of the temperature sensing grating 4 is suspended in the temperature measuring cavity 2, and the fixed end 7 is fixed to the bottom of the inner wall of the protective shell 3. Then, the strain sensing grating 5 is fixed to the area at the upper end of the temperature measuring cavity 2 in the protective shell 3. Then, the entire interlayer insulating gasket 1 is placed between the corresponding upper wire rod 11 and the lower wire rod 12. Then, the generator is started, and the temperature data of the temperature sensing grating 4 and the strain data of the strain sensing grating 5 are measured after running for a preset time.

[0066] The temperature data of the temperature sensing grating 4 is measured as follows: since one end of the temperature sensing grating 4 is a free end 6 and the other end is a fixed end 7, the temperature sensing grating 4 is not affected by external stress and is only affected by the ambient temperature. The temperature change will cause the grating center wavelength to drift;

[0067] The influence of the ambient temperature includes the thermal expansion and contraction effect which will affect the change of the grating period Λ, the thermo-optical effect which will cause the core refractive index n eff changes;

[0068] The formula for the change of the grating period caused by thermal expansion and contraction is as follows:

[0069]

[0070] The formula for the change in the core refractive index caused by the thermo-optical effect is as follows:

[0071]

[0072] Where: a is the thermal expansion coefficient of the optical fiber material, ξ is the thermo-optical coefficient of the optical fiber, and V is the normalized frequency of the optical fiber;

[0073] In a certain temperature range, the temperature change ΔTding is related to the grating period change ΔΛ and the core refractive index change Δn eff proportional to;

[0074] The influence of temperature change on FBG reflection wavelength drift is as follows:

[0075] Δλ1=λ1(α+ξ)ΔT=K T ΔT;

[0076] Among them, after the material of the sensing optical fiber 8 is determined, the thermal expansion coefficient α and the thermo-optical coefficient ξ are constants, so there is a linear change relationship between Δλ1 and ΔT. By measuring the wavelength change Δλ1 of the temperature sensing grating 4, the temperature of the measuring point in the stator winding is measured.

[0077] The strain sensing grating 5 is fixed in the protective housing 3, which causes it to be affected by both temperature and external stress. Changes in temperature and strain will cause the center wavelength of the grating to drift.

[0078] The influence of the external stress includes: mechanical stretching causing the change of the grating period Λ, the elastic effect causing the core refractive index n eff changes;

[0079] The mechanical stretching causes the grating period to change as follows:

[0080]

[0081] The formula for the change in the core refractive index caused by the elastic-optic effect is:

[0082]

[0083] Where σ is the fiber Bragg grating strain, P 11 、P 12 is the elastic-optical coefficient of the optical fiber, o is the Poisson's ratio, P ε is the effective elastic-optical coefficient;

[0084] The influence formula of the stress on the FBG reflection wavelength drift is:

[0085] Δλ B =λ B (1-P ε )ε=K ε ε.

[0086] The effects of temperature and strain on its wavelength drift are completely independent of each other and are linearly additive. The wavelength change is:

[0087] Δλ2=K T ΔT+K ε ε;

[0088] Because the strain sensing grating 5 and the temperature sensing grating 4 are subjected to the same stator winding interlayer temperature, the wavelength drift caused by temperature is equal. Therefore, the difference in the wavelength drift of the two gratings is related to the strain, that is, the strain between the winding layers is obtained as follows:

[0089] Δλ2-Δλ1=K ε ε.

[0090] The supplementary description of the present invention is as follows:

[0091] After multiple sensor optical cables are led out between multiple wire rod layers, they are routed along the bottom of the pressure plate through the cable tray and enter the fiber optic terminal box 13. When the optical cable is routed along the pressure plate and the cable tray, it is routed along the nearest round steel and fixed to the stator through multiple welding points to prevent damage to the optical cable due to long-term shaking. The fiber optic terminal box 13 is fixed on the stator base, and a sensor array is connected in series inside the fiber optic terminal box 13 and fused with a multi-core optical cable. The multi-core optical cable is led along the external cable tray to the fiber optic distribution frame 14 in the cabinet, and then the pigtail is used to access the fiber optic Bragg grating demodulator 15 for wavelength signal demodulation and data storage, and finally transmitted to the computer.

[0092] Example 1:

[0093] A stator winding interlayer optical fiber temperature and strain dual parameter monitoring device, the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device includes multiple interlayer insulating gaskets 1, a protective shell 3, a temperature sensing grating 4, a strain sensing grating 5, a sensing optical fiber 8, and a protective sleeve 9; each of the interlayer insulating gaskets 1 is arranged between an upper layer wire rod 11 and a lower layer wire rod 12, and multiple groups of upper layer wire rods 11 and lower layer wire rods 12 are staggered to form a stator winding, and the middle section of each interlayer insulating gasket 1 is provided with a protective shell 3 with a T-shaped cross section, the lower end of the protective sleeve 9 is sleeved on the outer side of the upper end of the protective shell 3, and the upper end of the protective sleeve 9 extends to the outer side of the interlayer insulating gasket 1, and a longitudinal The upper ends of all the sensing optical fibers 8 are arranged in a direction, and then the upper ends of all the sensing optical fibers 8 pass through the protective sleeve 9 and are gathered into an optical cable set in the optical fiber terminal box 13. The optical cable set is separated by the optical fiber distribution frame 14 and then connected to the optical fiber Bragg grating demodulator 15. The optical fiber Bragg grating demodulator 15 is connected to the terminal equipment 16 for signal connection; the lower end of the protective shell 3 is provided with a temperature measuring cavity 2, and a temperature sensing grating 4 for measuring temperature changes is provided on the sensing optical fiber 8 in the temperature measuring cavity 2. The lower end of the temperature sensing grating 4 is a free end 6, and the upper end of the temperature sensing grating 4 is a fixed end 7, which is connected to the inner wall of the protective shell 3. A strain sensing grating 5 for measuring stress changes is provided on the sensing optical fiber 8 at the upper end of the temperature sensing grating 4.

[0094] A method for using a stator winding interlayer optical fiber temperature and strain dual-parameter monitoring device comprises the following steps: first, one end of the sensing optical fiber 8 is inserted into a temperature measurement cavity 2 along the protective sleeve 9 and protective housing 3 of an interlayer insulating gasket 1; the other end of the sensing optical fiber 8 passes through the protective sleeve 9 and is then assembled into an optical cable set within an optical fiber terminal box 13; the optical cable set is separated by an optical fiber distribution frame 14 and then connected to a fiber optic Bragg grating (FBG) demodulator 15; the fiber optic Bragg grating (FBG) demodulator 15 is signal-connected to a terminal device 16; then, the free end 6 of the temperature sensing grating 4 is suspended in the temperature measurement cavity 2; the fixed end 7 is fixed to the bottom of the inner wall of the protective housing 3; then, the strain sensing grating 5 is fixed to the area within the protective housing 3 located at the upper end of the temperature measurement cavity 2; then, the entire interlayer insulating gasket 1 is placed between the corresponding upper wire rod 11 and lower wire rod 12; then, the generator is started; and after a preset operation time, the temperature data of the temperature sensing grating 4 and the strain data of the strain sensing grating 5 are measured.

[0095] Example 2:

[0096] Example 2 is basically the same as Example 1, except that:

[0097] A stator winding interlayer optical fiber temperature and strain dual parameter monitoring device, the protective shell 3 includes a front shell 31 and a rear shell 32, the upper end of the front shell 31 is connected to the lower end of the rear shell 32, and the upper end of the rear shell 32 is connected to the lower end of the protective sleeve 9; the temperature measuring cavity 2 is arranged in the front shell 31, and the strain sensing grating 5 is arranged in the rear shell 32; the temperature measuring cavity 2 and the rear shell 32 are filled with thermal conductive grease, and the free end 6 of the sensing optical fiber 8 is suspended in the temperature measuring cavity. In the cavity 2; a layer of aerospace optical glue 33 is provided at the bottom of the inner wall of the rear end shell 32, and the aerospace optical glue 33 is bonded to the sensing optical fiber 8 located in the rear end shell 32; the aerospace optical glue 33 forms a guide groove, and the sensing optical fiber 8 is longitudinally arranged along the guide groove formed by the aerospace optical glue 33; the protective sleeve 9 includes an outermost rubber layer 91, a middle layer of a tensile buffer layer 92, and an innermost flame retardant sleeve layer 93, and the rubber layer 91, the tensile buffer layer 92 and the flame retardant sleeve layer 93 are connected in sequence.

[0098] When applying:

[0099] The interlayer gasket 1 should be made of insulating material, and epoxy glass cloth laminate should be selected. The protective shell 3 is a rigid polymer stress-sensitive material with an insulation strength of F grade or above. It can not only transmit stress and strain, but also ensure that the optical fiber is not damaged during installation and generator operation, thereby improving the survival rate of the sensor. The rubber layer 91 adopts an insulation strength F grade rubber material, the tensile buffer layer 92 is an aramid tensile buffer material, and the flame retardant sleeve layer 9 adopts a flame retardant sleeve material with a temperature resistance of more than 250°C. Through the layer-by-layer protection structure, the safety of the optical fiber is further guaranteed, so that the bending loss of the optical fiber lead-out gasket is small, and it has a better protective structure and moisture-proof performance.

[0100] Example 3:

[0101] Example 3 is basically the same as Example 1, except that:

[0102] A method for using a stator winding interlayer optical fiber temperature and strain dual-parameter monitoring device, the method comprising the following steps:

[0103] First, one end of the sensing optical fiber 8 is inserted into the temperature measuring cavity 2 along the protective sleeve 9 and the protective shell 3 of the interlayer insulating pad 1. The other end of the sensing optical fiber 8 passes through the protective sleeve 9 and then the optical path is gathered into an optical cable set in the optical fiber terminal box 13. The optical cable set is separated by the optical fiber distribution frame 14 and connected to the optical fiber Bragg grating demodulator 15. The optical fiber Bragg grating demodulator 15 is connected to the terminal device 16 signal. Then the free end 6 of the temperature sensing grating 4 is suspended in the temperature measuring cavity 2. The sensing optical fiber 8 is in a free state as a whole. The purpose of this setting is to achieve stress-free temperature measurement. The stress caused by the gravity of the optical fiber itself is not affected by the temperature measurement. The force is small and can basically be ignored. Even if it is considered, the influence of gravity can be eliminated by calibration before measurement. The temperature sensing grating 4 in the temperature measuring cavity 2 cannot be fixed to the shell and must remain free. The fixed end 7 is fixed to the bottom of the inner wall of the protective shell 3, and then the strain sensing grating 5 is fixed to the area at the upper end of the temperature measuring cavity 2 in the protective shell 3, and then the entire interlayer insulating pad 1 is placed between the corresponding upper wire rod 11 and the lower wire rod 12, and then the generator is started. After running for a preset time, the temperature data of the temperature sensing grating 4 and the strain data of the strain sensing grating 5 are measured.

[0104] The temperature data of the temperature sensing grating 4 is measured as follows: since one end of the temperature sensing grating 4 is a free end 6 and the other end is a fixed end 7, the temperature sensing grating 4 is not affected by external stress and is only affected by the ambient temperature. Changes in temperature and strain will cause the grating center wavelength to drift.

[0105] The influence of the ambient temperature includes the thermal expansion and contraction effect which will affect the change of the grating period Λ, the thermo-optical effect which will cause the core refractive index n eff changes;

[0106] The formula for the change of the grating period caused by thermal expansion and contraction is as follows:

[0107]

[0108] The formula for the change in the core refractive index caused by the thermo-optical effect is as follows:

[0109]

[0110] Where: a is the thermal expansion coefficient of the optical fiber material, ξ is the thermo-optical coefficient of the optical fiber, and V is the normalized frequency of the optical fiber;

[0111] In a certain temperature range, the temperature change ΔTding is related to the grating period change ΔΛ and the core refractive index change Δn eff proportional to;

[0112] The influence of temperature change on FBG reflection wavelength drift is as follows:

[0113] Δλ1=λ1(α+ξ)ΔT=K T ΔT;

[0114] Among them, after the material of the sensing optical fiber 8 is determined, the thermal expansion coefficient α and the thermo-optical coefficient ξ are constants, so there is a linear change relationship between Δλ1 and ΔT. By measuring the wavelength change Δλ1 of the temperature sensing grating 4, the temperature of the measuring point in the stator winding is measured.

[0115] The strain sensing grating 5 is fixed to the guide groove in the protective housing 3 by aerospace optical glue. It will be affected by both external force and temperature. Therefore, the temperature sensing grating 4 can be used to compensate for the temperature and calculate the strain at that point.

[0116] The effects of stress on FBG include: mechanical stretching causing the change of grating period Λ, elastic-optical effect causing the core refractive index n eff changes;

[0117] The mechanical stretching causes the grating period to change as follows:

[0118]

[0119] The formula for the change in the core refractive index caused by the elastic-optic effect is:

[0120]

[0121] Where ε is the fiber Bragg grating strain, P 11 、P 12 is the elastic-optical coefficient of the optical fiber, o is the Poisson's ratio, P ε is the effective elastic-optical coefficient;

[0122] The influence formula of the stress on the FBG reflection wavelength drift is:

[0123] Δλ B =λ B (1-P ε )ε=K ε ε.

[0124] The effects of temperature and strain on the wavelength drift are completely independent of each other and are linearly additive. The wavelength change is:

[0125] Δλ2=K T ΔT+K ε ε;

[0126] Because the strain sensing grating 5 and the temperature sensing grating 4 are subjected to the same stator winding interlayer temperature, the wavelength drift caused by temperature is equal. Therefore, the difference in the wavelength drift of the two gratings is related to the strain, that is, the strain between the winding layers is obtained as follows:

[0127] Δλ2-Δλ1=K ε ε.

[0128] The stator winding of the generator is composed of multiple stator bars. The above sensor device is used to monitor the temperature strain between the layers of a single stator bar. For the entire stator winding, a stator winding interlayer optical fiber temperature strain monitoring system can be designed, such as Figure 4 As shown, a single optical fiber sensor is installed inside the winding layer spacer 1, and multiple monitoring points can be set according to monitoring requirements, such as the upper part of the layer, the middle part of the layer, the lower part of the layer, etc.

[0129] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. A stator winding interlayer optical fiber temperature and strain dual parameter monitoring device, characterized by: The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device comprises a plurality of interlayer insulating pads (1), a protective shell (3), a temperature sensing grating (4), a strain sensing grating (5), a sensing optical fiber (8), and a protective sleeve (9); Each interlayer insulating gasket (1) is arranged between an upper layer wire rod (11) and a lower layer wire rod (12), and a plurality of groups of staggered upper layer wire rods (11) and lower layer wire rods (12) form a stator winding. A protective shell (3) with a T-shaped cross section is provided in the middle section of each interlayer insulating gasket (1). The lower end of the protective sleeve (9) is sleeved on the outer side of the upper end of the protective shell (3), and the upper end of the protective sleeve (9) extends to the outer side of the interlayer insulating gasket (1). A longitudinally arranged sensing optical fiber (8) is provided in the protective shell (3). The upper ends of all the sensing optical fibers (8) pass through the protective sleeve (9) and are then gathered into an optical cable set in an optical fiber terminal box (13). The optical cable set is separated by an optical fiber distribution frame (14) and then connected to a fiber optic Bragg grating demodulator (15). The fiber optic Bragg grating demodulator (15) is connected to a terminal device (16) for signal connection. A temperature measuring cavity (2) is provided at the lower end of the protective shell (3); a temperature sensing grating (4) for measuring temperature changes is provided on the sensing optical fiber (8) and is located in the temperature measuring cavity (2); the lower end of the temperature sensing grating (4) is a free end (6); the upper end of the temperature sensing grating (4) is a fixed end (7); the fixed end (7) is connected to the inner wall of the protective shell (3); and a strain sensing grating (5) for measuring stress changes is provided on the sensing optical fiber (8) and is located at the upper end of the temperature sensing grating (4).

2. The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 1, characterized in that: The protective shell (3) comprises a front shell (31) and a rear shell (32), the upper end of the front shell (31) is connected to the lower end of the rear shell (32), and the upper end of the rear shell (32) is connected to the lower end of the protective sleeve (9); The temperature measuring cavity (2) is arranged in the front end housing (31), and the strain sensing grating (5) is arranged in the rear end housing (32).

3. The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 2, characterized in that: The temperature measuring cavity (2) and the rear end housing (32) are filled with heat-conducting grease, and the free end (6) of the sensing optical fiber (8) is suspended in the temperature measuring cavity (2).

4. The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 2, characterized in that: A layer of aerospace optical glue (33) is provided at the bottom of the inner wall of the rear end housing (32), and the aerospace optical glue (33) is bonded to the sensing optical fiber (8) located in the rear end housing (32).

5. The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 4, characterized in that: The aerospace optical adhesive (33) forms a guide groove, and the sensing optical fiber (8) is longitudinally arranged along the guide groove formed by the aerospace optical adhesive (33).

6. The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 1, characterized in that: The protective sleeve (9) comprises an outermost rubber layer (91), a middle tensile buffer layer (92), and an innermost flame retardant sleeve layer (93), wherein the rubber layer (91), the tensile buffer layer (92) and the flame retardant sleeve layer (93) are connected in sequence.

7. A method for using the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 1, characterized in that: The method for using the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device comprises the following steps: First, one end of the sensing optical fiber (8) is inserted into the temperature measuring cavity (2) along the protective sleeve (9) and the protective shell (3) of the interlayer insulating pad (1). The other end of the sensing optical fiber (8) passes through the protective sleeve (9) and is then assembled into an optical cable set in the optical fiber terminal box (13). The optical cable set is separated by the optical fiber distribution frame (14) and connected to the optical fiber Bragg grating demodulator (15). The optical fiber Bragg grating demodulator (15) is connected to the terminal device (16) for signal connection. Then, the free end of the temperature sensing grating (4) is connected to the temperature measuring cavity (2). (6) is suspended in the temperature measuring cavity (2), and the fixed end (7) is fixed to the bottom of the inner wall of the protective shell (3), and the strain sensing grating (5) is fixed to the area of ​​the protective shell (3) located at the upper end of the temperature measuring cavity (2), and the entire interlayer insulating pad (1) is placed between the corresponding upper wire rod (11) and the lower wire rod (12), and then the generator is started, and the temperature data of the temperature sensing grating (4) and the strain data of the strain sensing grating (5) are measured after running for a preset time.

8. The method for using the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 7 is characterized in that: The method for measuring the temperature data of the temperature sensing grating (4) is as follows: since one end of the temperature sensing grating (4) is a free end (6) and the other end is a fixed end (7), the temperature sensing grating (4) is not affected by external stress and is only affected by the ambient temperature, and the change in temperature will cause the center wavelength of the grating to drift; The influence of the ambient temperature includes the thermal expansion and contraction effect which will affect the change of the grating period Λ, the thermo-optical effect which will cause the core refractive index n eff changes; The formula for the change of the grating period caused by thermal expansion and contraction is as follows: The formula for the change in the core refractive index caused by the thermo-optical effect is as follows: Where: a is the thermal expansion coefficient of the optical fiber material, ξ is the thermo-optical coefficient of the optical fiber, and V is the normalized frequency of the optical fiber; In a certain temperature range, the temperature change ΔTding is related to the grating period change ΔΛ and the core refractive index change Δn eff proportional to; The influence of temperature change on FBG reflection wavelength drift is as follows: Δλ1=λ1(α+ξ)ΔT=K T ΔT; Among them, after the material of the sensing optical fiber (8) is determined, the thermal expansion coefficient α and the thermo-optical coefficient ξ are constants, so there is a linear relationship between Δλ1 and ΔT, and the temperature of the temperature measuring point in the stator winding is measured by measuring the wavelength change Δλ1 of the temperature sensing grating (4).

9. The method for using the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 7, characterized in that: The strain sensing grating (5) is fixed in the protective housing (3), so that it is affected by both temperature and external stress, and changes in temperature and strain will cause the center wavelength of the grating to drift; The influence of the external stress includes: mechanical stretching causing the change of the grating period Λ, the elastic effect causing the core refractive index n eff changes; The mechanical stretching causes the grating period to change as follows: The formula for the change in the core refractive index caused by the elastic-optic effect is: Where ε is the fiber Bragg grating strain, P 11 、P 12 is the elastic-optical coefficient of the optical fiber, o is the Poisson's ratio, P ε is the effective elastic-optical coefficient; The influence formula of the external stress on the FBG reflection wavelength drift is: Dl B =λ B (1-P ε )ε=K ε Yes.

10. The method for using the stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 9, characterized in that: The effects of temperature and strain on its wavelength drift are completely independent of each other and are linearly additive. The wavelength change is: Δλ2=K T ΔT+K ε e; Because the strain sensing grating (5) and the temperature sensing grating (4) are subjected to the same stator winding interlayer temperature, the wavelength drift caused by temperature is equal. Therefore, the difference in the wavelength drift of the two gratings is related to the strain, that is, the strain between the winding layers is obtained as follows: Δλ2-Δλ1=K ε Yes.

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