Stator winding interlayer optical fiber temperature and strain double-parameter monitoring device and using method thereof

Abstract

A stator winding interlayer optical fiber temperature and strain double-parameter monitoring device comprises a plurality of interlayer insulation filler strips, a protective shell, a temperature sensing grating, a strain sensing grating, a sensing optical fiber and a protective sleeve. Each interlayer insulation filler strip is arranged between the upper-layer winding bars and the lower-layer winding bars, the multiple groups of staggered upper-layer winding bars and lower-layer winding bars form a stator winding, the middle section of each interlayer insulation filler strip is provided with a protective shell with a T-shaped cross section, and the lower end of the protective sleeve is connected to the outer side of the upper end of the protective shell in a sleeving mode. The upper end of the protection sleeve extends to the outer side of the interlayer insulation filler strip, longitudinally-arranged sensing optical fibers are arranged in the protection shell, the upper ends of all the sensing optical fibers penetrate through the protection sleeve and then are gathered into an optical cable set in the optical fiber terminal box, and the optical cable set is separated through an optical fiber distribution frame and then is connected with a fiber bragg grating demodulator. And the fiber bragg grating demodulator is in signal connection with the terminal equipment. The temperature and the strain can be monitored at the same time, and monitoring is simple.

Description

Technical Field

[0001] The 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 interlayer temperature and strain of the stator winding of large-scale hydro-turbine generators affect the service 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 temperature and strain of the stator windings is of great significance. Currently, the interlayer temperature measurement of the stator windings of large-scale hydro-turbine generators mostly adopts platinum resistance or thermocouple methods, and the strain measurement mostly adopts electronic strain gauges. Both are measured and transmitted through electrical signals. The transmission medium wire is metal, which is easily interfered by strong electric and magnetic fields and cannot be measured correctly. In addition, metal materials are prone to arcing, corona, heating and other problems under the action of strong electric and magnetic fields, causing great harm. In the existing scheme, only the temperature parameter can be monitored, and the temperature and strain cannot be monitored at the same time.

[0003] The Chinese patent application with application number CN202311083542.5 and application date of August 25, 2023 discloses a method and device for measuring the temperature of the stator winding of a direct-drive permanent magnet wind turbine, which relates to the field of wind power generation measurement technology, including: installing a temperature acquisition module at the air gap of the outer wall of the rotor; collecting the temperature of the stator winding during the operation of the wind turbine generator set based on the temperature acquisition module to obtain a temperature signal; converting the temperature signal into an optical signal and transmitting it to the control terminal; based on the control terminal, determining the fault mode of the wind turbine according to the temperature signal, the reference temperature curve and / or auxiliary parameters. The infrared temperature sensor has the characteristics of high sensitivity and non-contact acquisition of temperature data. 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. Fewer infrared temperature sensors are required, which reduces the distortion of the magnetic field. This solution can only monitor the temperature change in real time online, but does not solve the problem that temperature and strain cannot be monitored simultaneously.

[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 acknowledging or suggesting in any form that the information constitutes the prior art already known to ordinary technicians in this field. 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 a method of using the device, which 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 strain dual parameter monitoring device, the stator winding interlayer optical fiber temperature strain dual parameter monitoring device comprises a plurality of interlayer insulating pads, a protective shell, a temperature sensing grating, a strain sensing grating, a sensing optical fiber, and a protective sleeve;

[0007] Each of the interlayer insulating pads is arranged between the upper wire rod and the lower wire rod, and multiple groups of staggered upper wire rods and lower wire rods form a 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, and the upper end of the protective sleeve extends to the outer side of the interlayer insulating pad. A longitudinally arranged sensing optical fiber is arranged in the protective shell. The upper ends of all the sensing optical fibers pass through the protective sleeve and are 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 arranged at the lower end of the protective shell, and a temperature sensing grating for measuring temperature changes is arranged 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, and a strain sensing grating for measuring stress changes is arranged on the upper end of the temperature sensing grating on the sensing optical fiber.

[0009] The protective shell comprises a front end shell and a rear end shell, the upper end of the front end shell is connected to the lower end of the rear end shell, and the upper end of the rear end 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 filled with heat-conducting 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 arranged at 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 glue forms a guide groove, and the sensing optical fiber is arranged longitudinally along the guide groove formed by the aerospace optical glue.

[0014] The protective sleeve comprises an outermost rubber layer, a middle tensile buffer layer, and an innermost flame retardant sleeve layer, and 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 strain dual parameter monitoring device, the method for using the stator winding interlayer optical fiber temperature strain dual parameter monitoring device 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 pad, and the other end of the sensing optical fiber passes through the protective sleeve and is 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, and the optical fiber Bragg grating demodulator is connected to the terminal device signal, and then the free end of the temperature sensing grating is suspended in the temperature measuring cavity, and then the fixed end is fixed to the bottom of the inner wall of the protective shell, and then the strain sensing grating is fixed to the area at the upper end of the temperature measuring cavity in the protective shell, and then the entire interlayer insulation pad is placed between the corresponding upper wire rod and the lower wire rod, and 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 method for measuring the temperature data of the temperature sensing grating is as follows: since one end of the temperature sensing grating is a free end and the other end is a fixed end, the temperature sensing grating will not be affected by external stress but only by the ambient temperature, and the change in temperature will cause the drift of the central wavelength of the grating;

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

[0025] The influence of the temperature change on the 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, so that it is 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 of 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 the wavelength drift are completely independent and 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 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:

[0040] Δλ2-Δλ1=K ε ε.

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

[0042] 1. In a stator winding interlayer optical fiber temperature strain dual parameter monitoring device and a method for using the same, an interlayer insulating pad is arranged between an upper layer wire rod and a lower layer wire rod, and a plurality of groups of upper layer wire rods and lower layer wire rods are staggered to form a stator winding. A protective shell with a T-shaped cross section is arranged in the middle section of each interlayer insulating pad. The lower end of the protective sleeve is sleeved on the outer side of the upper end of the protective sleeve. The upper end of the protective sleeve extends to the outer side of the interlayer insulating pad. A longitudinally arranged sensing optical fiber is arranged in the protective shell. The upper ends of all the sensing optical fibers penetrate the protective sleeve and are gathered into an optical cable set in an optical fiber terminal box. The optical cable set is separated from the optical fiber distribution frame and connected to the optical fiber terminal box. The fiber Bragg grating demodulator is connected, and the fiber Bragg grating demodulator is connected to the terminal device signal. When used, by writing the temperature sensing grating and the strain sensing grating on the sensing optical fiber in the monitoring area, the temperature sensing grating is not subject to stress, but is only affected by the ambient temperature. By monitoring the drift of the wavelength, 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 through the temperature sensing grating, the strain condition of the measurement area can be calculated, thereby realizing the use of one optical fiber and two gratings to simultaneously monitor the temperature and strain dual parameters, and at the same time better avoiding the influence of temperature and strain on each other, making the monitoring result more accurate. Therefore, the temperature and strain of the present invention can be monitored simultaneously, and the monitoring is simple.

[0043] 2. In the stator winding interlayer optical fiber temperature strain dual parameter monitoring device and its use method of the present invention, the sheath tube includes the outermost rubber layer, the middle layer of the tensile buffer layer, and the innermost flame retardant sleeve layer. The rubber layer, the tensile buffer layer and the flame retardant sleeve layer are connected in sequence. When used, the protective shell is a rigid polymer stress-sensitive material with an insulation strength of F grade or above, which 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 adopts a rubber material with an insulation strength of F grade, the tensile buffer layer is an aramid tensile buffer material, and the flame retardant sleeve layer adopts a high temperature resistant flame retardant sleeve material. 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 pad part is small, and there is a better protective structure and moisture-proof performance. Therefore, the present invention has good protection effect and is safe to use.

[0044] 3. In the stator winding interlayer optical fiber temperature-strain dual-parameter monitoring device and its use method of the present invention, the temperature measuring cavity is arranged in the front end housing, the strain sensing grating is arranged in the rear end housing, and a layer of aerospace optical glue is arranged at the bottom of the inner wall of the rear end housing, and the aerospace optical glue is bonded to the sensing optical fiber located in the rear end housing; when used, the temperature measuring cavity and the inner wall of the rear end housing are filled with thermal conductive paste, and the free end of the sensing optical fiber is suspended on the thermal conductive paste, which not only improves the thermal conductivity sensitivity, but also eliminates the influence of the generator stator winding vibration on the measurement. Therefore, the present invention improves the thermal conductivity sensitivity and eliminates the influence of the generator stator winding vibration on the 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 schematic diagram of the structure of the interlayer insulating pad strip in the present invention.

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

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

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

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

[0053] In the figure: interlayer insulating pad 1, temperature measuring cavity 2, protective shell 3, front end shell 31, rear end shell 32, aerospace optical glue 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 is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0055] See also Figures 1 to 8 A stator winding interlayer optical fiber temperature strain dual parameter monitoring device, the stator winding interlayer optical fiber temperature 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;

[0056] Each of the interlayer insulating gasket strips 1 is arranged between the upper wire rod 11 and the lower wire rod 12, and multiple groups of staggered upper wire rods 11 and lower wire rods 12 form a stator winding. The middle section of each interlayer insulating gasket strip 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 strip 1. A longitudinally arranged sensing optical fiber 8 is arranged 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 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;

[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, which 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 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 .

[0062] 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 .

[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 strain dual parameter monitoring device, the method for using the stator winding interlayer optical fiber temperature strain dual parameter monitoring device 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, and the other end of the sensing optical fiber 8 passes through the protective sleeve 9 and 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 then connected to the optical fiber Bragg grating demodulator 15. The optical fiber Bragg grating demodulator 15 is connected to the terminal device 16 signal, and then the free end 6 of the temperature sensing grating 4 is suspended in the temperature measuring cavity 2, and then 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 gasket 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.

[0066] 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 will not be affected by external stress but only by the ambient temperature, and the change in temperature will cause the drift of the grating center wavelength;

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

[0074] The influence of the temperature change on the 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, so that it is 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 of 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 the wavelength drift are completely independent and 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 in 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] Embodiment 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 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 of the interlayer insulating pads 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 middle section of each interlayer insulating pad 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 pad 1, and a longitudinal The upper ends of all the sensing optical fibers 8 are inserted through the protective sleeve 9 and then gathered into a cable set in the optical fiber terminal box 13. The 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 device 16 by signal. The lower end of the protective shell 3 is provided with a temperature measuring cavity 2. The sensing optical fiber 8 is provided with a temperature sensing grating 4 for measuring temperature change 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. The upper end of the temperature sensing grating 4 on the sensing optical fiber 8 is provided with a strain sensing grating 5 for measuring stress change.

[0094] A method for using a stator winding interlayer optical fiber temperature and strain dual parameter monitoring device, the method comprising the following steps: firstly, inserting one end of the sensing optical fiber 8 into a temperature measuring cavity 2 along a protective sleeve 9 and a protective shell 3 of an interlayer insulating pad 1, the other end of the sensing optical fiber 8 passes through the protective sleeve 9 and then is assembled 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 an optical fiber grating demodulator 15, the optical fiber grating demodulator 15 is connected to a terminal device 16 signal, then the free end 6 of the temperature sensing grating 4 is suspended in the temperature measuring cavity 2, 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 pad 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.

[0095] Embodiment 2:

[0096] Embodiment 2 is substantially the same as Embodiment 1, except that:

[0097] A stator winding interlayer optical fiber temperature 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 paste, and the free end 6 of the sensing optical fiber 8 is suspended and arranged in the temperature measuring cavity 2. In the cavity 2; a layer of aerospace optical glue 33 is arranged 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, which 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 insulating strength Class F rubber material, the tensile buffer layer 92 is an aramid tensile buffer material, and the flame retardant casing layer 9 adopts a flame retardant casing 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] Embodiment 3:

[0101] Embodiment 3 is substantially the same as Embodiment 1, except that:

[0102] A method for using a stator winding interlayer optical fiber temperature strain dual parameter monitoring device, the method for using the stator winding interlayer optical fiber temperature strain dual parameter monitoring device 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 The force is small and can basically be ignored. Even if it is considered, the influence of gravity can be removed 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, 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.

[0104] 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 will not be affected by external stress but only by the ambient temperature, and changes in temperature and strain will cause the drift of the grating center wavelength;

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

[0112] The influence of the temperature change on the 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, and will be affected by external force and temperature at the same time, so the temperature can be compensated by the temperature sensing grating 4 to obtain the strain at the point;

[0116] The effects of stress on FBG include: mechanical stretching causing the grating period Λ to change, and the 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 of 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 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 interlayer gasket 1, and multiple monitoring points can be set according to monitoring requirements, such as the upper part of the interlayer, the middle part of the interlayer, the lower part of the interlayer, 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 by 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 in that: The stator winding interlayer optical fiber temperature-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 arranged 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 arranged 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 an optical fiber Bragg grating demodulator (15). The optical fiber Bragg grating demodulator (15) is connected to a terminal device (16) by signal. A temperature measuring cavity (2) is arranged at the lower end of the protective shell (3); a temperature sensing grating (4) for measuring temperature changes is arranged on the sensing optical fiber (8) and 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 arranged on the sensing optical fiber (8) and located at the upper end of the temperature sensing grating (4).

2. According to claim 1, a stator winding interlayer optical fiber temperature and strain dual parameter monitoring device is 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 measurement cavity (2) is arranged in a front end housing (31), and the strain sensing grating (5) is arranged in a rear end housing (32).

3. The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 2 is 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 is 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 is characterized in that: The aerospace optical glue (33) forms a guide groove, and the sensing optical fiber (8) is arranged longitudinally along the guide groove formed by the aerospace optical glue (33).

6. The stator winding interlayer optical fiber temperature and strain dual parameter monitoring device according to claim 1 is 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-strain dual-parameter monitoring device according to claim 1, characterized in that: The method for using the stator winding interlayer optical fiber temperature 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 housing (3) of the interlayer insulating pad (1), and the other end of the sensing optical fiber (8) passes through the protective sleeve (9) and is 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) by signal, and 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 then 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 located 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 layer wire rod (11) and the lower layer wire rod (12), and then the generator is started, and 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.

8. The method for using the stator winding interlayer optical fiber temperature-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) will not be affected by external stress but only by the ambient temperature, and the change in temperature will cause the drift of the grating center wavelength; 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; Within a certain temperature range, the temperature change ΔTding is related to the grating period change ΔΛ and the core refractive index change Δn eff is proportional to; The influence of the temperature change on the 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 change relationship between Δλ1 and ΔT. By measuring the wavelength change Δλ1 of the temperature sensing grating (4), the temperature of the temperature measuring point in the stator winding can be measured.

9. The method for using the stator winding interlayer optical fiber temperature-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 central 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 of 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 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-strain dual-parameter monitoring device according to claim 9, characterized in that: The effects of temperature and strain on the wavelength drift are completely independent and 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 the 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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