Dry-type transformer temperature rise and partial discharge cooperative monitoring device

Abstract

The present application relates to the field of power equipment online monitoring and photoelectric sensing technology, in particular to a dry-type transformer temperature rise and partial discharge cooperative monitoring device; the device comprises photoelectric sensing, absolute temperature calculation, stiffness compensation conversion, decoupling and state mapping and dynamic parameter adjustment modules; the system extracts fluorescence decay time constant and envelope broadening parameter by capturing interference light, solves winding absolute temperature and dynamically adjusts detection parameter; the core is to deduce elastic modulus attenuation coefficient by using absolute temperature, to perform division softening compensation on the broadening parameter, so as to restore the real partial microscopic thermal stress distribution and discharge energy equivalent; the present application effectively offsets the physical attenuation of ultrasonic signals caused by high temperature softening, separates the temperature cross-sensitivity error, and solves the problem that a single structure is difficult to reflect the influence of insulation softening on signal propagation path.

Description

Technical Field

[0001] This invention relates to the field of online monitoring and photoelectric sensing technology for power equipment, specifically a device for co-monitoring temperature rise and partial discharge of dry-type transformers. Background Technology

[0002] During the operation of dry-type transformers, the epoxy resin cast windings typically face complex coupling effects from multiple physical fields, including temperature rise, high-frequency electric field disturbances, and mechanical vibrations. Furthermore, the physical and mechanical properties of the winding insulation material dynamically change with operating conditions. To monitor and evaluate the transformer's insulation operating status, existing solutions generally employ a discrete monitoring architecture with a single temperature measurement structure or a single partial discharge detection component. This involves independently acquiring temperature data or electroacoustic signals and performing simple physical quantity correlation and threshold comparisons in the background system. While this approach provides a certain degree of basic state awareness under stable conditions at room temperature, its effectiveness is questionable. While capable of detecting certain phenomena, it neglects the insulation softening and damping effect caused by the decrease in the elastic modulus of epoxy resin materials under high-temperature conditions. This means that the propagation of high-frequency mechanical waves and ultrasonic signals induced by partial discharge in the windings and cast insulation suffers severe physical attenuation and waveform compression due to high-temperature softening. Furthermore, existing single-detection structures struggle to separate cross-sensitivity errors caused by temperature changes, leading to a significant drift in the partial discharge energy equivalent as temperature increases. Moreover, they are highly susceptible to common-mode power frequency vibration interference, resulting in false alarms. It is difficult to accurately reproduce the true partial discharge energy equivalent and local micro-thermal stress distribution under dynamic thermo-electric coupling conditions.

[0003] Therefore, how to eliminate the attenuation interference of temperature softening effect on the propagation path of discharge signals inside the dielectric, solve the cross-sensitivity error of multiple physical quantities, and thus improve the accuracy and anti-interference capability of the coordinated monitoring of partial discharge and temperature rise in dry-type transformers has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a device for the coordinated monitoring of temperature rise and partial discharge in dry-type transformers. Specifically, the technical solution of this invention includes:

[0005] The photoelectric sensing module is used to inject probe light into the sensing arm fiber and the reference arm fiber in the H-shaped quartz resonant cavity attached to the surface of the dry transformer, and to capture the returned interference light in real time to obtain the envelope broadening parameter and fluorescence decay time constant of the interference spectrum.

[0006] An absolute temperature calculation module is used to extract the fluorescence decay time constant and calculate the absolute temperature of the current epoxy resin casting winding depth based on the fluorescence decay time constant.

[0007] The stiffness compensation conversion module is used to substitute the absolute temperature into the variable stiffness compensation model to calculate the elastic modulus attenuation coefficient.

[0008] The decoupling and state mapping module is used to divide the envelope broadening parameter of the interference spectrum by the elastic modulus attenuation coefficient for softening compensation, so as to restore the true local microscopic thermal stress distribution and the partial discharge energy equivalent.

[0009] The dynamic parameter adjustment module is used to dynamically adjust the gain multiplier and low-frequency bandwidth of the high-frequency envelope detector of the photoelectric sensing module according to the absolute temperature.

[0010] In one possible implementation, the photoelectric sensing module includes the H-shaped quartz resonant cavity, the sensing arm optical fiber, the reference arm optical fiber, a broadband light source, a single-mode optical fiber, and a photoelectric interferometer.

[0011] The central connecting beam of the H-shaped quartz resonant cavity is machined with a necking structure, and pre-compression stresses in opposite directions are applied to both ends of the necking structure.

[0012] The H-shaped quartz resonant cavity has a first micro-hole and a second micro-hole respectively opened along the axial direction inside the parallel longitudinal beams on both sides.

[0013] The sensing arm optical fiber is inserted into and bonded to the first micro-hole, and the reference arm optical fiber is inserted into and bonded to the second micro-hole.

[0014] In one possible implementation, both the sensing arm fiber and the reference arm fiber are made of erbium-doped microstructure polymer fiber.

[0015] The outer cladding walls of the sensing arm fiber and the reference arm fiber are formed with micro-nano grooves at equal intervals along the axial direction.

[0016] The micro-nano groove is filled with a composite dielectric layer, which is composed of a mixture of thermosensitive phase change liquid crystal and piezoelectric nanoparticles.

[0017] In one possible implementation, the input end of the sensing arm fiber is fused to the broadband light source via a single-mode fiber, and the output end of the sensing arm fiber is connected to the signal input port of the photoelectric interferometer.

[0018] The input end of the reference arm fiber is fused to the broadband light source, and the output end of the reference arm fiber is connected to the reference input port of the photoelectric interferometer.

[0019] In one possible implementation, the H-shaped quartz resonant cavity is fixedly attached to the surface of the epoxy resin cast winding of the dry-type transformer by an insulating bracket, so that heat and high-frequency electric field are conducted to the composite dielectric layer.

[0020] In one possible implementation, the absolute temperature calculation module is used for:

[0021] Extract the fluorescence decay time constant; divide the fluorescence decay time constant by the preset reference time constant, take the natural logarithm, multiply by the activation energy correlation coefficient, and perform inverse linear compensation in combination with the pre-calibrated zero-point compensation constant to obtain the absolute temperature.

[0022] In one possible implementation, the envelope broadening parameter of the interferometric spectrum is used to characterize the difference mode variable between the sensing arm fiber and the reference arm fiber.

[0023] The decoupling and state mapping module is used for:

[0024] The physical attenuation of the ultrasonic signal caused by high-temperature softening is offset by dividing the envelope broadening parameter of the interference spectrum by the elastic modulus attenuation coefficient, thereby mapping the current partial discharge energy equivalent.

[0025] In one possible implementation, the dynamic parameter adjustment module is configured to perform at least one of the following operations:

[0026] When the absolute temperature increases, causing the resin to soften and the acoustic attenuation of partial discharge to increase, the low-frequency bandwidth of the photoelectric sensing module is reduced, and the gain multiplier of the high-frequency envelope detector is increased to reduce the judgment threshold of high-frequency signals.

[0027] When the absolute temperature decreases, the balanced sampling gain is restored.

[0028] In one possible implementation, the composite dielectric layer is configured as follows:

[0029] When there is only a temperature rise during normal operation, the composite dielectric layer is isotropic, and the temperature signal transmitted by the optical field is in a rigid locked state.

[0030] When partial discharge occurs, the high-frequency transient electric field causes the piezoelectric nanoparticles to polarize and expand, changing the effective refractive index of the thermosensitive phase change liquid crystal and causing the composite dielectric layer to enter a flexible interference state.

[0031] The present invention has the following beneficial effects:

[0032] 1. This device obtains the fluorescence decay time constant and the envelope broadening parameter of the interference spectrum through the photoelectric sensing module. After the absolute temperature calculation module obtains the absolute temperature of the current winding depth, the stiffness compensation conversion module calculates the elastic modulus attenuation coefficient. Then, the decoupling and state mapping module divides the envelope broadening parameter of the interference spectrum by the elastic modulus attenuation coefficient for softening compensation. This design effectively offsets the physical attenuation of ultrasonic signals caused by high-temperature softening, separates temperature cross-sensitivity errors, and truly restores the local microscopic thermal stress distribution and partial discharge energy equivalent, solving the problem that a single structure cannot reflect the impact of insulation softening on the signal propagation path.

[0033] 2. This device fills a composite dielectric layer within the micro-nano grooves of an erbium-doped microstructured polymer optical fiber. During partial discharge, the high-frequency transient electric field causes the piezoelectric nanoparticles to polarize and expand, altering the effective refractive index of the thermosensitive phase-change liquid crystal and causing the composite dielectric layer to enter a flexible interference state. In conjunction with a dynamic parameter adjustment module, when the absolute temperature rises, causing the resin to soften and the acoustic attenuation of partial discharge to increase, the low-frequency bandwidth of the photoelectric interferometer is dynamically reduced and the gain multiplier of the high-frequency envelope detector is increased. This effectively lowers the judgment threshold of high-frequency signals and enables highly sensitive, adaptive, and accurate monitoring of partial discharge signals in transformers under complex temperature rise environments. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall structure of the device;

[0035] Figure 2 This is a schematic diagram of the epoxy resin casting winding structure of the device;

[0036] Figure 3 This is a schematic diagram of the erbium-doped microstructure polymer optical fiber structure of the device.

[0037] In the figure: 1. Dry-type transformer; 2. Epoxy resin cast winding; 3. Insulating support; 4. Thermally conductive insulating adhesive layer; 5. H-type quartz resonant cavity; 6. Longitudinal beam; 7. Central connecting beam; 8. Necked structure; 9. First micropore; 10. Second micropore; 11. Sensor arm fiber; 12. Reference arm fiber; 13. Erbium-doped microstructure polymer fiber; 14. Cladding outer wall; 15. Micro-nano groove; 16. Composite dielectric layer; 17. Thermosensitive phase-change liquid crystal; 18. Piezoelectric nanoparticles; 19. Single-mode fiber; 20. Broadband light source; 21. Photoelectric interferometer. Detailed Implementation

[0038] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0039] Example 1:

[0040] Combination Figures 1 to 3 As shown, a device for co-monitoring temperature rise and partial discharge of a dry-type transformer 1 includes:

[0041] The photoelectric sensing module is used to inject probe light into the sensing arm fiber 11 and the reference arm fiber 12 in the H-shaped quartz resonant cavity 5 attached to the surface of the dry transformer 1, and to capture the returned interference light in real time to obtain the envelope broadening parameter and fluorescence decay time constant of the interference spectrum.

[0042] The absolute temperature calculation module is used to extract the fluorescence decay time constant and calculate the absolute temperature of the current epoxy resin casting winding 2 based on the fluorescence decay time constant.

[0043] The stiffness compensation conversion module is used to substitute absolute temperature into the variable stiffness compensation model to calculate the elastic modulus attenuation coefficient.

[0044] The decoupling and state mapping module is used to divide the envelope broadening parameter of the interference spectrum by the elastic modulus attenuation coefficient for softening compensation, so as to restore the true local microscopic thermal stress distribution and the partial discharge energy equivalent.

[0045] The dynamic parameter adjustment module is used to dynamically adjust the gain multiplier and low-frequency bandwidth of the high-frequency envelope detector of the photoelectric sensing module according to the absolute temperature.

[0046] When the dry-type transformer 1 is running, the epoxy resin cast winding 2 is simultaneously subject to temperature rise, electric field disturbance and mechanical vibration. Traditional single temperature measurement structures are difficult to reflect the influence of insulation softening on the propagation path of partial discharge signals, and single partial discharge detection structures are difficult to separate the cross-sensitivity error caused by temperature changes. To solve this problem, this device adopts a cooperative monitoring device consisting of a photoelectric sensing module, an absolute temperature calculation module, a stiffness compensation conversion module, a decoupling and state mapping module and a dynamic parameter adjustment module.

[0047] The photoelectric sensing module injects probe light into the sensing arm fiber 11 and the reference arm fiber 12 located in the H-shaped quartz resonant cavity 5. The probe light can be a broadband light source 20 with a center wavelength of 1520nm to 1580nm and the output power can be set to 5mW to 20mW. The returned signal is photoelectrically converted by the photoelectric interferometer 21 and outputs the envelope broadening parameters of the interference spectrum and the fluorescence decay time constant.

[0048] In this invention, the fluorescence decay time constant refers to the time constant corresponding to the process in which the intensity of the fluorescence emitted by the erbium-doped microstructure polymer fiber 13 decays to one-third to one-tenth of its initial value after being excited. This quantity mainly reflects the local absolute temperature.

[0049] In this invention, the envelope broadening parameter of the interference spectrum refers to the change in the envelope width of the interference spectrum caused by the difference mode optical path change between the sensing arm fiber 11 and the reference arm fiber 12. This amount mainly reflects the superposition result of local microscopic thermal stress and deformation induced by partial discharge.

[0050] The absolute temperature calculation module receives the fluorescence decay time constant and calculates the deep absolute temperature of the winding. The stiffness compensation conversion module outputs the elastic modulus decay coefficient based on the pre-calibrated relationship between absolute temperature and epoxy resin elastic modulus. The decoupling and state mapping module performs softening compensation on the envelope broadening parameter and outputs the true local microscopic thermal stress distribution and partial discharge energy equivalent. The dynamic parameter adjustment module then adjusts the high-frequency envelope detector gain multiplier and low-frequency bandwidth based on the absolute temperature to match the detection sensitivity with the temperature rise state.

[0051] The monitoring process of this device can be repeatedly executed according to a sampling period of 10ms to 500ms, and a dynamic evaluation period of 100ms can be selected. After testing on the same 1000kVA dry-type transformer prototype, after adopting this device, the temperature drift of the partial discharge energy equivalent can be controlled to less than 40% of the pre-compensation level within the winding temperature range of 80℃ to 155℃, and the number of false alarms caused by common-mode power frequency vibration can be reduced by more than 50%.

[0052] To ensure clear data flow relationships between modules, the following sequence can be executed within each sampling period: the photoelectric sensing module synchronously acquires the raw photoelectric signals of the sensing arm channel and the reference arm channel, and forms a fluorescence decay time-domain sequence and an interference spectrum envelope sequence, respectively; the absolute temperature calculation module extracts the time constant from the fluorescence decay time-domain sequence and outputs the estimated absolute temperature T of the current sample.

[0053] The stiffness compensation conversion module uses absolute temperature T as the only temperature input, looks up or interpolates the factory-calibrated epoxy resin elastic modulus temperature correspondence table, and obtains the current elastic modulus attenuation coefficient η; the decoupling and state mapping module reads the envelope broadening parameter ΔW corresponding to the same sampling period, and uses η to complete softening compensation to generate the compensation envelope amount ΔWc, and then outputs the partial discharge energy equivalent and the corresponding real local microscopic thermal stress distribution data nodes according to the pre-established mapping level table;

[0054] The dynamic parameter adjustment module compares the absolute temperature T with the preset temperature range and outputs the low-frequency bandwidth range and high-frequency envelope detection gain range to be used in the next sampling period. In the above process, the fluorescence decay time constant is the temperature reference quantity, the elastic modulus decay coefficient is the compensation quantity for the influence of temperature on the mechanical propagation path, and the envelope broadening parameter is the local event response quantity. The three are logically passed sequentially and not used in parallel, thereby avoiding the direct misjudgment of temperature influence as partial discharge enhancement.

[0055] The variable stiffness compensation model is preferably implemented using a piecewise calibration table or a piecewise linear interpolation table, rather than being limited to using a single analytical formula. Specifically, the temperature range from 20℃ to 180℃ can be divided into several temperature intervals, for example, a calibration node can be set every 10℃ or every 20℃, and the reference elastic modulus ratio can be recorded at each node.

[0056] During operation, when the absolute temperature falls between two nodes, the elastic modulus ratio of the neighboring nodes is used for linear interpolation to obtain the elastic modulus attenuation coefficient η.

[0057] The physical meaning of this coefficient is the degree to which the current resin stiffness is maintained relative to the reference state. The smaller η is, the more obvious the material softening is, and the stronger the compressive effect on the propagation of mechanical waves induced by partial discharge and differential mode deformation is. Therefore, it is more necessary to compensate in subsequent mapping.

[0058] The variable stiffness compensation model is a sequentially executed logical conversion unit. Its purpose is to convert temperature information into information on the degree of softening of the propagation path, thereby correcting the response compression caused by the same partial discharge event under high temperature conditions.

[0059] Logically, this model does not directly deal with the intensity of discharge, but only with the physical causal chain that temperature affects material stiffness, material stiffness affects the propagation of mechanical disturbances, and the changes in propagation then affect the broadening of the envelope.

[0060] Its input terminal only receives the temperature value output by the absolute temperature calculation module. Internally, it sequentially completes four sub-processes: temperature zone identification, calibration node retrieval, inter-node interpolation or table lookup, and consistency limiting. The specific calculation logic for consistency limiting is as follows:

[0061] Pre-set the safety lower limit threshold of the elastic modulus attenuation coefficient With safety upper limit threshold When the temporary attenuation coefficient is obtained through inter-node interpolation or table lookup... satisfy At that time, force truncation and assignment. ;

[0062] When satisfied At that time, force truncation and assignment. If satisfied Then assign a value Its output terminal only outputs the elastic modulus attenuation coefficient η for the decoupling and state mapping module to call;

[0063] With this limitation, the model characterizes the effect of epoxy resin changing from high stiffness to low stiffness at different temperatures on the propagation ability of mechanical disturbances and thermal stress coupling response induced by partial discharge, rather than directly identifying partial discharge itself.

[0064] To ensure that the true local microscopic thermal stress distribution has a clear output form, when the device is equipped with a single sensing unit, the result can be expressed as a single-point thermal stress characterization value and its time variation trend; when the device is equipped with multiple sensing units arranged along the winding axis or circumference, the decoupling and state mapping module sorts the compensation envelope of each unit according to the spatial installation coordinates of the sensing unit to form a thermal stress distribution sequence, and marks the thermal stress concentration area, uniform area and abnormal change area accordingly.

[0065] An abnormal change zone can be defined as a region where the difference in the compensation envelope of two adjacent sensing units exceeds 1.5 to 3 times the average difference of the same group for two consecutive cycles. It is used to indicate the location of uneven local insulation heating or concentrated partial discharge activity.

[0066] Example 2:

[0067] Combination Figure 1 and Figure 2 As shown, the photoelectric sensing module includes an H-type quartz resonant cavity 5, a sensing arm fiber 11, a reference arm fiber 12, a broadband light source 20, a single-mode fiber 19, and a photoelectric interferometer 21.

[0068] Among them, the central connecting beam 7 of the H-type quartz resonant cavity 5 is processed with a necking structure 8, and the two ends of the necking structure 8 are subjected to pre-compression stresses in opposite directions.

[0069] Among them, the first micro-hole 9 and the second micro-hole 10 are respectively opened along the axial direction inside the parallel longitudinal beams 6 on both sides of the H-shaped quartz resonant cavity 5.

[0070] The sensing arm optical fiber 11 is inserted into and glued to the first micro-hole 9, and the reference arm optical fiber 12 is inserted into and glued to the second micro-hole 10.

[0071] The H-type quartz resonant cavity 5 in the photoelectric sensing module is formed by integral processing of high-purity quartz. Quartz material has high volume resistivity and low dielectric loss, and can maintain stable insulation under strong electric field conditions.

[0072] The total length of the H-type quartz resonant cavity 5 can be set to 20mm to 60mm, the total width can be set to 8mm to 20mm, the thickness of the longitudinal beam 6 can be set to 1mm to 3mm, and the thickness of the central connecting beam 7 can be set to 0.5mm to 2mm.

[0073] A necking structure 8 is formed in the middle of the central connecting beam 7. The width of the necking section can be 30% to 70% of the original width of the connecting beam, and the length of the necking section can be 1mm to 6mm. The purpose is to concentrate the differential mode deformation near the connecting beam and improve the response to strain induced by weak partial discharge.

[0074] The necking structure 8 is subjected to pre-compression stresses in opposite directions at both ends. This can be achieved by using a hot fitting fixture, a micro-displacement pressing mechanism, or a pre-curing tensioning clamp. The pre-compression strain on one side can be set to 5μm to 50μm, and the corresponding pre-stress can be set to 1MPa to 20MPa.

[0075] This reverse preloading method ensures that the two longitudinal beams 6 are under symmetrical stress conditions without external disturbance. When there is power frequency vibration or overall thermal expansion in the external environment, the deformation of the two longitudinal beams 6 tends to be consistent and manifests as common mode components. When a local discharge is near one side of the sensing arm, the differential mode response forms an asymmetric optical path change between the sensing arm and the reference arm.

[0076] The first micro-hole 9 and the second micro-hole 10 are respectively machined along the axial direction inside the parallel longitudinal beams 6 on both sides. The diameter of the micro-hole can be set from 125μm to 600μm. The parallelism error between the axis and the center line of the longitudinal beam 6 can be controlled within 0.05mm to ensure the consistency of axial strain transmission after the optical fiber is implanted.

[0077] The sensing arm fiber 11 is inserted into the first micro-hole 9, and the reference arm fiber 12 is inserted into the second micro-hole 10. Both fibers are fixed by epoxy resin bonding, the thickness of which can be set from 10μm to 80μm, and the curing temperature can be from 60℃ to 120℃. The technical means of this structure is to achieve physical suppression of common-mode mechanical interference through the H-type quartz resonant cavity 5, and at the same time, to provide a differential channel for interferometric measurement through the dual-arm arrangement, thereby reducing the dependence of subsequent algorithms on pure software filtering.

[0078] Example 3:

[0079] Combination Figure 3 As shown, both the sensing arm fiber 11 and the reference arm fiber 12 are made of erbium-doped microstructure polymer fiber 13.

[0080] Among them, the outer cladding wall 14 of the sensing arm fiber 11 and the reference arm fiber 12 is processed with micro-nano grooves 15 at equal intervals along the axial direction.

[0081] The micro-nano groove 15 is filled with a composite dielectric layer 16, which is composed of a mixture of a thermosensitive phase change liquid crystal 17 and piezoelectric nanoparticles 18.

[0082] Both the sensing arm fiber 11 and the reference arm fiber 12 are made of erbium-doped microstructure polymer fiber 13. The polymer matrix can be polymethyl methacrylate, cyclic olefin copolymer or its modified material. The erbium doping concentration can be from 100ppm to 3000ppm to balance fluorescence lifetime temperature measurement sensitivity and signal attenuation control.

[0083] The microstructured optical fiber can form an array of air holes or a low-refractive-index polymer array to improve mode confinement and enhance the influence of small external deformations on the optical path. Micro-nano grooves 15 are processed along the axial direction at equal intervals on the outer cladding wall 14 of the two optical fibers. The groove spacing can be set to 50μm to 500μm, the groove depth can be set to 100nm to 20μm, and the groove width can be set to 500nm to 50μm. The processing method can be femtosecond laser etching, reactive ion etching, or hot stamping.

[0084] The function of the micro-nano groove 15 is to form a local physical field coupling interface, so that there is a stable interface adhesion and a controllable refractive index perturbation path between the composite dielectric layer 16 and the optical fiber cladding. The composite dielectric layer 16 is composed of a mixture of thermosensitive phase change liquid crystal 17 and piezoelectric nanoparticles 18. The thermosensitive phase change liquid crystal 17 can be a nematic liquid crystal or a cholesteric liquid crystal, and the clearing point temperature can be set from 70℃ to 180℃.

[0085] The piezoelectric nanoparticles 18 can be barium titanate, lead zirconate titanate, or metaniobate particles, with a particle size of 20 nm to 500 nm and a mass fraction of 1% to 30%.

[0086] To prevent the phase change liquid crystal material from being lost under long-term thermal vibration conditions and to prevent contamination from external insulating impurities, the outer surface of the micro-nano groove 15 is coated with a light-transmitting refractive index matching encapsulation film. This encapsulation film is made of UV-cured fluorinated acrylate resin, and its thickness is controlled between 2μm and 10μm, which completely seals and cures the composite dielectric layer 16 inside the micro-nano groove 15.

[0087] Under normal temperature rise conditions, the molecular orientation of the composite dielectric layer 16 is mainly affected by temperature and maintains a relatively stable equivalent refractive index distribution. At this time, the erbium-doped fluorescence decay information can be used for temperature inversion. When local discharge occurs, the transient electric field acts on the piezoelectric nanoparticles 18, which undergo microscale deformation and change the arrangement of surrounding liquid crystal molecules, resulting in enhanced local effective refractive index perturbation and amplified interference spectrum response to local discharge.

[0088] The composite dielectric layer 16 is not simply a coating material, but is used to form a coupling interface between a temperature-sensitive channel and an electro-deformation-sensitive channel on the same optical fiber, so that absolute temperature and partial discharge information can be extracted synchronously from the same sensing link.

[0089] The input end of the sensing arm fiber 11 is fused to the broadband light source 20 through a single-mode fiber 19, and the output end of the sensing arm fiber 11 is connected to the signal input port of the photoelectric interferometer 21.

[0090] The input end of the reference arm fiber 12 is fused to the broadband light source 20, and the output end of the reference arm fiber 12 is connected to the reference input port of the photoelectric interferometer 21.

[0091] The broadband light source 20 can be a superluminescent diode, an erbium-doped broadband amplification source, or a laser light source that has been broadened, and its spectral width can be set to 20nm to 80nm. The input ends of the sensing arm fiber 11 and the reference arm fiber 12 are both connected to the broadband light source 20 through a single-mode fiber 19. The mode field diameter of the single-mode fiber 19 can be 8μm to 11μm. During fusion splicing, the mode mismatch between the polymer fiber and the quartz single-mode fiber 19 is reduced by using a transition fiber or a tapered transition section. The insertion loss of a single fusion splice can be controlled to be between 0.5dB and 2dB.

[0092] The output end of the sensing arm fiber 11 is connected to the signal input port of the photoelectric interferometer 21, and the output end of the reference arm fiber 12 is connected to the reference input port of the photoelectric interferometer 21. The photoelectric interferometer 21 can adopt a Michelson structure, a Mach-Zehnder structure or a white light low coherence interference structure, and its sampling frequency can be set from 1MS / s to 100MS / s.

[0093] The signal input port receives a composite optical signal that includes differential mode deformation induced by partial discharge and temperature-related refractive index changes. The reference input port receives a reference optical signal that mainly reflects common-mode environmental disturbances and reference temperature changes. The two signals are compared in phase inside the interferometer and then the interference spectrum envelope is output.

[0094] This connection method ensures that the sensing arm channel and the reference arm channel share the same broadband light source 20, reducing additional errors caused by light source drift.

[0095] Meanwhile, the dual-channel input to the photoelectric interferometer 21 enables the phase change to be differentially extracted, which facilitates the subsequent separation of the differential mode component induced by partial discharge from the envelope broadening parameters. Comparative tests on a set of prototypes show that the envelope drift standard deviation of the shared light source dual-arm interference structure can be reduced by more than 20% compared to the two independent light source structures.

[0096] The H-type quartz resonant cavity 5 is fixedly attached to the surface of the epoxy resin cast winding 2 of the dry-type transformer 1 by the insulating bracket 3, so that heat and high-frequency electric field are conducted to the composite dielectric layer 16.

[0097] The H-type quartz resonant cavity 5 is fixed to the surface of the epoxy resin cast winding 2 of the dry-type transformer 1 by an insulating bracket 3. The insulating bracket 3 can be made of alumina ceramic, polyimide composite board or epoxy glass fiber reinforced material, and the volume resistivity can be not less than 10 to the power of 12 Ω·cm. The thickness of the insulating bracket 3 can be set from 0.5mm to 5mm, which satisfies the mechanical fixing requirements and controls the heat transfer path length.

[0098] A thermally conductive insulating adhesive layer 4 can be provided on the bonding surface. The thickness of the adhesive layer can be set to 20μm to 300μm, and the thermal conductivity can be set to 0.5W / (m·K) to 3W / (m·K) to enhance the uniformity of heat conduction from the winding to the composite dielectric layer 16.

[0099] The insulating bracket 3 can be fixed by threaded press fitting, snap-fit ​​limiting or high-temperature resistant insulating adhesive bonding. The fixing position is preferably close to the axial middle of the winding or the edge of the heat dissipation channel, so as to take into account the representativeness of the thermal gradient and the sensitivity to partial discharge.

[0100] The contact distance between the H-type quartz resonator 5 and the winding surface is preferably controlled within the range of 0 mm to 0.3 mm, so that heat can be conducted to the composite dielectric layer 16 within one sampling cycle, and at the same time, the high-frequency electric field near the winding can be coupled to the piezoelectric nanoparticles 18.

[0101] The high-frequency electric field conduction here does not refer to conduction through a conductive path, but rather to the transient electric field of partial discharge acting on the composite dielectric layer 16 through spatial coupling and near-field action of the insulating medium, causing polarization deformation of the piezoelectric nanoparticles 18; the use of insulating bracket 3 for fixation can avoid the metal mounting parts from changing the original electric field distribution, thereby reducing the risk that the observation structure itself will become a new source of partial discharge.

[0102] In the test, the device was attached to the surface of a 10kV epoxy cast winding. After 72 hours of continuous operation, no electrical traces or local carbonization were observed on the support surface, indicating that the fixing method can meet the requirements for long-term insulation stability.

[0103] Example 4:

[0104] The absolute temperature calculation module is used for:

[0105] Extract the fluorescence decay time constant; divide the fluorescence decay time constant by the preset reference time constant, take the natural logarithm, multiply by the activation energy correlation coefficient, and combine with the pre-calibrated zero-point compensation constant to perform inverse linear compensation to obtain the absolute temperature;

[0106] The absolute temperature calculation module is deployed in an industrial control computer, field programmable gate array or digital signal processor, and is used to perform time-domain fitting of the fluorescence decay signal output by the photoelectric interferometer 21 and extract the fluorescence decay time constant. The extraction method can be single exponential fitting, multi-exponential principal term fitting or least squares decay envelope fitting, and the time constant τ is obtained under the condition that the number of sampling points is not less than 64.

[0107] In order to establish the temperature mapping relationship, the erbium-doped microstructure polymer fiber 13 was calibrated before leaving the factory. The sensing unit was placed in a constant temperature environment from 20℃ to 180℃, the τ value at different temperatures was recorded, and the activation energy correlation coefficient K was fitted.

[0108] In this invention, the activation energy correlation coefficient refers to the calibration scaling factor between the transition rate of the erbium-doped energy level and the temperature. Its value can be obtained by pre-experimental fitting, and the typical value range is 10 to 200.

[0109] The technical significance of this calculation method is that fluorescence lifetime is mainly affected by local temperature and is not sensitive to high-frequency electric field disturbances. Therefore, it can be used as an independent temperature reference in thermoelectric coupling environments.

[0110] After temperature chamber calibration, the temperature inversion error in the range of 30℃ to 160℃ can be controlled within ±2℃, which meets the input accuracy requirements for subsequent conversion of elastic modulus attenuation coefficient.

[0111] The specific execution steps of the absolute temperature calculation module are as follows:

[0112] Step 1: Read the fluorescence intensity decay sequence within a sampling period and remove the overshoot point at the start of excitation and the distortion point at the end that is lower than the noise floor. The specific quantization operation for this step is as follows: the overshoot point is removed by the initial sampling sequence within the first 1ms to 5ms after the forced discard of the light source turn-off command.

[0113] The removal of distortion points in the tail section is performed by pre-recording or real-time calculation of the background ambient noise amplitude under the corresponding no-light condition. Once it is found that the data value of three consecutive discrete sampling points of the signal amplitude in the current attenuation sequence is lower than 1.5 times the background ambient noise amplitude, it is determined to enter the tail section and its data points are automatically truncated and discarded, so as to retain only the pure exponential segment to ensure that the sequence participating in the downstream calculation has a high signal-to-noise ratio.

[0114] Step 2: Fit the retained decay sequence to obtain the single-cycle time constant τ;

[0115] Step 3: Extract the current time constant from this sampling period. Smoothing time constant of the output from the previous sampling period A consistency comparison is performed by calculating the determination formula: ;

[0116] in, This refers to the relative deviation rate; This is the current time constant extracted during this sampling period; The smoothing time constant of the output from the previous sampling period; when determining When the value exceeds a preset proportional threshold, the system determines that there is occasional jump noise and automatically switches to the moving average calculation logic to suppress the noise. Its discrete-time update equation is: ;

[0117] in, The time constant of the output after smoothing; The moving average smoothing coefficient; This is the current time constant extracted during this sampling period; The smoothing time constant of the output from the previous sampling period; when determining the relative deviation rate If the value exceeds the preset ratio threshold, then output directly. ;

[0118] Step four: Based on the fluorescence thermal quenching effect of erbium-doped fiber, the fluorescence decay time constant shortens with increasing temperature. This applies to the stabilized fiber... The ratio to the reference time constant is taken as the natural logarithm, and combined with the activation energy correlation coefficient. Perform reverse linear compensation and output absolute temperature results; the above preset ratio is preferably 5% to 15%, which is used to avoid misjudgment of instantaneous temperature jump caused by partial discharge pulse or transient interference pulse entering the fluorescence temperature channel;

[0119] The preferred method for determining the activation energy correlation coefficient K is calibration rather than real-time self-learning during runtime. Specifically, at least 5 temperature points, preferably 10 to 20, can be selected during the factory calibration stage. The steady-state τ value can be obtained at each temperature point, and then K can be fitted according to the monotonic relationship between temperature rise and the natural logarithm of τ. If there are individual differences in the same batch of optical fibers, an independent K value can be written for each sensing unit.

[0120] The advantage of this approach is that the temperature conversion can be completed on-site using only the already written K value and the real-time extracted τ value, without the need for complex fitting again, thereby improving on-site feasibility and result consistency.

[0121] In engineering implementation, obtaining absolute temperature can be understood as obtaining a temperature value or temperature characterization value that can be directly called by the subsequent stiffness compensation conversion module; when the system uses the Celsius temperature scale for display, a fixed zero-point conversion can be completed internally; when the system uses the absolute temperature scale for internal calculation, a unified temperature scale output is maintained.

[0122] Regardless of the display method used, the temperature data used by subsequent modules all originates from the same time constant extraction result and the same activation energy correlation coefficient calibration result. Therefore, it will not change the technical essence of obtaining the temperature based on the fluorescence decay time constant in this embodiment. The absolute temperature conversion in step four above is specifically achieved through the following formula: ;

[0123] in, For time constant A reference time constant with the same dimensions is used to ensure that the variables in logarithmic operations are dimensionless pure numbers; This is an estimated absolute temperature value from the current sample. The input is the fluorescence decay time constant; The activation energy correlation coefficient is stored in non-volatile memory; The zero-point compensation constant is the one pre-calibrated at the factory.

[0124] In the data flow of the microprocessor, the module reads the attenuation sequence from the analog-to-digital converter buffer, sends it to the digital signal processing kernel via the direct memory access channel to complete logarithmic and multiply-add operations, and finally writes the calculated absolute temperature T into the global shared memory pool according to the predetermined data frame format for the subsequent stiffness compensation conversion module and dynamic parameter adjustment module to read synchronously, thereby constructing the underlying data interaction path and ensuring the real-time processing.

[0125] Example 5:

[0126] The envelope broadening parameter of the interference spectrum is used to characterize the difference mode variable between the sensing arm fiber 11 and the reference arm fiber 12.

[0127] The decoupling and state mapping module is used for:

[0128] By dividing the envelope broadening parameter of the interference spectrum by the elastic modulus attenuation coefficient, the physical attenuation of the ultrasonic signal caused by high-temperature softening is offset, so as to map the current partial discharge energy equivalent.

[0129] The decoupling and state mapping module receives the envelope broadening parameter ΔW of the interference spectrum and the elastic modulus attenuation coefficient η output by the stiffness compensation conversion module. η can be defined as the ratio of the elastic modulus E of the epoxy resin at the current temperature to the elastic modulus E0 at the reference temperature, with a typical value range of 0.15 to 1.

[0130] The envelope broadening parameter ΔW comes from the differential mode optical path change between the sensing arm fiber 11 and the reference arm fiber 12. In this invention, it is not directly equivalent to the partial discharge intensity, but is a comprehensive characterization quantity after the combined effects of partial discharge-induced mechanical waves, dielectric thermal stress concentration and resin softening damping.

[0131] Considering that the elastic modulus of epoxy resin decreases at high temperatures, the propagation attenuation of high-frequency mechanical disturbances generated by partial discharge in the winding and casting resin is enhanced, which ultimately results in the compression of the measurable differential modulus between the sensing arm and the reference arm; if not compensated, partial discharge of the same energy level will exhibit a smaller ΔW at high temperatures.

[0132] Therefore, the decoupling and state mapping module obtains the compensated envelope broadening parameter ΔWc by normalizing ΔW according to η; when η is less than 1, the system regards the current envelope response as the result of high temperature softening and compression, and increases the corresponding event level in subsequent mappings; when η is close to 1, the system determines that the propagation path stiffness is close to the baseline state, and only performs weak compensation or no significant compensation.

[0133] In this invention, the partial discharge energy equivalent refers to the apparent charge or equivalent physical energy released by the insulation material when a partial discharge event of the same intensity occurs under the reference temperature and reference stiffness conditions, as mapped by the envelope broadening parameter of the differential mode interference signal after softening compensation and restoration by the variable stiffness compensation model.

[0134] Based on the mapping level table or interval correspondence table established by the factory calibration, the compensated parameters are converted into the partial discharge energy equivalent Qpd. The unit can be the equivalent value of picocoulomb, the equivalent value of millijoule, or a custom energy level. The actual local microscopic thermal stress distribution can be measured in parallel by multiple axially arranged sensing units. The ΔWc values ​​of each unit are arranged according to their spatial positions to form a distribution curve, which is used to characterize the local thermal stress concentration area.

[0135] In this invention, local microscopic thermal stress refers to the microscale acoustic impedance abrupt change gradient formed inside the insulating medium due to the combined effect of thermal gradient and transient electric field, rather than macroscopic overall stress. After using this module, when performing equal-amplitude pulse discharge simulation at around 120℃, the partial discharge energy equivalent before compensation can reach more than 30%, and the deviation after compensation can be reduced to less than 10%.

[0136] The technical purpose of the decoupling and state mapping module is not simply to amplify the signal, but to decompose the currently measured response into two factors: the strength of the event itself and the degree of softening of the propagation path. Logically, the module can be divided into two parts: the compensation sub-process and the mapping sub-process. The compensation sub-process receives ΔW and η and outputs the compensation envelope ΔWc. The mapping sub-process then sends ΔWc to the partial discharge level determination channel and the thermal stress spatial sorting channel, respectively.

[0137] The first channel is used to give the partial discharge energy equivalent or risk level, and the second channel is used to compare the relative degree of anomaly at different sensing locations. After this processing, it can be clearly shown that the module represents the physical causal relationship that high temperature softening changes the mechanical propagation path, the mechanical propagation path changes the interference envelope response, and the envelope response is used to reflect the partial discharge activity after compensation.

[0138] The extraction process of the envelope broadening parameter ΔW can be performed in the following order: first, extract the effective frequency band data of the current sampling period from the original interference spectrum output by the photoelectric interferometer 21; then, perform envelope detection on the effective frequency band data to obtain the single-period envelope curve;

[0139] The main broadening region near the peak is extracted from the envelope curve, and the increase in the main broadening region relative to the reference envelope width is measured. This increase is defined as ΔW. In the actual engineering calculation, the above process of extracting the main broadening region adopts the half-amplitude width boundary judgment rule.

[0140] The system addresses the global absolute highest peak point data of the single-cycle frequency domain envelope curve within the working window, and searches in both forward and reverse directions with this peak point as the origin. When the system scans to the two frequency points corresponding to the first decay of the discrete amplitude to 50% of the amplitude of the highest peak data point, it performs boundary truncation locking.

[0141] The absolute frequency difference between these two frequency points is the current main expansion width. Finally, subtracting the expansion width under the factory no-load standard reference condition from this main expansion width gives the precise increase ΔW.

[0142] The preferred reference envelope width here is the initial width recorded when the device is installed and there is no partial discharge and the temperature is at the reference operating condition, or the average width of the most recent several abnormal cycles; after such limitation, ΔW has a clear reference source and is no longer just an abstract description of spectral changes.

[0143] To ensure that the physical attenuation of ultrasonic signals caused by high-temperature softening has executable logic, the determination of η is preferably completed in the following manner: During the manufacturing stage, a temperature-elastic modulus correspondence table is established for similar epoxy resin winding materials; during operation, the temperature value output by the absolute temperature calculation module is read, and the ratio of the current elastic modulus to the reference elastic modulus is found in the correspondence table; this ratio is then input as η into the compensation circuit.

[0144] When the temperature increases and η decreases, the system determines that the propagation path softens and is enhanced, thus automatically amplifying the energy estimate corresponding to ΔW; when the temperature decreases and η approaches 1, the system determines that no significant compensation is needed, thus avoiding excessive amplification of the equivalent value of partial discharge under low temperature and high stiffness conditions.

[0145] The physical attenuation of ultrasonic signals mentioned here can be understood in engineering as the propagation attenuation of high-frequency mechanical disturbances induced by partial discharge in the cast insulator and its indirect compression of the differential mode optical path change. It does not require that the sound waves be directly received by an independent ultrasonic transducer.

[0146] The mapping of partial discharge energy equivalent is preferably achieved by a graded calibration method. Specifically, multiple sets of partial discharge pulses of known levels can be applied to the prototype first, and the corresponding ΔWc range under each level can be recorded. Then, these ranges can be written into the mapping level table, for example, ΔWc can be divided into three or more level intervals: low risk, medium risk, and high risk.

[0147] During operation, as long as the current ΔWc falls within the corresponding range, the corresponding partial discharge energy equivalent level or equivalent value will be output. The advantage of this method is that it does not require real-time solution of complex models on site, which facilitates on-site implementation.

[0148] When the system outputs both the actual local microscopic thermal stress distribution and the partial discharge energy equivalent, although they share the same compensation envelope ΔWc, their uses are different: the former focuses on reflecting the relative abnormal distribution along the spatial location and is used to locate the thermal stress concentration area; the latter focuses on reflecting the strength of the partial discharge activity of a single sensing location in the current cycle and is used for alarm and trend statistics.

[0149] By sending the same compensation amount separately to the spatial sorting subprocess and the energy level mapping subprocess, the logical division of labor between the output results becomes clearer. The specific processing steps of the softening compensation and mapping process of the decoupling and state mapping module are as follows: In each evaluation cycle, the module reads the current envelope broadening parameter ΔW and elastic modulus attenuation coefficient η from shared memory, and calculates the compensation envelope amount through the floating-point arithmetic unit. The specific calculation logic formula is as follows: ;

[0150] in, Indicates the compensation envelope; This represents the extracted interference spectrum envelope broadening parameter; This represents the elastic modulus attenuation coefficient input to this module; for example, in quantization: assuming that... The system obtains the result by looking up a table internally. for If the measured input from the preceding stage is at this time for The true envelope value restored after division compensation is: ;

[0151] The module will Substitute the pre-stored mapping level threshold judgment array into the boundary comparison; when When the value falls within the 15 to 30 judgment range, the system determines and outputs a partial discharge energy equivalent Qpd marked as moderate, and assembles the judgment result with the associated sensor unit coordinates into a standard diagnostic message structure and sends it to the monitoring terminal.

[0152] Example 6:

[0153] The dynamic parameter adjustment module is used to perform at least one of the following operations:

[0154] When the absolute temperature increases, causing the resin to soften and the acoustic attenuation of partial discharge to increase, the low-frequency bandwidth of the photoelectric sensing module is reduced, and the gain multiplier of the high-frequency envelope detector is increased to reduce the judgment threshold of high-frequency signals.

[0155] When the absolute temperature decreases, the balanced sampling gain is restored;

[0156] The dynamic parameter adjustment module adjusts the sampling parameters of the photoelectric interferometer 21 online based on the temperature value T output by the absolute temperature calculation module;

[0157] The module has a pre-stored temperature partition table and corresponding parameter group. For example, when T is below 80℃, the low frequency bandwidth can be set to 500Hz to 2kHz, and the high frequency envelope detector gain multiplier can be set to 1 to 2 times.

[0158] When T is between 80℃ and 120℃, the low-frequency bandwidth can be set to 200Hz to 800Hz, and the gain multiplier can be set to 2 to 5 times; when T is above 120℃, the low-frequency bandwidth can be further reduced to 50Hz to 300Hz, and the gain multiplier can be increased to 5 to 12 times.

[0159] The low-frequency bandwidth adjustment here is used to suppress low-frequency envelope disturbances caused by power frequency vibration, core-transmitted vibration, and slow thermal expansion and contraction. The high-frequency envelope detector gain multiplier adjustment is used to improve the detection probability of weak partial discharge response.

[0160] To avoid frequent switching near the temperature critical point, the dynamic parameter adjustment module can be set with a hysteresis range of 2℃ to 10℃, and the slope of parameter change is limited to no more than one increment per second; the judgment threshold can be set based on the noise floor N and the temperature correlation coefficient β: ;

[0161] in, Indicates the threshold for judging high-frequency signals; Indicates the temperature correlation coefficient; The root mean square value representing the noise floor; as the temperature rises, the high-frequency signal judgment threshold is reduced by increasing the gain multiplier and decreasing β.

[0162] Noise floor The acquisition has the following fixed boundary logic: Each time the equipment is powered on in a cold state and the transformer determines that there is no high-voltage input, the system consistently collects at least 1 second of high-frequency interferometric disturbance envelope signal sequence, calculates its root mean square (RMS) value, and solidifies it as a stationary characterization quantity, N; specifically, the microprocessor calculates this RMS value and solidifies it as N. The discrete digital signal processing model is as follows: ;

[0163] in, The root mean square value of the noise floor; This represents the total number of discrete sampling points for high-frequency interferometry within a continuous 1-second time window. The sampling point number; The first one extracted by the analog-to-digital converter The instantaneous amplitude of the disturbed envelope signal at each sampling point;

[0164] Similarly, β completely avoids the difficulty of manual experience-based parameter tuning by using a discrete state machine fixed value replacement strategy. When the current temperature T is not 80℃, β is assigned a value and locked in the empirical value range of 4 to 6.

[0165] If the temperature exceeds this limit and enters the range of 80℃ to 120℃, β drops to 3 to 4 to perform the judgment; once the absolute temperature exceeds the severe decay region threshold of 120℃, the microprocessor immediately calls a matching low value constant of 1.5 to 2.5 to replace the original β value in order to maintain the minimum judgment condition.

[0166] By determining a measurable β-state switching superimposed on the front-end amplifier hardware multiplier increase, the signal fading caused by the irreversible conduction mechanism is effectively and reproducibly compensated, significantly reducing the system's heavy reliance on complex and redundant parameter calibration; after the temperature decreases, the module restores the low-frequency bandwidth and gain multiplier to the predetermined equalization value to avoid over-amplification of the signal under low-noise conditions.

[0167] This adjustment method allows the sampling parameters to adapt to the degree of resin softening, reducing missed detections and false detections under a fixed threshold. The actual test results show that when the transformer load increases from 50% to 100%, the partial discharge pulse recognition rate can be improved by 15% to 35% compared with the fixed parameter mode after enabling dynamic parameter adjustment.

[0168] The core judgment process of the dynamic parameter adjustment module is implemented as a deterministic state machine with hysteresis characteristics at the software level; the system main control program maintains a built-in judgment table, which matches the three state enumeration values ​​corresponding to below 80℃, 80 to 120℃ and above 120℃ in real time according to the temperature T in memory.

[0169] When a state transition occurs and the hysteresis constraint is met, the firmware immediately reads the two specific hardware configuration words corresponding to that state and writes them to the gain setting register of the programmable amplifier and updates the tap coefficient array of the digital bandpass filter via the universal serial bus.

[0170] Taking the damping attenuation case of pulse weakening due to resin softening at high temperatures as an example, when the temperature T exceeds 120℃, the program pointer directly extracts the highest gain configuration setting, increases the amplifier gain to 8 times, and simultaneously adjusts the judgment threshold equation in the high-frequency signal pulse capture subroutine. ;

[0171] Among them, the coefficient β is rewritten to a lower set value to realize the adaptive adjustment process of the device;

[0172] Example 7:

[0173] The composite dielectric layer 16 is configured such that when there is only a temperature rise during normal operation, the composite dielectric layer 16 is isotropic, and the temperature signal transmitted by the optical field is in a rigid locked state.

[0174] When partial discharge occurs, the high-frequency transient electric field causes the piezoelectric nanoparticles 18 to polarize and expand, changing the effective refractive index of the thermosensitive phase change liquid crystal 17, and causing the composite dielectric layer 16 to enter a flexible interference state.

[0175] The functional configuration of the composite dielectric layer 16 is achieved through material ratio, phase change temperature setting and micro-nano interface structure. Under the condition of only temperature rise and no partial discharge, the thermosensitive phase change liquid crystal 17 is in a temperature-dominated molecular orientation state, and the piezoelectric nanoparticles 18 are not subjected to significant transient electric field excitation. Therefore, the composite dielectric layer 16 as a whole is approximately isotropic or can be regarded as an isotropic stable medium in engineering judgment. When the light field is transmitted along the optical fiber, it mainly carries fluorescence lifetime related information, and the temperature signal is in a rigid locked state.

[0176] The rigid locking state here refers to the composite dielectric layer 16 not producing a significant refractive index jump in response to short-term high-frequency disturbances, and the change in the interference spectrum is mainly due to slow temperature changes. To obtain this state, the phase transition range of the thermosensitive phase change liquid crystal 17 should cover the commonly used operating temperature range of the transformer, and the volume fraction of the piezoelectric nanoparticles 18 should be controlled within a range that does not cause a significant increase in scattering loss at room temperature, typically 2% to 15%.

[0177] When partial discharge occurs, a high-frequency transient electric field at the nanosecond to microsecond level is formed near the discharge source. This electric field acts on the piezoelectric nanoparticles 18 and causes them to polarize and expand. The expansion amplitude can reach the picometer to nanometer level. The local deformation of the piezoelectric nanoparticles 18 breaks the original arrangement balance of the liquid crystal molecules, causing the effective refractive index neff of the thermosensitive phase change liquid crystal 17 to undergo a transient change, causing the composite dielectric layer 16 to enter a flexible interference state.

[0178] The flexible interference state here refers to the reversible refractive index modulation capability of the composite dielectric layer 16 to high-frequency electric fields and microscale mechanical disturbances, making the differential mode interference signal more sensitive to partial discharge pulses; the switching of this state does not depend on metal probes or external electrodes, and therefore does not significantly change the high-frequency electric field distribution of the original winding.

[0179] Comparative experiments show that, with the composite dielectric layer 16, under the same partial discharge pulse injection conditions, the transient response amplitude of the interference spectrum can be increased by 1.2 to 3 times compared to the fiber without the composite dielectric layer 16, while the temperature measurement channel still maintains a stable output.

[0180] To clarify the causal relationship between isotropy and entering a flexible interference state, it can be understood as two working phenomena exhibited by the same composite dielectric layer 16 under two excitation conditions, rather than necessarily an irreversible material phase transition:

[0181] When the input is only a slow temperature rise, the liquid crystal molecules maintain a relatively uniform orientation under the constraint of the groove and the average field of the surrounding medium. The amplitude of the local refractive index perturbation is lower than the interference judgment threshold, so the system classifies it into an isotropic stable transport state.

[0182] When a transient electric field of partial discharge is input, the piezoelectric nanoparticles 18 first undergo polarization deformation, and then drive the adjacent liquid crystal molecules to rearrange briefly, thereby causing the local refractive index disturbance to exceed the judgment threshold. Based on this, the system identifies it as a flexible interference state.

[0183] In the former state, the refractive index change mainly drifts slowly with temperature, so it is suitable as a temperature measurement baseline; because the refractive index change in the latter state is pulsed and reversible, it is suitable as a partial discharge enhancement response channel.

[0184] To avoid misjudging the slow refractive index change caused by normal temperature rise as a flexible interference triggered by partial discharge, the system can combine time scale to determine the state: when the refractive index change of the composite dielectric layer 16 changes continuously and slowly over multiple sampling periods, it is determined to be a temperature-dominated state.

[0185] When the refractive index change shows a sudden enhancement within a single or a few sampling periods and appears synchronously with the high-frequency envelope of the interference spectrum, it is determined to be a partial discharge triggered state. By adding this determination logic, the causal relationship between the material behavior of the composite dielectric layer 16, the signal source, and its corresponding output becomes more direct.

[0186] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A device for co-monitoring temperature rise and partial discharge of a dry-type transformer, characterized in that, include: The photoelectric sensing module is used to inject probe light into the sensing arm fiber (11) and the reference arm fiber (12) in the H-type quartz resonant cavity (5) attached to the surface of the dry transformer (1), and to capture the returned interference light in real time to obtain the envelope broadening parameter and fluorescence decay time constant of the interference spectrum. The absolute temperature calculation module is used to extract the fluorescence decay time constant and calculate the absolute temperature of the current epoxy resin casting winding (2) based on the fluorescence decay time constant. The stiffness compensation conversion module is used to substitute the absolute temperature into the variable stiffness compensation model to calculate the elastic modulus attenuation coefficient. The decoupling and state mapping module is used to divide the envelope broadening parameter of the interference spectrum by the elastic modulus attenuation coefficient for softening compensation, so as to restore the true local microscopic thermal stress distribution and the partial discharge energy equivalent. The dynamic parameter adjustment module is used to dynamically adjust the gain multiplier and low-frequency bandwidth of the high-frequency envelope detector of the photoelectric sensing module according to the absolute temperature.

2. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 1, characterized in that, The photoelectric sensing module includes the H-type quartz resonant cavity (5), the sensing arm fiber (11), the reference arm fiber (12), the broadband light source (20), the single-mode fiber (19), and the photoelectric interferometer (21). The central connecting beam (7) of the H-shaped quartz resonant cavity (5) is processed with a necking structure (8), and the two ends of the necking structure (8) are subjected to pre-compression stresses in opposite directions. Among them, the first micro-hole (9) and the second micro-hole (10) are respectively opened along the axial direction inside the parallel longitudinal beams (6) on both sides of the H-shaped quartz resonant cavity (5). The sensing arm fiber (11) is inserted into and glued to the first micro-hole (9), and the reference arm fiber (12) is inserted into and glued to the second micro-hole (10).

3. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 2, characterized in that, Both the sensing arm fiber (11) and the reference arm fiber (12) are made of erbium-doped microstructure polymer fiber (13). The outer cladding wall (14) of the sensing arm fiber (11) and the reference arm fiber (12) is provided with micro-nano grooves (15) at equal intervals along the axial direction. The micro-nano groove (15) is filled with a composite dielectric layer (16), which is composed of a mixture of thermosensitive phase change liquid crystal (17) and piezoelectric nanoparticles (18).

4. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 2, characterized in that, The input end of the sensing arm fiber (11) is fused to the broadband light source (20) through the single-mode fiber (19), and the output end of the sensing arm fiber (11) is connected to the signal input port of the photoelectric interferometer (21). The input end of the reference arm fiber (12) is fused to the broadband light source (20), and the output end of the reference arm fiber (12) is connected to the reference input port of the photoelectric interferometer (21).

5. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 3, characterized in that, The H-type quartz resonant cavity (5) is fixedly attached to the surface of the epoxy resin cast winding (2) of the dry transformer (1) by an insulating bracket (3) so that heat and high-frequency electric field are conducted to the composite dielectric layer (16).

6. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 1, characterized in that, The absolute temperature calculation module is used for: Extract the fluorescence decay time constant; divide the fluorescence decay time constant by the preset reference time constant, take the natural logarithm, multiply by the activation energy correlation coefficient, and perform inverse linear compensation in combination with the pre-calibrated zero-point compensation constant to obtain the absolute temperature.

7. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 1, characterized in that, The envelope broadening parameter of the interference spectrum is used to characterize the difference mode variable between the sensing arm fiber (11) and the reference arm fiber (12); The decoupling and state mapping module is used for: The physical attenuation of the ultrasonic signal caused by high-temperature softening is offset by dividing the envelope broadening parameter of the interference spectrum by the elastic modulus attenuation coefficient, thereby mapping the current partial discharge energy equivalent.

8. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 1, characterized in that, The dynamic parameter adjustment module is configured to perform at least one of the following operations: When the absolute temperature increases, causing the resin to soften and the acoustic attenuation of partial discharge to increase, the low-frequency bandwidth of the photoelectric sensing module is reduced, and the gain multiplier of the high-frequency envelope detector is increased to reduce the judgment threshold of high-frequency signals. When the absolute temperature decreases, the balanced sampling gain is restored.

9. The dry-type transformer temperature rise and partial discharge co-monitoring device according to claim 3, characterized in that, The composite dielectric layer (16) is configured as follows: When there is only a temperature rise during normal operation, the composite dielectric layer (16) is isotropic, and the temperature signal transmitted by the optical field is in a rigid locked state. When partial discharge occurs, the high-frequency transient electric field causes the piezoelectric nanoparticles (18) to polarize and expand, changing the effective refractive index of the thermosensitive phase change liquid crystal (17) and causing the composite dielectric layer (16) to enter a flexible interference state.

Images