Ultra-thin flexible sensor and system for online monitoring of inter-turn short circuit of generator rotor

Abstract

This invention belongs to the field of online monitoring technology for electrical equipment, and discloses an ultra-thin flexible sensor and system for online monitoring of inter-turn short circuits in generator rotors. The ultra-thin flexible sensor includes two flexible substrates, a sensing layer, and a shielding layer. The sensing layer is a planar coil attached between the two flexible substrates. The shielding layer covers the surface of one of the flexible substrates away from the planar coil. This invention exhibits ultra-thin and flexible structural features, enabling it to closely conform to the complex curved surfaces of generator stator slot wedges or teeth, significantly improving installation fit and online monitoring reliability.

Description

Technical Field

[0001] This invention relates to the field of online monitoring technology for electrical equipment, and specifically to an ultra-thin flexible sensor and system for online monitoring of inter-turn short circuits in generator rotors. Background Technology

[0002] In recent years, with the rapid growth of installed capacity of new energy power generation, thermal power generating units have increasingly undertaken the tasks of peak shaving and frequency regulation, resulting in frequent changes in their operating conditions. Frequent load adjustments not only affect the turbine system but also place significant stress on the generator itself. During load changes, the generator rotor temperature fluctuates. Due to the difference in thermal expansion coefficients between the core and windings, relative movement can easily occur, potentially damaging the inter-turn insulation and causing rotor inter-turn short-circuit faults. While minor inter-turn short circuits have limited impact on unit operation, if not detected in time, the fault will gradually worsen, leading to abnormally increased excitation current, intensified unit vibration, and in severe cases, even causing major accidents such as rotor grounding and burnout, resulting in unplanned shutdowns and posing a serious threat to grid safety and the economic benefits of power plants.

[0003] Currently, one of the most effective methods for online monitoring of rotor inter-turn short circuits is the detection coil waveform method. By installing a magnetic flux sensor on the stator teeth or slot wedges, the change in leakage magnetic flux in the air gap is detected when the rotor rotates, and the magnetic signal is converted into a voltage waveform. The presence of an inter-turn short circuit fault is determined by analyzing the waveform characteristics.

[0004] However, most existing magnetic flux sensors are probes encapsulated with rigid materials such as epoxy resin, which have the following drawbacks: First, they are large and heavy, and when installed inside a high-speed rotating generator, they are prone to shaking or even falling off, posing a potential risk to the safe operation of the generator; second, the rigid structure is difficult to adapt to the complex curved surfaces of the stator slot wedges or teeth, resulting in poor installation fit.

[0005] Therefore, the existing technology has problems such as large size, heavy weight, and poor fit of magnetic flux sensors to the complex curved surfaces of stator slot wedges or teeth, which urgently need to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide an ultra-thin flexible sensor and system for online monitoring of inter-turn short circuits in generator rotors, in order to overcome the problems existing in the prior art. This invention features an ultra-thin and flexible structure, which can closely fit the complex curved surfaces of generator stator slot wedges or teeth, significantly improving the installation fit and the reliability of online monitoring.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, comprising a sensor body, the sensor body comprising two flexible substrates, a sensing layer and a shielding layer; The sensing layer is a planar coil attached between the two flexible substrates to sense air gap leakage flux and generate an induced voltage signal. The shielding layer covers the surface of one of the flexible substrates away from the planar coil to suppress rotor-side electric field interference.

[0008] According to one embodiment of the present invention, the flexible substrate is made of one of polyimide, polyethylene terephthalate, polyethylene naphthalate, polytetrafluoroethylene, and polycarbonate. The thickness of the flexible substrate is 0.1 mm to 0.5 mm.

[0009] According to one embodiment of the present invention, the material of the planar coil is copper or silver; The number of turns in a planar coil ranges from 5 to 50. The line width of the planar coil is 0.05mm to 0.5mm; The thickness of the planar coil is 0.05mm to 0.2mm.

[0010] According to one embodiment of the present invention, the planar coil has a rectangular spiral structure or a circular spiral structure.

[0011] According to one embodiment of the present invention, the material of the shielding layer is copper or silver; The thickness of the shielding layer is 0.01mm to 0.1mm.

[0012] According to one embodiment of the present invention, a protective layer is further included, which covers the outer surface of the sensor body.

[0013] According to one embodiment of the present invention, the material of the protective layer is polyimide, polyethylene terephthalate, polyethylene naphthalate, polytetrafluoroethylene, or polycarbonate. The present invention also provides one such material.

[0014] According to one embodiment of the present invention, it further includes a lead-out end, which is integrally formed or welded to the planar coil, and the lead-out end is connected to a micro connector.

[0015] The present invention also provides a system for online monitoring of inter-turn short circuits in generator rotors, comprising: Several of the above-described embodiments of ultra-thin flexible sensors for online monitoring of inter-turn short circuits in generator rotors, wherein several of the ultra-thin flexible sensors are arranged along the generator axial and circumferential directions on the stator slot wedges or tooth surfaces; A signal conditioning module, connected to the planar coil of the ultrathin flexible sensor, is used to condition the induced voltage signal; The data acquisition unit is connected to the signal conditioning module and is used to perform analog-to-digital conversion on the conditioned signal. The diagnostic analysis platform, connected to the data acquisition unit, is used to process and analyze the acquired waveform data to determine the rotor inter-turn short circuit fault.

[0016] According to one embodiment of the present invention, the signal conditioning module has a built-in amplifier circuit and a filter circuit.

[0017] The above technical solution has the following advantages or beneficial effects: Firstly, this invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors. By setting the sensing layer as a planar coil attached between two flexible substrates, and cooperating with a shielding layer covering the outside of the flexible substrates, the sensor exhibits an ultra-thin and flexible structure. This allows it to closely conform to the complex curved surfaces of the generator stator slot wedges or teeth, significantly improving installation fit and online monitoring reliability. Compared to existing bulky and heavy flux sensors, this sensor is lightweight, easy to arrange, and hardly alters the original air gap magnetic field distribution. Simultaneously, the shielding layer effectively suppresses rotor-side electric field interference, ensuring the accuracy and stability of the induced voltage signal. This achieves highly sensitive online monitoring of inter-turn short circuit faults in the rotor, providing reliable technical support for the safe operation of the generator.

[0018] In some embodiments, by selecting high-performance flexible materials such as polyimide as the substrate and controlling its thickness within the range of 0.1 mm to 0.5 mm, while ensuring that the sensor has good flexibility and mechanical strength, the overall thickness and weight are further reduced, making it more adaptable to the complex curved surfaces of the stator slot wedges and teeth. This makes installation convenient and less prone to falling off, effectively solving the problems of large size and poor fit of existing flux sensors, and providing a more stable and reliable installation foundation for online monitoring of rotor turn short circuits.

[0019] In some embodiments, by optimizing and limiting the number of turns, line width, thickness, and material of the planar coil, using copper or silver material and setting the number of turns to 5 to 50, the line width to 0.05 mm to 0.5 mm, and the thickness to 0.05 mm to 0.2 mm, the coil can maintain ultra-thin flexibility while having sufficient induction area and conductivity, which can efficiently capture changes in air gap leakage flux and output an induced voltage signal with appropriate amplitude and stability, effectively improving the monitoring sensitivity and signal reliability of rotor inter-turn short circuit faults.

[0020] In some embodiments, the planar coil can be configured as a rectangular spiral structure or a circular spiral structure, which can be flexibly selected according to the specific installation position of the generator stator slot wedge and teeth. The rectangular spiral structure is easy to arrange on the surface of the narrow slot wedge, while the circular spiral structure is more suitable for installation in compact areas such as teeth. While ensuring the ultra-thin and flexible characteristics, it effectively improves the sensing efficiency of air gap leakage flux and enhances the installation adaptability of the sensor and the stability of the monitoring signal.

[0021] In some embodiments, by using copper or silver as the shielding layer material and controlling its thickness within the range of 0.01 mm to 0.1 mm, the shielding layer still possesses excellent electric field shielding performance even at an extremely thin thickness. This effectively suppresses the interference of the high-voltage electric field on the rotor side on the sensing signal, while not increasing the overall thickness and rigidity of the sensor, maintaining the installation fit of the ultra-thin flexible structure, thereby significantly improving the anti-interference capability and signal accuracy of the rotor inter-turn short circuit online monitoring.

[0022] In some embodiments, by providing a protective layer covering the outer surface of the sensor body, adverse factors such as oil, moisture, dust and mechanical wear in the field environment can be effectively isolated, significantly improving the sensor's weather resistance, insulation performance and service life, ensuring stable and reliable sensing performance under long-term generator operation conditions. At the same time, the protective layer does not change the sensor's ultra-thin and flexible characteristics, ensuring the installation fit and long-term stability of the monitoring signal.

[0023] In some embodiments, by selecting high-performance materials such as polyimide and polyethylene terephthalate as protective layers, the sensor is endowed with excellent insulation performance, high temperature resistance and corrosion resistance, while forming a good match with the flexible substrate material. This ensures that the ultra-thin and flexible characteristics of the overall structure are not affected, effectively extending the service life of the sensor under the harsh operating conditions of the generator, and providing a long-term, stable and reliable guarantee for online monitoring of rotor turn-to-turn short circuits.

[0024] In some embodiments, by setting an output end integrally formed or welded with the planar coil and equipped with a miniature connector, high reliability and low impedance output of the sensing signal are achieved. The integral structure avoids the risk of breakage caused by additional solder joints, and the welding method facilitates flexible processing. The miniature connector is small in size, does not damage the ultra-thin and flexible characteristics of the sensor, is easy to install and has a stable connection, ensuring the continuity of signal transmission and long-term operational reliability of the online monitoring system.

[0025] Secondly, this invention provides a system for online monitoring of inter-turn short circuits in generator rotors. By arranging multiple ultra-thin flexible sensors along the generator's axial and circumferential directions on the stator slot wedges or tooth surfaces, and combining them with a signal conditioning module, a data acquisition unit, and a diagnostic analysis platform, a distributed online monitoring system is constructed. This system can comprehensively perceive the spatial distribution changes of air gap leakage flux, enabling accurate location and severity assessment of rotor inter-turn short circuit faults. The system has a compact structure, is easy to install, and significantly improves the comprehensiveness, accuracy, and real-time performance of fault diagnosis.

[0026] In some embodiments, by incorporating amplification and filtering circuits in the signal conditioning module, the weak induced voltage signal output by the ultra-thin flexible sensor can be effectively amplified, and high-frequency noise and power frequency interference can be filtered out, significantly improving the signal-to-noise ratio and stability of the signal. This provides high-quality, low-distortion waveform data for subsequent data acquisition and diagnostic analysis, thereby enhancing the measurement accuracy and fault identification reliability of the rotor inter-turn short circuit online monitoring system. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the layered structure of the ultrathin flexible sensor shown in an embodiment of the present invention; Figure 2 This is a schematic diagram of the rectangular spiral structure shown in an embodiment of the present invention; Figure 3 This is a schematic diagram of the circular spiral structure shown in an embodiment of the present invention; Figure 4 This is a schematic diagram of the shielding layer structure shown in an embodiment of the present invention; Figure 5 This is a schematic diagram of the physical structure of the planar coil as shown in an embodiment of the present invention; Figure 6 This is a schematic diagram of the actual structure of the shielding layer shown in an embodiment of the present invention; Figure 7 This is a schematic diagram of the system structure shown in an embodiment of the present invention; Figure 8 This is a graph showing measured data from a power plant, as illustrated in an embodiment of the present invention. In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1. Flexible substrate; 2. Planar coil; 3. Shielding layer; 4. Protective layer; 5. Lead-out terminal; 10. Ultra-thin flexible sensor; 11. Signal conditioning module; 12. Data acquisition unit; 13. Diagnostic analysis platform. Detailed Implementation

[0028] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0029] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Currently, one of the most effective methods for online monitoring of rotor inter-turn short circuits is the detection coil waveform method. By installing a magnetic flux sensor on the stator teeth or slot wedges, the change in leakage magnetic flux in the air gap is detected when the rotor rotates, and the magnetic signal is converted into a voltage waveform. The presence of an inter-turn short circuit fault is determined by analyzing the waveform characteristics.

[0035] However, most existing magnetic flux sensors are probes encapsulated with rigid materials such as epoxy resin, which have the following drawbacks: First, they are large and heavy, and when installed inside a high-speed rotating generator, they are prone to shaking or even falling off, posing a potential risk to the safe operation of the generator; second, the rigid structure is difficult to adapt to the complex curved surfaces of the stator slot wedges or teeth, resulting in poor installation fit.

[0036] Therefore, existing technologies suffer from problems such as large size, heavy weight, inability to adapt to complex curved surfaces of stator slot wedges or teeth, and poor installation fit. There is an urgent need for a sensor that is small in size, thin in thickness, flexible and fits well, safe and reliable, and easy to install, so as to achieve efficient online monitoring of rotor turn short circuits.

[0037] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors. This sensor is characterized by being ultra-thin, flexible, lightweight, and highly sensitive. It can be tightly attached to the surface of the stator slot wedge or tooth of the generator and can be installed without removing the rotor. It can also significantly improve the accuracy and safety of monitoring. The sensor includes two flexible substrates 1, a sensing layer, and a shielding layer 3. The sensing layer is a planar coil 2, which is attached between the two flexible substrates 1 to sense the air gap leakage flux and generate an induced voltage signal. The shielding layer 3 covers the surface of one of the flexible substrates 1 away from the planar coil 2 to suppress rotor-side electric field interference.

[0038] By attaching the planar coil 2 between two flexible substrates 1 to form a sensing layer, the distribution of the air gap magnetic field changes when an inter-turn short circuit occurs in the generator rotor, and the leakage flux is effectively induced by the planar coil to generate a corresponding induced voltage signal. At the same time, the shielding layer 3 covering the outside is made of conductive material to form an electric field shield, which effectively suppresses the interference of the high voltage electric field on the rotor side on the weak sensing signal and ensures the authenticity of the signal.

[0039] The ultra-thin structure of the planar coil 2 sandwiched between two flexible substrates 1 gives the sensor excellent flexibility and minimal thickness, allowing it to fit tightly to the complex curved surfaces of the stator slot wedges or teeth. This solves the problem of poor fit in traditional sensor installations and does not affect the original magnetic field distribution in the air gap. The shielding layer 3 effectively filters out electric field interference, improving the accuracy of signal acquisition and anti-interference capabilities. The overall structure is lightweight and flexible, enabling distributed installation. It provides a highly sensitive and reliable online monitoring method for short-circuit faults between generator rotor turns, effectively ensuring the safe and stable operation of the generator set.

[0040] Example 1: This invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, comprising a sensor body, which includes two flexible substrates 1, a sensing layer, and a shielding layer 3; The sensing layer is a planar coil 2, which is attached between the two flexible substrates 1 to sense the air gap leakage flux and generate an induced voltage signal. The shielding layer 3 covers the surface of one of the flexible substrates 1 away from the planar coil 2 to suppress rotor-side electric field interference and improve the signal-to-noise ratio.

[0041] Specifically, the flexible substrate 1 is made of polyimide (PI), which is a flexible polymer film that is resistant to high temperature and corona discharge. The flexible substrate 1 has a thickness of 0.2 mm and has excellent electrical insulation properties, heat resistance properties and mechanical flexibility.

[0042] For details, see Figure 2 and Figure 5 The planar coil 2 is formed between the two flexible substrates 1 by printed circuit technology. The two ends of the planar coil 2 are lead-out solder joints. The material of the planar coil 2 is copper (conductive material). It adopts a rectangular spiral structure with 13 turns, a line width of 0.2 mm, a line spacing of 0.08 mm, and a thickness of 0.08 mm to ensure that the total thickness of the sensor does not exceed 1 mm.

[0043] Specifically, the shielding layer 3 is mainly used to shield the electric field. It is made of copper foil (highly conductive material) and deposited on the surface of the flexible substrate 1 away from the planar coil 2 by sputtering. The thickness is 0.02 mm. The area of ​​the shielding layer 3 is basically the same as the projected area of ​​the planar coil 2, so as to shield the interference electric field from the rotor side.

[0044] For details, see Figure 4 and Figure 6It also includes a protective layer 4, which covers the outer surface of the sensor body for encapsulation. The material of the protective layer 4 is a polyimide (PI) film with a thickness of 0.025 mm. The sensor body is encapsulated by lamination, with the solder joints exposed to allow connection of the lead wires, preventing mechanical damage and environmental impact.

[0045] Specifically, it also includes a lead-out end, which is a flexible flat cable. The lead-out end is integrally formed or welded with the planar coil 2. The lead-out end is connected to (equipped with) a miniature connector for easy connection to the signal conditioning module.

[0046] Specifically, one end of the lead is soldered to the lead solder joint and reinforced with insulating glue, while the other end of the lead is connected to a micro connector.

[0047] The ultra-thin flexible sensor in this embodiment has an overall thickness of approximately 0.5 mm, and its width and length can be customized according to the installation location, for example, a width of 40 mm and a length of 60 mm, and its overall weight is less than 20 g.

[0048] This invention also provides a system for online monitoring of inter-turn short circuits in generator rotors, see [link to relevant documentation]. Figure 7 It includes: the ultra-thin flexible sensor 10, signal conditioning module 11, data acquisition unit 12 and diagnostic analysis platform 13 used for online monitoring of inter-turn short circuits in generator rotors; Several ultra-thin flexible sensors 10 are arranged along the generator axial and circumferential directions on the stator slot wedges or tooth surfaces; the signal conditioning module 11 is connected to the lead-out end of the ultra-thin flexible sensor 10 and is used to condition the induced voltage signal; the data acquisition unit 12 is connected to the signal conditioning module 11 and is used to perform analog-to-digital conversion on the conditioned signal; the diagnostic analysis platform 13 is connected to the data acquisition unit 12 and is used to process and analyze the acquired waveform data to determine the rotor inter-turn short circuit fault.

[0049] Specifically, during installation, the ultra-thin flexible sensor 10 is adhered to the inner surface (near the air gap side) of the generator stator slot wedge using a high-temperature resistant adhesive. Due to its flexibility, it can fit completely and tightly. The wires and grounding wires of the ultra-thin flexible sensor 10 lead-out end run along the inner wall of the stator and are led out through the stator ventilation holes to the junction box outside the housing.

[0050] Specifically, the signal conditioning module 11 has built-in amplification and filtering circuits. After amplifying, filtering and impedance matching the induced voltage signal, the signal conditioning module 11 transmits it to the data acquisition unit 12 for analog-to-digital conversion.

[0051] Specifically, the signal conditioning module 11 consists of a multi-channel differential amplifier, a bandpass filter, and a gain controller. It conditions the weak voltage signal (typically in the millivolt range) output by the ultra-thin flexible sensor 10 to a suitable acquisition range (0-5 V) and filters out power frequency and high-frequency noise. The data acquisition unit 12 uses a multi-channel synchronous sampling ADC with a sampling rate of 100kHz to convert the analog signal into a digital waveform.

[0052] Specifically, the diagnostic analysis platform 13 is an industrial control computer with built-in dedicated analysis software. The process of processing and analyzing the collected waveform data to determine the rotor inter-turn short circuit fault includes: processing the waveform data: first, performing preprocessing such as normalization on the original waveform; then, extracting features such as peak and valley values ​​from the preprocessed waveform and comparing it with historical normal waveforms or a standard waveform library; performing trend analysis based on the comparison results; if the waveform distortion or feature value exceeds the set threshold, it is determined to be an inter-turn short circuit fault, and the fault severity estimate and location information are given to achieve early warning of the fault.

[0053] Specifically, the diagnostic analysis platform 13 employs a machine learning algorithm based on convolutional neural networks to perform pattern recognition on waveform data. In its implementation, the platform first performs normalization and denoising preprocessing on the original waveform to eliminate individual sensor differences and environmental interference. Then, it extracts temporal features such as peak values, valley values, root mean square values, and waveform factors using a sliding window method, while simultaneously extracting frequency domain features such as energy proportions in specific frequency bands using fast Fourier transform. The constructed feature vectors are input into a pre-trained convolutional neural network classification model. This model employs a three-layer convolutional layer and a two-layer fully connected layer structure, and is trained using labeled normal and fault waveform datasets. The model outputs the fault probability and classification results. When the fault probability exceeds 0.8, it is determined to be an inter-turn short-circuit fault. Simultaneously, it uses multi-sensor spatial location information to achieve quantitative assessment of the fault severity and accurate location of the fault area, enabling early warning of the fault.

[0054] Taking Example 1 as an example, the fabrication method of the ultrathin flexible sensor for online monitoring of inter-turn short circuits in generator rotors according to the present invention is as follows: Two flexible substrates 1 (polyimide films) are used as the base. After cleaning, photoresist is coated on the mating surfaces of the two substrates 1, and a coil pattern is formed by photolithography. A copper seed layer is then sputtered, followed by electroplating to thicken it to the required thickness. After removing the photoresist, a planar coil 2 is formed. A shielding layer 3 is formed on the surface of one of the flexible substrates 1 away from the planar coil 2 by screen printing silver paste. After drying and curing, the sensor body is obtained. Finally, a polyimide protective film is laminated onto the surface of the sensor body, and the pads are exposed through openings. The leads are soldered to the pads and fixed with adhesive. This method can achieve mass production with good consistency.

[0055] See Figure 8 The graph shows actual measured data from the power plant. In this study, an ultra-thin flexible sensor 10 was used to collect the generator rotor air gap leakage flux waveform. Comparing the normal and fault curves, it can be seen that the fault waveform exhibits a significant amplitude dip in the 90°~120° range, with overall symmetry disrupted and waveform distortion obvious. The peak value is significantly lower than the normal waveform, consistent with the typical magnetic field distortion characteristics of a rotor inter-turn short circuit. The ultra-thin flexible sensor 10 of this invention has high fit, strong anti-interference capability, high signal-to-noise ratio in the measured signal, and clear fault characteristics, enabling accurate location of the fault range. Based on the comprehensive assessment, the generator rotor has a moderate inter-turn short circuit, and the fault severity has reached the warning threshold. It is recommended to strengthen online monitoring and, when appropriate, shut down the unit for inspection to prevent further escalation of the fault, which could lead to increased unit vibration, rotor burnout, and other safety risks.

[0056] Example 2: This invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, which differs from Embodiment 1 in that: The flexible substrate 1 is made of polyethylene terephthalate (PET) and has a thickness of 0.1 mm. It has excellent electrical insulation properties, heat resistance properties and mechanical flexibility.

[0057] See Figure 3 The planar coil 2 is formed between the two flexible substrates 1 by an etching process. The material of the planar coil 2 is silver (conductive material), and it adopts a circular spiral structure with 50 turns, a line width of 0.05 mm, a line spacing of 0.05 mm, and a thickness of 0.05 mm.

[0058] The shielding layer 3 is made of silver paste (a highly conductive material) and is deposited on the surface of the flexible substrate 1 away from the planar coil 2 by coating, with a thickness of 0.01 mm.

[0059] The protective layer 4 is coated on the outer surface of the sensor body, and the material of the protective layer 4 is polyethylene terephthalate (PET).

[0060] Example 3: This invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, which differs from Embodiment 1 in that: The planar coil 2 adopts a circular spiral structure with 20 turns, a line width of 0.1 mm, and a line spacing of 0.1 mm to improve spatial resolution.

[0061] The thickness of the shielding layer 3 is 0.05 mm. The lead-out end uses a (micro) coaxial cable for better transmission of high-frequency signals.

[0062] Example 4: This invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, which differs from Embodiment 1 in that: The flexible substrate 1 is made of polyethylene naphthalate (PEN) and has a thickness of 0.5 mm. It has excellent electrical insulation properties, heat resistance properties and mechanical flexibility.

[0063] The planar coil 2 is formed between the two flexible substrates 1 by a deposition process, with 5 turns, a line width of 0.5 mm, and a thickness of 0.2 mm.

[0064] The shielding layer 3 is deposited on the surface of the flexible substrate 1 away from the planar coil 2 by printing, and has a thickness of 0.1 mm.

[0065] The material of the protective layer 4 is polyethylene naphthalate (PEN).

[0066] Example 5: This invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, which differs from Embodiment 1 in that: The flexible substrate 1 is made of polytetrafluoroethylene film (PTFE film), and the protective layer 4 is made of polytetrafluoroethylene film (PTFE film).

[0067] Example 6: This invention provides an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, which differs from Embodiment 1 in that: The flexible substrate 1 is made of polycarbonate film (PC film), and the protective layer 4 is made of polycarbonate film (PC film).

[0068] The ultra-thin flexible sensor described in this application uses a polymer material as a substrate with a total thickness of less than 1 mm. It can be tightly fitted to the complex curved surfaces of stator slot wedges or teeth without affecting the generator's air gap and ventilation. Furthermore, it poses no risk of detachment after installation, ensuring high safety. Its overall weight is extremely light, controlled to within 20 g, and has no impact on the rotor's dynamic characteristics, making it suitable for high-speed rotating motors. Its planar coil 2 structure is optimized, resulting in high magnetic field induction efficiency. Combined with the shielding layer 3, it effectively suppresses spatial electric field interference and improves the signal-to-noise ratio. Since the planar coil 2 has virtually no thickness, it avoids the magnetic field induction attenuation problem caused by the thickness of traditional coils, making it particularly suitable for high-precision detection of tangential magnetic fields. In addition, the ultra-thin flexible sensor described in this invention is easy to install and maintain. It can be directly mounted to a predetermined position through stator ventilation holes or at the end without removing the rotor, significantly reducing construction difficulty and cost.

[0069] The structure and working principle of the present invention will be further explained below: This specification describes an ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, illustrated in some embodiments. Its core working principle is based on the law of electromagnetic induction. When the generator is operating normally, the magnetic field generated by the rotor windings forms a stable distributed magnetic field in the air gap. When an inter-turn short circuit fault occurs in the rotor, a circulating current is generated within the short-circuit ring. The demagnetizing effect of this circulating current causes a change in the local air gap leakage flux. The planar coil 2 in the ultra-thin flexible sensor 10 acts as the sensing element. When its magnetic flux changes, according to Faraday's law of electromagnetic induction, an induced voltage signal proportional to the rate of change of magnetic flux is generated at both ends of the planar coil 2. Because the planar coil 2 is attached between two flexible substrates 1, it can closely adhere to the stator slot wedge or tooth surface, thereby effectively capturing the air gap leakage flux distortion signal caused by the rotor inter-turn short circuit.

[0070] The shielding layer 3 of the ultra-thin flexible sensor 10 covers the surface of the flexible substrate near the rotor side and is made of conductive materials such as copper or silver. Utilizing the principle of electromagnetic shielding, it can effectively suppress the interference of the high-voltage electric field on the rotor side on the coil induced signal. When the high-voltage electric field on the rotor side acts on the shielding layer 3, an induced current is generated within the shielding layer 3. The counter-magnetic field formed by this current cancels the influence of the external electric field on the internal planar coil 2, ensuring that the signal collected by the planar coil 2 mainly reflects the change in air gap leakage flux, thereby improving the purity and reliability of the signal. The thickness of the shielding layer 3 is controlled within the range of 0.01 mm to 0.1 mm, ensuring shielding effectiveness without affecting the ultra-thin and flexible characteristics of the sensor.

[0071] The sensor is covered with a protective layer 4, made of high-performance insulating materials such as polyimide, which provides electrical insulation, moisture protection, dust protection, and wear resistance, ensuring long-term stable operation of the sensor under harsh generator conditions. The number of turns, line width, and thickness of the planar coil 2 have been optimized to balance sensing sensitivity and flexible structure requirements, enabling sufficient induced electromotive force to be obtained within a limited space. The lead-out terminals are integrally formed with or welded to the planar coil 2 and connected to a miniature connector to achieve low-loss, high-reliability transmission of weak signals. The induced voltage signal is then led out to the subsequent signal conditioning circuit for amplification, filtering, and data analysis, ultimately achieving accurate identification and location of rotor inter-turn short-circuit faults.

[0072] This specification describes a system for online monitoring of inter-turn short circuits in generator rotors, based on distributed leakage flux detection and multi-dimensional signal analysis. In use, several ultra-thin flexible sensors 10 are arranged along the generator's axial and circumferential directions on the inner surface of the stator slot wedges near the air gap. Utilizing the sensors' ultra-thin and flexible characteristics, they are tightly bonded to the complex curved surface using high-temperature resistant adhesive, forming a distributed sensing array. When an inter-turn short circuit fault occurs in the rotor, the circulating current generated within the short-circuit ring causes distortion of the local air gap leakage flux. The ultra-thin flexible sensors 10 at each location, based on the principle of electromagnetic induction, convert the induced leakage flux change into a millivolt-level induced voltage signal. This signal is then led out through the stator ventilation holes to the external junction box via leads and grounding wires, achieving low-loss transmission of the weak signal.

[0073] The signal conditioning module 11 receives the induced voltage signals output by each ultra-thin flexible sensor 10, amplifies the weak signals through a built-in multi-channel differential amplifier, filters out power frequency and high-frequency noise interference through a bandpass filter, and performs impedance matching by a gain controller to condition the signals to a suitable voltage range for acquisition. The conditioned analog signals are then sent to the data acquisition unit 12, where a multi-channel synchronous sampling analog-to-digital converter performs analog-to-digital conversion at a set sampling rate, converting the analog waveform into high-precision digital waveform data to ensure the synchronization and integrity of the signals from each channel.

[0074] The diagnostic analysis platform 13, as the core processing unit of the system, has built-in dedicated analysis software. First, it performs preprocessing such as normalization on the collected waveform data to eliminate the influence of individual sensor differences and environmental factors. Then, it extracts key characteristic parameters such as waveform peaks and valleys and compares them with historical normal waveforms or standard waveform libraries. Based on the comparison results, it performs fault characteristic trend analysis. When the degree of waveform distortion or characteristic value change exceeds the set threshold, the system automatically determines the rotor inter-turn short circuit fault and realizes quantitative estimation of the fault degree and accurate location of the fault based on the deployment information of the ultra-thin flexible sensor 10, thereby achieving early warning and accurate diagnosis of rotor inter-turn short circuit faults.

[0075] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the above embodiments should be considered exemplary rather than restrictive in all respects; the scope of protection of the present invention is defined by the appended claims, not by the foregoing description, and thus all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0076] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity; those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention fall within the scope of protection of the claims of this invention.

Claims

1. An ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors, characterized in that, Includes a sensor body, which includes two flexible substrates (1), a sensing layer and a shielding layer (3). The sensing layer is a planar coil (2), which is attached between the two flexible substrates (1) to sense the air gap leakage flux and generate an induced voltage signal. The shielding layer (3) covers the surface of one of the flexible substrates (1) away from the planar coil (2) to suppress rotor-side electric field interference.

2. The ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors according to claim 1, characterized in that, The flexible substrate (1) is made of one of the following materials: polyimide, polyethylene terephthalate, polyethylene naphthalate, polytetrafluoroethylene, and polycarbonate. The thickness of the flexible substrate (1) is 0.1 mm to 0.5 mm.

3. The ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors according to claim 1, characterized in that, The material of the planar coil (2) is copper or silver; The number of turns in the planar coil (2) is 5 to 50; The line width of the planar coil (2) is 0.05 mm to 0.5 mm; The thickness of the planar coil (2) is 0.05 mm to 0.2 mm.

4. The ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors according to claim 1, characterized in that, The planar coil (2) has a rectangular spiral structure or a circular spiral structure.

5. The ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors according to claim 1, characterized in that, The material of the shielding layer (3) is copper or silver; The thickness of the shielding layer (3) is 0.01 mm to 0.1 mm.

6. The ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors according to claim 1, characterized in that, It also includes a protective layer (4), which covers the outer surface of the sensor body.

7. The ultra-thin flexible sensor for online monitoring of inter-turn short circuits in a generator rotor according to claim 6, characterized in that, The protective layer (4) is made of one of the following materials: polyimide, polyethylene terephthalate, polyethylene naphthalate, polytetrafluoroethylene, and polycarbonate.

8. The ultra-thin flexible sensor for online monitoring of inter-turn short circuits in generator rotors according to claim 1, characterized in that, It also includes a lead-out end, which is integrally formed or welded to the planar coil (2), and the lead-out end is connected to a micro connector.

9. A system for online monitoring of inter-turn short circuits in a generator rotor, characterized in that, include: Several ultra-thin flexible sensors for online monitoring of inter-turn short circuits in generator rotors as described in any one of claims 1-8, wherein several of the ultra-thin flexible sensors (10) are arranged along the generator axial and circumferential directions on the stator slot wedges or tooth surfaces; The signal conditioning module (11) is connected to the planar coil (2) of the ultrathin flexible sensor (10) and is used to condition the induced voltage signal; The data acquisition unit (12) is connected to the signal conditioning module (11) and is used to perform analog-to-digital conversion on the conditioned signal; The diagnostic analysis platform (13) is connected to the data acquisition unit (12) and is used to process and analyze the acquired waveform data to determine the rotor inter-turn short circuit fault.

10. A system for online monitoring of inter-turn short circuits in a generator rotor according to claim 8, characterized in that, The signal conditioning module (11) has built-in amplifier and filter circuits.

Images