A high-temperature-resistant turbine adjusting door auxiliary spring fracture real-time monitoring and DCS alarm system

Abstract

The present application relates to the technical field of steam turbine state monitoring, and discloses a kind of high-temperature-resistant steam turbine governing valve auxiliary spring fracture real-time monitoring and DCS alarm system, comprising: induction unit, processing unit, transmission unit and DCS unit.Eddy current sensor shell of induction unit is equipped with heat dissipation fin and built-in temperature compensation module, reduce the measurement error under high temperature environment, and realize the mechanical positioning of initial gap by mounting bracket.Processing unit outputs deterioration early warning by calculating the difference between real-time physical gap and theoretical working displacement, carries out double fracture determination in combination with displacement mutation threshold and step displacement, eliminates false alarm caused by normal quick closing of governing valve.The system uses normally closed dry contact output to cooperate with DCS digital input module, realizes safety alarm under fracture or broken wire state, and forces the electro-hydraulic servo valve opening degree command to zero through DCS protection linkage program, to prevent equipment from running with disease.

Description

Technical Field

[0001] This invention relates to the field of turbine condition monitoring technology, specifically to a real-time monitoring and DCS alarm system for the fracture of the auxiliary spring of a high-temperature turbine control valve. Background Technology

[0002] The auxiliary spring of the turbine inlet control valve is a component that maintains the normal opening and closing action of the valve and the safe operation of the unit. In actual operation, the area around the control valve is in a high-temperature environment. Conventional displacement sensors experience temperature drift at high temperatures, causing changes in sensitivity and resulting in errors in the collected displacement data. For determining spring breakage, existing monitoring systems mostly use a single threshold comparison method, which cannot distinguish the displacement change caused by spring breakage from the normal mechanical action of the control valve under emergency closing conditions, easily leading to false alarms. Furthermore, most monitoring devices use normally open contacts to output alarm signals. When the field cable is broken or the connection is loose, the control system cannot receive the fault signal, resulting in missed alarms. Current monitoring methods typically only provide audible and visual alarm prompts and lack protection linkage with the distributed control system (DCS). After confirming spring breakage, the control system cannot lock the opening control command issued for that control valve, leading to the risk of continued operation of the equipment under fault conditions. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a real-time monitoring and DCS alarm system for the fracture of the auxiliary spring of a high-temperature steam turbine control valve. This system solves the problems of existing steam turbine inlet control valve auxiliary spring monitoring methods, which suffer from large measurement errors in high-temperature environments, are easily affected by normal rapid closing actions of equipment, and are prone to missed alarms and lack linkage protection functions when line breakage occurs.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a real-time monitoring and DCS alarm system for the fracture of auxiliary springs in a high-temperature steam turbine control valve, comprising a sensing unit, a processing unit, a transmission unit, and a DCS unit. The sensing unit is installed at each auxiliary spring of the steam turbine inlet control valve to collect the physical displacement changes of the corresponding auxiliary spring and convert these changes into electrical signals. The processing unit conditions and performs logical judgments on the received electrical signals, and outputs a switch alarm signal when the fracture judgment condition is met. The transmission unit connects the sensing unit and the processing unit, and also connects the processing unit and the DCS unit, for transmitting the electrical signals and the switch alarm signals. The DCS unit receives the switch alarm signals and executes corresponding alarm actions and data recording.

[0006] In this invention, the sensing unit includes a target plate and an eddy current sensor. The target plate is made of heat-resistant stainless steel and is rigidly fixed to the flat side of the connecting pin shaft of the turbine inlet regulating valve. The geometric sensing area of ​​the target plate is larger than the cross-sectional area of ​​the eddy current sensor probe. The probe housing of the eddy current sensor is equipped with heat dissipation fins, and the internal hardware circuitry includes a temperature compensation module. The temperature compensation module senses the real-time ambient temperature through a built-in thermistor and injects a reverse compensation current into the internal conditioning circuit based on the measured temperature change to maintain a constant calibration sensitivity coefficient K value for the eddy current sensor. The sensing unit also includes a mounting bracket with a fine-tuning mechanism. The mounting bracket consists of a base connecting plate, an angle adjustment joint, a linear feed sleeve, and a locking nut. The base connecting plate is fixed on a stable base near the steam turbine inlet regulating valve body. The inner wall of the linear feed sleeve is provided with fine thread, and the probe housing of the eddy current sensor is machined with matching external thread. The angle adjustment joint is configured to keep the probe end face of the eddy current sensor parallel to the surface of the target plate; The eddy current sensor is configured to generate a linear feed displacement along the central axis of the linear feed sleeve through the engagement of the external thread and the fine thread, which is used to set the initial physical gap between the end face of the eddy current sensor probe and the target plate. The locking nut is configured to tighten against the end face of the linear feed sleeve, forming a mechanical interference locking.

[0007] The processing unit is located at a preset safe distance outside the high-temperature core area of ​​the turbine control valve, and the preset safe distance is greater than or equal to 1.5m; The processing unit includes a processing box, inside which a conditioning board and a microprocessor are installed; The conditioning board integrates an isolation amplifier circuit and a low-pass filter circuit. The low-pass filter circuit is used to filter the electrical signal. The cutoff frequency of the low-pass filter circuit is set to be greater than the highest frequency of the displacement change signal and less than the lowest frequency of environmental interference noise. The microprocessor integrates an analog-to-digital converter, which is used to convert filtered electrical signals into digital voltage signals. The microprocessor is configured to allocate a contiguous block of memory in the internally configured storage medium as a sliding window and to manage the sampled data using a first-in-first-out data queue structure; The microprocessor is configured to push the latest digital voltage signal to the tail of the data queue and remove the oldest digital voltage signal from the head of the data queue, and to perform an arithmetic average of all digital voltage signals within the sliding window to generate a filtered digital voltage signal.

[0008] The microprocessor is configured to subtract the initial bias voltage of the system circuit stored in the microprocessor's storage medium from the filtered digital voltage signal, and then divide the difference obtained by the calibration sensitivity coefficient K of the eddy current sensor to calculate the value of the real-time physical gap between the probe end face of the eddy current sensor and the target plate. The microprocessor is configured to execute decision logic based on dual criteria and early warning, including a low-level warning of spring performance degradation; The microprocessor is configured to receive the current opening feedback signal of the turbine inlet regulating valve from the DCS unit via a communication interface, and convert the current opening feedback signal into the corresponding theoretical working displacement; The microprocessor is configured to subtract the theoretical working displacement from the real-time physical gap between the eddy current sensor probe end face and the target plate, and then perform a subtraction operation with the initial physical gap between the eddy current sensor probe end face and the target plate pre-cured in the storage medium to obtain the absolute difference value. When the duration of a state where the absolute difference is greater than or equal to a low-level degradation threshold pre-stored in the storage medium reaches or exceeds a confirmation time threshold pre-stored in the storage medium, the microprocessor generates a low-level warning signal.

[0009] The dual criteria include a first criterion, which is a sudden change criterion based on the rate of displacement change; The microprocessor is configured to extract the real-time physical gap between the eddy current sensor probe end face and the target sheet calculated at the current sampling time, and retrieve the real-time physical gap between the eddy current sensor probe end face and the target sheet at historical moments with multiple sampling cycles in the cache queue. The difference between these two real-time physical gaps with multiple cycles in between is calculated, and the difference is divided by the corresponding time interval length to calculate the real-time displacement change rate of the target sheet. When the absolute value of the calculated real-time displacement change rate is greater than or equal to the displacement mutation threshold stored in the storage medium in advance, the first criterion is determined to be true. The value of the displacement mutation threshold is set to be greater than the maximum mechanical action speed of the hydraulic servo system of the turbine inlet regulating valve under emergency closing conditions.

[0010] The dual criteria include a second criterion, which is a steady-state criterion based on step displacement; After the first criterion is met, the microprocessor is configured to start an evaluation time window that is pre-stored in the storage medium. During the timing of the evaluation time window, the microprocessor continuously stores the collected real-time physical gaps into the cache, but does not perform the break logic determination. The microprocessor is configured to extract sampled data of a continuous real-time physical gap after the evaluation time window ends, calculate the arithmetic mean of the continuous sampled data, and use the arithmetic mean as the steady-state physical gap after the fracture. Calculate the absolute difference between the steady-state physical gap after fracture and the historical physical gap before the first criterion is triggered, and obtain the step displacement before and after the fracture event; The second criterion is established when the step displacement is greater than or equal to the fracture step threshold stored in the storage medium.

[0011] The transmission unit includes a shielded cable and a control cable; the shielded cable connects the sensing unit and the processing unit and is used to transmit electrical signals. The outer side of the shielded cable is fitted with a protective sleeve, which is made of flexible metal corrugated pipe or silicone sleeve wrapped with glass fiber; The inner insulation layer of the shielded cable is made of polytetrafluoroethylene, and the outer metal braided shielding layer is provided. The metal braided shielding layer is connected to the internal grounding terminal at the end where the processing unit is located to adopt a single-end grounding wiring method. The control cable connects the processing unit and the DCS unit to transmit switch alarm signals.

[0012] The processing unit is equipped with a relay module. The switch alarm signal is output as a passive dry contact signal by the mechanical contact closed by the relay module. The DCS unit includes a digital input module, which is equipped with a DC query power supply. The DC query power supply outputs a DC voltage and applies the DC voltage to the physical circuit formed by the control cable and the mechanical contacts of the relay module. The dry contact output is configured as a normally closed contact, so that the mechanical contacts of the relay module are in a closed state during the normal operation of the auxiliary spring of the turbine inlet regulating valve, and the mechanical contacts are opened when the processing unit determines that the spring has broken and drives the relay module to operate, thus breaking the physical circuit. The optocoupler circuit inside the digital input module is configured to convert the detected loop current disappearance state to a logic low level and trigger an alarm when the loop current disappears. Alternatively, if the control cable is accidentally disconnected during operation, the digital input module will also read a logic low level and trigger an alarm.

[0013] The DCS unit is equipped with equipment protection linkage program, DCS main controller and operator station. The DCS main controller is configured with Boolean software variables to characterize the state of the spring. The DCS main controller is configured to flip the value of a Boolean software variable from 1 to 0 when a logic low level indicating spring breakage is detected, and to trigger an audible and visual alarm command and a pop-up command on the operator station. The equipment protection linkage program is configured to output commands, lock the servo drive circuit for the opening direction control command issued by the corresponding steam turbine inlet regulating valve, force the opening command output value of the corresponding electro-hydraulic servo valve of the corresponding steam turbine inlet regulating valve to be set to zero and block the positive integral accumulation calculation of the internal PID controller.

[0014] This invention provides a real-time monitoring and DCS alarm system for the fracture of the auxiliary spring of a high-temperature steam turbine control valve. It has the following beneficial effects: 1. The eddy current sensor probe housing of the present invention is provided with heat dissipation fins, and the internal circuit is configured with a temperature compensation module including a thermistor. The calibration sensitivity coefficient is kept constant by injecting a reverse compensation current according to the temperature change. With the help of the mounting bracket with fine thread and angle adjustment joint, the measurement error caused by temperature drift can be reduced in the high temperature operating environment of steam turbine, and the mechanical positioning and locking of the initial physical gap between the probe and the target plate can be completed.

[0015] 2. The processing unit of this invention employs a judgment logic based on dual criteria and early warning; the microprocessor calculates the absolute difference between the real-time physical gap and the theoretical working displacement to trigger a low-level deterioration warning. During the fracture judgment process, the system combines a first criterion based on the displacement change rate and a second criterion based on the step displacement for judgment; wherein, the displacement mutation threshold is set to be greater than the maximum mechanical action speed of the hydraulic servo system under emergency shutdown conditions, eliminating false alarms caused by the normal fast closing action of the turbine control valve, and ensuring the accuracy of fracture judgment.

[0016] 3. The alarm circuit of this invention adopts a structure of normally closed dry contact output combined with DCS digital input module; in the event of spring breakage driving relay action or accidental breakage of control cable, the physical circuit can be disconnected and a logic low-level alarm can be triggered, preventing missed alarms caused by line breakage faults. Through the equipment protection linkage program, the corresponding electro-hydraulic servo valve opening command is forcibly set to zero and the integral accumulation calculation is blocked, cutting off the opening control command output by the servo drive circuit in the state of spring failure. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the system architecture of the present invention; Figure 2 This is a schematic diagram of the method flow of the present invention; Figure 3 This is a diagram showing the dynamic response and dual-criteria triggering curve of the secondary spring fracture in this invention. Figure 4 This is a comparative test chart showing the core performance indicators of different monitoring systems of the present invention.

[0018] The components are as follows: 10. Sensing unit; 11. Target plate; 12. Eddy current sensor; 20. Processing unit; 21. Processing box; 22. Conditioning board; 30. Transmission unit; 31. Shielded cable; 32. Control cable; 40. DCS unit; 41. Digital input module; 42. Operator station. Detailed Implementation

[0019] The technical solutions in 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.

[0020] Please see the appendix Figure 1 This invention provides a real-time monitoring and DCS alarm system for the fracture of the auxiliary spring of a high-temperature steam turbine control valve, comprising: a sensing unit 10, a processing unit 20, a transmission unit 30, and a DCS unit 40.

[0021] The sensing unit 10 is installed at each auxiliary spring of the turbine inlet regulating valve. The sensing unit 10 is used to collect the physical displacement change of the corresponding auxiliary spring and convert the physical displacement change into an electrical signal output.

[0022] The transmission unit 30 connects the sensing unit 10 and the processing unit 20. The transmission unit 30 is used to transmit the electrical signal output by the sensing unit 10 to the processing unit 20.

[0023] The processing unit 20 is located at a preset safe distance outside the high-temperature core area of ​​the turbine control valve. The preset safe distance is greater than or equal to 1.5m. The processing unit 20 is used to condition and logically determine the received electrical signals, and outputs a switch alarm signal when the breakage determination condition is met.

[0024] The transmission unit 30 is also connected to the processing unit 20 and the DCS unit 40. The DCS unit 40 is located in the central control room of the power plant. The DCS unit 40 is used to receive the switch alarm signals output by the processing unit 20 and to execute corresponding alarm actions and record data.

[0025] Please see the appendix Figure 2 This invention provides a method for real-time monitoring and DCS alarm of fracture of auxiliary spring of high-temperature steam turbine control valve, including the following steps: S10, the eddy current sensor 12 in the sensing unit 10 continuously monitors the tension state of the corresponding auxiliary spring. When the turbine regulating valve causes the length of the auxiliary spring to change, the physical gap between the eddy current sensor 12 and the target plate 11 fixed at the end of the auxiliary spring changes. The eddy current sensor 12 converts the change in physical gap into a voltage signal. S20, the voltage signal is transmitted to the processing box 21 in the processing unit 20 via the shielded cable 31 in the transmission unit 30. The conditioning board 22 in the processing box 21 performs filtering and smoothing operations on the input voltage signal to eliminate high-frequency interference signals introduced by on-site mechanical vibration. S30, the microprocessor built into the conditioning board 22 calculates in real time the displacement change rate and steady-state displacement value represented by the voltage signal after smoothing. When the microprocessor detects that the displacement mutation value exceeds the preset mutation threshold within a set time, and determines that the displacement after the mutation is stable within the error band indicating spring relaxation, it determines that the secondary spring has broken. S40, when the microprocessor determines that the secondary spring has broken, the processing unit 20 drives the internal relay module to operate and outputs a closed dry contact signal. The dry contact signal is transmitted to the digital input module 41 of the DCS unit 40 via the control cable 32 in the transmission unit 30. S50, in response to the closed dry contact signal received by the digital input module 41, the DCS unit 40 triggers an audible and visual alarm command and a screen pop-up command at the operator station 42. The DCS unit 40 writes the fracture event with a timestamp into the event sequence recording system and archives and stores the monitoring data before and after the fault.

[0026] The sensing unit 10 includes a target plate 11 and an eddy current sensor 12. The target plate 11 works in conjunction with the eddy current sensor 12, serving as the target detection surface for electromagnetic field sensing. During turbine operation, the auxiliary spring is subjected to alternating tensile stress for a long time. The target plate 11, as a moving part that moves with the auxiliary spring, generates relative displacement with the stationary eddy current sensor 12. The sensing unit 10 obtains the fatigue elongation state or fracture state of the auxiliary spring by monitoring the relative displacement change of the target plate 11.

[0027] When setting the physical structure parameters of the target plate 11, it is made of heat-resistant stainless steel, and the thickness of the target plate 11 is set to 3mm. The geometric sensing area of ​​the target plate 11 is larger than the cross-sectional area of ​​the eddy current sensor 12 probe to prevent edge effects from interfering with the electromagnetic field distribution. The side of the target plate 11 facing the eddy current sensor 12 is treated with a flat surface. The heat-resistant stainless steel material can avoid surface oxidation and peeling in the working environment of the steam turbine control valve at temperatures above 150℃, maintaining the material uniformity of the detection area of ​​the eddy current sensor 12. The 3mm thick metal body can meet the eddy current penetration depth requirements during high-frequency electromagnetic field detection, preventing magnetic lines of force from penetrating the back of the target plate 11 and causing reflection interference and detection signal distortion.

[0028] Regarding the mounting reference position of the target plate 11 on the turbine control valve assembly, the target plate 11 is arranged on the side of the connecting pin shaft at the lower end of the left auxiliary spring and the right auxiliary spring. When the turbine unit operates under variable load and drives the control valve to move, the auxiliary spring undergoes axial stretching and compression under the drive of the main shaft. The connecting pin shaft, as the end force-bearing fixed part of the auxiliary spring, directly reflects the actual deformation length of the auxiliary spring in terms of its spatial displacement. The target plate 11 is arranged on the side of the connecting pin shaft, so that the target plate 11 has the same following property as the deformation of the auxiliary spring.

[0029] After the installation location is selected, a rigid mechanical coupling operation is performed between the target plate 11 and the surface of the connecting pin. The target plate 11 is rigidly fixed to the flat side of the connecting pin by metal welding or bolt fastening. When using metal welding, argon arc welding is used to fully weld around the periphery of the target plate 11 during the unit's cold state after shutdown. When using bolt fastening, high-temperature alloy bolts equipped with anti-loosening washers are used to lock the target plate 11 into the pre-made threaded hole of the pin. The rigid mechanical coupling eliminates the relative movement gap between the target plate 11 and the connecting pin, preventing the target plate 11 from loosening or shifting under high-frequency vibration conditions of the turbine valve body.

[0030] The design of the turbine inlet regulating valve body structure and the conventional mechanical assembly dimensions of the auxiliary spring can be confirmed by consulting the power plant turbine equipment drawings. The specific mechanical layout and basic assembly principle are well-known technologies in this field and will not be elaborated here.

[0031] The sensing unit 10 also includes an eddy current sensor 12. The eddy current sensor 12 is arranged corresponding to the target plate 11. The operating temperature range of the eddy current sensor 12 is -30℃ to 400℃, and its housing protection rating is IP67. This operating temperature range and protection rating allow the eddy current sensor 12 to adapt to the ambient temperature near the turbine control valve and to working environments with dust and oil contamination.

[0032] The probe housing of the eddy current sensor 12 is provided with heat dissipation fins. The heat dissipation fins are evenly distributed along the outer circumferential surface of the probe housing. The heat dissipation fins increase the contact area between the probe housing and the surrounding ambient air, guiding the heat generated by the coil inside the probe and the radiant heat transferred by the regulating body to dissipate outward, maintaining the temperature balance of the measuring elements inside the eddy current sensor 12.

[0033] The eddy current sensor 12 is fixed to a stable base on the turbine inlet regulating valve via a mounting bracket with a fine-tuning mechanism. The mounting bracket includes a fixed base, a movable adjusting sleeve, and a locking assembly. The fixed base is fixed to the surface of the stable base. The movable adjusting sleeve is connected to the fixed base via a fine-pitch thread, and the eddy current sensor 12 passes through and is fixed inside the movable adjusting sleeve. During cold-shutdown installation, the angle of the fixed base is adjusted so that the probe end face of the eddy current sensor 12 is parallel to the surface of the target plate 11. By rotating the movable adjusting sleeve, the eddy current sensor 12 moves along the normal direction towards or away from the target plate 11.

[0034] The initial physical gap between the eddy current sensor probe end face and the target plate is set using the aforementioned fine-tuning mechanism. The initial physical gap is set within the range of 2mm to 5mm. This value is used to prevent physical collisions between the target plate 11 and the eddy current sensor 12 caused by thermal expansion or mechanical vibration during turbine operation, and to ensure that the displacement change of the target plate 11 remains within the linear measurement range of the eddy current sensor 12. In one specific embodiment, the initial physical gap between the eddy current sensor probe end face and the target plate is set to 3mm. After setting, a locking assembly is used to interferolock the movable adjusting sleeve to prevent displacement changes in the eddy current sensor 12 due to mechanical vibration.

[0035] During system operation, the eddy current sensor 12 measures displacement using the principle of electromagnetic induction. An alternating current is applied to the coil inside the eddy current sensor 12 probe, generating an alternating magnetic field around the probe. This alternating magnetic field induces eddy currents on the surface of the metal target plate 11. When the secondary spring is stretched, causing the target plate 11 to move relative to the eddy current sensor 12, the real-time physical gap between the target plate 11 and the eddy current sensor 12 probe changes. This change in distance causes a change in the magnetic field reaction force of the eddy currents, which in turn changes the impedance of the coil inside the probe. The conditioning circuit inside the eddy current sensor 12 converts this impedance change into a continuous voltage signal for output.

[0036] The conversion relationship between the voltage signal output by the eddy current sensor 12 and the physical gap between the probe and the target is expressed by the following formula: ; in: This is the voltage signal output by the eddy current sensor; The calibration sensitivity coefficient of the eddy current sensor is determined by the hardware parameters of the eddy current sensor and the on-site temperature compensation settings. The real-time physical gap between the probe end face of the eddy current sensor and the target plate is limited by the measurement range of the eddy current sensor. This is the initial bias voltage of the system circuit. The value of the initial bias voltage of the system circuit is measured and stored when the gap between the end face of the eddy current sensor probe and the target plate is the initial physical gap between the end face of the eddy current sensor probe and the target plate, and when the turbine control valve is in a static, inactive state.

[0037] For the welding method or drilling and tapping fixing operation between the fixed base and the turbine stable base in the mounting bracket, those skilled in the art can refer to the mechanical installation manual for implementation. The basic assembly principle is a well-known technology in this field and will not be elaborated here.

[0038] The internal structure and external protection design of the eddy current sensor 12 in the sensing unit 10 are designed to withstand the high temperatures and dusty, oily working environment of the turbine control valve area. At the physical structure level, the probe end face of the eddy current sensor 12 is encapsulated with high-temperature resistant ceramic material, and the internal detection coil is wound with high-temperature resistant metal wire and filled with high-temperature resistant curing adhesive. These hardware design features ensure that the eddy current sensor 12 maintains its physical structure unchanged and prevents short circuits in its internal electrical connections within an ambient temperature range of -30℃ to 400℃.

[0039] The eddy current sensor 12 employs a fully enclosed probe housing design, achieving an IP67 protection rating. In the actual operating environment of a steam turbine inlet regulating valve, there is lubricating oil mist, insulation material powder, and condensed water droplets. The eddy current sensor 12 detects these substances using a non-contact electromagnetic induction principle. The alternating magnetic field generated by its probe can penetrate the aforementioned non-metallic oil, dust, and water vapor media, generating eddy current reactions only on the surface of the metallic target plate 11. This magnetic field penetration characteristic, combined with the fully enclosed housing design, avoids component damage and false alarms caused by contact oxidation, external impurities, or mechanical link fatigue in mechanical contact sensors.

[0040] To address the ambient temperature gradient fluctuations in the control valve area caused by turbine start-up and shutdown processes or variable load operation, the eddy current sensor 12 incorporates a temperature compensation module within its internal hardware circuitry. Changes in ambient temperature cause temperature drift in the DC resistance and inductive reactance of the probe's internal detection coil, leading to output signal distortion. The temperature compensation module senses the real-time ambient temperature through a built-in thermistor and injects a reverse compensation current into the internal conditioning circuit based on the measured temperature change.

[0041] The compensation current counteracts the temperature drift of the detection coil impedance, thereby maintaining the calibrated sensitivity coefficient of the eddy current sensor. The numerical value remains constant. The calibration sensitivity coefficient of the eddy current sensor. The value is determined by the hardware parameters of the eddy current sensor and the on-site temperature compensation settings. Under the adjustment of the temperature compensation module, the voltage signal output by the eddy current sensor... The numerical variation is only affected by the real-time physical gap between the probe end face of the eddy current sensor and the target. Numerical variation control. Real-time physical gap between the eddy current sensor probe end face and the target. The numerical range is limited by the measurement range of the eddy current sensor. This electrical compensation mechanism eliminates displacement measurement errors introduced by ambient temperature fluctuations.

[0042] For the specific winding method of the detection coil inside the eddy current sensor 12, the potting and curing process, and the specific topology of the resistor-capacitor matching circuit in the temperature compensation module, those skilled in the art can refer to the electronic component design and manufacturing specifications for implementation. The basic electronic circuit design and manufacturing principles are well-known technologies in this field and will not be elaborated here. The sensing unit 10 includes a mounting bracket with a fine-tuning mechanism. The mounting bracket is used to achieve precise spatial alignment between the probe end face of the eddy current sensor 12 and the surface of the target plate 11, and to accurately adjust the initial physical gap between the probe end face of the eddy current sensor and the target plate. The displacement measurement of the eddy current sensor 12 is based on the electromagnetic field distribution. The parallelism between the probe end face and the target plate 11, and the initial physical gap between the probe end face of the eddy current sensor and the target plate, determine the accuracy of the system measurement.

[0043] The mounting bracket consists of a base connecting plate, an angle adjusting joint, and a linear feed sleeve. The base connecting plate is fixed to a stable base near the turbine inlet regulating valve body using high-temperature alloy bolts. The base connecting plate has orthogonally distributed elongated mounting holes. These holes provide adjustment margin for the two-dimensional translation of the base connecting plate in the horizontal plane, enabling preliminary positioning of the eddy current sensor 12 in the X and Y axes. The angle adjusting joint is located between the base connecting plate and the linear feed sleeve, providing spatial rotation adjustment functionality.

[0044] During system assembly while the turbine is in a cold, shut-down state, the pitch and yaw angles of the linear feed sleeve are adjusted in space by loosening the fastening bolts on the angle adjustment joint. This operation ensures that the probe end face of the eddy current sensor 12, which is inserted and fixed inside the linear feed sleeve, remains parallel to the surface of the target plate 11 welded to the auxiliary spring connecting pin. This parallel orientation prevents the alternating magnetic field generated by the eddy current sensor 12 probe from producing uneven eddy current distribution on the surface of the target plate 11, thus reducing displacement measurement errors caused by spatial misalignment.

[0045] After adjusting the parallel posture and locking the joint, the distance between the probe and the target 11 is adjusted using a linear feed sleeve. The inner wall of the linear feed sleeve has fine threads, and the outer surface of the eddy current sensor 12 has matching external threads. The operator rotates the eddy current sensor 12, causing it to generate a linear feed displacement along the central axis of the linear feed sleeve. This linear feed displacement constitutes the Z-axis displacement adjustment in the three-dimensional adjustment. The eddy current sensor 12 gradually moves closer to or further away from the target 11 through this Z-axis displacement adjustment. Based on the known pitch parameters of the fine threads, the displacement feed is precisely calculated and executed by controlling the number of rotations.

[0046] By adjusting the linear feed displacement as described above, the initial physical gap between the eddy current sensor probe end face and the target plate is set to 3mm. This 3mm initial physical gap between the eddy current sensor probe end face and the target plate falls within the set measurement range of 2mm to 5mm. After setting the initial physical gap between the eddy current sensor probe end face and the target plate, the matching locking nut is tightened against the end face of the linear feed sleeve to form a mechanical interference lock. The locked nut can resist the high-frequency mechanical vibration generated during the operation of the turbine unit, preventing the eddy current sensor 12 from axially disengaging and changing displacement after long-term operation.

[0047] For the specific mechanical meshing structure of the multi-degree-of-freedom adjustable joint in the mounting bracket, the machining tolerance of the fine thread, and the selection requirements of the anti-loosening washer, those skilled in the art can consult the mechanical design manual for implementation. The specific mechanical transmission and spatial positioning principles are well-known technologies in this field and will not be elaborated here.

[0048] The system provided by this invention adopts a cold and hot separation architecture in its physical spatial layout. The sensing unit 10, which needs to collect real-time displacement changes of the turbine regulating valve auxiliary spring, is located near the high-temperature heat radiation area of ​​the valve body. The processing unit 20, containing a microprocessor and electronic conditioning circuitry, is located at a predetermined safe distance from the high-temperature core area of ​​the regulating valve.

[0049] The preset safety distance is set to be greater than or equal to 1.5m. This value is based on the spatial attenuation law of the thermal radiation intensity of the steam turbine body. Under the operating conditions of the steam turbine, the ambient temperature of the physical space beyond 1.5m from the control valve body drops to within the rated operating temperature range of the electronic components inside the processing unit 20. The industrial-grade microprocessor and conditioning circuit inside the processing unit 20 typically require an operating ambient temperature below 65℃. A physical distance of greater than or equal to 1.5m ensures that the ambient temperature of the space where the processing unit 20 is located meets this operating condition. The cold and hot separation architecture prevents the processing unit 20 from experiencing component aging, circuit thermal breakdown, and abnormal logic operations due to being in a high-temperature environment.

[0050] The transmission unit 30 is positioned between the sensing unit 10 and the processing unit 20, carrying the voltage signal for spatial cross-regional transmission. The transmission unit 30 includes a shielded cable 31. The inner insulation layer of the shielded cable 31 is made of polytetrafluoroethylene (PTFE), and an outer metal braided shielding layer is provided. The PTFE material prevents the inner insulation layer from melting and short-circuiting within the heat radiation area. The metal braided shielding layer blocks the alternating electromagnetic fields generated by large motors or transformers around the turbine, preventing external electromagnetic fields from inducing clutter voltages inside the shielded cable 31 and superimposing them onto the original voltage signal.

[0051] To increase the physical resistance of the line, a protective sleeve is fitted on the outside of the shielded cable 31. The protective sleeve is made of flexible metal corrugated tubing or silicone tubing wrapped with fiberglass. The protective sleeve protects against mechanical impacts and abrasions caused by on-site maintenance operations and isolates the valve lubricating oil from corrosion by high-temperature moisture. After passing through the protective sleeve, the shielded cable 31 is led out along the metal cable tray and laid to the access end of the processing unit 20.

[0052] Regarding the grounding layout for electromagnetic interference suppression, the metal braided shielding layer of the shielded cable 31 is connected to the internal grounding terminal at the end where the processing unit 20 is located, and finally merges into the power plant's field grounding grid. This single-ended grounding wiring method prevents grounding loop currents from being generated due to the inconsistency in ground potential between the area where the induction unit 10 is located and the area where the processing unit 20 is located, thus maintaining the signal-to-noise ratio for long-distance voltage signal transmission.

[0053] For the welding and fixing methods of on-site metal cable trays, the joint binding process of flexible bushings, and the grounding resistance testing standards of grounding grids, those skilled in the art can consult electrical engineering construction specifications for implementation. The basic electrical laying principles are well-known technologies in this field and will not be elaborated here.

[0054] The processing unit 20 includes a processing box 21 and built-in hardware components. The processing box 21 is made of cold-rolled steel plate with an anti-corrosion coating. The processing box 21 is mounted on a stable wall or column at least 1.5m away from the outside of the control valve body at the turbine site via a wall-mounted bracket. The configuration of the internal hardware components and the signal flow connection relationships of the processing box 21 are as follows: At the hardware access end, the processing box 21 is equipped with an input terminal block and a power module. The power module is connected to the 220V AC power supply of the power plant, and through internal transformer, rectification and voltage regulation circuits, it converts the AC power into the low-voltage DC power required for the operation of the internal electronic circuits. The shielded cable 31 in the transmission unit 30 passes through the waterproof cable connector at the bottom of the processing box 21 and enters the box, connecting the voltage signal output by the eddy current sensor to the input terminal block.

[0055] The input terminal block transmits the voltage signal to the conditioning board 22. The conditioning board 22 integrates an isolation amplifier circuit and a low-pass filter circuit. The isolation amplifier circuit uses optocouplers or an analog isolation amplifier to block the common ground connection between the sensing unit and the processing unit, preventing interference introduced by ground potential difference. The low-pass filter circuit filters out noise signals generated by high-frequency mechanical vibration and electromagnetic coupling in the voltage signal. In the turbine operating environment, the frequencies of mechanical vibration and electromagnetic interference are higher than the displacement change frequency when the auxiliary spring fatigues or breaks. The cutoff frequency of the low-pass filter circuit is set to be greater than the highest frequency of the displacement change signal and less than the lowest frequency of environmental noise, in order to retain the true displacement voltage signal and attenuate high-frequency noise.

[0056] The conditioning board 22 sends the filtered analog voltage signal to the microprocessor. The microprocessor's peripheral circuitry is connected to an external clock crystal and storage medium. The microprocessor integrates an analog-to-digital converter (ADC). The ADC discretizes the analog voltage signal according to a set sampling frequency, converting it into a digital signal. The set sampling frequency is determined according to the Nyquist sampling theorem and is greater than twice the cutoff frequency of the low-pass filter circuit to prevent aliasing distortion of the digital signal. The microprocessor's processing core receives this digital signal and performs logical comparisons and breakage checks.

[0057] The processing box 21 also houses a relay module. When the microprocessor determines that the secondary spring has broken, the microprocessor's general-purpose input / output pin outputs a level signal to the relay module's drive circuit. The electromagnetic coil inside the relay module is energized, generating a magnetic force that attracts the corresponding mechanical contacts, changing the on / off state of the contacts.

[0058] The mechanical contacts of the closed relay module serve as a passive dry contact signal output. This dry contact signal is connected to the output terminal block inside the processing box 21. The output terminal block is connected to the control cable 32 in the transmission unit 30, transmitting the physical state of the relay module's opening and closing to the DCS unit 40 in the central control room.

[0059] For the transformer and rectifier circuit structure of the power supply module inside the processing box 21, the calculation of the resistor and capacitor parameters of the low-pass filter circuit, and the coil drive circuit principle of the relay module, those skilled in the art can refer to the hardware circuit design manual for implementation. The selection of basic electronic components and circuit wiring design are well-known technologies in this field and will not be elaborated here.

[0060] After acquiring the digital voltage signal output from the analog-to-digital converter, the microprocessor inside the processing unit executes a front-end signal filtering and preprocessing mechanism. The low-pass filter circuit in the hardware circuit is used to filter out high-frequency noise; however, at the turbine operating site, the control valve body is still subject to low-frequency basic mechanical vibration interference or occasional transient electromagnetic spike interference. These interferences cause local fluctuations in the digital voltage signal. To extract a stable signal reflecting the true deformation state of the auxiliary spring, the microprocessor uses a moving average filtering algorithm to smooth the digital voltage signal.

[0061] A contiguous storage space is allocated in the microprocessor's memory as a sliding window. The sliding window uses a first-in, first-out (FIFO) data queue structure to manage the sampled data. Whenever the analog-to-digital converter completes a new sampling, the microprocessor pushes the latest digital voltage signal to the tail of the data queue and removes the oldest digital voltage signal from the head of the queue. The microprocessor performs an arithmetic average on all digital voltage signals within the sliding window to generate a filtered digital voltage signal. From a signal processing perspective, the arithmetic average operation, through cumulative averaging, reduces the impact of randomly occurring transient high or low level spikes on the overall signal amplitude. Simultaneously, when the sliding window's time span covers the complete mechanical vibration cycle, the positive and negative offset components in the displacement fluctuation signal cancel each other out during the averaging calculation, thereby extracting a stable displacement reference signal.

[0062] The calculation relationship of the moving average filtering algorithm is expressed by the following formula: ; in: For the first The filtered digital voltage signal at the next sampling time; The number of sampling points within the sliding window is the minimum value of the number of sampling points within the sliding window. The minimum value is the sampling frequency of the analog-to-digital converter divided by the lowest frequency of the mechanical vibration of the control gate, and the integer part is taken to ensure that the time length of the sliding window covers at least one complete low-frequency vibration cycle. For the first The digital voltage signal acquired at the next sampling time; The time series index number of the current sampling time; This is the time series offset number of the historical sampling points within the sliding window.

[0063] After digital filtering, the microprocessor performs a physical quantity inverse calculation on the filtered digital voltage signal. The microprocessor's internal storage medium stores the calibration sensitivity coefficient of the eddy current sensor and the initial bias voltage of the system circuit. Based on the filtered digital voltage signal, the microprocessor subtracts the initial bias voltage of the system circuit and divides the difference by the calibration sensitivity coefficient of the eddy current sensor to calculate the real-time physical gap between the eddy current sensor probe face and the target. This inverse calculation process corresponds to the inverse operation of the front-end sensing unit hardware measurement formula, mapping the dimensionless electrical signal back to a distance parameter with actual physical meaning.

[0064] For pointer addressing operations of the internal data queue of the microprocessor, low-level assembly instruction calls for floating-point division, and timing control of read and write control of the storage medium, those skilled in the art can consult the microcontroller programming manual for implementation. The basic embedded software development principles are well-known technologies in this field and will not be elaborated here.

[0065] After acquiring the real-time physical gap between the eddy current sensor probe face and the target plate, the microprocessor inside the processing unit executes a judgment logic based on dual criteria and early warning. The dual criteria are divided into two levels: low-level warning and high-level alarm. This judgment logic includes a low-level warning for spring performance degradation. During the long-term operation of the steam turbine, the auxiliary spring of the steam inlet regulating valve is exposed to a high-temperature environment and subjected to alternating mechanical stress. The metal material of the auxiliary spring will undergo irreversible plastic deformation, i.e., creep. Creep causes the free length of the auxiliary spring to increase or decrease, thereby causing the physical gap between the target plate and the eddy current sensor to deviate from the initially set state.

[0066] The microprocessor calculates and monitors the creep offset of the auxiliary spring. During normal load regulation, the rising and falling motion of the turbine control valve stem synchronously compresses or extends the auxiliary spring, generating normal mechanical displacement. The microprocessor needs to distinguish between this normal mechanical displacement and the creep offset caused by spring material aging. The microprocessor receives the current valve opening feedback signal from the DCS unit 40 via the communication interface and converts the current valve opening feedback signal into the corresponding theoretical working displacement.

[0067] The microprocessor subtracts the theoretical working displacement from the real-time physical gap between the eddy current sensor probe end face and the target plate, and then performs a subtraction operation with the initial physical gap between the eddy current sensor probe end face and the target plate pre-preserved in the storage medium to obtain the absolute difference value. This absolute difference value represents the pure creep offset generated by the auxiliary spring itself after eliminating the factors of normal valve operation. The microprocessor compares this absolute difference value with a low-level degradation threshold.

[0068] The low-level degradation threshold is set based on the fatigue life test data of the auxiliary spring at the time of manufacture and the empirical value of the aging of turbine unit materials. It is used to characterize the maximum allowable plastic deformation of the spring before it reaches critical failure. In one embodiment, the low-level degradation threshold is set to 1.0 mm. When the calculated absolute difference is greater than or equal to the low-level degradation threshold, it indicates that the fatigue level of the auxiliary spring's metal material has reached a warning state, and there is a risk of subsequent fracture.

[0069] During the rapid opening and closing of the turbine control valve, the mechanical transmission mechanism experiences brief oscillations and overshoot, causing a momentary spike in the calculated absolute difference. To prevent transient mechanical displacements caused by normal valve opening and closing from being misinterpreted as spring deterioration, the microprocessor incorporates a time-delay confirmation mechanism in its decision-making logic. The microprocessor has an internal timer. When the absolute difference is greater than or equal to a low-level deterioration threshold, the timer begins accumulating time. Only when the duration of this state (absolute difference greater than or equal to the low-level deterioration threshold) reaches or exceeds the confirmation time threshold does the microprocessor generate a low-level warning signal.

[0070] The confirmation time threshold is set based on the longest mechanical action time of the turbine control valve from fully open to fully closed, thus filtering out displacement changes caused by the normal valve stroke. This confirmation time threshold is typically set to be greater than 10 seconds. Creep in spring materials is a slow physical process that can take months, while the timescale of transient mechanical oscillations is only on the order of seconds. The time-delay confirmation mechanism utilizes the difference in timescale between these two physical phenomena to prevent false logic triggering.

[0071] The low-level warning condition for spring performance degradation is represented by the following logical expression: and ; in: This refers to the real-time physical gap between the probe end face of the eddy current sensor and the target plate. This is the theoretical working displacement; This refers to the initial physical gap between the eddy current sensor probe end face and the target plate. This is the low-level degradation threshold; The duration of the gap difference exceeding the limit; To confirm the time threshold.

[0072] After generating a low-level warning signal, the microprocessor sends a digital message containing the deterioration status and the current gap value to the DCS unit 40 via the data communication interface. The DCS unit 40 receives the message and generates a warning prompt on the monitoring screen, guiding maintenance personnel to preventively replace the auxiliary spring during the next unit shutdown maintenance.

[0073] For the register configuration of the microprocessor's internal timer, the software call of the absolute value function, and the underlying transmission protocol of the data communication interface, those skilled in the art can consult the microcontroller programming manual for implementation. The basic software timing and communication principles are well-known technologies in this field and will not be elaborated here.

[0074] After executing the low-level warning logic, the microprocessor inside the processing unit simultaneously executes the high-level alarm logic to determine whether the secondary spring has physically broken. The high-level alarm logic includes two criteria, the first of which is a sudden change criterion based on the rate of displacement change.

[0075] The auxiliary spring of the turbine inlet regulating valve is subjected to high compressive stress under normal operating conditions. When the metal structure of the auxiliary spring fractures, the mechanical strain energy stored within it is released in a very short time. This energy release causes a jump in the physical position of the remaining end of the auxiliary spring and the target plate rigidly connected to it. The fracture process manifests as a rapid displacement abrupt change on the time axis. The microprocessor captures this abrupt change by calculating the time derivative characteristics of the displacement signal.

[0076] In the specific digital calculation process, the microprocessor uses the discrete difference principle to calculate the displacement change rate. In digital signal processing, simple differential operations between two adjacent sampling points can amplify the weak high-frequency fluctuations remaining in the signal, easily leading to logical misjudgments. To overcome this amplification effect, the microprocessor employs a cross-cycle extraction differential calculation method. Based on the sampling clock cycle of the analog-to-digital converter, the microprocessor extracts the real-time physical gap between the eddy current sensor probe end face and the target plate calculated at the current sampling moment, and retrieves the real-time physical gaps between the eddy current sensor probe end face and the target plate at historical moments separated by multiple sampling cycles from the cache queue. The microprocessor calculates the difference between these two real-time physical gaps separated by multiple cycles and divides this difference by the corresponding time interval length to calculate the real-time displacement change rate of the target plate. This real-time displacement change rate represents the instantaneous velocity of the target plate along the motion axis.

[0077] The microprocessor compares the absolute value of the calculated real-time displacement change rate with the displacement mutation threshold. The magnitude of the displacement mutation threshold defines the logical boundary by which the system distinguishes between normal mechanical actions and abnormal breakage actions. When a steam turbine encounters a grid fault and performs an emergency load shedding operation, its hydraulic servo system drives the inlet steam control valve to close rapidly. To prevent this normal rapid mechanical action from being misinterpreted as spring breakage, the displacement mutation threshold is set to be greater than the maximum mechanical action speed of the control valve's hydraulic servo system under emergency closing conditions. This threshold setting method utilizes the physical limit difference of mechanical kinematic parameters to distinguish the uncontrolled movement speed when the spring breaks from the controllable displacement speed under hydraulic cylinder control.

[0078] Typically, the mechanical stroke of the turbine inlet regulating valve is approximately 100 mm, and its hydraulically controlled emergency closing action time ranges from 0.15 s to 0.3 s. Based on the division relationship between displacement and time, the maximum mechanical action speed of the regulating valve under emergency closing conditions is within the range of 300 mm / s to 600 mm / s. Based on the aforementioned mechanical operating boundary conditions, the displacement mutation threshold in this embodiment is set to 800 mm / s to provide sufficient judgment margin.

[0079] When the absolute value of the calculated real-time displacement change rate is greater than or equal to the displacement mutation threshold, it indicates that the target's moving speed has exceeded the physical limit of the steam inlet regulating valve's hydraulic mechanical system. The microprocessor then determines that the auxiliary spring has experienced a momentary mechanical instability, thus confirming the first criterion. After the first criterion is confirmed, the flag in the microprocessor's internal alarm status register is set, entering an intermediate state awaiting verification by the second criterion.

[0080] For the data reading operation of the microprocessor's internal cache queue, the specific software code implementation of the discrete difference algorithm, and the query and acquisition method of the maximum action speed of the regulating valve hydraulic servo system, those skilled in the art can refer to the microprocessor control principle and the turbine hydraulic system manual for implementation. The basic data processing and mechanical kinematic calculations are well-known technologies in this field and will not be elaborated here.

[0081] After the first criterion is met, the microprocessor inside the processing unit enters an intermediate state awaiting verification by the second criterion. The second criterion is a steady-state criterion based on step displacement. This criterion is used to eliminate false alarms caused by instantaneous signal mutations due to non-fracture factors such as occasional strong electromagnetic interference at the turbine site, loose probe wiring, or impacts from heavy objects.

[0082] After the secondary spring breaks, its metal remnants will re-establish mechanical equilibrium within the spring seat. During this rebalancing process, the broken metal remnants will collide and rebound within a confined space, creating brief mechanical oscillations. Once the mechanical oscillations have completely decayed, the target plate will remain in its new spatial position, causing an irreversible and permanent step change in the physical gap between the eddy current sensor probe end face and the target plate. The second criterion confirms the breakage by verifying the persistence and stability of this step displacement.

[0083] At the moment the first criterion is met, a timer inside the microprocessor initiates an evaluation time window. The length of the evaluation time window is set based on the mechanical decay time required for the fractured remnant to complete its rebound oscillation and reach a stationary state. In the mechanical structure of a large steam turbine inlet regulating valve, after the secondary spring with high preload breaks, the decay process of its mechanical oscillation typically takes 1 to 3 seconds. Therefore, the evaluation time window is set to 3 seconds. During the evaluation time window, the microprocessor continuously stores the acquired real-time physical gap into a cache, but does not perform fracture logic determination, in order to pass through the unstable mechanical oscillation period.

[0084] When the evaluation time window ends, the microprocessor extracts a segment of continuous sampled data following the evaluation time window, calculates its arithmetic mean, and uses it as the steady-state physical gap after fracture. The microprocessor retrieves the historical physical gap before the first criterion is triggered. The microprocessor calculates the absolute difference between the steady-state physical gap after fracture and the historical physical gap before the first criterion is triggered, obtaining the step displacement before and after the fracture event.

[0085] The microprocessor compares the step displacement with the fracture step threshold. The fracture step threshold is set based on the design preload of the auxiliary spring. When the auxiliary spring breaks, the lost support force causes the valve stem and target plate to shift and fall, and this drop is positively correlated with the spring's preload. To avoid displacement errors caused by normal mechanical wear, the fracture step threshold is set to 30% to 50% of the auxiliary spring's design preload. In conventional steam turbine units, the physical value of this threshold is within the range of 3mm to 5mm. When the calculated step displacement is greater than or equal to the fracture step threshold, it indicates that the target plate's position has undergone a permanent shift consistent with the physical characteristics of spring fracture, and the microprocessor determines that the second criterion is met.

[0086] The core logic of the second criterion is expressed by the following relation: ; in: The steady-state physical gap after fracture; This refers to the historical physical gap prior to the triggering of the first criterion; This is the fracture step threshold.

[0087] When both the first criterion for sudden change and the second criterion for steady state are met within the set logical timing, the microprocessor confirms a genuine mechanical breakage of the intake regulating valve auxiliary spring and triggers an advanced breakage alarm. The microprocessor's general purpose input / output pins output a drive signal to the relay module. The relay module's contacts close, transmitting the physical open / closed state to the DCS unit 40 in the central control room via control cable 32. Upon receiving this hardware-level alarm signal, the DCS unit 40 activates the alarm equipment in the control room and generates a breakage alarm indication on the operator station's monitoring screen, prompting operators to perform a shutdown and maintenance procedure.

[0088] For the configuration process of the microprocessor's internal timer interrupt, the cache retrieval operation of the time window data, and the electrical isolation driving method of the relay module contacts, those skilled in the art can refer to the embedded system development manual for implementation. The basic software flow control and hardware driving principles are well-known technologies in this field and will not be elaborated here.

[0089] After confirming that the logic criteria for the advanced fracture alarm are met, the microprocessor inside the processing unit 20 drives the internal relay module to activate and transmit the alarm signal to the central control room.

[0090] The microprocessor controls the energization and de-energization of the electromagnetic coil inside the relay module through a drive circuit, thereby changing the physical on / off state of the external mechanical contacts. The external mechanical contacts function as passive dry contact outputs. The dry contacts themselves do not carry a voltage or current source; they only exhibit a physical connected or disconnected state. This passive output mode blocks the direct electrical connection between the processing unit 20 and the DCS unit 40 in the central control room, preventing grounding loops caused by potential differences between the two locations from damaging electronic equipment.

[0091] The dry contact signal is transmitted to the DCS unit 40 via the control cable 32 in the transmission unit 30. The control cable 32 is a copper core shielded cable 31 with cross-linked polyethylene insulation and polyvinyl chloride sheath. The control cable 32 is laid in the cable trench or metal cable tray at the power plant site. In terms of physical laying path, the control cable 32 is laid independently on a separate layer from the high-voltage power cable and maintains a spatial isolation distance to avoid low-frequency electromagnetic coupling interference generated during the start-up and shutdown of large power equipment from entering the alarm transmission circuit.

[0092] The end of the control cable 32 is connected to the digital input module 41 inside the DCS unit 40 cabinet. The digital input module 41 is equipped with a DC power supply. The DC power supply outputs a DC voltage of 24V or 48V and applies this DC voltage to the physical circuit formed by the control cable 32 and the mechanical contacts of the relay module.

[0093] To ensure fail-safe operation in industrial settings and prevent alarm failure due to a break in control cable 32, the dry contact output is configured as a normally closed contact. During normal operation of the intake valve auxiliary spring, the mechanical contacts of the relay module are closed, current flows through the circuit, and the detection channel of the digital input module 41 reads a logic high level. When the microprocessor determines that the spring has broken and drives the relay module, the mechanical contacts open, and the physical circuit is broken. The optocoupler circuit inside the digital input module 41 detects the disappearance of the circuit current and converts it to a logic low level, confirming the receipt of the breakage alarm signal at the hardware level. If the control cable 32 is accidentally broken during operation, the digital input module 41 will also read a logic low level and trigger the alarm, thus preventing the actual breakage event from being masked by cable failure. This signal transmission and reading mechanism using physical hard-wired connections avoids the network latency and data packet loss risks associated with software communication protocols, ensuring the determinism of alarm response in emergency breakage situations.

[0094] For the selection of contact capacity of relay module, the stripping and crimping process of shielded cable 31 and the channel configuration of digital input module 41, those skilled in the art can refer to the construction specifications of automated instrumentation for implementation. The basic instrumentation wiring and hardware wiring are well-known technologies in this field and will not be described in detail here.

[0095] After the digital input module 41 inside the DCS unit 40 converts the physical circuit disconnect state to a logic low level at the hardware level, this level signal is transmitted to the DCS main controller through the backplane bus inside the cabinet. The DCS main controller reads the status data on the backplane bus according to the set scan cycle and executes internal logic operations and multi-dimensional response mechanisms.

[0096] In the DCS engineering station of the power plant, technicians pre-configure the control logic. The control logic configuration uses industrial programming languages ​​such as function block diagrams or ladder diagrams to map the physical addresses of the hardware channels of the digital input module 41 to Boolean software variables within the DCS. When the main controller detects a low logic level indicating spring breakage, the value of this Boolean software variable flips from 1 to 0.

[0097] The state change of the Boolean software variable is synchronously pushed to operator station 42 in the central control room via industrial Ethernet. Upon receiving the state reversal signal, the monitoring software on operator station 42 triggers a linkage mechanism between audible and visual alerts and control protection. On the monitoring screen, operator station 42 invokes the graphics rendering engine to change the color of the corresponding equipment element on the human-machine interface to red and make it flash. A banner displaying the alarm location and fault type pops up at the top of the monitoring screen. For auditory alerts, operator station 42 outputs an audio signal to the loudspeaker in the control room to play an alarm sound. The alarm management service in the operator station 42's backend writes the alarm event along with a millisecond-level timestamp of its occurrence into the historical database, generating an event sequence record for subsequent unit fault analysis and accident replay.

[0098] In addition to audible and visual alarms, the DCS main controller also has a device protection linkage program configured in its logic settings. When the Boolean software variable representing spring breakage flips to 0, the device protection linkage program outputs a command to lock the servo drive circuit's opening direction control command for that steam inlet valve. At the DCS control logic level, the locking mechanism is implemented by forcibly setting the opening command output value of the electro-hydraulic servo valve corresponding to the steam inlet valve to zero and blocking the positive integral accumulation operation of the internal PID controller. This locking mechanism, at the logic level, cuts off the valve opening oil path of the valve hydraulic cylinder, preventing the broken secondary spring remnant from jamming the valve stem and causing continuous pressure overload of the hydraulic servo system.

[0099] For the overall shutdown protection of the steam turbine, considering that a single external contact failure may trigger an unplanned shutdown, the equipment protection linkage program does not use the logic of directly triggering a trip with a single signal during configuration. The equipment protection linkage program treats the spring break alarm signal as a high-priority indication of abnormal equipment operation. When the alarm occurs, the DCS main controller automatically disconnects the unit's automatic power generation control mode to maintain the stability of the current power generation load. Simultaneously, a mandatory confirmation dialog box pops up on the operator station 42's human-machine interface, requiring operators to cross-verify the vibration monitoring parameters of the steam turbine itself and the steam pressure parameters before and after the regulating valves. Only after the operators confirm the spring breakage and authorize it will the equipment protection linkage program send a shutdown trip request signal to the steam turbine emergency trip system, driving all main steam valves and inlet regulating valves to close forcibly, ensuring the safe operation of the steam turbine unit.

[0100] For the communication protocol of the DCS internal backplane bus, the method of binding and drawing the elements of the monitoring screen, and the storage structure of the historical database, those skilled in the art can refer to the Distributed Control System Configuration Manual for implementation. The basic industrial control software programming and database management are well-known technologies in this field and will not be elaborated here.

[0101] The system's on-site installation and commissioning were carried out during the maintenance window when the steam turbine was shut down and in a cold state. On-site maintenance personnel machined threaded holes at the mechanically movable end of the auxiliary spring of the steam inlet regulating valve and rigidly connected the metal target plate to the end of the auxiliary spring using mechanical fasteners. In electromagnetic measurement principles, the penetration depth of a high-frequency alternating magnetic field inside a metal conductor is limited by the skin effect. To ensure that the electromagnetic eddy current field can form a closed loop inside the target plate and prevent high-frequency magnetic lines of force from penetrating the target plate and causing measurement errors, the metal target plate is made of a metal material with good electrical or magnetic conductivity. In conventional embodiments, the metal target plate is made of 45# carbon steel or 304 stainless steel, and the solid thickness of the target plate is set to be greater than 2mm.

[0102] Maintenance personnel welded a rigid bracket to the outside of the turbine valve housing. The eddy current sensor probe was fixed to the rigid bracket with a nut. During installation, maintenance personnel adjusted the initial physical gap between the probe end face and the target plate by rotating the external thread of the eddy current sensor probe. This initial physical gap between the probe end face and the target plate was set in the middle range of the eddy current sensor's linear measurement range, ensuring that the target plate would not exceed the sensor's measurement range throughout the entire mechanical stroke of the fully open and fully closed steam inlet valve. The mechanical micro-motion stroke of the steam inlet valve during normal operation is typically between 1 and 2 mm. The high-temperature eddy current sensor selected for this system generally has a linear measurement range of 0 to 10 mm. Combining the valve's micro-motion stroke and the sensor's linear range, the initial physical gap between the eddy current sensor probe end face and the target plate was set to 4 mm to 6 mm. This installation position retains a buffer distance for the reverse ejection of the spring fragments after breakage, preventing the target plate from directly impacting and mechanically damaging the eddy current sensor probe.

[0103] After completing the mechanical installation, instrumentation personnel performed electrical wiring and verification. The shielded cable 31 output from the eddy current sensor 12 was laid through a metal protective conduit to the processing unit outside the turbine body. Instrumentation personnel used a multimeter to test the insulation resistance between the internal core wires and the external metal shielding layer of the shielded cable 31, checking for any damage or leakage in the insulation material under high-temperature conditions. The shielding layer of the signal cable was single-ended grounded on the grounding copper busbar on the processing unit side to discharge spatial electromagnetic coupling interference current and prevent potential difference circulating currents from interfering with the measurement signal due to multiple grounding points.

[0104] The relay module inside the processing unit is connected to the digital input module 41 of the DCS unit 40 via control cable 32. Instrument personnel perform a continuity test at both ends of control cable 32 to confirm that the physical connection of the dry contact output channel is free of open circuits or incorrect connections. After the test, the instrument personnel turn on the power supply to the processing unit. The microprocessor powers on and completes the hardware initialization self-test. Maintenance personnel retrieve the status variables of this channel on the monitoring screen of the DCS operator station 42 to verify whether the hardware connection and logic level display in the static state are consistent. The microprocessor reads the digital voltage signal output by the analog-to-digital converter in the current cold state of shutdown, converts it into a physical distance, and stores it in the internal medium as the initial physical gap reference between the eddy current sensor probe end face and the target plate for subsequent creep warning and fracture determination.

[0105] For the mechanical fastening and anti-loosening treatment of metal targets, the waterproof insulation wrapping of cable joints, and the basic operating procedures of multimeters, those skilled in the art can refer to the mechanical equipment assembly specifications and electrical installation manuals for implementation. The basic electromechanical installation and instrument debugging principles are well-known technologies in this field and will not be elaborated here.

[0106] After completing the mechanical installation and electrical wiring verification work under cold shutdown conditions, on-site maintenance personnel performed on-site parameter threshold tuning and system commissioning procedures. The on-site maintenance personnel used a portable computer connected to the processing unit via a serial communication interface. The portable computer ran dedicated configuration and debugging software. Using this software, the maintenance personnel wrote the various judgment thresholds calculated in conjunction with the turbine's mechanical parameters into the non-volatile storage medium inside the microprocessor. The written parameters included low-level degradation thresholds, confirmation time thresholds, displacement mutation thresholds, and fracture step thresholds. To ensure the reliability of data transmission in an industrial environment, the configuration and debugging software included a cyclic redundancy check code when issuing parameters. After receiving the data, the microprocessor verified it and read back the parameters written to the non-volatile storage medium to the portable computer for comparison, confirming that the tuning data was correct. The microprocessor can read these parameters from the non-volatile storage medium during subsequent power-off restarts to prevent configuration data loss.

[0107] After the parameters were tuned, maintenance personnel conducted closed-loop simulation debugging of the fracture alarm logic. Considering that destructive testing could not be performed in the industrial field, the debugging test adopted a simulation method of physical signal injection. Maintenance personnel disconnected the shielded cable 31 of the eddy current sensor 12 on the processing unit side and connected the output terminal of the standard signal generator to the analog input channel of the processing unit.

[0108] On-site personnel operate a standard signal generator to inject simulated displacement voltage signals into the processing unit. The injected signal includes alternating voltage simulating normal mechanical micro-motion, and a step drop voltage simulating the instantaneous breakage of a spring. During the simulated breakage condition, maintenance personnel use the waveform editing function of the standard signal generator to set the slope of the voltage jump so that its converted displacement change rate is greater than the displacement abrupt change threshold, and simultaneously set the voltage drop amplitude so that its converted displacement offset is greater than the breakage step threshold. The analog-to-digital converter inside the microprocessor converts the analog voltage into a digital quantity and performs calculations based on dual-criteria logic. When the microprocessor detects that the displacement change rate of the injected signal is greater than the displacement abrupt change threshold, and its step change is greater than the breakage step threshold, it confirms that the advanced breakage alarm conditions are met.

[0109] After receiving the judgment result indicating that the conditions are met, the microprocessor drives the internal relay module to operate, causing its normally closed mechanical contacts to open. The DCS unit 40 in the central control room detects the physical circuit break and sets the status data on the backplane bus to a logic low level. The operators in the control room check the response status of the monitoring screen on the operator station 42, confirming that the equipment element color of the steam inlet regulating valve has changed and is flashing, and at the same time confirming that the corresponding alarm tone has been broadcast by the control room's public address system.

[0110] The technicians responsible for logic configuration retrieved the real-time running status of the equipment protection linkage program from the DCS engineering station backend. They verified whether the opening command output value of the electro-hydraulic servo valve corresponding to the steam inlet regulating valve was forcibly set to zero, and whether the positive integral accumulation operation of the internal PID controller was successfully blocked. This end-to-end closed-loop test verified the complete hardware and software functionality from the bottom-level hardware voltage sampling to the top-level DCS logic execution. After confirming that all software responses and hardware interlocking mechanisms acted according to the design logic, the system closed-loop debugging test was deemed successful.

[0111] After the joint commissioning test was completed, the on-site maintenance personnel removed the standard signal generator and reconnected the shielded cable 31 of the eddy current sensor 12 to the input terminal of the processing unit. The operators performed an alarm reset operation on the DCS operator station 42 interface, clearing the event sequence records and historical alarm data generated during the joint commissioning process. The processing unit underwent a hardware reset and restart, and the system entered standby monitoring mode, awaiting the hot start-up of the turbine unit.

[0112] For the baud rate configuration of the portable computer serial communication protocol, the voltage range setting of the standard signal generator, and the clearing of historical alarm data of the DCS system, those skilled in the art can refer to the instruction manual of the automated instrument and meter for implementation. The basic equipment debugging and system reset are well-known technologies in the field and will not be described in detail here.

[0113] Specific application examples: To verify the performance of the real-time monitoring and DCS alarm system for the fracture of the auxiliary spring of the high-temperature turbine control valve provided in this embodiment of the invention, a turbine control valve fatigue testing test bench was built. This test bench is equipped with a hydraulic servo cylinder, a heat tracing and insulation jacket (simulating a high-temperature environment of 300℃-400℃), and the actual auxiliary spring assembly.

[0114] The experimental test set up three typical working conditions: Opening and closing conditions: Simulate the closing action of the control valve driven by the hydraulic servo system during an emergency load shedding of the steam turbine to verify the system's ability to prevent false alarms.

[0115] Spring creep degradation condition: Through prolonged over-temperature and overload stretching, the creep of the spring material is accelerated to verify the triggering conditions of the low-level early warning criterion.

[0116] Mechanical fracture condition: By prefabricating a spring crack and applying pressure to it under a specific load until it fractures, the triggering of the advanced fracture alarm dual criteria (displacement change rate mutation criterion and step displacement steady-state criterion) is verified.

[0117] Experimental data analysis of the core criteria: Please see the appendix Figure 3 This invention provides a real-time monitoring curve of displacement and displacement change rate during the fracture process of a secondary spring.

[0118] In the mechanical fracture test, during the initial stage (0 to 1.0 s), the initial physical gap between the end face of the eddy current sensor probe and the target plate stabilized at 4.0 mm.

[0119] At t=1.0s, the secondary spring breaks. The microprocessor inside the processing unit captures the displacement change at this moment, and the absolute value of the real-time displacement change rate calculated by the cross-cycle differential algorithm reaches 1250mm / s, which is greater than the set displacement mutation threshold (800mm / s), and the first criterion (mutation criterion) is met.

[0120] Subsequently, the fractured metal fragment underwent mechanical oscillations, with the displacement curve fluctuating between 1.0s and 2.5s. The microprocessor entered a 3s evaluation time window, during which no alarm was triggered.

[0121] At t=4.0s (the end of the evaluation time window), the mechanical oscillation stops, and the target plate comes to rest. The microprocessor calculates the steady-state physical gap after fracture to be 8.2mm. The step displacement of this steady-state physical gap compared to the historical physical gap before fracture (4.0mm) is 4.2mm, which is greater than the set fracture step threshold (3.0mm), and the second criterion (steady-state criterion) is met.

[0122] The system outputs a dry contact alarm signal to the DCS unit. The fault identification process is not affected by noise interference during the oscillation period, and the judgment logic satisfies the mechanical change characteristics of spring breakage.

[0123] During the opening and closing test, the hydraulic cylinder drove the gate to close at the maximum design speed. The measured maximum displacement change rate was 520 mm / s, which is less than the sudden change threshold of 800 mm / s. The system avoided false alarms caused by normal mechanical actions.

[0124] Comparison of the effects of different monitoring systems Please see the appendix Figure 4 This invention provides a comparison chart of core performance indicators of different monitoring systems.

[0125] The system provided by this invention was compared with traditional vibration spectrum monitoring systems and mechanical limit switches in a comparative experiment. The test sample consisted of 100 simulated actions under different working conditions (including 10 actual fractures, 30 vibration disturbances, and 60 normal actions).

[0126] Average response time: The response time of the system of this invention (including filtering, differential calculation and 3s evaluation window) is 3.2s; the vibration spectrum monitoring system requires long-period FFT (Fast Fourier Transform) cumulative calculation, and the response time is 8.5s; the mechanical limit switch has a short response time, but it may jam and fail in high-temperature environments.

[0127] False alarm rate: Under the interference of vibration and opening and closing conditions, the false alarm rate of mechanical limit switch due to contact chatter is 15%; the false alarm rate of vibration spectrum monitoring system is 8% because it cannot distinguish between turbine body vibration and spring breakage vibration; the false alarm rate of the system of this invention is 0% based on dual criteria and moving average filtering algorithm.

[0128] Fault detection accuracy: In the spring fracture fault test, the detection rate of the system of this invention is 100%; the detection rate of the vibration spectrum monitoring system is 85% (the fracture energy signal is affected by environmental noise); the detection rate of the mechanical limit switch is 70% (affected by the linkage jamming caused by high temperature oxidation).

[0129] Experimental tests show that, while ensuring adaptability to high-temperature operating environments, the embodiments of the present invention reduce the false alarm rate and the missed alarm rate in the monitoring of turbine control valve auxiliary spring fracture, and improve the operational reliability of the monitoring equipment.

Claims

1. A real-time monitoring and DCS alarm system for fracture of auxiliary spring of high-temperature steam turbine control valve, characterized in that, include: The sensing unit is installed at each auxiliary spring of the turbine inlet regulating valve to collect the physical displacement change of the corresponding auxiliary spring and convert the physical displacement change into an electrical signal output. The processing unit is used to condition and logically determine the received electrical signals, and output a switch alarm signal when the breakage determination condition is met. The transmission unit connects the sensing unit and the processing unit, and also connects the processing unit and the DCS unit, for transmitting the electrical signal and the switch quantity alarm signal; The DCS unit is used to receive the switch alarm signal and execute corresponding alarm actions and data recording.

2. The real-time monitoring and DCS alarm system for fracture of the auxiliary spring of a high-temperature steam turbine control valve as described in claim 1, characterized in that, The sensing unit includes a target plate and an eddy current sensor; The target plate is made of heat-resistant stainless steel and is rigidly fixed to the flat side of the connecting pin shaft of the steam turbine inlet regulating valve. The geometric sensing area of ​​the target plate is larger than the cross-sectional area of ​​the eddy current sensor probe. The probe housing of the eddy current sensor is equipped with heat dissipation fins, and the internal hardware circuit is equipped with a temperature compensation module. The temperature compensation module senses the real-time ambient temperature through a built-in thermistor and injects a reverse compensation current into the internal conditioning circuit based on the measured temperature change, in order to maintain the constant value of the calibration sensitivity coefficient K of the eddy current sensor.

3. The real-time monitoring and DCS alarm system for fracture of the auxiliary spring of a high-temperature steam turbine control valve as described in claim 2, characterized in that, The sensing unit also includes a mounting bracket with a fine-tuning mechanism; The mounting bracket consists of a base connecting plate, an angle adjusting joint, a linear feed sleeve, and a locking nut. The base connecting plate is fixed on a stable base near the turbine inlet regulating valve body, the inner wall of the linear feed sleeve is provided with fine thread, and the probe housing surface of the eddy current sensor is machined with matching external thread. The angle adjustment joint is configured to keep the probe end face of the eddy current sensor parallel to the surface of the target plate; The eddy current sensor is configured to generate a linear feed displacement along the central axis of the linear feed sleeve through the engagement of the external thread and the fine thread, which is used to adjust the initial physical gap between the end face of the eddy current sensor probe and the target plate. The locking nut is configured to tighten against the end face of the linear feed sleeve, forming a mechanical interference lock.

4. The real-time monitoring and DCS alarm system for fracture of the auxiliary spring of a high-temperature steam turbine control valve as described in claim 3, characterized in that, The processing unit is located at a preset safe distance outside the high-temperature core area of ​​the turbine control valve, and the preset safe distance is greater than or equal to 1.5m; Furthermore, the processing unit includes a processing box, and the processing box contains a conditioning board and a microprocessor; The conditioning board integrates an isolation amplifier circuit and a low-pass filter circuit. The low-pass filter circuit is used to filter the electrical signal. The cutoff frequency of the low-pass filter circuit is set to be greater than the highest frequency of the displacement change signal and less than the lowest frequency of environmental interference noise. The microprocessor integrates an analog-to-digital converter, which is used to convert the filtered electrical signal into a digital voltage signal. The microprocessor is configured to allocate a contiguous storage space in the internally configured storage medium as a sliding window and use a first-in-first-out data queue structure to manage the sampled data; The microprocessor is configured to push the latest digital voltage signal into the tail of the data queue and remove the oldest digital voltage signal from the head of the data queue, and to perform an arithmetic average operation on all digital voltage signals within the sliding window to generate a filtered digital voltage signal.

5. The real-time monitoring and DCS alarm system for fracture of the auxiliary spring of a high-temperature steam turbine control valve as described in claim 4, characterized in that, The microprocessor is configured to subtract the initial bias voltage of the system circuit stored in the storage medium of the microprocessor from the filtered digital voltage signal, and divide the difference obtained by subtraction by the calibration sensitivity coefficient K of the eddy current sensor to calculate the value of the real-time physical gap between the probe end face of the eddy current sensor and the target plate. The microprocessor is configured to execute decision logic based on dual criteria and early warning, the decision logic including a low-level warning of spring performance degradation; The microprocessor is configured to receive a feedback signal from the DCS unit regarding the current opening degree of the turbine inlet regulating valve via a communication interface, and to convert the current opening feedback signal into the corresponding theoretical working displacement. The microprocessor is configured to subtract the theoretical working displacement from the real-time physical gap between the end face of the eddy current sensor probe and the target plate, and then perform a subtraction operation with the initial physical gap between the end face of the eddy current sensor probe and the target plate pre-frozen in the storage medium to obtain the absolute difference value. When the duration of the state where the absolute difference is greater than or equal to the low-level degradation threshold pre-stored in the storage medium reaches or exceeds the confirmation time threshold pre-stored in the storage medium, the microprocessor generates a low-level warning signal.

6. The real-time monitoring and DCS alarm system for fracture of the auxiliary spring of a high-temperature steam turbine control valve as described in claim 5, characterized in that, The dual criteria include a first criterion, wherein the first criterion is a sudden change criterion based on the rate of displacement change; The microprocessor is configured to extract the real-time physical gap between the end face of the eddy current sensor probe and the target plate calculated at the current sampling time, retrieve the real-time physical gap between the end face of the eddy current sensor probe and the target plate at historical times with multiple sampling cycles in the cache queue, calculate the difference between the two real-time physical gaps with multiple cycles in the cache queue, and divide the difference by the corresponding time interval length to calculate the real-time displacement change rate of the target plate. When the absolute value of the calculated real-time displacement change rate is greater than or equal to the displacement mutation threshold stored in the storage medium in advance, the first criterion is determined to be true. The value of the displacement mutation threshold is set to be greater than the maximum mechanical action speed of the hydraulic servo system of the turbine inlet regulating valve under emergency closing conditions.

7. The real-time monitoring and DCS alarm system for fracture of the auxiliary spring of a high-temperature steam turbine control valve as described in claim 6, characterized in that, The dual criteria include a second criterion, which is a steady-state criterion based on step displacement; After the first criterion is met, the microprocessor is configured to start an evaluation time window that is pre-stored in the storage medium. During the timing of the evaluation time window, the microprocessor continuously stores the collected real-time physical gap into the cache, but does not perform the break logic determination. The microprocessor is configured to extract a continuous segment of sampling data of the real-time physical gap after the evaluation time window ends, calculate the arithmetic mean of the continuous sampling data, and use the arithmetic mean as the steady-state physical gap after the fracture. Calculate the absolute difference between the steady-state physical gap after the fracture and the historical physical gap before the first criterion is triggered, and obtain the step displacement before and after the fracture event; The second criterion is determined to be true when the step displacement is greater than or equal to the fracture step threshold pre-stored in the storage medium.

8. The real-time monitoring and DCS alarm system for fracture of the auxiliary spring of a high-temperature steam turbine control valve as described in claim 1, characterized in that, The transmission unit includes a shielded cable and a control cable; The shielded cable connects the sensing unit and the processing unit, and is used to transmit the electrical signal; The shielded cable is fitted with a protective sleeve on the outside, which is a flexible metal corrugated tube or a silicone sleeve wrapped with glass fiber. The inner insulation layer of the shielded cable is made of polytetrafluoroethylene material, and the outer metal braided shielding layer is provided. The metal braided shielding layer is connected to the internal grounding terminal at the end where the processing unit is located to adopt a single-end grounding wiring method. The control cable connects the processing unit and the DCS unit and is used to transmit the switch alarm signal.

9. A real-time monitoring and DCS alarm system for fracture of a high-temperature steam turbine regulating valve auxiliary spring according to claim 8, characterized in that, The processing unit is equipped with a relay module, and the switch alarm signal is output as a passive dry contact signal by the closed mechanical contacts of the relay module. The DCS unit includes a digital input module, which is equipped with a DC query power supply. The DC query power supply outputs a DC voltage and applies the DC voltage to the physical circuit formed by the control cable and the mechanical contacts of the relay module. The dry contact output is configured as a normally closed contact, so that the mechanical contact of the relay module is in a closed state during the normal operation of the auxiliary spring of the turbine inlet regulating valve, and the mechanical contact is opened when the processing unit determines that the spring has broken and drives the relay module to operate, thereby breaking the physical circuit. The optocoupler circuit inside the digital input module is configured to convert the detected loop current disappearance state to a logic low level and trigger an alarm when the loop current disappears, or when the control cable is accidentally disconnected during operation, the digital input module will also read a logic low level and trigger an alarm.

10. A real-time monitoring and DCS alarm system for fracture of a high-temperature steam turbine regulating valve auxiliary spring according to claim 9, characterized in that, The DCS unit is equipped with a device protection linkage program, a DCS main controller, and an operator station. The DCS main controller is configured with Boolean software variables to characterize the state of the spring. The DCS main controller is configured to flip the value of the Boolean software variable from 1 to 0 when it detects a logic low level indicating spring breakage, and trigger an audible and visual alarm command and a pop-up command at the operator station. The equipment protection linkage program is configured to output commands, lock the servo drive circuit for the opening direction control command issued by the corresponding turbine inlet regulating valve, force the opening command output value of the corresponding electro-hydraulic servo valve of the turbine inlet regulating valve to be set to zero and block the positive integral accumulation calculation of the internal PID controller.

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