An adaptive fastening method and system based on substation bolt torque

Abstract

A kind of self-adapting fastening method and system based on substation bolt torque, the method comprises: real-time acquisition bolt image and the temperature of the electrical connection point corresponding to bolt position and pre-processing, obtain bolt loosening angle, connecting plate offset angle and connection point temperature;Calculate bolt connection loosening index, when bolt connection loosening index is not less than predetermined loosening threshold, corresponding bolt is as pre-tightening bolt;Based on the rated current of bolt electrical connection node and predefined maximum safety temperature, determine target contact resistance;Based on target contact resistance and bolt contact interface material, calculate target pretightening force and correct, determine target torque;The torque of pre-tightening bolt is adjusted to target torque, and the contact resistance under target torque is obtained;When the contact resistance is not less than reference resistance, the target torque is adaptively adjusted.The present application improves the long-term operation safety and reliability of substation bolt connection by constructing adaptive closed-loop fastening control mechanism.

Description

Technical Field

[0001] This invention belongs to the field of substation maintenance technology, specifically relating to an adaptive tightening method and system based on substation bolt torque. Background Technology

[0002] As a crucial node in the power system, the safe and stable operation of substations is of paramount importance. Substations house a large number of primary and secondary equipment, such as transformers, circuit breakers, disconnectors, busbars, and insulator strings. These devices are connected by bolts to achieve mechanical connections and electrical conduction. During long-term operation, these bolted connections are continuously subjected to the combined effects of electromagnetic vibrations from the equipment, thermal expansion and contraction caused by load fluctuations, changes in outdoor temperature and humidity, and wind disturbances. Consequently, loose or improperly tightened bolts can easily lead to increased contact resistance, localized overheating, and electrical discharge erosion, which in severe cases can cause equipment failure, power outages, and even safety hazards.

[0003] Traditional methods use a fixed torque value, typically applying the same torque to all bolts for retightening. However, during long-term operation of substation equipment, factors such as temperature cycling, equipment vibration, and aging and creep of insulator materials can cause the clamping force of bolt connections to loosen. Even under the same set torque, the actual axial preload can vary significantly, resulting in insufficient preload on some bolts, posing a risk of loosening; while excessive preload on other bolts may lead to yielding or breakage, thereby damaging the equipment.

[0004] Currently, existing bolt fastening methods mainly include torque method, angle method, tension method, thermal expansion method, image recognition method, and the use of smart bolts or specially designed anti-loosening structures. For example, patent application CN117576197A discloses a method for identifying, locating, tightening, and maintaining substation capacitor bolts, along with a maintenance robot. This method uses image recognition to roughly determine the bolt's axis and outer contour, then precisely locates the bolt's axis, and uses a robotic arm to precisely tighten the bolt. Patent application CN115091178A discloses a method for calculating and controlling bolt tightening torque. It uses torque and angle methods to obtain the bolt's pre-tightening torque and tightening angle, determines the bolt tightening torque at the tightening angle, and continuously monitors it, ensuring the accuracy of the clamping force provided after bolt tightening and preventing abnormal tightening torque during actual tightening. Patent application CN119795096A discloses an intelligent torque feedback and adaptive adjustment method, device, and computer equipment. This method can monitor real-time torque values ​​and automatically adjust the bolt torque to achieve the target torque value, realizing precise torque adjustment in actual bolt tightening operations and improving work efficiency and safety.

[0005] In summary, existing methods can identify and locate bolts and control torque during the tightening process; however, these methods do not take into account the overall safety of electrical connection operation and do not consider the coupling relationship between electrical performance parameters and mechanical fastening parameters, thus making it difficult to achieve adaptive fastening oriented towards electrical safety constraints. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an adaptive tightening method and system based on substation bolt torque. The method involves real-time acquisition and preprocessing of bolt images and the temperature of the electrical connection points corresponding to the bolt positions to obtain the bolt loosening angle, connection plate offset angle, and connection point temperature. A bolt connection loosening index is calculated; when the loosening index is not less than a predetermined loosening threshold, the corresponding bolt is designated as a pre-tightening bolt. Based on the rated current of the bolt electrical connection node and a predefined maximum safe temperature, a target contact resistance is determined. Based on the target contact resistance and the material of the bolt contact interface, a target preload is calculated and corrected to determine the target torque. The torque of the pre-tightening bolt is adjusted to the target torque, and the contact resistance at the target torque is obtained. When this contact resistance is not less than a reference resistance, the target torque is adaptively adjusted. This invention improves the long-term operational safety and reliability of substation bolt connections by constructing an adaptive closed-loop tightening control mechanism.

[0007] The present invention adopts the following technical solution: A first aspect of the present invention provides an adaptive tightening method based on the torque of substation bolts, comprising: S1. Real-time acquisition and preprocessing of bolt images and the temperature of electrical connection points corresponding to bolt positions to obtain bolt loosening angle, connection plate offset angle and connection point temperature; S2. Calculate the relative temperature difference of the bolt connection points based on the connection point temperature; comprehensively consider the bolt loosening angle, the connection plate offset angle, the connection point temperature and the relative temperature difference to calculate the bolt connection loosening index; when the bolt connection loosening index is not less than the predetermined loosening threshold, the corresponding bolt is used as a pre-tightening bolt. S3. Based on the rated current and predefined maximum safe temperature of the bolt electrical connection node, calculate the maximum allowable contact resistance of the bolt under thermal stability constraints and determine the target contact resistance; based on the target contact resistance and the material of the bolt contact interface, calculate the target preload and correct the target preload by calculating the preload loss caused by bolt thermal expansion; based on the corrected target preload, determine the target torque. S4. Adjust the torque of the pre-tightening bolt to the target torque and obtain the contact resistance under the target torque; when the contact resistance is not less than the reference resistance, based on the target torque and the contact resistance under the target torque at different iteration numbers, set the target torque increment for the corresponding iteration number and adaptively adjust the target torque.

[0008] Preferably, the process of calculating the relative temperature difference at the bolt connection point in S2 is as follows: For any bolt, the difference between the corresponding connection point temperature and the predefined reference temperature is used as the numerator, and the difference between the connection point temperature and the ambient temperature is used as the denominator to calculate the corresponding relative temperature difference.

[0009] Preferably, the process of calculating the bolt loosening index in S2 is as follows: Determine whether any one of the bolt loosening angle, connecting plate offset angle, and relative temperature difference exceeds the corresponding allowable value; if so, set the bolt connection loosening index to the predetermined loosening threshold. If not, the ratio of the bolt loosening angle to the predefined allowable bolt loosening angle is taken as the bolt loosening item, and the ratio of the connecting plate offset angle to the predefined allowable connecting plate offset angle is taken as the connecting plate offset item; the connection point temperature is normalized, and the maximum value between the normalized connection point temperature and the ratio of the relative temperature difference to the relative allowable temperature difference is taken as the temperature anomaly item; the bolt loosening item, the connecting plate offset item, and the temperature anomaly item are weighted to obtain the bolt connection loosening index.

[0010] Preferably, the process of determining the target contact resistance in S3 is as follows: Obtain the rated current of the bolt electrical connection node, multiply the difference between the highest safe temperature and the ambient temperature by the predefined convective heat transfer coefficient and the effective heat dissipation area corresponding to the bolt position as the numerator, and use the square of the rated current of the bolt electrical connection node as the denominator to calculate the maximum allowable contact resistance under thermal stability constraints. The minimum value between the maximum allowable contact resistance and the predefined upper limit of the allowable resistance according to operation and maintenance standards is taken as the target contact resistance.

[0011] Preferably, the process of calculating the target preload in S3 is as follows: Multiply the resistivity of the bolt contact interface by a predefined contact coefficient and divide by the target contact resistance as the base. Use the reciprocal of the predefined contact index as the exponent to calculate the contact pressure under the target contact resistance as the target preload.

[0012] Preferably, the process of determining the target torque in S3 is as follows: The difference in linear expansion coefficients of the connecting plate material and the bolt material is multiplied by the predefined bolt axial stiffness and the effective length of the bolt under force, and then multiplied by the difference between the connection point temperature and the predefined reference temperature to obtain the preload loss caused by bolt thermal expansion. The target preload and the preload loss are added together to obtain the corrected target preload. The corrected target preload is then multiplied by the torque coefficient and the bolt diameter to obtain the target torque.

[0013] Preferably, the process of setting the target torque increment for the corresponding iteration number in S4 is as follows: For any number of iterations, obtain the target torque and the contact resistance at the target torque for the current iteration; take the difference between the contact resistance at the previous iteration and the current iteration as the numerator, and the difference between the target torque at the current iteration and the previous iteration as the denominator to obtain the resistance change rate at the current iteration; calculate the ratio of the difference between the contact resistance and the reference resistance at the current iteration to the resistance change rate, and multiply this ratio by a predefined damping coefficient to obtain the target torque increment at the current iteration.

[0014] Preferably, the sum of the target torque and the target torque increment at the current iteration number is calculated, and the minimum value of the sum in the predefined safe upper limit torque is used as the target torque for the next iteration number; Obtain the contact resistance under the target torque for the next iteration. If the contact resistance is less than the reference resistance or the target torque for the next iteration is equal to the safety upper limit torque, it indicates that the tightening operation of the pre-tightened bolt has been completed; otherwise, continue the target torque iteration and bolt tightening operation.

[0015] A second aspect of the present invention provides an adaptive fastening system based on substation bolt torque, using an adaptive fastening method based on substation bolt torque, comprising: The data acquisition module collects bolt images and the temperature of the electrical connection points corresponding to the bolt positions in real time and preprocesses them to obtain the bolt loosening angle, the connection plate offset angle, and the connection point temperature. The bolt tightness judgment module calculates the relative temperature difference of the bolt connection point based on the connection point temperature; it comprehensively considers the bolt loosening angle, the connection plate offset angle, the connection point temperature, and the relative temperature difference to calculate the bolt connection loosening index; when the bolt connection loosening index is not less than the predetermined loosening threshold, the corresponding bolt is regarded as a pre-tightening bolt. The bolt torque determination module calculates the maximum allowable contact resistance of the bolt under thermal stability constraints based on the rated current of the bolt electrical connection node and the predefined maximum safe temperature, and determines the target contact resistance; based on the target contact resistance and the material of the bolt contact interface, it calculates the target preload, and corrects the target preload by calculating the preload loss caused by bolt thermal expansion; based on the corrected target preload, it determines the target torque. The bolt torque adaptive adjustment module adjusts the torque of the pre-tightened bolt to the target torque and obtains the contact resistance at the target torque. When the contact resistance is not less than the reference resistance, based on the target torque and the contact resistance at the target torque under different iterations, the module sets the target torque increment for the corresponding iteration number and adaptively adjusts the target torque.

[0016] A third aspect of the present invention provides a terminal, including a processor and a storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform steps according to an adaptive tightening method based on substation bolt torque.

[0017] A fourth aspect of the invention provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of an adaptive tightening method based on the torque of substation bolts.

[0018] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. This invention acquires bolt images and electrical connection point temperature information in real time, extracts bolt loosening angle, connection plate offset angle, and connection point temperature, and further constructs relative temperature difference parameters. Based on this, a bolt connection loosening index model is established, achieving a fusion assessment of mechanical structure condition and abnormal temperature condition. Compared to judging bolt condition solely based on torque or a single temperature parameter, this method can more accurately identify potential loosening risks, effectively avoid misjudgments and omissions, and improve the reliability and foresight of operation and maintenance inspections.

[0019] 2. This invention derives the maximum permissible contact resistance under thermally stable conditions based on the rated current and maximum safe temperature of electrical connection nodes. It then determines the target contact resistance using maintenance standards. Based on this, it calculates the target preload and target torque in reverse, while also considering corrections made for material resistivity, contact characteristic parameters, and preload loss due to thermal expansion. This ensures that fastening control no longer relies solely on empirical torque values, but rather prioritizes electrical safety, guaranteeing connection reliability from the outset.

[0020] 3. This invention detects the contact resistance in real time after the target torque is reached, and adaptively calculates the target torque increment based on the resistance change rate under different iterations. It achieves iterative optimization control through a safety upper limit constraint. This closed-loop adjustment method can dynamically correct the torque value according to the actual contact state, avoiding over-tightening or under-tightening, thereby significantly improving the stability and long-term operational safety of bolt electrical connections and reducing the risks of overheating, ablation, and power outages caused by abnormal contact resistance. Attached Figure Description

[0021] Figure 1 The flowchart of a substation bolt torque adaptive tightening method provided by the present invention is shown. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0023] Example 1 Embodiment 1 of the present invention provides an adaptive tightening method based on the bolt torque of a substation, see reference. Figure 1 The process includes the following steps: S1. Real-time acquisition and preprocessing of bolt images and the temperature of electrical connection points corresponding to bolt positions to obtain bolt loosening angle, connection plate offset angle, and connection point temperature.

[0024] The acquired bolt images are registered with reference bolt images to eliminate deviations caused by shooting angles. The registered bolt images are then subjected to distortion correction, grayscale processing, edge detection, and edge extraction to extract the contour edges of the bolts and connecting plates. The Hough transform algorithm is used to extract the geometric features of the bolts and connecting plates, which are then compared with feature points in the reference bolt images to obtain the bolt loosening angle and connecting plate offset angle. The reference bolt image is the bolt image of the corresponding position acquired during the initial operation of the equipment. The bolt loosening angle represents the relative rotation angle between the bolt and the bolt in the reference bolt image. The connecting plate offset angle is the relative tilt angle between the connecting plate and the connecting plate in the reference bolt image.

[0025] This embodiment uses a high-definition camera to capture bolt images and an infrared thermal imaging sensor to collect the temperature of the electrical connection point area. The highest temperature in the corresponding electrical connection point area is taken as the corresponding connection point temperature. The electrical connection points include: equipment clamps, T-clamps, equipment joints (such as the connection between a circuit breaker and a lead wire), bushing end plates, disconnector contacts, etc. The high-definition camera and infrared thermal imaging sensor can be set in front of the equipment where the bolt is located as a fixed acquisition device, or they can be set on an inspection robot for periodic inspection data collection.

[0026] S2. Calculate the relative temperature difference of the bolt connection point based on the connection point temperature; comprehensively consider the bolt loosening angle, the connection plate offset angle, the connection point temperature and the relative temperature difference to calculate the bolt connection loosening index; when the bolt connection loosening index is not less than the predetermined loosening threshold, the corresponding bolt is used as a pre-tightening bolt.

[0027] For any bolt, the relative temperature difference is calculated by taking the difference between the corresponding connection point temperature and the predefined reference temperature as the numerator, and the difference between the connection point temperature and the ambient temperature as the denominator; specifically expressed as: ; In the formula, The relative temperature difference at the bolt connection points; Temperature at the connection point; The predefined reference temperature; The ambient temperature at which the bolt is located; Determine whether any one of the bolt loosening angle, connecting plate offset angle, and relative temperature difference exceeds the corresponding allowable value; if so, set the bolt connection loosening index to the predetermined loosening threshold. If not, the ratio of the bolt loosening angle to the predefined allowable bolt loosening angle is taken as the bolt loosening term, and the ratio of the connecting plate offset angle to the predefined allowable connecting plate offset angle is taken as the connecting plate offset term; the connection point temperature is normalized, and the maximum value between the normalized connection point temperature and the ratio of the relative temperature difference to the relative allowable temperature difference is taken as the temperature anomaly term; the bolt loosening term, connecting plate offset term, and temperature anomaly term are weighted to obtain the bolt connection loosening index; the specific formula is: ; In the formula, The bolt loosening index; The predetermined loosening threshold; , These are the bolt loosening angle and the predefined allowable bolt loosening angle, respectively. , These are the connecting plate offset angle and the predefined allowable offset angle for the connecting plate, respectively. For a predefined relative allowable temperature difference; The maximum permissible safe temperature; , and These are the weighting coefficients for the bolt loosening item, the connecting plate offset item, and the temperature anomaly item, respectively, with values ​​ranging from the interval [insert range here]. Inside and ; When the loosening index of a bolt connection is not less than the predetermined loosening threshold, the corresponding bolt needs to be tightened and is used as a pre-tightening bolt.

[0028] In this embodiment, the connection status of bolts is comprehensively evaluated by integrating multiple parameters such as bolt loosening angle, connecting plate offset angle, and relative temperature difference corrected for ambient temperature, thereby significantly improving the diagnostic accuracy of bolt connection loosening faults. Specifically, by introducing temperature difference calculations relative to ambient temperature and reference temperature, the interference of environmental factors on temperature data is effectively eliminated. At the same time, normalization processing enables different physical quantities to be weighted and fused on the same scale, achieving a quantitative evaluation of the connection status. Based on this, a quantified bolt connection loosening index is obtained through weighted calculation and compared with a preset threshold, which can clearly identify pre-tightened bolts that need to be tightened, providing clear data support for preventive maintenance.

[0029] S3. Based on the rated current of the bolt electrical connection node and the predefined maximum safe temperature, calculate the maximum allowable contact resistance of the bolt under thermal stability constraints and determine the target contact resistance; based on the target contact resistance and the material of the bolt contact interface, calculate the target preload and correct the target preload by calculating the preload loss caused by bolt thermal expansion; based on the corrected target preload, determine the target torque.

[0030] As a preferred implementation, the rated current of the bolted electrical connection node is obtained. The difference between the highest safe temperature and the ambient temperature is multiplied sequentially by a predefined convective heat transfer coefficient and the effective heat dissipation area corresponding to the bolt position as the numerator, and the square of the rated current of the bolted electrical connection node is used as the denominator to calculate the maximum allowable contact resistance under thermal stability constraints. The specific calculation formula is as follows: ; In the formula, Maximum permissible contact resistance; The convective heat transfer coefficient is a predefined value and is related to wind speed and equipment structure. The effective heat dissipation area of ​​the bolted electrical connection node is the equivalent heat dissipation area of ​​the connection part exposed to the air. The rated current of the bolt electrical connection node is, in this embodiment, the rated current of the corresponding equipment under the electrical connection node, such as the rated current marked on the nameplate of the circuit breaker, disconnector, transformer winding, etc., or the maximum continuous current of the busbar. The minimum value between the maximum allowable contact resistance and the predefined upper limit of the allowable resistance according to operation and maintenance standards is taken as the target contact resistance.

[0031] In a preferred embodiment, the material resistivity of the bolt contact interface is multiplied by a predefined contact coefficient and then divided by the target contact resistance as the base. The reciprocal of a predefined contact index is used as the exponent to calculate the contact pressure under the target contact resistance as the target preload. The specific formula is as follows: ; In the formula, Preload for the target; The resistivity of the material at the bolt contact interface; The contact coefficient is a comprehensive coefficient that typically characterizes the actual conductive contact and contact area efficiency. In this embodiment, it can be obtained through experimental data fitting or finite element simulation. Target contact resistance; The contact index represents the nonlinear relationship between contact area and contact pressure, and its value ranges from [value range missing]. Inside; The difference in linear expansion coefficients of the connecting plate material and the bolt material is multiplied sequentially by the predefined bolt axial stiffness and the effective length of the bolt under load, and then multiplied by the difference between the connection point temperature and the predefined reference temperature to obtain the preload loss caused by bolt thermal expansion. The target preload and the preload loss are added together to obtain the corrected target preload. The specific formula is as follows: ; ; In the formula, This is due to preload loss; This represents the axial stiffness of the bolt, indicating the force change per unit length under load. , These are the linear expansion coefficients of the connecting plate material and the bolt material, respectively; This is the effective length of the bolt under force, i.e., the clamping length; The reference temperature for mounting bolts; The corrected target preload.

[0032] The target preload is obtained by multiplying the corrected target preload by the torque coefficient and the bolt diameter; the specific formula is as follows: ; In the formula, The target torque; The torque coefficient is set to 0.2 in this embodiment; This refers to the bolt diameter.

[0033] This embodiment calculates the maximum allowable contact resistance under thermal stability constraints based on rated current, convective heat transfer coefficient, and heat dissipation area. The minimum value between this maximum and the allowable value in the maintenance standard is taken as the target contact resistance, thus ensuring from the outset that bolted connections will not experience dangerous temperature rises due to excessive contact resistance under rated operating conditions. Furthermore, utilizing the physical relationship between contact resistance and contact pressure, the target preload required to achieve this target resistance is derived from the material resistivity and contact coefficient, accurately mapping electrical safety indicators to mechanical fastening parameters. On this basis, compensation is introduced for preload loss caused by temperature changes at the connection point and differences in the linear expansion coefficient of the materials, resulting in a corrected target preload. This effectively eliminates the adverse effects of thermal effects on connection reliability, making the calculation results more closely reflect actual operating conditions. Finally, the corrected target preload is converted into a target torque that can be directly applied during construction using a torque coefficient, providing maintenance personnel with precise and executable fastening operation guidelines. The entire process achieves closed-loop decoupling and quantitative calculation from electrical safety boundaries to mechanical fastening parameters, ensuring the dual electrical and mechanical reliability of the connection nodes throughout their entire lifespan and under varying temperature environments.

[0034] S4. Adjust the torque of the pre-tightening bolt to the target torque and obtain the contact resistance under the target torque; when the contact resistance is not less than the reference resistance, based on the target torque and the contact resistance under the target torque at different iteration numbers, set the target torque increment for the corresponding iteration number and adaptively adjust the target torque.

[0035] Adjust the torque of the pre-tightening bolt to the target torque and obtain the contact resistance at the target torque; when the contact resistance is less than the predefined reference resistance, it indicates that the pre-tightening bolt has been tightened. When the contact resistance is not less than the reference resistance, the target torque is adaptively adjusted; the specific process is as follows: For any number of iterations, obtain the target torque and the contact resistance at the target torque for the current iteration. Use the difference between the contact resistance at the previous iteration and the current iteration as the numerator, and the difference between the target torque at the current iteration and the previous iteration as the denominator to obtain the resistance change rate at the current iteration. Calculate the ratio of the difference between the contact resistance and the reference resistance at the current iteration to the resistance change rate, and multiply this ratio by a predefined damping coefficient to obtain the target torque increment at the current iteration. The specific calculation formula is as follows: ; ; In the formula, Number of iterations i Rate of change of resistance; and They are the number of iterations. i -1 andi Contact resistance of the bolt under the target torque; and They are the number of iterations. i -1 and i The target torque; Indicates the initial target torque. The contact resistance under the initial target torque; Number of iterations i The target torque increment, This represents the target torque increment at the initial iteration number. This is the adjustment coefficient; The reference resistance, in this embodiment, is the average contact resistance under historical maintenance conditions when the bolts are tightened. The damping coefficient is a predefined value, typically taken as 0.4 to 0.7; Calculate the sum of the target torque and the target torque increment at the current iteration number, and use the minimum value of this sum from the predefined safe upper limit torque as the target torque for the next iteration number; the specific calculation formula is as follows: ; In the formula, Number of iterations i Target torque at +1; The predefined safety upper limit torque; Obtain the contact resistance under the target torque for the next iteration. If the contact resistance is less than the reference resistance or the target torque for the next iteration is equal to the safety upper limit torque, it indicates that the tightening operation of the pre-tightened bolt has been completed; otherwise, continue the target torque iteration and bolt tightening operation.

[0036] This embodiment achieves closed-loop precise control of the bolt tightening process by introducing an adaptive torque adjustment mechanism based on real-time feedback of contact resistance. When the contact resistance under the initial target torque does not meet the benchmark requirements, the torque increment is dynamically calculated using the contact resistance and torque change rate of the two iterations, thereby quickly approaching the optimal torque value that makes the contact resistance meet the standard. This avoids the under-tightening or over-tightening problems that may be caused by traditional single torque control. At the same time, by introducing a safety upper limit torque as a constraint, it is ensured that the connecting parts will not be damaged or safety hazards will be caused by excessive force during the iterative optimization process, thus taking mechanical safety into account while meeting electrical contact performance. This adaptive method effectively overcomes the impact of uncertain factors such as material differences, friction coefficient fluctuations, and thermal effects on the tightening effect, significantly improving the intelligence level and first-time success rate of operation and maintenance.

[0037] Example 2 Embodiment 2 of the present invention provides an adaptive fastening system based on the bolt torque of a substation, comprising: The data acquisition module collects bolt images and the temperature of the electrical connection points corresponding to the bolt positions in real time and preprocesses them to obtain the bolt loosening angle, the connection plate offset angle, and the connection point temperature. The bolt tightness judgment module calculates the relative temperature difference of the bolt connection point based on the connection point temperature; it comprehensively considers the bolt loosening angle, the connection plate offset angle, the connection point temperature, and the relative temperature difference to calculate the bolt connection loosening index; when the bolt connection loosening index is not less than the predetermined loosening threshold, the corresponding bolt is regarded as a pre-tightening bolt. The bolt torque determination module calculates the maximum allowable contact resistance of the bolt under thermal stability constraints based on the rated current of the bolt electrical connection node and the predefined maximum safe temperature, and determines the target contact resistance; based on the target contact resistance and the material of the bolt contact interface, it calculates the target preload, and corrects the target preload by calculating the preload loss caused by bolt thermal expansion; based on the corrected target preload, it determines the target torque. The bolt torque adaptive adjustment module adjusts the torque of the pre-tightened bolt to the target torque and obtains the contact resistance at the target torque. When the contact resistance is not less than the reference resistance, based on the target torque and the contact resistance at the target torque under different iterations, the module sets the target torque increment for the corresponding iteration number and adaptively adjusts the target torque.

[0038] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0039] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0040] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0041] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. An adaptive tightening method based on the bolt torque in a substation, characterized in that, include: S1. Real-time acquisition and preprocessing of bolt images and the temperature of electrical connection points corresponding to bolt positions to obtain bolt loosening angle, connection plate offset angle and connection point temperature; S2. Calculate the relative temperature difference of the bolt connection points based on the connection point temperature; comprehensively consider the bolt loosening angle, the connection plate offset angle, the connection point temperature and the relative temperature difference to calculate the bolt connection loosening index; when the bolt connection loosening index is not less than the predetermined loosening threshold, the corresponding bolt is used as a pre-tightening bolt. S3. Based on the rated current and predefined maximum safe temperature of the bolt electrical connection node, calculate the maximum allowable contact resistance of the bolt under thermal stability constraints and determine the target contact resistance; Based on the target contact resistance and the material of the bolt contact interface, the target preload is calculated, and the target preload is corrected by calculating the preload loss caused by bolt thermal expansion; based on the corrected target preload, the target torque is determined. S4. Adjust the torque of the pre-tightening bolt to the target torque and obtain the contact resistance at the target torque; When the contact resistance is not less than the reference resistance, based on the target torque and the contact resistance under the target torque at different iteration numbers, the target torque increment is set for the corresponding iteration number, and the target torque is adaptively adjusted. The process of determining the target torque in S3 is as follows: The difference between the linear expansion coefficients of the connecting plate material and the bolt material is multiplied by the predefined bolt axial stiffness and the effective length of the bolt under force, and then multiplied by the difference between the connection point temperature and the predefined reference temperature to obtain the preload loss caused by bolt thermal expansion; the target preload and the preload loss are added together to obtain the corrected target preload. The target torque is obtained by multiplying the corrected target preload by the torque coefficient and the bolt diameter in sequence.

2. The adaptive tightening method based on substation bolt torque according to claim 1, characterized in that: The process for calculating the relative temperature difference at the bolt connection point in S2 is as follows: For any bolt, the difference between the corresponding connection point temperature and the predefined reference temperature is used as the numerator, and the difference between the connection point temperature and the ambient temperature is used as the denominator to calculate the corresponding relative temperature difference.

3. The adaptive tightening method based on substation bolt torque according to claim 1, characterized in that: The process for calculating the bolt loosening index in S2 is as follows: Determine whether any one of the bolt loosening angle, connecting plate offset angle, and relative temperature difference exceeds the corresponding allowable value; if so, set the bolt connection loosening index to the predetermined loosening threshold. If not, the ratio of the bolt loosening angle to the predefined allowable bolt loosening angle is taken as the bolt loosening item, and the ratio of the connecting plate offset angle to the predefined allowable connecting plate offset angle is taken as the connecting plate offset item; the connection point temperature is normalized, and the maximum value between the normalized connection point temperature and the ratio of the relative temperature difference to the relative allowable temperature difference is taken as the temperature anomaly item; the bolt loosening item, the connecting plate offset item, and the temperature anomaly item are weighted to obtain the bolt connection loosening index.

4. The adaptive tightening method based on substation bolt torque according to claim 1, characterized in that: The process for determining the target contact resistance in S3 is as follows: Obtain the rated current of the bolt electrical connection node, multiply the difference between the highest safe temperature and the ambient temperature by the predefined convective heat transfer coefficient and the effective heat dissipation area corresponding to the bolt position as the numerator, and use the square of the rated current of the bolt electrical connection node as the denominator to calculate the maximum allowable contact resistance under thermal stability constraints. The minimum value between the maximum allowable contact resistance and the predefined upper limit of the allowable resistance according to operation and maintenance standards is taken as the target contact resistance.

5. The adaptive tightening method based on substation bolt torque according to claim 1, characterized in that: The process for calculating the target preload in S3 is as follows: Multiply the resistivity of the bolt contact interface by a predefined contact coefficient and divide by the target contact resistance as the base. Use the reciprocal of the predefined contact index as the exponent to calculate the contact pressure under the target contact resistance as the target preload.

6. The adaptive tightening method based on substation bolt torque according to claim 1, characterized in that: The process of setting the target torque increment for the corresponding number of iterations in S4 is as follows: For any number of iterations, obtain the target torque and the contact resistance at the target torque for the current iteration number; The difference between the contact resistance at the previous iteration number and the current iteration number is used as the numerator, and the difference between the target torque at the current iteration number and the previous iteration number is used as the denominator to obtain the resistance change rate at the current iteration number. Calculate the ratio of the difference between the contact resistance and the reference resistance at the current iteration number to the resistance change rate, and multiply this ratio by a predefined damping coefficient to obtain the target torque increment at the current iteration number.

7. An adaptive tightening method based on substation bolt torque according to claim 1 or 6, characterized in that: Calculate the sum of the target torque and the target torque increment at the current iteration number, and use the minimum of this sum and the predefined safe upper limit torque as the target torque for the next iteration number; Obtain the contact resistance under the target torque for the next iteration. If the contact resistance is less than the reference resistance or the target torque for the next iteration is equal to the safety upper limit torque, it indicates that the tightening operation of the pre-tightened bolt has been completed; otherwise, continue the target torque iteration and bolt tightening operation.

8. An adaptive fastening system based on substation bolt torque, using the method described in any one of claims 1-7, characterized in that, include: The data acquisition module collects bolt images and the temperature of the electrical connection points corresponding to the bolt positions in real time and preprocesses them to obtain the bolt loosening angle, the connection plate offset angle, and the connection point temperature. The bolt tightness judgment module calculates the relative temperature difference of the bolt connection point based on the connection point temperature; it comprehensively considers the bolt loosening angle, the connection plate offset angle, the connection point temperature, and the relative temperature difference to calculate the bolt connection loosening index; when the bolt connection loosening index is not less than the predetermined loosening threshold, the corresponding bolt is regarded as a pre-tightening bolt. The bolt torque determination module calculates the maximum allowable contact resistance of the bolt under thermal stability constraints based on the rated current of the bolt electrical connection node and the predefined maximum safe temperature, and determines the target contact resistance. Based on the target contact resistance and the material of the bolt contact interface, the target preload is calculated, and the target preload is corrected by calculating the preload loss caused by bolt thermal expansion; based on the corrected target preload, the target torque is determined. The bolt torque adaptive adjustment module adjusts the torque of the pre-tightened bolt to the target torque and obtains the contact resistance at the target torque. When the contact resistance is not less than the reference resistance, based on the target torque and the contact resistance under the target torque at different iteration numbers, the target torque increment is set for the corresponding iteration number, and the target torque is adaptively adjusted. The process of determining the target torque in the bolt torque determination module is as follows: The difference between the linear expansion coefficients of the connecting plate material and the bolt material is multiplied by the predefined bolt axial stiffness and the effective length of the bolt under force, and then multiplied by the difference between the connection point temperature and the predefined reference temperature to obtain the preload loss caused by bolt thermal expansion; the target preload and the preload loss are added together to obtain the corrected target preload. The target torque is obtained by multiplying the corrected target preload by the torque coefficient and the bolt diameter in sequence.

9. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1-7.

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