A system and method for detecting wear of signal cables inside an electromechanical equipment enclosure

Abstract

A system and method for detecting signal cable wear inside an electromechanical equipment enclosure includes a host computer, a control system, and a cable protection structure. The cable protection structure is wrapped around the signal cable and, from the outside in, includes a first outer shell layer, a second hollow layer, and a third insulation layer. A resistance band is wound within the second hollow layer. The resistance band has a longitudinal opening on its side, allowing for the insertion of a lead wire at any break point, which is then pressed together with the outer layer of the cable protection structure. The resistance band connects to a signal terminal of the control system from a first break point via a first lead wire, and from a second break point via a second lead wire to a ground terminal of the control system. The control system collects the loop current value at the signal terminal and calculates the length of the resistance band connected to the loop. This invention determines wear by detecting the loop current value formed by the resistance band covering the signal cable, providing timely alerts and control to prevent significant losses caused by signal cable wear.

Description

Technical Field

[0001] This invention relates to the field of signal cable testing, and in particular to a system and method for detecting wear of signal cables inside an electromechanical equipment enclosure. Background Technology

[0002] In the industrial sector, most large-scale power machinery often experiences significant foundation vibrations during operation, such as steam turbines and centrifuges. Foundation vibration is an inherent characteristic of power machinery and is difficult to avoid. Therefore, few equipment is placed in the vibration zone around the machinery. However, some auxiliary electromechanical equipment, such as hydraulic servo mechanisms and pneumatic quick-closing valves, are critical safety components of the power machinery and even the entire process system and must be placed close to it. During long-term vibration, their signal cables may come into contact with the electromechanical equipment enclosure or mechanical transmission components. After continuous friction, the signal cables will wear down. If this is not detected in time, the outer insulation layer of the signal cable may wear down to ground or even break. This can cause the control signals of critical electromechanical equipment to become disordered and out of control. At best, it can lead to unexpected shutdown of the process system; at worst, it can cause serious personal injury, equipment damage, and incalculable economic losses. Summary of the Invention

[0003] The main objective of this invention is to provide a signal cable wear detection system and method for electromechanical equipment enclosures. By detecting the loop current value formed by the resistance band covering the outside of the signal cable, the system can determine the presence of wear, provide timely warnings, and prevent significant losses caused by signal cable wear.

[0004] The present invention adopts the following technical solution:

[0005] On one hand, a signal cable wear detection system for an electromechanical equipment enclosure includes a host computer, a control system, and a cable protection structure. The cable protection structure is wound around the signal cable and, from the outside to the inside, includes a first outer shell layer, a second hollow layer, and a third insulation layer. A winding resistance strip is disposed within the second hollow layer. The winding resistance strip has a longitudinal opening on its side, allowing a lead wire to be inserted and pressed into the outer layer of the cable protection structure at any break point. The winding resistance strip is connected to a signal terminal of the control system from a first break point via a first lead wire, and from a second break point via a second lead wire to a ground terminal of the control system to form a loop. A fixed resistor is disposed on the loop. The control system collects the loop current value of the signal terminal, calculates the length of the resistance strip connected to the loop based on the loop current value, compares the resistance strip length with the resistance strip installation length entered by the host computer, and issues a prompt signal when the difference between the two exceeds a threshold range. The prompt and control signals include at least one of an alarm signal, a passivation signal, and a braking signal.

[0006] Preferably, the wound resistance strip serves as the filler for the second hollow layer of the cable protection structure, forming an integral structure with the first outer shell layer and the third insulation layer.

[0007] Preferably, the winding resistor strip has a longitudinal opening on its side to form two end pressure interfaces for inserting lead wires, and the signal terminals connected to each winding resistor strip are different.

[0008] Preferably, the outer surface of the first outer shell layer is provided with a distance scale, which is used to record the length of the cable protection structure as the resistor strip installation length during installation, and to input the resistor strip installation length into the host computer and locate the wear point according to the alarm signal during use.

[0009] Preferably, the third insulation layer is a plastic buffer layer, used to eliminate or reduce the impact and damage of external vibrations on the signal cable during use.

[0010] Preferably, the control system includes a DCS system or a PLC system; the host computer is the human-machine interface external device of the control system.

[0011] On the other hand, a method for detecting wear of signal cables inside an electromechanical equipment enclosure, based on any one of the aforementioned signal cable wear detection systems for electromechanical equipment enclosures, includes:

[0012] Calculate the total resistance of the circuit based on the circuit current and circuit voltage values;

[0013] Subtract the fixed resistance value from the total resistance value to obtain the resistance value of the wound resistance tape connected to the circuit;

[0014] The length of the resistance band of the access loop is calculated based on the resistance value of the resistance band of the access loop.

[0015] Compare the resistor strip length with the resistor strip installation length entered by the host computer and calculate the difference between the two.

[0016] When the difference exceeds the threshold range, wear is detected, the wear location value is calculated, a prompt and control signal are issued, and the result is displayed on the host computer; the difference exceeding the threshold range means that the difference is less than the lower threshold or greater than the upper threshold.

[0017] Preferably, the length of the resistance band of the access circuit is calculated based on the resistance value of the resistance band of the access circuit, as follows:

[0018]

[0019] Among them, L c Indicates the length of the resistor band in the circuit; K represents the resistance length coefficient of the resistor band; U represents the circuit voltage, which is a fixed value; I c Indicates the loop current value; R LIndicates the resistance value of a fixed resistor; This indicates the resistance value of the resistor connected to the circuit.

[0020] Preferably, the method for obtaining the lower threshold and upper threshold is as follows:

[0021] After the control system detects the overall start signal of the process system, it performs real-time cyclic detection and calculation on the current value of the loop, and transmits the real-time calculation results. The deviation is compared with the resistor strip installation length entered by the host computer, and the upper and lower bounds of the deviation are selected within the time interval from the overall start-up of the process system to the stable operating condition; among them, I t This represents the loop current monitored in real time during the time interval from startup to stable operating condition;

[0022] Use the upper bound of the deviation as the upper bound of the threshold, and the lower bound of the deviation as the lower bound of the threshold;

[0023] The upper and lower bounds of the deviation are updated by triggering the deviation comparison when the process system re-issues an overall start-up signal from a stopped state.

[0024] Preferably, issuing prompts and control signals specifically includes:

[0025] When the difference between the length of a resistor strip wound inside the same electromechanical equipment enclosure and the corresponding installation length of the resistor strip exceeds the threshold range, the control system is triggered to output an alarm signal and display it.

[0026] When the difference between the length of at least two wound resistor strips and their respective installation lengths exceeds the threshold range within the same electromechanical equipment enclosure, the control system is triggered to output an alarm signal and display it, as well as output a passivation control signal for the electromechanical equipment; the passivation control signal includes at least one of delaying, clipping, interrupting, and locking the equipment control command, and also includes issuing a safety set command to the electromechanical equipment to make it move to a working state that ensures the safety of the process system;

[0027] When the entire process system has two or more redundant electromechanical devices, and the difference between the length of the winding resistor strip on each electromechanical device and the corresponding installation length of the resistor strip exceeds the threshold range, the control system is triggered to output an alarm signal and display, output the passivation control signal of the electromechanical device, and output the emergency braking signal of the process system; the emergency braking signal of the process system is to issue an emergency braking safety command to the process system to make it move to a safe shutdown state.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The present invention determines the presence of wear by detecting the loop current value formed by the resistance band covering the outside of the signal cable, and provides timely warning to prevent the wear of the signal cable from causing significant losses.

[0030] (2) The cable protection structure of the present invention is wound around the outside of the signal cable and is an open-wound self-positioning structure. Therefore, it is not necessary to remove the fixed wiring of the signal cable during installation and adjustment, and it will not affect the existing signal operation. The cable protection structure includes a first outer shell layer, a second hollow layer and a third insulation layer from the outside to the inside. The winding resistance strip is set in the second hollow layer. The winding resistance strip detection adopts a 24V and below level instrument detection circuit and is isolated from the signal cable through the third insulation layer. Therefore, it will not cause signal interference.

[0031] (3) During use and installation, the cable protection structure often needs to be adjusted in length according to the length and location of the signal cable to be protected (specifically by cutting off the excess length at one or both ends). Therefore, the cable protection structure of the present invention has a distance scale printed on the outer surface of the first outer shell (in the same winding direction), which can record the adjusted length of the cable protection structure during use and installation, and use the adjusted length as the resistor strip installation length for input by the host computer human-machine interface, so as to compare it with the calculated resistor strip length of the circuit during use to determine whether there is wear and locate the wear position.

[0032] (4) The cable protection structure of the present invention has a longitudinal opening on the side of the winding resistor strip, which naturally forms the two end crimping interfaces for inserting the lead wire, so that the wire can be inserted and crimped on the outer layer of the cable protection structure even if it is disconnected at any position.

[0033] (5) The cable protection structure of the present invention is simple. It only requires connecting the winding resistance strip to the existing control system and combining the software processing of the host computer of the control system to realize real-time detection and prompting. The processing is simple and easy to implement, and the cost is low.

[0034] (6) When wear is detected, the control system of the present invention controls the issuance of at least one of an alarm signal, a passivation signal or a braking signal according to the position and quantity of the worn winding resistor strip, so as to ensure the safety of the process system during operation and prevent personal injury accidents and process system damage accidents. Attached Figure Description

[0035] Figure 1 This is a structural block diagram of the signal cable wear detection system inside the electromechanical equipment enclosure according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the cable protection structure according to an embodiment of the present invention. Figure 1 ;

[0037] Figure 3 This is a schematic diagram of the cable protection structure according to an embodiment of the present invention. Figure 1 A sectional view;

[0038] Figure 4 This is a schematic diagram of the cable protection structure according to an embodiment of the present invention. Figure 2 ;

[0039] Figure 5 This is a schematic diagram showing the connection between the cable protection structure and the lead wire in an embodiment of the present invention;

[0040] Figure 6 This is a flowchart of a method for detecting wear of signal cables inside an electromechanical equipment enclosure according to an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0042] See Figures 1 to 5 As shown in the figure, this embodiment discloses a signal cable wear detection system inside an electromechanical equipment enclosure, including a host computer 10, a control system 20, and a cable protection structure 40. The cable protection structure 40 is wound around the outside of the signal cable 50 and, from the outside to the inside, includes a first outer shell layer 401, a second hollow layer 402, and a third insulation layer 403. A wound resistance strip 404 is disposed inside the second hollow layer 402. The wound resistance strip 404 has a longitudinal opening 4041 on its side, allowing for the insertion of a lead wire at any break point and pressing it into the outer layer of the cable protection structure. The wound resistance strip 404 is connected to a signal terminal of the control system from the first break point 405 via a first lead wire 80, and from the second break point 406 via a second lead wire 90 to the ground terminal of the control system to form a loop. A fixed resistor R is disposed on the loop. L ( Figure 1 R in L1 R L2 (etc.); The control system 20 collects the loop current value of the signal terminal, calculates the length of the resistor band connected to the loop based on the loop current value, compares the length of the resistor band with the installation length of the resistor band entered by the host computer 10, and issues a prompt and control signal when the difference between the two exceeds the threshold range; the prompt and control signal includes at least one of the following: alarm signal, passivation signal and braking signal.

[0043] The host computer 10 receives the cable protection structure installation length information (i.e. resistor strip installation length) entered by the human-machine interface, and establishes a wear detection software module using the configuration language of the control system 20. The wear detection software module is transmitted to the control system 20 via the host computer 10. The control system 20 collects the loop current value of the signal terminal for calculation, and issues alarm, passivation, braking and other signals when the calculation result exceeds the threshold change of the wear detection software module.

[0044] Specifically, the host computer 10 can be a computing device such as a computer, and the control system 20 can be a DCS system or a PLC system. The host computer 10 is a human-machine interface external device of the control system 20. The host computer 10 is equipped with a human-machine interface or can be connected to an external human-machine interface. This embodiment does not impose any restrictions on the specifics.

[0045] In this embodiment, the wound resistance strip 404 serves as the filler for the second hollow layer 402 of the cable protection structure, forming an integral structure with the first outer shell layer 401 and the third insulation layer 403. During use and installation, it can be cut off at any length as needed for the signal cable inside the electromechanical equipment enclosure 60.

[0046] See Figure 1 As shown, in this embodiment, the wound resistor strip 404 forms two end pressure interfaces for inserting lead wires through its side longitudinal opening 4041. Each wound resistor strip 404 is connected to a different signal terminal so as to perform independent testing.

[0047] from Figure 1 As can be seen, the signal cable 50 in this embodiment is installed inside the electromechanical equipment housing 60. The purpose of the signal cable 50 may be different, such as some being connected to control components and some being connected to signal feedback components. This embodiment does not limit the purpose of the signal cable 50.

[0048] Furthermore, the electromechanical equipment enclosure 60 is equipped with multiple mechanical transmission components 70. These components vibrate upon startup, causing the entire enclosure 60 and signal cable 50 to vibrate. During this continuous vibration, the cable protection structure 40 wrapped around the signal cable 50 rubs against the enclosure 60 or the mechanical transmission components 70, resulting in wear on the first outer shell 401 of the cable protection structure and wear on the winding resistance strip 404 within the second hollow layer 402. When the winding resistance strip 404 contacts the enclosure 60 or the mechanical transmission components 70, the circuit grounding point changes, causing a change in the corresponding resistance value, ultimately resulting in a change in the detected circuit current. Therefore, detecting this circuit current can determine whether wear has occurred.

[0049] Furthermore, by detecting the loop current, the resistance value and length of the wound resistor strip 404 connected to the loop can be deduced, thereby locating the wear position and facilitating maintenance personnel to quickly find the wear location. Since a large number of signal cables 50 are often arranged inside the electromechanical equipment enclosure 60, locating the wear position is crucial.

[0050] See Figures 2-5 As shown, in this embodiment, the wound resistance strip 404 disposed within a cable protection structure 40 comprises one strip. Wear in various directions can be detected using a single wound resistance strip 404.

[0051] Of course, in order to increase detection accuracy or prevent possible detection failures, two or more wound resistor strips 404 can be set according to the layout of the control components and feedback components. Each wound resistor strip 404 is connected to a different signal terminal 201 to realize detection and comparison respectively.

[0052] In this embodiment, the first outer shell layer 401 is a rigid plastic layer. The outer surface of the first outer shell layer 401 (in the same winding direction) is printed with a distance scale 4011, which is used to record the length of the cable protection structure 40 as the resistor strip installation length during installation, and to input the resistor strip installation length into the human-machine interface of the host computer 10 and locate the wear point according to the alarm signal during use.

[0053] The third insulation layer 403 is a soft plastic buffer layer, used to eliminate or reduce the impact and damage of external vibrations on the signal cable during use.

[0054] The cable protection structure 40 of the present invention is wrapped around the outside of the signal cable 50, so it will not damage the signal cable 50; and the cable protection structure 40 includes, from the outside to the inside, a first outer shell layer 401, a second hollow layer 402 and a third insulating layer 403. The winding resistance strip 404 is disposed inside the second hollow layer 402, and the winding resistance strip 404 is isolated from the signal cable 50 by the third insulating layer 403, so it will not cause signal interference.

[0055] See Figure 6 As shown, a method for detecting wear on signal cables inside an electromechanical equipment enclosure, based on the aforementioned signal cable wear detection system for electromechanical equipment enclosures, includes:

[0056] S601 calculates the total resistance of the circuit based on the circuit current and circuit voltage values;

[0057] S602, subtract the fixed resistance value from the total resistance value to obtain the resistance value of the wound resistance strip connected to the circuit;

[0058] S603, calculate the length of the resistance band of the access circuit based on the resistance value of the resistance band of the access circuit;

[0059] S604 compares the resistor strip length with the resistor strip installation length entered by the host computer and calculates the difference between the two.

[0060] S605, when the difference exceeds the threshold range, it is determined that wear has occurred, the wear location value is calculated, a prompt and control signal is issued and displayed on the host computer; the difference exceeding the threshold range means that the difference is less than the lower threshold or greater than the upper threshold.

[0061] It should be noted that the calculated difference is actually the real value of the deviation, and the deviation exceeding the threshold range means that the negative real value of the deviation is less than the lower limit of the threshold or the positive real value of the deviation is greater than the upper limit of the threshold.

[0062] In this embodiment, the length of the resistance band of the access loop is calculated based on the resistance value of the resistance band of the access loop, as follows:

[0063]

[0064] Among them, L c Indicates the length of the resistor band in the circuit; K represents the resistance length coefficient of the resistor band; U represents the circuit voltage, which is a fixed value; I c Indicates the loop current value; R L Indicates the resistance value of a fixed resistor; This indicates the resistance value of the resistor connected to the circuit.

[0065] In this embodiment, the calculation of the total resistance value of the loop based on the loop current value and the loop voltage value also includes the termination of real-time calculation. Specifically, after receiving the overall shutdown signal of the process system, the wear detection software module stops the real-time calculation and displays the loop current value, loop voltage value and the calculated total resistance value of the loop at the last calculation time on the host computer human-machine interface.

[0066] In this embodiment, it also includes error verification of the resistor strip installation length value entered by the host computer based on the actual measured current value of the circuit. When the actual measured current value of the circuit is I c With current verification value I s If the deviation exceeds the deviation threshold, an alarm will be triggered indicating an error in the input value of the output resistor band installation length.

[0067] Specifically as follows:

[0068]

[0069]

[0070]

[0071] Among them, I s This represents the current verification value, a theoretical value calculated based on the resistor strip installation length value entered by the host computer; I c Represents the measured current value of the circuit; U represents the circuit voltage, which is a fixed value; R L Indicates the resistance value of a fixed resistor; R P This represents the theoretical resistance value calculated based on the resistor strip installation length value entered by the host computer; C is the error limit coefficient. Used to determine the deviation threshold.

[0072] The methods for obtaining the lower and upper bounds of the threshold are as follows:

[0073] After the control system detects the overall start signal of the process system, it performs real-time cyclic detection and calculation on the current value of the loop, and transmits the real-time calculation results. The deviation is compared with the resistor strip installation length entered by the host computer, and the upper and lower bounds of the deviation are selected within the time interval from the overall start-up of the process system to the stable operating condition; among them, I t This represents the loop current monitored in real time during the time interval from startup to stable operating condition.

[0074] The upper bound of the deviation is used as the upper bound of the threshold, and the lower bound of the deviation is used as the lower bound of the threshold.

[0075] Specifically, after the control system detects the overall start signal of the process system, it activates the wear detection software module to perform real-time cyclic detection and calculation of the loop current value, and calculates the result. The deviation is compared with the installation length information entered by the host computer human-machine interface. During the time interval from the overall start-up of the process system to the stable operating condition (e.g., 18-24 hours), the detection software module filters out the upper and lower bounds of the deviation. The deviation comparison of the wear detection software module is terminated by the stable operating condition signal of the process system. The values ​​of the upper and lower bounds of the deviation are used as the upper and lower thresholds and substituted into the wear detection software module to start the signal cable wear detection. The upper and lower bounds of the deviation are triggered by the next overall start-up signal issued by the process system from the stopped state to update the deviation comparison.

[0076] The issuance of prompts and control signals specifically includes:

[0077] When the difference between the length of a resistor strip wound inside the same electromechanical equipment enclosure and the corresponding installation length of the resistor strip exceeds the threshold range, the control system is triggered to output an alarm signal and display it.

[0078] When the difference between the length of at least two wound resistor strips and their respective installation lengths exceeds the threshold range within the same electromechanical equipment enclosure, the control system is triggered to output an alarm signal and display it, as well as output a passivation control signal for the electromechanical equipment; the passivation control signal includes at least one of delaying, clipping, interrupting, and locking the equipment control command, and also includes issuing a safety set command to the electromechanical equipment to make it move to a working state that ensures the safety of the process system;

[0079] When the entire process system has two or more redundant electromechanical devices, and the difference between the length of the winding resistor strip on each electromechanical device and the corresponding installation length of the resistor strip exceeds the threshold range, the control system is triggered to output an alarm signal and display, output the passivation control signal of the electromechanical device, and output the emergency braking signal of the process system; the emergency braking signal of the process system is to issue an emergency braking safety command to the process system to make it move to a safe shutdown state.

[0080] Specifically, the control system issues alarm, passivation, or braking signals based on the detection results of the wear detection software module. Specifically, when the difference between the real-time cyclically calculated length of the resistor band and the installed length information in the module exceeds a threshold range, the control system is triggered to output an alarm signal and display it on the host computer. When there are cable protection structures for two or more signal cables within the same electromechanical equipment enclosure, and the difference between the real-time cyclically calculated length of the resistor band and the installed length information in the module for each cable simultaneously exceeds its respective threshold range, the control system is triggered to output an alarm signal and display it, as well as a passivation control signal for the electromechanical equipment, which is also displayed on the host computer. The passivation control signal includes, but is not limited to, delaying, clipping, interrupting, and blocking the equipment control commands, and also includes... The system can issue a safety setting command to activate the system to ensure the safety of the process system and process flow. When two or more critical process electromechanical devices with redundant functions in the entire process system have their respective real-time cyclic calculations of the difference between the resistor strip length and the installation length information in the module exceeding their respective threshold ranges, the system triggers the output of an alarm signal and displays it, as well as a passivation control signal for the electromechanical device and an emergency braking signal for the process system, which are also displayed on the host computer. The emergency braking signal for the process system is an emergency braking safety command issued to the process system to activate the system to a basic safety shutdown state to prevent personal injury accidents and process system damage accidents.

[0081] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. An electromechanical equipment enclosure internal signal cable wear detection system, characterized by, The cable protection structure is wound outside the signal cable and comprises a first shell layer, a second hollow layer and a third insulation layer from outside to inside, and a winding resistance band is arranged in the second hollow layer; a longitudinal opening is formed in the side edge of the winding resistance band, and the winding resistance band can be inserted into the lead wire at any position and connected by crimping the outer layer of the cable protection structure, so that the signal cable fixed wire does not need to be removed during the installation and adjustment process; The winding resistance band is connected to a signal terminal of the control system through a first lead wire from a first disconnected position, and is connected to a grounding terminal of the control system through a second lead wire from a second disconnected position to form a loop, and a fixed resistance is arranged on the loop; the control system collects the loop current value of the signal terminal, calculates the length of the resistance band connected to the loop based on the loop current value, compares the length of the resistance band with the installed length of the resistance band input by the host computer, and sends a prompt signal when the difference between the two exceeds a threshold range; the prompt and control signal includes at least one of an alarm signal, a passivation signal and a braking signal; wherein the winding resistance band has two end crimping interfaces formed by the longitudinal opening in the side edge for inserting the lead wire, and the signal terminals connected by each winding resistance band are different; The winding resistance band is used as the filler of the second hollow layer of the cable protection structure, and forms an integrated structure with the first shell layer and the third insulation layer.

2. The electromechanical equipment enclosure internal signal cable wear detection system of claim 1, wherein, A distance scale is arranged on the outer surface of the first shell layer to record the length of the cable protection structure as the installed length of the resistance band during the installation process, and the installed length of the resistance band is input by the host computer and located at the wear point according to the alarm signal during use.

3. The electromechanical equipment enclosure internal signal cable wear detection system of claim 1, wherein, The third insulation layer is a plastic buffer layer.

4. The electromechanical equipment enclosure internal signal cable wear detection system of claim 1, wherein, The control system includes a DCS system or a PLC system; and the host computer is a human-computer interface external device of the control system.

5. A method of detecting wear of a signal cable within an electromechanical equipment enclosure, the method comprising: The signal cable wear detection system in the electromechanical equipment box according to any one of claims 1-4; comprising: The total resistance value of the loop is calculated based on the loop current value and the loop voltage value; The resistance value of the winding resistance band connected to the loop is obtained by subtracting the fixed resistance value from the total resistance value; The length of the resistance band connected to the loop is calculated based on the resistance value of the resistance band connected to the loop; The difference between the length of the resistance band and the installed length of the resistance band input by the host computer is calculated; When the difference exceeds a threshold range, it is judged that wear occurs, a wear positioning value is calculated, a prompt and control signal is sent, and the signal is displayed on the host computer; the threshold range refers to the difference being less than the lower threshold or greater than the upper threshold.

6. The method of claim 5, wherein the step of detecting the wear of the signal cable is performed by a sensor. The length of the resistance band connected to the loop is calculated based on the resistance value of the resistance band connected to the loop, and the specific method is as follows: ； wherein, represents the resistance band length of the access circuit; represents the resistance band resistance length coefficient; represents the circuit voltage, which is a fixed value; represents the circuit current value; represents the fixed resistance value; represents the resistance value of the resistance band of the access circuit.

7. The method of claim 5, wherein the step of detecting the wear of the signal cable is performed by a sensor. The threshold lower limit and the threshold upper limit are obtained as follows: After the control system detects the overall start signal of the process system, the loop current value is detected and calculated in real time, and the real-time calculation result The deviation comparison is performed between the resistance belt installation length entered by the upper computer and the resistance belt installation length, and the upper deviation limit and the lower deviation limit are screened out in the time interval from the overall start of the process system to the stable working condition. The loop current monitored in real time in the time interval from the start to the stable working condition is represented. The upper limit of the deviation is taken as the threshold upper limit, and the lower limit of the deviation is taken as the threshold lower limit; Wherein, the deviation upper limit and the deviation lower limit are triggered by the deviation comparison update when the process system is restarted from the stop state.

8. The method of claim 7, wherein the step of detecting the wear of the signal cable is performed by a sensor. The prompt and control signal is sent, and the specific method includes: When the difference between the length of the resistance band wound around the resistance band and the corresponding installation length of the resistance band exceeds the threshold range in the same electromechanical equipment box, the control system outputs an alarm signal and displays; When the difference between the length of the resistance band wound around the resistance band and the corresponding installation length of the resistance band exceeds the threshold range in the same electromechanical equipment box, the control system outputs an alarm signal and displays, and outputs the passivation control signal of the electromechanical equipment; the passivation control signal includes at least one of the delay, clipping, interruption and locking of the equipment control instruction, and also includes the safety setting instruction sent to the electromechanical equipment to make it act to the working state that ensures the safety of the process system; When there are two or more functionally redundant electromechanical equipments in the entire process system, and the difference between the length of the resistance band wound around the resistance band and the corresponding installation length of the resistance band exceeds the threshold range on each electromechanical equipment, the control system outputs an alarm signal and displays, outputs the passivation control signal of the electromechanical equipment, and outputs the emergency braking signal of the process system; the emergency braking signal of the process system is the emergency braking safety instruction sent to the process system to make it act to the safe shutdown state.

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