Power cable joint internal temperature monitoring system based on iterative inversion

Abstract

The invention is applied to the technical field of power cables, and particularly discloses a power cable joint internal temperature monitoring system based on iterative inversion, which comprises a central processor, a data acquisition module, a data processing module, a data display module and a monitoring alarm module. According to the power cable joint internal temperature monitoring system based on iterative inversion, a fiber bragg grating temperature sensor is installed outside a cable to measure the external temperature of the cable, the situation that an insulating layer of the cable is damaged in the sensor implanting process is avoided, and the internal and external theoretical temperatures of the cable are deduced through a heat conduction formula; the theoretical temperature obtained through calculation is compared with sensor data, and parameters in a formula are calculated without continuous iteration, so that errors in the internal temperature derivation process are reduced, the influence of external interference on a calculation result in the operation process of the cable is reduced, and the monitoring efficiency of the cable temperature is improved.

Description

Technical Field

[0001] The invention relates to the technical field of power cables, and in particular to an iterative inversion-based internal temperature monitoring system for a power cable joint. Background Art

[0002] Power cable refers to a device used to transmit electrical energy. The cable can effectively transmit electrical energy from one place to another and is used in scenarios such as urban power grids, factory power supply, and internal power supply of buildings. The cable is an important part of the power grid, so the stability of the cable is directly related to the safe operation of the power grid. During the operation of the cable, the internal conductor of the cable will generate heat under the action of the current. The temperature can comprehensively reflect the cable's load current, environment, status and other parameters, thereby monitoring the cable status in real time and effectively reducing the failure rate and downtime.

[0003] Since the hot spot of the cable is hidden inside the insulation layer, which is a poor thermal conductor, implanting a sensor will damage the insulation layer. Therefore, the hot spot temperature of the cable is difficult to measure directly. Currently, the temperature inside the cable is measured indirectly by measuring the cable surface temperature. Due to the ever-changing environmental heat dissipation conditions and random load fluctuations, if fixed parameters are used, interference cannot be eliminated. The surface temperature measurement method cannot accurately reflect the internal temperature state of the cable joint, and thus cannot be used to guide the safe operation and maintenance of the cable. Summary of the invention

[0004] The purpose of the present invention is to provide a power cable joint internal temperature monitoring system based on iterative inversion to solve the problem in the above background technology that the external temperature of the cable cannot accurately reflect the internal temperature of the cable due to the influence of external interference on the temperature.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a system for monitoring the internal temperature of a power cable joint based on iterative inversion, comprising a central processor, a data acquisition module, a data processing module, a data display module and a monitoring and alarm module, wherein the central processor is the core part of the system, the central processor is connected to the data acquisition module, the data acquisition module collects the temperature of the cable joint surface, the central processor is connected to the data processing module, the data processing module processes and analyzes the collected temperature data, the central processor is connected to the data display module, the data display module visualizes the processed temperature data, the central processor is connected to the monitoring and alarm module, the monitoring and alarm module monitors and warns the cable joint temperature;

[0006] Preferably, the data acquisition module is provided with a fiber Bragg grating temperature sensor to collect temperature data of the cable surface, and a plurality of the fiber Bragg grating temperature sensors are provided, and the plurality of the fiber Bragg grating temperature sensors are equidistantly and parallelly distributed on the outer surface of the cable, and the distance between two adjacent fiber Bragg grating temperature sensors is marked as D, and the distance D between the fiber Bragg grating temperature sensors can be adjusted as needed.

[0007] By adopting the above technical solution, the fiber grating temperature sensor can be used to realize the collection process of cable surface temperature data.

[0008] Preferably, the data processing module adopts an iterative inversion algorithm to calculate the internal temperature of the cable using the external temperature of the cable collected by the data acquisition module. The iterative inversion algorithm includes a forward model building part, an inversion iterative calculation part and a forward parameter updating part.

[0009] By adopting the above technical solution, the calculation process of the internal temperature of the cable can be realized by using an iterative inversion algorithm.

[0010] Preferably, the forward model is constructed based on Fourier's law of heat conduction, that is, during the heat conduction process, the amount of heat conducted through a given cross section per unit time is proportional to the temperature change rate and the cross-sectional area in the direction perpendicular to the cross section. During the forward model construction process, the cable is equivalent to a cylindrical structure, and the cable uses a cylindrical coordinate system (r, θ, z) to represent the position of each point inside the cable, and a forward model of the internal temperature of the cable is constructed. The heat conduction formula is as follows: Wherein, ρ is the cable material density, c is the specific heat capacity, T is the temperature, t is the time, and q is the heat source intensity per unit volume;

[0011]

[0012] Substituting the above formula into the cylindrical coordinate system (r, θ, z), it can be transformed into:

[0013]

[0014] The theoretical temperature distribution data inside and outside the cable is calculated using the formula, and the calculated external theoretical temperature is compared with the temperature data collected by the fiber Bragg grating temperature sensor of the data acquisition module. The external theoretical temperature is marked as X, and the corresponding temperature collected by the fiber Bragg grating temperature sensor is marked as Y. The error between X and Y is marked as E, and E is calculated using the mean square error function. The calculation formula is as follows:

[0015]

[0016] The parameter values ​​in the forward model are adjusted and updated through the computer optimization algorithm, and the iterative formula of the parameters is generated by the gradient descent method.

[0017]

[0018] where μ n+1 is the parameter after iteration, μ is the parameter before iteration, α is the learning rate, is the gradient of the error function;

[0019] The minimum value of the error function is calculated using the iterative formula, so that the parameters of the forward model are continuously updated and iterated.

[0020] By adopting the above technical solution, the parameters of the forward model can be continuously updated using an iterative formula, thereby reducing the error value in the temperature calculation process.

[0021] Preferably, the data display module is provided with a display terminal, the data display module calls the cable internal temperature data calculated by the data processing module for visual display, and the data display module displays the cable internal temperature data in the display terminal in the form of a line graph showing the time trend change.

[0022] By adopting the above technical solution, the temperature inside the cable can be visualized using a display terminal, making it convenient for staff to monitor the operating status of the cable in real time.

[0023] Preferably, the monitoring and alarm module includes a monitoring interface and an alarm interface. The monitoring interface is connected to the display terminal of the data display module to display the temperature in the cable model in the form of a three-dimensional graph. The temperature display of the monitoring interface is differentiated by color, and the color gradually deepens according to the temperature gradient. The alarm interface includes an alarm and a prompt terminal. The alarm interface pre-sets a temperature threshold, and the alarm reference temperature is set to 0. The temperature is divided into alarm gradients from 0 to the temperature threshold. Every time the temperature in the cable reaches an alarm gradient, a text signal is sent to the prompt terminal. When the temperature in the cable exceeds the temperature threshold, the alarm sends a sound and light alarm signal.

[0024] By adopting the above technical solution, the cable temperature can be monitored by using the monitoring alarm module, and the high temperature room can give an alarm in time.

[0025] Compared with the prior art, the beneficial effects of the present invention are: the power cable joint internal temperature monitoring system based on iterative inversion:

[0026] 1. In the present invention, a fiber Bragg grating temperature sensor is installed on the outside of the cable to measure the external temperature of the cable, thereby avoiding damage to the insulation layer of the cable during the sensor implantation process. The internal and external theoretical temperatures of the cable are derived using a heat conduction formula, and the calculated theoretical temperature is compared with the sensor data. The various parameters in the calculation formula are not continuously iterated, thereby reducing the error in the internal temperature derivation process, reducing the influence of external interference on the calculation results during the operation of the cable, and improving the monitoring efficiency of the cable temperature;

[0027] 2. The present invention takes the central processor as the center and associates multiple modules, so that the calculated internal temperature of the cable can be visualized in various forms through the display terminal of the data display module, which is convenient for the staff to monitor the cable status in real time. The monitoring alarm module sets the temperature gradient and sends text signals to the prompt terminal in time for different gradient temperatures. When the temperature threshold is exceeded, the alarm will generate a sound signal to prompt the staff to check for hidden dangers in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the module structure of the present invention;

[0029] Figure 2 This is a schematic diagram of the sensor installation structure of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] See also Figure 1-Figure 2 The present invention provides a technical solution: an internal temperature monitoring system for a power cable joint based on iterative inversion.

[0032] The central processor is the central part of the system. The central processor is connected to a data acquisition module, which collects the temperature of the cable joint surface. The central processor is connected to a data processing module, which processes and analyzes the collected temperature data. The central processor is connected to a data display module, which visualizes the processed temperature data. The central processor is connected to a monitoring and alarm module, which monitors and warns the cable joint temperature. The data acquisition module is provided with a fiber Bragg grating temperature sensor to collect the temperature data of the cable surface. A plurality of fiber Bragg grating temperature sensors are provided, and the plurality of fiber Bragg grating temperature sensors are equidistantly and parallelly distributed on the outer surface of the cable. The distance between two adjacent fiber Bragg grating temperature sensors is marked as D, and the distance D between the fiber Bragg grating temperature sensors can be adjusted as needed.

[0033] like Figure 1 and Figure 2 As shown, the fiber Bragg grating temperature sensor in the data acquisition module is installed on the surface of the cable. The fiber Bragg grating temperature sensors are distributed in parallel on the surface of the cable at a distance D. The fiber Bragg grating temperature sensor is used to collect the external temperature data of the cable, and the collected external temperature data is input into the central processor. The central processor transmits the data to the data processing module, and the internal temperature of the cable is calculated using the external temperature of the cable, and the calculated temperature data is returned to the central processor. The central processor transmits the processed temperature data to the data display module for visual display. At the same time, the monitoring alarm module is used to monitor the internal temperature of the cable in real time, and timely alarm is issued to ensure the safety of the cable during operation.

[0034] The data processing module adopts an iterative inversion algorithm, and uses the external temperature of the cable collected by the data acquisition module to calculate the internal temperature of the cable. The iterative inversion algorithm includes a forward model construction part, an inversion iterative calculation part, and a forward parameter update part. The forward model is constructed based on Fourier's law of heat conduction, that is, during the heat conduction process, the amount of heat conducted through a given cross section per unit time is proportional to the temperature change rate and the cross-sectional area in the direction perpendicular to the cross section. During the forward model construction process, the cable is equivalent to a cylindrical structure, and the cable uses a cylindrical coordinate system (r, θ, z) to represent the position of each point inside the cable. The forward model of the internal temperature of the cable is constructed. The heat conduction formula is as follows: Wherein, ρ is the cable material density, c is the specific heat capacity, T is the temperature, t is the time, and q is the heat source intensity per unit volume;

[0035]

[0036] Substituting the above formula into the cylindrical coordinate system (r, θ, z), it can be transformed into:

[0037]

[0038] The theoretical temperature distribution data inside and outside the cable is calculated using the formula, and the calculated external theoretical temperature is compared with the temperature data collected by the fiber Bragg grating temperature sensor of the data acquisition module. The external theoretical temperature is marked as X, and the corresponding temperature collected by the fiber Bragg grating temperature sensor is marked as Y. The error between X and Y is marked as E, and E is calculated using the mean square error function. The calculation formula is as follows:

[0039]

[0040] The parameter values ​​in the forward model are adjusted and updated through the computer optimization algorithm, and the iterative formula of the parameters is generated by the gradient descent method.

[0041]

[0042] where μ n+1 is the parameter after iteration, μ is the parameter before iteration, α is the learning rate, is the gradient of the error function; the minimum value of the error function is calculated using the iterative formula, so as to continuously update and iterate the parameters of the forward model;

[0043] like Figure 1 As shown, the central processor inputs the cable external temperature collected in the data acquisition module into the data processing module. The forward model is constructed in the data processing module using Fourier's heat conduction law. The forward model can be used to calculate the theoretical temperature inside and outside the cable. The calculated external theoretical temperature is marked as X. The calculated X is compared with the data Y collected in the data acquisition module to calculate the error E between X and Y. The process is calculated using the mean square error function, and the error E is used to implement parameter iteration in the forward model. By calculating the gradient of the mean square error function to the model parameters, the parameters can be quickly updated, so that the model can be optimized in the direction of reducing the error, reducing the impact of external interference on the cable internal temperature calculation process.

[0044] The data display module sets a display terminal. The data display module calls the cable internal temperature data calculated by the data processing module for visual display. The data display module displays the cable internal temperature data in the form of a line graph showing the time trend change on the display terminal. The monitoring and alarm module includes a monitoring interface and an alarm interface. The monitoring interface is connected to the display terminal of the data display module, and the temperature is displayed in the cable model in the form of a three-dimensional graph. The temperature display of the monitoring interface is distinguished by color, and the color gradually deepens according to the temperature gradient. The alarm interface includes an alarm and a prompt terminal. The alarm interface pre-sets a temperature threshold, and the alarm base temperature is set to 0. The temperature is divided into an alarm gradient from 0 to the temperature threshold. Every time the temperature in the cable reaches an alarm gradient, a text signal is sent to the prompt terminal. When the temperature in the cable exceeds the temperature threshold, the alarm sends a sound and light alarm signal.

[0045] like Figure 1 As shown, the internal temperature of the cable calculated in the data processing module is input into the data display module, and is displayed in the display terminal in the form of a line graph showing the time trend change, so that the staff can observe the temperature change trend of the cable. The monitoring interface in the monitoring and alarm module distinguishes the temperature in the cable by color according to the temperature gradient, and displays it in the three-dimensional diagram of the cable in the form of gradually deepening the color of the temperature gradient, so that the staff can monitor the cable status intuitively. The alarm interface in the monitoring and alarm module pre-sets the temperature threshold and divides the alarm gradient from 0 to the temperature threshold. Every time the temperature reaches an alarm gradient, a text signal is sent to the prompt terminal, so that the staff can observe in real time. When the temperature exceeds the temperature threshold, the alarm sends a sound and light alarm signal to remind the staff to quickly conduct the cable troubleshooting process.

[0046] Working principle: The fiber Bragg grating temperature sensor is installed on the surface of the cable and distributed in parallel on the cable surface at an interval D. The external temperature data of the cable is collected and input into the data processing module for processing. A forward model is constructed in the data processing module. The theoretical temperature inside and outside the cable can be calculated by using the forward model. The error E is obtained by comparing the calculated external theoretical temperature with the data collected in the data acquisition module. The error E is used to update and iterate the parameters of the forward model, so that the model can be optimized in the direction of reducing the error and reducing the influence of external interference on the calculation process of the internal temperature of the cable. The temperature calculated in the data processing module is transmitted to the data display module and visualized in different modes on the display terminal. The line graph of time trend change is convenient for the staff to observe the temperature change trend of the cable. The different color models of the three-dimensional graph of the cable enable the staff to intuitively monitor the temperature status of various parts of the cable. When the temperature inside the cable exceeds the threshold, the alarm sends an alarm signal to remind the staff to quickly check the cable status.

[0047] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A power cable joint internal temperature monitoring system based on iterative inversion, comprising a central processor, a data acquisition module, a data processing module, a data display module and a monitoring alarm module, characterized in that: The central processor is the core part of the system. The central processor is connected to a data acquisition module, which collects the temperature of the cable joint surface. The central processor is connected to a data processing module, which processes and analyzes the collected temperature data. The central processor is connected to a data display module, which visualizes the processed temperature data. The central processor is connected to a monitoring and alarm module, which monitors and warns the cable joint temperature.

2. The power cable joint internal temperature monitoring system based on iterative inversion according to claim 1 is characterized in that: The data acquisition module is provided with a fiber Bragg grating temperature sensor to collect temperature data of the cable surface. A plurality of fiber Bragg grating temperature sensors are provided, and the plurality of fiber Bragg grating temperature sensors are equidistantly and parallelly distributed on the outer surface of the cable. The distance between two adjacent fiber Bragg grating temperature sensors is marked as D, and the distance D between the fiber Bragg grating temperature sensors can be adjusted as needed.

3. The power cable joint internal temperature monitoring system based on iterative inversion according to claim 1 is characterized in that: The data processing module adopts an iterative inversion algorithm to calculate the internal temperature of the cable using the external temperature of the cable collected by the data acquisition module. The iterative inversion algorithm includes a forward model building part, an inversion iterative calculation part and a forward parameter updating part.

4. The power cable joint internal temperature monitoring system based on iterative inversion according to claim 3 is characterized in that: The forward model is constructed based on Fourier's law of heat conduction, that is, in the process of heat conduction, the amount of heat conducted through a given cross section per unit time is proportional to the temperature change rate and the cross-sectional area in the direction perpendicular to the cross section. In the process of constructing the forward model, the cable is equivalent to a cylindrical structure. The cable uses a cylindrical coordinate system (r, θ, z) to represent the position of each point inside, and a forward model of the internal temperature of the cable is constructed. The heat conduction formula is as follows: Wherein, ρ is the cable material density, c is the specific heat capacity, T is the temperature, t is the time, and q is the heat source intensity per unit volume; Substituting the above formula into the cylindrical coordinate system (r, θ, z), it can be transformed into: The theoretical temperature distribution data inside and outside the cable is calculated using the formula, and the calculated external theoretical temperature is compared with the temperature data collected by the fiber Bragg grating temperature sensor of the data acquisition module. The external theoretical temperature is marked as X, and the corresponding temperature collected by the fiber Bragg grating temperature sensor is marked as Y. The error between X and Y is marked as E, and E is calculated using the mean square error function. The calculation formula is as follows: The parameter values ​​in the forward model are adjusted and updated through the computer optimization algorithm, and the iterative formula of the parameters is generated by the gradient descent method. where μ n+1 is the parameter after iteration, μ is the parameter before iteration, α is the learning rate, is the gradient of the error function; The minimum value of the error function is calculated using the iterative formula, so that the parameters of the forward model are continuously updated and iterated.

5. The power cable joint internal temperature monitoring system based on iterative inversion according to claim 1, characterized in that: The data display module sets a display terminal, and the data display module calls the cable internal temperature data calculated by the data processing module for visual display. The data display module displays the cable internal temperature data in the display terminal in the form of a line graph according to the time trend change.

6. The power cable joint internal temperature monitoring system based on iterative inversion according to claim 1, characterized in that: The monitoring and alarm module includes a monitoring interface and an alarm interface. The monitoring interface is connected to the display terminal of the data display module to display the temperature in the cable model in the form of a three-dimensional graph. The temperature display of the monitoring interface is distinguished by color, and the color gradually deepens according to the temperature gradient. The alarm interface includes an alarm and a prompt terminal. The alarm interface pre-sets a temperature threshold. The base temperature of the alarm is set to 0. The temperature is divided into alarm gradients from 0 to the temperature threshold. Every time the temperature in the cable reaches an alarm gradient, a text signal is sent to the prompt terminal. When the temperature in the cable exceeds the temperature threshold, the alarm sends a sound and light alarm signal.

Images