A cable conductor temperature monitoring method and system based on distributed optical fiber temperature measurement

Abstract

This invention discloses a method and system for monitoring cable conductor temperature based on distributed optical fiber temperature measurement. The method includes: laying a temperature-measuring optical fiber on the outer surface of the cable insulation layer and connecting it to a distributed optical fiber temperature measurement host; the host emitting laser pulses, demodulating the intensity ratio of the backscattered light to the Stokes light, obtaining the temperature distribution data of the insulation outer surface, and transmitting it to a data processing unit; and a current acquisition unit acquiring and uploading the real-time load current of the cable. The unit calls upon the cable's structural parameters, calculates the thermal resistance of the insulation layer and the conductor power loss, and calculates the insulation temperature difference and conductor temperature based on the outer surface temperature. After comparing these results with a preset threshold, the monitoring results and alarm signals are output. This invention simplifies the conductor temperature calculation process, reduces computational complexity, and improves the real-time performance and accuracy of cable conductor temperature monitoring. As a method and system for monitoring cable conductor temperature based on distributed optical fiber temperature measurement, this invention can be widely applied in the field of temperature monitoring technology.

Description

Technical Field

[0001] This invention relates to the field of temperature monitoring technology, and in particular to a method and system for monitoring the temperature of cable conductors based on distributed optical fiber temperature measurement. Background Technology

[0002] Power cables are a crucial component of power systems, and their operating temperature directly affects their current-carrying capacity and service life. Cable conductor temperature is a key parameter reflecting the cable's operating status; excessively high conductor temperatures accelerate insulation aging and can even lead to cable failures. Therefore, real-time and accurate monitoring of cable conductor temperature is of paramount importance for ensuring the safe operation of power systems.

[0003] Distributed temperature sensing (DTS) technology, based on the principle of fiber Raman scattering, enables continuous temperature measurement along the entire length of the fiber. It offers advantages such as long measurement distance, dense measurement points, and resistance to electromagnetic interference, and has been widely applied in cable temperature monitoring. However, because the cable conductor is located inside the cable, the temperature-sensing fiber is typically laid on the surface of the cable's outer sheath or insulation layer. This makes it impossible to directly measure the conductor temperature; instead, the conductor temperature must be inferred from the measured surface temperature.

[0004] Currently, related technologies include methods for calculating cable conductor temperature based on distributed optical fiber temperature measurement. For example, one algorithm for calculating the current-carrying capacity of a single-core cable based on distributed optical fiber sensing technology establishes a mathematical model for calculating the core temperature of a single-core cable. By calculating parameters such as the thermal resistance of each layer of the cable and the environment, and the loss of each layer of the cable, combined with the temperature of the cable's outer sheath measured by sensors, the cable conductor temperature is calculated in reverse, and then the cable current-carrying capacity is calculated. Another example is a method for measuring reference data of power cable optical fiber temperature measurement using a real-world and digital model. This method builds a real-world model of cable load temperature measurement, records the change curve of the optical fiber sensing temperature on the cable's outer surface over time, and after digital modeling, inputs the actual load current and optical fiber sensing temperature into the digital model to obtain the cable conductor temperature under the corresponding real-world operating conditions. Yet another example is a cable electrical fault analysis method based on distributed optical fiber temperature measurement. This method establishes a transient thermal circuit model of the cable according to the IEC 60287 standard, combines the fault current obtained from electromagnetic transient simulation, calculates the transient temperature of the cable during a fault, and establishes a thermodynamic finite element model of the cable and the temperature-sensing optical fiber for temperature field simulation. Alternatively, a cable conductor temperature estimation method based on a distributed optical fiber online temperature measurement system can be used. This method constructs a model data sequence, uses an LSTM deep learning model, and inputs load current data, ambient temperature data, and cable sheath temperature data into the model to estimate the cable conductor temperature.

[0005] However, the related technologies have the following technical problems, such as:

[0006] 1) The location of the temperature-measuring fiber optic cable is unreasonable. In related technologies, the temperature-measuring fiber optic cable is usually laid on the surface of the outer sheath of the cable. Since there are also structures such as metal shielding layer and armor layer between the outer sheath and the insulation layer, the heat conduction path is long, resulting in a large temperature difference between the measured outer sheath temperature and the conductor temperature. It is necessary to establish a complex multi-layer thermal circuit model to accurately calculate the conductor temperature, which increases the calculation complexity and error.

[0007] 2) The computational model is highly complex. The relevant technologies require accurate acquisition of the physical parameters (such as thermal resistivity, loss coefficient, etc.) of each layer of the cable (conductor layer, insulation layer, metal shielding layer, outer sheath, etc.) as well as environmental parameters (such as soil thermal resistivity, ambient temperature, etc.). These parameters are often difficult to obtain accurately in practical applications, and there are significant differences between different cable models and laying environments, resulting in insufficient universality and accuracy of the computational model.

[0008] 3) Insufficient real-time performance: The relevant technologies need to be tested through real-world models or trained with a large amount of historical data to provide accurate conductor temperature calculations quickly in the early stages of cable installation or when parameters change, which limits the effectiveness of real-time monitoring and early warning.

[0009] 4) It relies on complex numerical simulations. The related technologies depend on complex numerical calculations such as electromagnetic transient simulation and finite element thermal analysis. The calculation time is long and it is difficult to meet the needs of real-time online monitoring. Summary of the Invention

[0010] To address the aforementioned technical problems, the present invention aims to provide a method and system for monitoring cable conductor temperature based on distributed optical fiber temperature measurement, which can simplify the conductor temperature calculation process, reduce computational complexity, and improve the real-time performance and accuracy of cable conductor temperature monitoring.

[0011] The first technical solution adopted in this invention is: a cable conductor temperature monitoring method based on distributed optical fiber temperature measurement, applied to a cable conductor temperature monitoring system. The cable conductor temperature monitoring system includes a distributed optical fiber temperature measurement host, a temperature measuring optical fiber, a current acquisition unit, a data processing unit, and an alarm output unit. The method includes:

[0012] The temperature-sensing optical fiber is laid along the length of the cable on the outer surface of the cable insulation layer, and the temperature-sensing optical fiber is connected to the distributed optical fiber temperature measurement host, so that the temperature-sensing optical fiber senses the temperature of the outer surface of the insulation layer and transmits the temperature-corresponding optical signal to the distributed optical fiber temperature measurement host.

[0013] The distributed optical fiber temperature measurement host emits laser pulses to the temperature measurement optical fiber and receives the backscattered light signal generated by the temperature measurement optical fiber. It demodulates the backscattered light signal according to the intensity ratio of the anti-Stokes light and the Stokes light to obtain the temperature distribution data of the outer surface of the insulation layer along the length of the temperature measurement optical fiber, and outputs the temperature distribution data of the outer surface of the insulation layer to the data processing unit.

[0014] The current acquisition unit acquires the real-time load current data of the cable and outputs the real-time load current data to the data processing unit. The data processing unit receives the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, and calls the preset cable structure parameters. The cable structure parameters include at least the inner diameter of the insulation layer, the outer diameter of the insulation layer, the thermal resistivity of the insulation material, and the resistance per unit length of the conductor.

[0015] The data processing unit calculates the thermal resistance of the insulation layer based on the inner diameter, outer diameter, and thermal resistivity of the insulation material; calculates the conductor resistance loss power based on the real-time load current data and the conductor resistance per unit length; and calculates the insulation layer temperature difference and conductor temperature at corresponding locations based on the insulation layer thermal resistance, conductor resistance loss power, and temperature distribution data on the outer surface of the insulation layer. The unit compares the conductor temperature with a preset temperature threshold and outputs the conductor temperature monitoring result and corresponding alarm signal based on the comparison result.

[0016] Furthermore, the method of laying the temperature-measuring optical fiber along the length of the cable on the outer surface of the cable insulation layer further includes:

[0017] During the cable manufacturing process, single-mode or multi-mode optical fibers are simultaneously twisted with the cable insulation core, so that the temperature-sensing optical fiber is continuously laid along the length of the cable and in close contact with the outer surface of the insulation layer.

[0018] After the temperature-sensing optical fiber and the insulating core are twisted together synchronously, a wrapping tape is wrapped around the outside of the temperature-sensing optical fiber and the insulating core to fix the relative position of the temperature-sensing optical fiber and the insulating core.

[0019] In a three-core cable, a temperature-measuring optical fiber is installed on the outer surface of the insulation layer corresponding to each phase conductor. After the cable is bundled together, the temperature-measuring optical fibers of each phase are gathered together at both ends of the cable. After the cable ends are connected to the distributed optical fiber temperature measurement host by optical fiber fusion splicing to form a continuous optical fiber, the distributed optical fiber temperature measurement host can obtain the temperature distribution data of the outer surface of the insulation layer along each phase of the cable.

[0020] Furthermore, the data processing unit calculates the thermal resistance of the insulating layer based on the inner diameter of the insulating layer, the outer diameter of the insulating layer, and the thermal resistivity of the insulating material. The method further includes:

[0021] The radial thermal resistance per unit length of the insulating layer is determined based on the inner diameter of the insulating layer, the outer diameter of the insulating layer, and the thermal resistivity of the insulating material, and the radial thermal resistance is used as the thermal resistance of the insulating layer.

[0022] The conductor resistance loss power is calculated based on the real-time load current data and the conductor resistance per unit length. The conductor resistance loss power is related to the square of the real-time load current data and the conductor resistance per unit length.

[0023] The temperature difference of the insulation layer is calculated based on the conductor resistance loss power and the insulation layer thermal resistance, and the temperature of the outer surface of the insulation layer is superimposed with the temperature difference of the insulation layer to obtain the conductor temperature at the corresponding position;

[0024] The inner diameter of the insulation layer, the outer diameter of the insulation layer, the thermal resistivity of the insulation material, and the resistance per unit length of the conductor are stored in the data processing unit as pre-set structural and electrical parameters when the cable leaves the factory. After receiving the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, the corresponding parameters are called to calculate the conductor temperature.

[0025] Furthermore, the temperature distribution data of the outer surface of the insulation layer output by the distributed optical fiber temperature measurement host and the real-time load current data output by the current acquisition unit are synchronously input into the data processing unit. The data processing unit performs positional mapping of the temperature distribution data of the outer surface of the insulation layer according to the cable position, and calculates the conductor temperature at each position according to the real-time load current data at the corresponding position. The current acquisition unit acquires the real-time load current data through a current transformer, Rogowski coil or cable monitoring system, and converts the real-time load current data into a digital signal before outputting it to the data processing unit.

[0026] Furthermore, after obtaining the conductor temperature, the data processing unit outputs the conductor temperature to the host computer monitoring platform and generates a temperature relationship curve between the conductor temperature and the outer surface temperature of the insulation layer based on the conductor temperature. The method further includes:

[0027] When the temperature of the conductor at any location exceeds a preset temperature threshold, the data processing unit outputs an alarm control signal to the alarm output unit. The alarm output unit outputs alarm information according to the alarm control signal via audible and visual alarm, SMS alarm, or network communication, and transmits the alarm information to the host computer monitoring platform.

[0028] The host computer monitoring platform displays the calculated results of the outer surface temperature of the insulation layer, the real-time load current, the resistance per unit length of the conductor, the thermal resistance of the insulation layer, and the temperature of the conductor, and marks the corresponding data points of the outer surface temperature of the insulation layer and the conductor temperature on the temperature relationship curve.

[0029] The second technical solution adopted in this invention is: a cable conductor temperature monitoring system based on distributed optical fiber temperature measurement, comprising a distributed optical fiber temperature measurement host, a temperature measuring optical fiber, a current acquisition unit, a data processing unit, and an alarm output unit, wherein:

[0030] The temperature-sensing optical fiber is laid along the length of the cable on the outer surface of the cable's insulation layer and connected to the distributed optical fiber temperature measurement host. It is used to sense the temperature of the outer surface of the insulation layer and transmit the corresponding optical signal to the distributed optical fiber temperature measurement host.

[0031] The distributed optical fiber temperature measurement host is used to emit laser pulses into the temperature measurement optical fiber and receive the backscattered light signal generated by the temperature measurement optical fiber. Based on the intensity ratio of the anti-Stokes light and the Stokes light in the backscattered light signal, it demodulates the temperature distribution data of the outer surface of the insulation layer along the length of the temperature measurement optical fiber and outputs the temperature distribution data of the outer surface of the insulation layer to the data processing unit.

[0032] The current acquisition unit is used to acquire the real-time load current data of the cable and output the real-time load current data to the data processing unit.

[0033] The data processing unit is connected to the distributed optical fiber temperature measurement host and the current acquisition unit, respectively, and is used to receive the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, call the preset cable structure parameters, calculate the thermal resistance of the insulation layer according to the cable structure parameters, calculate the conductor resistance loss power according to the real-time load current data and the conductor unit length resistance, and calculate the conductor temperature according to the thermal resistance of the insulation layer, the conductor resistance loss power and the temperature distribution data of the outer surface of the insulation layer.

[0034] The alarm output unit is connected to the data processing unit and is used to receive the alarm control signal output by the data processing unit based on the comparison result of the conductor temperature and the preset temperature threshold, and to output alarm information based on the alarm control signal.

[0035] Furthermore, the temperature-sensing optical fiber is a single-mode or multi-mode optical fiber. During the cable manufacturing process, the temperature-sensing optical fiber is twisted synchronously with the insulating core and fixed to the outside of the insulating core with a wrapping tape, so that the temperature-sensing optical fiber is in close contact with the outer surface of the insulation layer throughout the entire process. When the cable is a three-core cable, one temperature-sensing optical fiber is respectively set on the outer surface of the insulation layer corresponding to each phase conductor. After the cable is bundled, the three temperature-sensing optical fibers are uniformly gathered at both ends of the cable and connected in series through optical fiber fusion splicing to form a continuous optical fiber. The continuous optical fiber is connected to the distributed optical fiber temperature measurement host through optical fiber patch cords.

[0036] Furthermore, the data processing unit stores cable structure parameters corresponding to the cable. These parameters include conductor type, conductor material, conductor cross-sectional area, conductor outer diameter, insulation material, insulation layer inner diameter, insulation layer outer diameter, insulation layer single-sided thickness, insulation material thermal resistivity, and conductor unit length resistance. The data processing unit calculates the insulation layer thermal resistance based on the insulation layer inner diameter, insulation layer outer diameter, and insulation material thermal resistivity; calculates the conductor resistance loss power based on the real-time load current data and conductor unit length resistance; calculates the insulation layer temperature difference based on the insulation layer thermal resistance and conductor resistance loss power; and calculates the conductor temperature based on the insulation layer outer surface temperature and insulation layer temperature difference.

[0037] The cable structure parameters are provided with the cable at the factory and are pre-stored in the data processing unit for conductor temperature calculation.

[0038] Furthermore, the current acquisition unit is located at the cable outlet end and acquires the real-time load current of the cable through a current transformer or Rogowski coil. The real-time load current is then converted into a digital signal and transmitted to the data processing unit, wherein:

[0039] The distributed fiber optic temperature measurement host transmits the temperature distribution data of the outer surface of the insulation layer to the data processing unit through a digital communication line. The data processing unit simultaneously receives the temperature distribution data of the outer surface of the insulation layer and the real-time load current, and outputs the calculated conductor temperature to the host computer monitoring platform.

[0040] Furthermore, the alarm output unit includes at least one of an audible and visual alarm, an SMS alarm module, and a host computer communication interface, wherein:

[0041] When the conductor temperature at any location exceeds a preset alarm threshold, the data processing unit outputs an alarm control signal to the alarm output unit. The alarm output unit then drives an on-site audible and visual alarm, sends an SMS alarm message to maintenance personnel, or uploads an alarm message to the host computer monitoring platform via a communication network, based on the alarm control signal.

[0042] The host computer monitoring platform is equipped with a parameter input area, a calculation result display area, and a temperature relationship curve display area. The parameter input area is used to input conductor type, conductor material, conductor cross-sectional area, conductor outer diameter, insulation material, single-sided thickness of insulation layer, outer surface temperature of insulation layer, and operating current. The calculation result display area is used to display the conductor resistance per unit length, insulation layer thermal resistance, and conductor temperature. The temperature relationship curve display area is used to display the correspondence between the outer surface temperature of insulation layer and conductor temperature.

[0043] The beneficial effects of the method and system of this invention are as follows: This invention deploys temperature-sensing optical fibers close to the outer surface of the cable insulation layer throughout the entire cable route. A distributed optical fiber temperature monitoring host acquires temperature distribution data of the outer surface of the cable insulation layer along the route. Combined with real-time load current and preset cable structure parameters, the conductor resistance loss power, insulation layer temperature difference, and conductor temperature are calculated based on the insulation layer thermal resistance model, thereby achieving continuous and real-time monitoring of the cable conductor temperature. Simultaneously, by monitoring the temperature of each phase conductor of the three-core cable separately, it can promptly identify local overheating caused by single-phase overload and three-phase load imbalance, and issue alarms via sound and light, SMS, or host computer communication when the conductor temperature exceeds a preset threshold. Since the temperature-sensing optical fibers are deployed on the outer surface of the insulation layer rather than the outer sheath of the cable, the influence of multiple layers such as armor and shielding on heat conduction can be avoided. Temperature conversion only needs to be performed based on the insulation layer thermal resistance. While ensuring continuous temperature monitoring along the route, this simplifies the conductor temperature calculation process, reduces computational complexity, and improves the real-time performance and accuracy of cable conductor temperature monitoring. Attached Figure Description

[0044] Figure 1 This is a flowchart of the steps of a cable conductor temperature monitoring method based on distributed optical fiber temperature measurement according to the present invention.

[0045] Figure 2 This is a structural block diagram of a cable conductor temperature monitoring system based on distributed optical fiber temperature measurement according to the present invention.

[0046] Figure 3 This is a schematic diagram of the connection between the cable manufacturing plant and the on-site complete equipment production provided in a specific embodiment of the present invention;

[0047] Figure 4 This is a schematic diagram of the cable structure cross-section provided in a specific embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of the interface for calculating the temperature of a cable conductor provided in a specific embodiment of the present invention. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0050] Reference Figure 1 This invention provides a method for monitoring cable conductor temperature based on distributed optical fiber temperature measurement, applied to a cable conductor temperature monitoring system. The cable conductor temperature monitoring system includes a distributed optical fiber temperature measurement host, a temperature measuring optical fiber, a current acquisition unit, a data processing unit, and an alarm output unit. The method includes:

[0051] The temperature-sensing optical fiber is laid along the length of the cable on the outer surface of the cable insulation layer and connected to the distributed optical fiber temperature measurement host so that the temperature-sensing optical fiber can sense the temperature of the outer surface of the insulation layer and transmit the corresponding optical signal to the distributed optical fiber temperature measurement host.

[0052] In this process, temperature-sensing optical fibers are laid along the length of the cable on the outer surface of the cable insulation layer. During cable manufacturing, single-mode or multi-mode optical fibers are simultaneously twisted with the cable insulation core, ensuring the continuous laying of the temperature-sensing optical fibers along the cable length and close contact with the outer surface of the insulation layer. After the temperature-sensing optical fibers and insulation core are simultaneously twisted, wrapping tape is wrapped around the outside of the temperature-sensing optical fibers and insulation core to fix their relative positions. In a three-core cable, a temperature-sensing optical fiber is installed on the outer surface of the insulation layer corresponding to each phase conductor. After the cable is bundled, the temperature-sensing optical fibers of each phase are gathered together at both ends of the cable. At the cable terminal, the optical fibers are fused together to form a continuous optical fiber, which is then connected to a distributed optical fiber temperature measurement host to obtain the temperature distribution data of the outer surface of the insulation layer along each phase of the cable.

[0053] The distributed fiber optic temperature measurement host emits laser pulses into the temperature measurement fiber and receives the backscattered light signal generated by the temperature measurement fiber. Based on the intensity ratio of the anti-Stokes light and the Stokes light in the backscattered light signal, it demodulates the temperature distribution data of the outer surface of the insulation layer along the length of the temperature measurement fiber and outputs the temperature distribution data of the outer surface of the insulation layer to the data processing unit.

[0054] The distributed fiber optic temperature measurement host outputs the insulation layer outer surface temperature distribution data and the current acquisition unit outputs the real-time load current data, which are synchronously input into the data processing unit. The data processing unit matches the insulation layer outer surface temperature distribution data with the cable location and calculates the conductor temperature at each location according to the real-time load current data at the corresponding location. The current acquisition unit obtains the real-time load current data through a current transformer, Rogowski coil, or cable monitoring system, converts the real-time load current data into a digital signal, and outputs it to the data processing unit.

[0055] The current acquisition unit acquires the real-time load current data of the cable and outputs the real-time load current data to the data processing unit. The data processing unit receives the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, and calls the preset cable structure parameters. The cable structure parameters include at least the inner diameter of the insulation layer, the outer diameter of the insulation layer, the thermal resistivity of the insulation material, and the resistance per unit length of the conductor.

[0056] The data processing unit calculates the thermal resistance of the insulation layer based on the inner diameter, outer diameter, and thermal resistivity of the insulation material. It calculates the conductor resistance loss power based on real-time load current data and conductor resistance per unit length. It also calculates the insulation layer temperature difference and conductor temperature at the corresponding location based on the insulation layer thermal resistance, conductor resistance loss power, and insulation layer outer surface temperature distribution data. The unit compares the conductor temperature with a preset temperature threshold and outputs the conductor temperature monitoring result and corresponding alarm signal based on the comparison result.

[0057] The data processing unit calculates the thermal resistance of the insulation layer based on its inner diameter, outer diameter, and thermal resistivity. It also determines the radial thermal resistance per unit length of the insulation layer, using this radial resistance as the overall insulation layer thermal resistance. Furthermore, it calculates the conductor resistance loss power based on real-time load current data and the conductor's resistance per unit length. This conductor resistance loss power is related to the square of the real-time load current data and the conductor's resistance per unit length. Finally, it calculates the insulation layer temperature difference based on the conductor resistance loss power and the insulation layer thermal resistance, and then superimposes the insulation layer's outer surface temperature with this temperature difference to obtain the conductor temperature at the corresponding location. The insulation layer's inner diameter, outer diameter, thermal resistivity, and conductor resistance per unit length are stored in the data processing unit as pre-set structural and electrical parameters when the cable leaves the factory. Upon receiving the insulation layer's outer surface temperature distribution data and real-time load current data, the unit retrieves the corresponding parameters to calculate the conductor temperature.

[0058] Furthermore, after obtaining the conductor temperature, the data processing unit outputs the conductor temperature to the host computer monitoring platform and generates a temperature relationship curve between the conductor temperature and the outer surface temperature of the insulation layer. When the conductor temperature at any location exceeds the preset temperature threshold, the data processing unit outputs an alarm control signal to the alarm output unit. The alarm output unit outputs alarm information through audible and visual alarm, SMS alarm, or network communication based on the alarm control signal and transmits the alarm information to the host computer monitoring platform. The host computer monitoring platform displays the calculated results of the outer surface temperature of the insulation layer, real-time load current, conductor unit length resistance, insulation layer thermal resistance, and conductor temperature, and marks the corresponding data points of the outer surface temperature of the insulation layer and conductor temperature on the temperature relationship curve.

[0059] In summary, the method steps of this embodiment of the invention include:

[0060] 1) Lay the temperature-measuring optical fiber close to the outer surface of the cable insulation layer and connect it to the distributed optical fiber temperature measurement host;

[0061] 2) The distributed fiber optic temperature measurement host measures the temperature distribution along the temperature measurement fiber in real time to obtain the outer surface temperature of the cable insulation layer;

[0062] 3) The current acquisition unit collects the cable load current in real time;

[0063] 4) The data processing unit calculates the insulation thermal resistance and conductor resistance power loss based on the cable structure parameters (insulation inner diameter, outer diameter, thermal resistivity, conductor resistance);

[0064] 5) The data processing unit calculates the temperature difference of the insulation layer and the temperature of the conductor;

[0065] 6) Compare the calculated conductor temperature with the preset threshold. If the temperature exceeds the threshold, an alarm signal is issued through the alarm output unit.

[0066] Reference Figure 2 A cable conductor temperature monitoring system based on distributed optical fiber temperature measurement includes a distributed optical fiber temperature measurement host, a temperature measuring optical fiber, a current acquisition unit, a data processing unit, and an alarm output unit, wherein:

[0067] The temperature-sensing optical fiber is laid along the length of the cable on the outer surface of the cable's insulation layer and connected to the distributed optical fiber temperature measurement host. It is used to sense the temperature of the outer surface of the insulation layer and transmit the corresponding optical signal to the distributed optical fiber temperature measurement host.

[0068] Among them, the temperature measuring optical fiber is a single-mode optical fiber or a multi-mode optical fiber. During the cable manufacturing process, the temperature measuring optical fiber is twisted synchronously with the insulated core and fixed to the outside of the insulated core with wrapping tape so that the temperature measuring optical fiber is in close contact with the outer surface of the insulation layer throughout the process. When the cable is a three-core cable, a temperature measuring optical fiber is set on the outer surface of the insulation layer corresponding to each phase conductor. After the cable is bundled, the three temperature measuring optical fibers are gathered together at both ends of the cable and connected in series through optical fiber fusion splicing to form a continuous optical fiber. The continuous optical fiber is connected to the distributed optical fiber temperature measuring host through optical fiber jumpers.

[0069] The distributed fiber optic temperature measurement host is used to emit laser pulses into the temperature measurement fiber and receive the backscattered light signal generated by the temperature measurement fiber. Based on the intensity ratio of the anti-Stokes light and the Stokes light in the backscattered light signal, it demodulates the temperature distribution data of the outer surface of the insulation layer along the length of the temperature measurement fiber and outputs the temperature distribution data of the outer surface of the insulation layer to the data processing unit.

[0070] The current acquisition unit is used to acquire real-time load current data of the cable and output the real-time load current data to the data processing unit.

[0071] Furthermore, the current acquisition unit is set at the cable outlet end and acquires the real-time load current of the cable through a current transformer or Rogowski coil. After converting the real-time load current into a digital signal, it is transmitted to the data processing unit. The distributed fiber optic temperature measurement host transmits the temperature distribution data of the outer surface of the insulation layer to the data processing unit through a digital communication line. The data processing unit simultaneously receives the temperature distribution data of the outer surface of the insulation layer and the real-time load current, and outputs the calculated conductor temperature to the host computer monitoring platform.

[0072] The data processing unit is connected to the distributed fiber optic temperature measurement host and the current acquisition unit, respectively. It is used to receive the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, call the preset cable structure parameters, calculate the thermal resistance of the insulation layer according to the cable structure parameters, calculate the conductor resistance loss power according to the real-time load current data and the conductor unit length resistance, and calculate the conductor temperature according to the thermal resistance of the insulation layer, the conductor resistance loss power and the temperature distribution data of the outer surface of the insulation layer.

[0073] Furthermore, the data processing unit stores cable structural parameters corresponding to the cable. These parameters include conductor type, conductor material, conductor cross-sectional area, conductor outer diameter, insulation material, insulation layer inner diameter, insulation layer outer diameter, insulation layer single-sided thickness, insulation material thermal resistivity, and conductor unit length resistance. The data processing unit calculates the insulation layer thermal resistance based on the insulation layer inner diameter, insulation layer outer diameter, and insulation material thermal resistivity; calculates the conductor resistance loss power based on real-time load current data and conductor unit length resistance; calculates the insulation layer temperature difference based on the insulation layer thermal resistance and conductor resistance loss power; and calculates the conductor temperature based on the insulation layer outer surface temperature and insulation layer temperature difference. The cable structural parameters are provided with the cable at the factory and pre-stored in the data processing unit for conductor temperature calculation.

[0074] The alarm output unit, connected to the data processing unit, is used to receive the alarm control signal output by the data processing unit based on the comparison result between the conductor temperature and the preset temperature threshold, and to output alarm information based on the alarm control signal.

[0075] Furthermore, the alarm output unit includes at least one of an audible and visual alarm, an SMS alarm module, and a host computer communication interface. When the conductor temperature at any location exceeds a preset alarm threshold, the data processing unit outputs an alarm control signal to the alarm output unit. The alarm output unit then drives an on-site audible and visual alarm, sends an SMS alarm to maintenance personnel, or uploads alarm information to the host computer monitoring platform via a communication network, based on the alarm control signal. The host computer monitoring platform includes a parameter input area, a calculation result display area, and a temperature relationship curve display area. The parameter input area is used to input conductor type, conductor material, conductor cross-sectional area, conductor outer diameter, insulation material, insulation layer thickness on one side, insulation layer outer surface temperature, and operating current. The calculation result display area displays the conductor unit length resistance, insulation layer thermal resistance, and conductor temperature. The temperature relationship curve display area displays the correspondence between the insulation layer outer surface temperature and the conductor temperature.

[0076] In summary, the system of this invention includes:

[0077] The distributed fiber optic temperature measurement host uses the Raman scattering principle to emit laser pulses into the temperature measurement fiber and receive backscattered light signals. By demodulating the intensity ratio of the anti-Stokes light and the Stokes light, it obtains the temperature distribution data along the entire length of the fiber.

[0078] Temperature-sensing optical fiber, which can be single-mode or multi-mode, is laid close to the outer surface of the cable insulation layer and runs along the entire length of the cable. It is used to sense the temperature of the outer surface of the insulation layer and transmit the temperature information to the distributed optical fiber temperature measurement host in the form of optical signals.

[0079] The current acquisition unit is used to acquire the load current data of the cable in real time.

[0080] The data processing unit receives the temperature distribution data of the outer surface of the insulation layer from the distributed fiber optic temperature measurement host and the real-time current data from the current acquisition unit. Based on the preset cable structure parameters and thermal resistance model, it automatically calculates the temperature of the cable conductor.

[0081] The alarm output unit outputs an alarm signal when the conductor temperature calculated by the data processing unit exceeds a preset temperature threshold.

[0082] The conductor temperature calculation method used by the data processing unit is as follows:

[0083] First, based on the structural parameters of the cable insulation layer, including the inner diameter, outer diameter, and thermal resistivity of the insulation material, the thermal resistance of the insulation layer is calculated. The unit of the thermal resistivity of the insulation material is... The unit for the outer diameter of the insulation layer is The unit for the inner diameter of the insulation layer is .

[0084] Then, based on the real-time collected cable load current and conductor resistance, the conductor resistance loss power is calculated. The unit of load current is Amperes (A), and the unit of conductor resistance per unit length is 100 kilometres per second (m). .

[0085] Next, the temperature of the cable conductor is calculated based on the temperature of the outer surface of the insulation layer measured by the temperature-sensing optical fiber. The temperature-sensing optical fiber is laid in the following way: during the cable manufacturing process, the temperature-sensing optical fiber is twisted together with the insulation core to ensure that the temperature-sensing optical fiber is in close contact with the outer surface of the insulation layer, and an outer layer of wrapping tape is wrapped around it to stabilize the relative position of the temperature-sensing optical fiber and the insulation core.

[0086] The spatial resolution of the distributed fiber optic temperature measurement host is: Temperature resolution is The measured distance is .

[0087] The current acquisition unit can be a current transformer, a Rogowski coil, or a current signal directly obtained from a cable monitoring system.

[0088] The alarm output unit includes an audible and visual alarm, an SMS alarm module, or a communication interface with a host computer monitoring system. When the conductor temperature exceeds a preset threshold, an alarm is issued through audible and visual signals, SMS, or network communication.

[0089] Furthermore, the present invention will be explained and illustrated in conjunction with specific embodiments:

[0090] Specific Implementation Example 1: Temperature Monitoring of a Single-Core 10kV Power Cable Conductor:

[0091] This embodiment focuses on real-time conductor temperature monitoring of a single-core 10kV cross-linked polyethylene (XLPE) insulated power cable. The structural parameters of the cable are as follows:

[0092] 1) The conductor's cross-sectional area is The outer diameter of the conductor is .

[0093] 2) The insulation layer material is cross-linked polyethylene, and the insulation layer thickness is [missing information]. The outer diameter of the insulation layer is .

[0094] 3) The thermal resistivity of the insulating material is .

[0095] 4) Conductor resistance ( hour) .

[0096] The specific steps for system installation include:

[0097] 1) During the cable manufacturing process, multimode optical fiber (core diameter) is used... It is twisted together with the insulated core and fixed by the wrapping layer.

[0098] 2) Connect both ends of the temperature-sensing optical fiber to the distributed optical fiber temperature measurement host (model DTS-100, spatial resolution: Temperature resolution Measuring distance ).

[0099] 3) Install a current transformer at the cable outlet to collect the cable load current in real time and transmit the current signal to the data processing unit.

[0100] 4) The data processing unit pre-inputs the cable structure parameters and sets the conductor temperature alarm threshold to [value missing]. .

[0101] Furthermore, the conductor temperature calculation process is as follows:

[0102] 1) Calculate the thermal resistance of the insulation layer;

[0103] 2) Assuming the current transformer measures a load current of 450A at a certain moment, calculate the conductor resistance loss power;

[0104] 3) Calculate the temperature difference of the insulation layer;

[0105] 4) Assume the distributed fiber optic temperature measurement host measures the outer surface temperature of the insulation layer as: Calculate the conductor temperature;

[0106] 5) Due to the calculated conductor temperature Below the alarm threshold The system does not issue an alarm and continues real-time monitoring.

[0107] When the load current increases to 600A, the calculation is recalculated, assuming that the temperature of the outer surface of the insulation layer rises to [temperature value missing]. Then due to the temperature of the conductor Exceeding alarm threshold The alarm output unit immediately issues an audible and visual alarm and notifies maintenance personnel via SMS to take load reduction measures.

[0108] Specific Implementation Example 2: Temperature Monitoring of Conductors in a Three-Core 35kV Power Cable

[0109] This embodiment focuses on real-time conductor temperature monitoring of a three-core 35kV cross-linked polyethylene insulated power cable. The cable has a three-core structure, with each phase conductor independently insulated, and the three phases are twisted together with an additional overall shielding layer and outer sheath.

[0110] First, the structural parameters of a single-phase cable are:

[0111] 1) The conductor's cross-sectional area is The outer diameter of the conductor is .

[0112] 2) The thickness of the insulation layer is The outer diameter of the insulation layer is .

[0113] 3) The thermal resistivity of the insulating material is .

[0114] 4) Conductor resistance ( hour) .

[0115] Furthermore, the system installation steps specifically include:

[0116] 1) During the cable manufacturing process, a temperature-measuring optical fiber is laid on the outer surface of the insulation layer of each phase conductor, for a total of three optical fibers, which are twisted together and fixed.

[0117] 2) The three temperature-measuring optical fibers are connected in series using optical fiber fusion splicing technology to form a continuous optical fiber, which is then connected to the distributed optical fiber temperature measurement host.

[0118] 3) Install current transformers for each phase at the cable outlet to collect the three-phase load current in real time;

[0119] 4) The data processing unit calculates the temperature of each of the three phase conductors and sets the alarm threshold as follows: .

[0120] The specific process for calculating conductor temperature (taking phase A as an example) is as follows:

[0121] 1) Calculate the thermal resistance of the insulation layer;

[0122] 2) Assuming the current in phase A is 550A at a certain moment, calculate the power loss due to conductor resistance;

[0123] 3) Calculate the temperature difference of the insulation layer;

[0124] 4) Assume the distributed fiber optic temperature measurement host measures the outer surface temperature of the insulation layer of phase A as follows: Calculate the temperature of phase A conductor.

[0125] Similarly, calculate the temperatures of phase B and phase C conductors respectively. Assume the phase B current is 560A and the outer surface temperature of the insulation layer is... Then the temperature of phase B conductor is C-phase current 540A, outer surface temperature of insulation layer Then the temperature of phase C conductor is .

[0126] The system displays the temperature of the three-phase conductors in real time, and will detect when the temperature of any phase conductor exceeds a certain threshold. An alarm was triggered. Since the temperatures of all three phase conductors were below the threshold, the system operated normally.

[0127] In this embodiment, by laying temperature-measuring optical fibers for each phase conductor of the three-core cable, independent monitoring of the temperature of the three phase conductors is achieved, which can promptly detect local overheating problems caused by single-phase overload or unbalanced load, and improve the precision of monitoring.

[0128] Finally, the embodiments of the present invention will be explained and described in conjunction with the accompanying drawings:

[0129] like Figure 3 The diagram shown illustrates the connection between the cable manufacturing plant and the on-site production equipment.

[0130] For the cable factory production section (front end):

[0131] 1) Insulated core stranding station: The temperature measuring optical fiber is stranded and wrapped with tape along with the insulated core to complete the pre-embedding of the optical fiber;

[0132] 2) Cable forming and sheathing processing station: Three-phase optical fibers are uniformly gathered at both ends of the cable, and optical fiber pigtails are reserved;

[0133] 3) Factory-provided specifications: The cable comes with factory-provided structural parameters, which are used as preset parameters for the data processing unit.

[0134] For the substation on-site installation of connection sections (back-end complete links), including:

[0135] 1) Optical signal path (orange solid line, temperature-sensing fiber): The three-phase temperature-sensing fiber optic cables pre-embedded at the cable terminal are spliced ​​and connected in series to form a single fiber optic cable, which is then connected to the optical transceiver port of the DTS distributed fiber optic temperature measurement host via fiber optic patch cords. The DTS host demodulates the surface temperature of the insulation layer along the entire cable and outputs the temperature data to the data processing unit via a digital communication line. Host technical specifications: spatial resolution Temperature resolution The measurement distance is 1~10km.

[0136] 2) Current acquisition path (black solid line, secondary signal line): The cable outlet cabinet is equipped with a current transformer (CT) on three phases. The secondary signal line of the transformer is connected to the current acquisition unit. The acquisition unit converts the real-time load current into a digital signal and uploads it to the data processing unit. The acquisition equipment is compatible with both CT and Rogowski coil specifications.

[0137] 3) Data processing path (digital communication line): The data processing unit synchronously receives the insulation surface temperature and real-time load current, retrieves the cable's factory-preset insulation structure parameters, and completes the conductor temperature calculation according to the single-layer insulation thermal resistance model; the calculation results are synchronously sent to the alarm output unit and the host computer monitoring platform (equipped with a calculation interface).

[0138] 4) Alarm output path (switch control line): The alarm output unit integrates an audible and visual alarm, an SMS alarm module, and a host computer communication interface; when the conductor temperature exceeds the factory-preset alarm threshold (35kV cable)... It outputs two signals: the control line drives the on-site audible and visual alarms, and the communication line transmits the alarm to the host computer in the background.

[0139] Furthermore, such as Figure 4 The diagram shows a cross-sectional view of the cable structure. The cross-section is divided into layers (from the inside out): conductor, XLPE insulation layer, temperature-sensing optical cable (optical fiber), filler, wrapping tape, isolation sleeve, armor, and outer sheath.

[0140] For the production and laying process: After the cable extrusion insulation process is completed, the single-mode / multi-mode temperature measuring optical fiber is twisted synchronously with the insulation core and fixed by wrapping tape so that the optical fiber is in close contact with the outer surface of the insulation layer throughout; for each phase A / B / C of the three-core cable, a temperature measuring optical fiber is arranged separately on the outside of the insulation.

[0141] Cable forming process: After the three-core wires are cabled, the three-phase temperature measuring optical fibers are uniformly gathered together; the optical fibers are not arranged on the outside of the cable outer sheath to avoid the armor and shielding multi-layer heat insulation structure, reduce the temperature difference between the insulation surface and the conductor, and only a single layer of insulation thermal resistance is needed to complete the conductor temperature conversion, reducing calculation errors.

[0142] like Figure 5 As shown, the left side is the parameter input and calculation module, which includes selection boxes for conductor type, conductor material, insulation material, conductor area, conductor outer diameter, insulation single-sided thickness, insulation surface temperature, and working current input, as well as display bars for the calculation results of DC resistance, insulation thermal resistance, and conductor temperature. A calculation trigger button is located at the bottom.

[0143] The area on the right is a plotting area for temperature relationship visualization curves, with the horizontal axis representing the temperature of the insulating surface (unit: ...). The vertical axis represents the conductor temperature (unit: ). The red straight line represents the curve showing the relationship between the insulation surface temperature and the conductor temperature. Data points are marked on the curve, and the insulation surface temperature X value and the corresponding conductor temperature T value at that point are displayed simultaneously, intuitively presenting the linear correlation between the two.

[0144] This interface allows users to input cable structure, electrical, and thermal parameters, calculate the actual operating temperature of the conductor with one click, and generate a corresponding temperature curve, enabling quantitative calculation and visual display of cable conductor temperature rise.

[0145] In summary, the embodiments of the present invention embed the temperature-sensing optical fiber inside the cable, close to the outer surface of the cable insulation layer, to directly measure the temperature of the outer surface of the insulation layer. Combined with real-time current data and a simplified thermal resistance model of the insulation layer, the temperature of the cable conductor is automatically calculated, achieving high-precision, real-time, and simple cable conductor temperature monitoring. This solves the problems of large temperature measurement errors, complex calculations, and insufficient real-time performance in the prior art, and achieves the technical effects of improving monitoring accuracy, simplifying the calculation process, and enhancing the practicality of the system.

[0146] The content of the above method embodiments is applicable to this system embodiment. The specific functions implemented in this system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0147] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this is not intended to limit the scope of the embodiments of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the embodiments of the present application.

Claims

1. A method for monitoring the temperature of cable conductors based on distributed optical fiber temperature measurement, characterized in that, The method is applied to a cable conductor temperature monitoring system, which includes a distributed fiber optic temperature measurement host, a temperature measurement fiber, a current acquisition unit, a data processing unit, and an alarm output unit. The temperature-sensing optical fiber is laid along the length of the cable on the outer surface of the cable insulation layer, and the temperature-sensing optical fiber is connected to the distributed optical fiber temperature measurement host, so that the temperature-sensing optical fiber senses the temperature of the outer surface of the insulation layer and transmits the temperature-corresponding optical signal to the distributed optical fiber temperature measurement host. The distributed optical fiber temperature measurement host emits laser pulses to the temperature measurement optical fiber and receives the backscattered light signal generated by the temperature measurement optical fiber. It demodulates the backscattered light signal according to the intensity ratio of the anti-Stokes light and the Stokes light to obtain the temperature distribution data of the outer surface of the insulation layer along the length of the temperature measurement optical fiber, and outputs the temperature distribution data of the outer surface of the insulation layer to the data processing unit. The current acquisition unit acquires the real-time load current data of the cable and outputs the real-time load current data to the data processing unit. The data processing unit receives the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, and calls the preset cable structure parameters. The cable structure parameters include at least the inner diameter of the insulation layer, the outer diameter of the insulation layer, the thermal resistivity of the insulation material, and the resistance per unit length of the conductor. The data processing unit calculates the thermal resistance of the insulation layer based on the inner diameter, outer diameter, and thermal resistivity of the insulation material; calculates the conductor resistance loss power based on the real-time load current data and the conductor resistance per unit length; and calculates the insulation layer temperature difference and conductor temperature at corresponding locations based on the insulation layer thermal resistance, conductor resistance loss power, and temperature distribution data on the outer surface of the insulation layer. The unit compares the conductor temperature with a preset temperature threshold and outputs the conductor temperature monitoring result and corresponding alarm signal based on the comparison result.

2. The method for monitoring cable conductor temperature based on distributed optical fiber temperature measurement according to claim 1, characterized in that, The method of laying the temperature-measuring optical fiber along the length of the cable on the outer surface of the cable insulation layer further includes: During the cable manufacturing process, single-mode or multi-mode optical fibers are simultaneously twisted with the cable insulation core, so that the temperature-sensing optical fiber is continuously laid along the length of the cable and in close contact with the outer surface of the insulation layer. After the temperature-sensing optical fiber and the insulating core are twisted together synchronously, a wrapping tape is wrapped around the outside of the temperature-sensing optical fiber and the insulating core to fix the relative position of the temperature-sensing optical fiber and the insulating core. In a three-core cable, a temperature-measuring optical fiber is installed on the outer surface of the insulation layer corresponding to each phase conductor. After the cable is bundled together, the temperature-measuring optical fibers of each phase are gathered together at both ends of the cable. After the cable ends are connected to the distributed optical fiber temperature measurement host by optical fiber fusion splicing to form a continuous optical fiber, the distributed optical fiber temperature measurement host can obtain the temperature distribution data of the outer surface of the insulation layer along each phase of the cable.

3. The method for monitoring cable conductor temperature based on distributed optical fiber temperature measurement according to claim 2, characterized in that, The data processing unit calculates the thermal resistance of the insulating layer based on the inner diameter of the insulating layer, the outer diameter of the insulating layer, and the thermal resistivity of the insulating material. The method further includes: The radial thermal resistance per unit length of the insulating layer is determined based on the inner diameter of the insulating layer, the outer diameter of the insulating layer, and the thermal resistivity of the insulating material, and the radial thermal resistance is used as the thermal resistance of the insulating layer. The conductor resistance loss power is calculated based on the real-time load current data and the conductor resistance per unit length. The conductor resistance loss power is related to the square of the real-time load current data and the conductor resistance per unit length. The temperature difference of the insulation layer is calculated based on the conductor resistance loss power and the insulation layer thermal resistance, and the temperature of the outer surface of the insulation layer is superimposed with the temperature difference of the insulation layer to obtain the conductor temperature at the corresponding position; The inner diameter of the insulation layer, the outer diameter of the insulation layer, the thermal resistivity of the insulation material, and the resistance per unit length of the conductor are stored in the data processing unit as pre-set structural and electrical parameters when the cable leaves the factory. After receiving the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, the corresponding parameters are called to calculate the conductor temperature.

4. The cable conductor temperature monitoring method based on distributed optical fiber temperature measurement according to claim 3, characterized in that, The temperature distribution data of the outer surface of the insulation layer output by the distributed optical fiber temperature measurement host and the real-time load current data output by the current acquisition unit are synchronously input into the data processing unit. The data processing unit performs positional mapping of the temperature distribution data of the outer surface of the insulation layer according to the cable position, and calculates the conductor temperature at each position according to the real-time load current data at the corresponding position. The current acquisition unit acquires the real-time load current data through a current transformer, Rogowski coil or cable monitoring system, and converts the real-time load current data into a digital signal before outputting it to the data processing unit.

5. The method for monitoring cable conductor temperature based on distributed optical fiber temperature measurement according to claim 4, characterized in that, After obtaining the conductor temperature, the data processing unit outputs the conductor temperature to the host computer monitoring platform and generates a temperature relationship curve between the conductor temperature and the outer surface temperature of the insulation layer based on the conductor temperature. The method further includes: When the temperature of the conductor at any location exceeds a preset temperature threshold, the data processing unit outputs an alarm control signal to the alarm output unit. The alarm output unit outputs alarm information according to the alarm control signal via audible and visual alarm, SMS alarm, or network communication, and transmits the alarm information to the host computer monitoring platform. The host computer monitoring platform displays the calculated results of the outer surface temperature of the insulation layer, the real-time load current, the resistance per unit length of the conductor, the thermal resistance of the insulation layer, and the temperature of the conductor, and marks the corresponding data points of the outer surface temperature of the insulation layer and the conductor temperature on the temperature relationship curve.

6. A cable conductor temperature monitoring system based on distributed optical fiber temperature measurement, characterized in that, It includes a distributed fiber optic temperature measurement host, a temperature measurement fiber, a current acquisition unit, a data processing unit, and an alarm output unit, wherein: The temperature-sensing optical fiber is laid along the length of the cable on the outer surface of the cable's insulation layer and connected to the distributed optical fiber temperature measurement host. It is used to sense the temperature of the outer surface of the insulation layer and transmit the corresponding optical signal to the distributed optical fiber temperature measurement host. The distributed optical fiber temperature measurement host is used to emit laser pulses into the temperature measurement optical fiber and receive the backscattered light signal generated by the temperature measurement optical fiber. Based on the intensity ratio of the anti-Stokes light and the Stokes light in the backscattered light signal, it demodulates the temperature distribution data of the outer surface of the insulation layer along the length of the temperature measurement optical fiber and outputs the temperature distribution data of the outer surface of the insulation layer to the data processing unit. The current acquisition unit is used to acquire the real-time load current data of the cable and output the real-time load current data to the data processing unit. The data processing unit is connected to the distributed optical fiber temperature measurement host and the current acquisition unit, respectively, and is used to receive the temperature distribution data of the outer surface of the insulation layer and the real-time load current data, call the preset cable structure parameters, calculate the thermal resistance of the insulation layer according to the cable structure parameters, calculate the conductor resistance loss power according to the real-time load current data and the conductor unit length resistance, and calculate the conductor temperature according to the thermal resistance of the insulation layer, the conductor resistance loss power and the temperature distribution data of the outer surface of the insulation layer. The alarm output unit is connected to the data processing unit and is used to receive the alarm control signal output by the data processing unit based on the comparison result of the conductor temperature and the preset temperature threshold, and to output alarm information based on the alarm control signal.

7. The cable conductor temperature monitoring system based on distributed optical fiber temperature measurement according to claim 6, characterized in that, The temperature-sensing optical fiber is a single-mode or multi-mode optical fiber. During the cable manufacturing process, the temperature-sensing optical fiber is twisted synchronously with the insulating core and fixed to the outside of the insulating core with a wrapping tape, so that the temperature-sensing optical fiber is in close contact with the outer surface of the insulation layer throughout the entire process. When the cable is a three-core cable, one temperature-sensing optical fiber is respectively set on the outer surface of the insulation layer corresponding to each phase conductor. After the cable is bundled, the three temperature-sensing optical fibers are gathered together at both ends of the cable and connected in series by optical fiber fusion splicing to form a continuous optical fiber. The continuous optical fiber is connected to the distributed optical fiber temperature measurement host through optical fiber patch cords.

8. The cable conductor temperature monitoring system based on distributed optical fiber temperature measurement according to claim 7, characterized in that, The data processing unit stores cable structure parameters corresponding to the cable. These parameters include conductor type, conductor material, conductor cross-sectional area, conductor outer diameter, insulation material, insulation layer inner diameter, insulation layer outer diameter, insulation layer single-sided thickness, insulation material thermal resistivity, and conductor unit length resistance. The data processing unit calculates the insulation layer thermal resistance based on the insulation layer inner diameter, insulation layer outer diameter, and insulation material thermal resistivity; calculates the conductor resistance loss power based on the real-time load current data and the conductor unit length resistance; calculates the insulation layer temperature difference based on the insulation layer thermal resistance and conductor resistance loss power; and calculates the conductor temperature based on the insulation layer outer surface temperature and the insulation layer temperature difference. Wherein: The cable structure parameters are provided with the cable at the factory and are pre-stored in the data processing unit for conductor temperature calculation.

9. The cable conductor temperature monitoring system based on distributed optical fiber temperature measurement according to claim 8, characterized in that, The current acquisition unit is located at the cable outlet and acquires the real-time load current of the cable through a current transformer or Rogowski coil. The real-time load current is then converted into a digital signal and transmitted to the data processing unit, wherein: The distributed fiber optic temperature measurement host transmits the temperature distribution data of the outer surface of the insulation layer to the data processing unit through a digital communication line. The data processing unit simultaneously receives the temperature distribution data of the outer surface of the insulation layer and the real-time load current, and outputs the calculated conductor temperature to the host computer monitoring platform.

10. The cable conductor temperature monitoring system based on distributed optical fiber temperature measurement according to claim 9, characterized in that, The alarm output unit includes at least one of the following: an audible and visual alarm, an SMS alarm module, and a host computer communication interface, wherein: When the conductor temperature at any location exceeds a preset alarm threshold, the data processing unit outputs an alarm control signal to the alarm output unit. The alarm output unit then drives an on-site audible and visual alarm, sends an SMS alarm message to maintenance personnel, or uploads an alarm message to the host computer monitoring platform via a communication network, based on the alarm control signal. The host computer monitoring platform is equipped with a parameter input area, a calculation result display area, and a temperature relationship curve display area. The parameter input area is used to input conductor type, conductor material, conductor cross-sectional area, conductor outer diameter, insulation material, single-sided thickness of insulation layer, outer surface temperature of insulation layer, and operating current. The calculation result display area is used to display the conductor resistance per unit length, insulation layer thermal resistance, and conductor temperature. The temperature relationship curve display area is used to display the correspondence between the outer surface temperature of insulation layer and conductor temperature.

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