Cable condition monitoring system and method

Abstract

This invention discloses a cable condition monitoring system and method. The system includes sensors, a monitoring module, a cloud server, a user terminal, and a remote server. The output of the sensor is connected to the input of the monitoring module. The monitoring module is connected to the cloud server via a wireless network, and the cloud server is connected to the remote server via a wireless network. The sensor acquires the induced voltage of the cable line and sends it to the monitoring module. The monitoring module determines the cable line's condition based on the induced voltage. When an abnormality occurs in the cable line, an alarm signal is generated and sent to the cloud server. The cloud server pushes the alarm signal to the user terminal and the remote server. This system monitors the induced voltage in real time using sensors, eliminating the need for personnel to operate with the power on, greatly ensuring the safety and reliability of personnel. Remote monitoring via the wireless cloud server significantly facilitates frontline maintenance and repair work.

Description

Technical Field

[0001] This invention relates to the field of cable condition detection technology, and in particular to a cable condition monitoring system and method. Background Technology

[0002] Power cables are laid underground in a relatively harsh operating environment, making them prone to failure, sudden power outages, and fire hazards. Cable lines are also susceptible to theft and other acts of vandalism, all of which can cause significant economic losses to businesses. Both power supply and consumption companies invest substantial human and material resources annually in cable maintenance and management. Existing distribution switch monitoring terminals (FTUs) can provide information on the operation of the power distribution system, including various parameters and monitoring and control data. They also communicate with the distribution automation master station, executing commands issued by the master station to adjust and control the power distribution equipment.

[0003] However, existing FTUs can only be installed on 10kV and 33kV overhead distribution lines, and cannot provide status information of distribution network cable lines; moreover, using the internal network of the power system, the electronic map updates slowly and cannot display the current operating status of the distribution network in real time. When a line fault occurs, it is impossible to know the fault type and fault point in time, resulting in a huge workload for front-line maintenance personnel. The main reasons for the above problems are: (1) The current FTU uses traditional instrument transformers to collect voltage and current information, and cannot monitor the current of each phase of the three-core cable; (2) The current FTU does not have Internet of Things communication function, and cannot update the line operating status information measured by the equipment in the electronic map in real time; (3) The existing FTU has a complex structure and is expensive, and cannot be installed in a large-scale distributed manner. Summary of the Invention

[0004] This invention provides a cable condition monitoring system and method, aiming to solve the problem of difficulty in accurately monitoring cable condition in the prior art.

[0005] In a first aspect, embodiments of the present invention provide a cable condition monitoring system, including a sensor, a monitoring module, a cloud server, a user terminal, and a remote server. The output end of the sensor is connected to the input end of the monitoring module, the monitoring module is connected to the cloud server via a wireless network, and the cloud server is connected to the remote server via a wireless network.

[0006] The sensor is used to acquire the induced voltage of the cable line and send it to the monitoring module;

[0007] The monitoring module is used to determine the status information of the cable line based on the induced voltage. When an abnormality occurs in the cable line, an alarm signal is generated and sent to the cloud server. The status information includes at least the status quantity of the current of each phase of the cable, the three-phase voltage imbalance, the cable trench temperature, and the cable trench humidity.

[0008] The cloud server is used to push alarm signals to user terminals and remote servers.

[0009] Secondly, embodiments of the present invention provide a cable condition monitoring method, comprising:

[0010] The sensor monitors the induced voltage of the power distribution network cable lines and sends the induced voltage to the monitoring module;

[0011] The monitoring module converts the induced voltage to obtain three-phase voltage, calculates the voltage imbalance based on the three-phase voltage to obtain the voltage imbalance of the distribution network cable line, and determines whether there is an abnormality in the cable line based on the voltage imbalance. If there is an abnormality, an alarm signal is generated and sent to the cloud server.

[0012] The cloud server transmits alarm signals to remote servers and user terminals.

[0013] This invention provides a cable condition monitoring system and method. The system includes sensors, a monitoring module, a cloud server, a user terminal, and a remote server. The output of the sensor is connected to the input of the monitoring module. The monitoring module is connected to the cloud server via a wireless network, and the cloud server is connected to the remote server via a wireless network. The sensor acquires the induced voltage of the cable line and sends it to the monitoring module. The monitoring module determines the cable line's condition based on the induced voltage. When an abnormality occurs in the cable line, an alarm signal is generated and sent to the cloud server. The condition information includes at least the state of each phase current, three-phase voltage imbalance, cable trench temperature, and cable trench humidity. The cloud server pushes the alarm signal to the user terminal and the remote server. This system is based on the principle of electromagnetic induction, using sensors to monitor the induced voltage in the cable in real time. Operators do not need to operate the cable while it is energized, greatly ensuring the safety and reliability of their work. The monitoring module can be quickly deployed, and remote monitoring is achieved through a wireless cloud server, greatly facilitating frontline maintenance and repair work. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a system block diagram of a cable condition monitoring system provided in an embodiment of the present invention;

[0016] Figure 2 A flowchart illustrating the cable condition monitoring method provided in an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of the sensor structure in an embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram of the structure of the monitoring module provided in an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram comparing the magnitude of the three-phase imbalance in different states according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0022] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0023] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0024] Please see Figure 1 This is a system block diagram of a cable condition monitoring system provided in an embodiment of the present invention.

[0025] Figure 1 A cable condition monitoring system was demonstrated, which includes a sensor 1, a monitoring module 2, a cloud server 3, a user terminal 4, and a remote server 5. The output of the sensor 1 is connected to the input of the monitoring module 2. The monitoring module 2 is connected to the cloud server 3 via a wireless network. The cloud server 3 is connected to the remote server 5 via a wireless network 4.

[0026] Sensor 1 is used to acquire the induced voltage of the 10KV power distribution network cable line and send it to the monitoring module 2;

[0027] The monitoring module 2 is used to determine the status information of the cable line based on the induced voltage. When an abnormality occurs in the cable line, an alarm signal is generated and sent to the cloud server 3. The status information includes at least the status quantity of the current of each phase of the cable, the three-phase voltage imbalance, the cable trench temperature, and the cable trench humidity.

[0028] Cloud server 3 is used to push alarm signals to user terminal 4 and remote server 5.

[0029] In this embodiment, sensor 1 monitors the induced voltage of the power distribution network cable line and then sends the induced voltage to monitoring module 2. Monitoring module 2 calculates the voltage imbalance of the power distribution network cable line based on the induced voltage and determines whether there is an abnormality in the cable line based on the voltage imbalance. When an abnormality occurs in the cable line, an alarm signal is generated and sent to cloud server 3. The cloud server pushes the alarm signal to user terminal 4 and remote server 5 to realize remote monitoring of cable status.

[0030] In one embodiment, the sensor consists of three racetrack-shaped coils arranged side by side. For example... Figure 3 As shown, three coils are arranged side-by-side on insulating cloth, with a spacing equal to one-third of the cable's outer circumference and the difference between the coil width and the coil width. The sensor is mounted on the cable using a sphygmomanometer-style installation method, with the three coils spatially separated by 120 degrees after the cable is covered. If the cable is operating normally, the three-phase currents in the cable line generate a circular rotating magnetic field, and the amplitudes of the three-phase induced electromotive forces generated by the sensor are equal. The magnitude of the induced electromotive forces is proportional to the cable current, and the magnitude of the induced electromotive forces can be used to determine the magnitude of the current in each phase of the three-core cable. If the cable experiences imbalance, phase loss, or open circuit faults, an elliptical magnetic field is generated. In this case, the amplitudes of the three-phase induced electromotive forces generated by the sensor will no longer be equal. Therefore, the magnitude of the voltage imbalance can be used to determine whether a fault has occurred in the cable line.

[0031] like Figure 4As shown, in one embodiment, the monitoring module includes a conditioning circuit 8, a DSP processor 9, a power management module 11, and an alarm module 10. The input terminal of the conditioning circuit 8 is connected to the output terminal of the sensor, the output terminal of the conditioning circuit is connected to the input terminal of the DSP processor 9, the output terminal of the DSP processor 9 is connected to the input terminal of the alarm module 10, and the output terminal of the power management module 11 is connected to the DSP processor 9, the conditioning circuit 8, and the alarm module 10, respectively. Specifically, the conditioning circuit 8 amplifies the induced voltage output by the sensor and converts it into a positive voltage that meets the input range of the DSP; the DSP processor 9 collects and calculates the voltage data output by the conditioning circuit 8, calculates the voltage imbalance of the cable based on the voltage data, performs analog-to-digital conversion based on the voltage imbalance, and sends an alarm signal to the alarm module 10 if the voltage imbalance is lower than a preset threshold; the power management module 11 supplies power to the DSP processor 9, the conditioning circuit 8, and the alarm module 10; and the alarm module 10 receives the alarm signal sent by the DSP processor 9 and sounds an alarm.

[0032] In one embodiment, the A / D conversion module in the DSP processor converts analog signals into digital signals. Using the IEC 61850 standard's specified 80 points / cycle as the sampling rate, and sampling for 10 cycles, 800 voltage data points can be acquired. The formula for calculating the effective value of each phase voltage is as follows:

[0033]

[0034] In the formula, N represents the number of sampling points, which is 800, u n This represents the discrete voltage value at the nth sampling point.

[0035] In this context, unbalance refers to the degree of three-phase imbalance in a power system. Currently, there is no unified and clear standard for calculating three-phase unbalance, and many different calculation versions exist. This invention adopts the voltage unbalance calculation method defined in IEEE Std 936-1987, which is equal to the ratio of the difference between the effective values ​​of the maximum and minimum voltages in the three phases to the average phase voltage of the three phases. The specific formula is as follows:

[0036]

[0037] In the formula, U ave U represents the average value of the three-phase voltage RMS value; where U is the average value of the three-phase voltage RMS value. max U represents the maximum phase voltage of the three-phase voltage RMS value; min The smallest phase voltage representing the effective value of the three-phase voltage.

[0038] In this embodiment, during installation, staff register the geographical location information of the corresponding monitoring module. The cloud server, combined with the geographic information system, can intuitively display the real-time operating status of the 10kV cables within the area. Simultaneously, when staff access the cloud server remotely, they can directly observe the energized status of the 10kV cable lines within the area, as well as the magnitude of the three-phase current and three-phase imbalance. When the cloud server receives an alarm signal from a monitoring module, it can also display the geographical location information of the corresponding problematic monitoring module, facilitating troubleshooting by staff.

[0039] In one embodiment, the conditioning circuit includes an isolation amplifier, a differential operational amplifier, and a voltage follower. The input terminal of the isolation amplifier is connected to the two output terminals of each phase coil in the sensor, and the output terminal of the isolation amplifier is connected to the input terminal of the differential operational amplifier. The output terminal of the differential operational amplifier is connected to the input terminal of the voltage follower, and the output terminal of the voltage follower is connected to the input terminal of the DSP processor. Specifically, the isolation operational amplifier receives the induced voltage output by the sensor and sends it to the differential operational amplifier; the differential operational amplifier receives the induced voltage output by the isolation operational amplifier, amplifies it, and sends it to the voltage follower; the voltage follower detects the induced voltage output by the differential operational amplifier, and if the induced voltage is negative, converts it to a positive voltage and sends the converted positive voltage to the DSP processor.

[0040] In one embodiment, the DSP processor further includes an analog-to-digital conversion module and a communication module. The analog-to-digital conversion module is used to acquire the value of the induced voltage. The communication module is an NB-I / OT module, which is connected to the serial communication port of the DSP processor via a serial port. The DSP processor receives commands sent from the cloud server through the NB-I / OT module and sends the cable line status monitoring information to the cloud server through the NB-I / OT module. The DSP processor is connected to the communication module via the serial port. DSP processors have inherent advantages in signal processing due to their low power consumption, high performance, ease of programming, and real-time capabilities. The DSP collects and calculates the data obtained after processing by the conditioning circuit to obtain the three-phase imbalance data and transmits the data to the remote server. The main function of its analog-to-digital conversion module is signal sampling and processing, ensuring real-time data transmission.

[0041] In one embodiment, the alarm module includes an alarm light and an alarm horn, both of which are connected to the DSP processor via I / O pins.

[0042] In this embodiment, the alarm module has light and sound alarm functions. When the power distribution network cable line is operating normally, the alarm module is in a sleep state. When the power distribution network cable line experiences faults such as phase loss, short circuit, or open circuit, the alarm module receives the alarm signal and issues a flashing alarm signal and a warning sound.

[0043] In one embodiment, the power management module includes a power supply battery, a power conversion circuit, and a power conversion IC. The power supply battery is connected to the power conversion circuit, the power conversion circuit is connected to the power conversion IC, and the output terminal of the power conversion IC is connected to the input terminal of the DSP processor. The power conversion IC includes a battery and a battery power detection circuit.

[0044] In this embodiment, the power management module supplies power to the monitoring module using four 3.7V batteries connected in series, outputting a 15V voltage. The power conversion circuit converts the 15V power to a 5V power supply. The power conversion IC uses a TTL to 232 module to convert the 5V power to a regulated 3.3V power supply to power the detection circuit and the DSP processor.

[0045] Reference Figure 2 , Figure 2 A flowchart illustrating the cable condition monitoring method provided in an embodiment of the present invention;

[0046] This invention also provides a cable condition monitoring method, applied to the cable condition monitoring system described above. The cable condition monitoring method includes:

[0047] Step S110: The sensor monitors the induced voltage of the power distribution network cable line and sends the induced voltage to the monitoring module;

[0048] Step S120: The monitoring module converts the induced voltage to obtain three-phase voltage, calculates the voltage imbalance based on the three-phase voltage to obtain the voltage imbalance of the distribution network cable line, and determines whether there is an abnormality in the cable line based on the voltage imbalance. If there is an abnormality, an alarm signal is generated and sent to the cloud server.

[0049] Step S130: The cloud server transmits the alarm signal to the remote server and the user terminal.

[0050] This embodiment describes the status monitoring of power distribution network cable lines. Sensors monitor the induced voltage of the cable lines, and a monitoring module calculates the three-phase voltage based on this induced voltage. Based on the three-phase voltage, the voltage imbalance of the cable is calculated, and finally, the voltage imbalance is used to determine if there is an anomaly in the cable line. If an anomaly is found, an alarm signal is generated and sent to a cloud server. The cloud server then transmits the alarm signal to a remote server and user terminals, thereby achieving remote monitoring of the cable status. Specifically, the process of determining whether there is an anomaly in the cable line based on the voltage imbalance includes: determining whether the voltage imbalance reaches a preset threshold; if yes, the cable line is determined to be abnormal; otherwise, the cable line is determined to be normal.

[0051] In this embodiment, a test environment is constructed, consisting of a three-phase 380V power supply, a three-phase air switch, a 10KVA three-phase voltage regulator, a 300*3 cable, three 15-ohm / 1000-watt load resistors (star-connected), several resistors simulating short circuits and voltage imbalance, sensors, detection equipment, an oscilloscope, and a computer. The cable is wrapped with sensors, which consist of three-phase coils (a, b, and c). A characteristic of normal system operation is that the induced voltage imbalance is less than 5%, and the phase difference is approximately 120 degrees. Compared to a balanced three-phase system, one characteristic of unbalanced operation is an increased voltage asymmetry, which can be determined by calculating the voltage asymmetry in the DSP program. When an open-circuit fault occurs in the cable, the voltage imbalance reaches approximately 60%, and there are instances of phase in-phase operation. If the positions of the three conductors in the cable are known, sensors can be installed at corresponding positions above them to determine the specific open-circuit phase. When phase A is open-circuited, the induced electromotive force (EMF) in the coil corresponding to phase A is the smallest among the three-phase induced EMFs; when phase B is open-circuited, the induced EMF in the coil corresponding to phase B is the smallest; and when phase C is open-circuited, the induced EMF in the coil corresponding to phase C is the smallest. Given that the system has been determined to be open-circuited, this can be used to determine which phase (A, B, C) has experienced the open-circuit fault. If the three-phase voltage imbalance is much less than 60% but greater than 10% and the three-phase phase difference is approximately 120 degrees, then the cable is three-phase unbalanced. Figure 5 The diagram shown is a comparison of the magnitude of the three-phase imbalance in each state of the present invention.

[0052] Furthermore, to ensure that the induced electromotive force detected by the sensor is large enough to be detected by subsequent devices, this invention provides a method for designing sensor parameters. Four parameters need to be determined for the sensor: wire diameter φ, number of coil turns n, coil width w, and coil length l. To ensure high sensor sensitivity, the induced current detected by the sensor should be as large as possible. The magnitude of the induced electromotive force generated by the coil is proportional to the coil length and the number of turns. Let the induced electromotive force generated by a single-turn coil per unit length be u, the resistance of the wire per unit length be r, and the inductive reactance of the coil per unit length be x, then the expression for the induced current is as follows:

[0053]

[0054] As can be seen from the above formula, the longer the coil length, the larger the induced current and the larger the induced electromotive force, resulting in higher detection sensitivity and easier detection. However, the corresponding cost and processing difficulty will also increase accordingly, and the coil length needs to be selected in conjunction with other variables. The wire diameter φ affects the coil resistance; the larger the wire diameter, the larger the cross-sectional area of ​​the conductor, the smaller the resistance, and the larger the induced current. Three-phase induction coils cannot have electrical contact; therefore, the size of the coil wire diameter will affect the maximum number of turns that can be used. When the two sides of the coil are 180° apart, the potential generated by the two sides is in opposite directions, and the detected induced electromotive force is the largest. However, the corresponding coil resistance also increases, and the maximum number of turns of the coil needs to be reduced. It is necessary to find an optimal coil width w that satisfies the condition of sufficiently small mutual inductance between the three-phase coils and maximizes the induced current of the coil. As can be seen from the expression, the selection of the coil turns n needs to be determined based on the coil inductive reactance calculated by simulation. The three variables of coil wire diameter, width, and number of turns affect each other, and the optimal coil parameters that maximize the induced current, increase sensitivity, and meet the requirements for induced electromotive force detection need to be determined using the controlled variable method and COMSOL simulation software. In addition, the selection of coil parameters also needs to be adjusted according to processing factors.

[0055] Those skilled in the art will readily understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention.

[0056] In the embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Units with the same function may be grouped into one unit. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or units, or it may be an electrical, mechanical, or other form of connection.

[0057] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention, depending on actual needs.

[0058] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0059] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), magnetic disks, or optical disks.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cable condition monitoring system, characterized in that, It includes sensors for acquiring cable line measurement data, a monitoring module for determining the status information of the cable line, a cloud server, a user terminal, and a remote server. The sensor includes three racetrack-shaped coils arranged side by side on an insulating cloth. The cable is a three-core cable. The sensor is wrapped around the three-core cable in a blood pressure monitor-style installation method. After wrapping, the three racetrack-shaped coils are 120 degrees apart in spatial position. The sensor is used to determine the magnitude of the current in each phase of the three-core cable when the three-core cable is operating normally. When the three-core cable is in normal operation, the three-phase current of the three-core cable generates a circular rotating magnetic field. The amplitude of the three-phase induced electromotive force generated by the sensor is equal, and the magnitude of the induced electromotive force is proportional to the cable current. When the three-core cable experiences an imbalance, phase loss, or open circuit fault, the three-phase current of the three-core cable generates an elliptical magnetic field. The amplitude of the three-phase induced electromotive force generated by the sensor is unequal. The magnitude of the voltage imbalance is used to determine whether the three-core cable has experienced a fault.

2. A cable condition monitoring method for a cable condition monitoring system as described in claim 1, characterized in that, include: The sensor monitors the induced voltage of the power distribution network cable lines and sends the induced voltage to the monitoring module; The monitoring module converts the induced voltage to obtain three-phase voltage, calculates the voltage imbalance based on the three-phase voltage to obtain the voltage imbalance of the distribution network cable line, and determines whether there is an abnormality in the cable line based on the voltage imbalance. If there is an abnormality, an alarm signal is generated and sent to the cloud server. The cloud server transmits alarm signals to remote servers and user terminals; The method of determining whether there is an abnormality in the cable line based on the voltage imbalance includes: determining whether the voltage imbalance reaches a preset threshold; if yes, then the cable line is determined to be abnormal; if no, then the cable line is determined to be normal; wherein, the preset threshold is that the voltage imbalance is less than 60% but greater than 10%.

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