Online monitoring method and monitoring system for grounding defects of outer metal sheath of high-voltage cable

Abstract

The invention discloses a high-voltage cable outer metal sheath grounding defect on-line monitoring method and monitoring system, which can work under the condition that a cable is not powered off, realizes on-line monitoring, and realizes on-line monitoring through the cooperation of a current sensor, a voltage sensor, a single-chip microcomputer and an upper computer. And the equipment can quickly detect when a fault occurs and is convenient for maintenance workers to timely eliminate obstacles, so that the risk of major electric power accidents is reduced. The algorithm is similar to an improved neural network algorithm and is used for diagnosing the defects of the outer metal sheath of the cable, the weight is obtained through training learning, and finally the defects of the outer metal sheath of the high-voltage cable are determined. The protection content covers each component of the technical scheme, and comprises a monitoring method, a device structure, a sensor technology, a data processing algorithm, a neural network learning algorithm and the like.

Description

Technical field:

[0001] The present invention focuses on the field of high-voltage cable detection technology, and specifically relates to an online monitoring method and monitoring system for grounding defects of the outer metal sheath of a high-voltage cable. Innovation in this technical field helps to improve the operation and maintenance level of high-voltage cables and prevent power failures. The present invention can solve the problems existing in the current detection of grounding defects of the outer metal sheath of high-voltage cables, and provide strong support for the reliable operation of the power system. Background technology:

[0002] With the development of economy, the electricity consumption is increasing rapidly, and this change has put forward more stringent requirements on all aspects of power transmission. In the power system, high-voltage cables are key components, which undertake the task of transmitting a large amount of electric energy. Their safe operation is directly related to the stability and efficiency of the entire power supply. However, statistics show that the faults caused by the grounding defects of the outer metal sheath of the cable account for a large proportion of cable faults.

[0003] Traditional detection methods require that the cable must be in a power-off state before monitoring can be carried out. This will bring great inconvenience to production and life, and will also significantly increase the cost and workload of power operation and maintenance. In addition, the offline monitoring cycle is usually long, and monitoring can only be carried out at fixed time intervals, which may lead to grounding defects that cannot be discovered in time between two monitorings. In the actual operating environment, grounding defects may develop rapidly in a short period of time, evolving from minor potential problems to serious faults, and then causing power outages.

[0004] The existing method for monitoring grounding defects of the outer metal sheath of high-voltage cables has the following shortcomings:

[0005] (1) The sheath current monitoring method is limited to detecting abnormal circulating current caused by damage to the cable outer sheath.

[0006] (2) The infrared temperature measurement method can directly detect abnormal heating of the cable, but it is only effective for long-term continuous heating points at the defective location of the equipment, making it difficult to detect defects early.

[0007] (3) Offline ground loop resistance measurement method: This method requires power outage and a large number of personnel, is inefficient and lacks economic benefits. Summary of the invention:

[0008] The purpose of the present invention is to solve the above problems and to provide an online monitoring method for grounding defects of the outer metal sheath of a high-voltage cable. The method is used to judge the defects of the outer metal sheath of a high-voltage cable without power outage, so as to discover abnormal operation problems of the cable, ensure the safe transmission of electric energy, and improve the safety and stability of the power system.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for online monitoring of grounding defects of a high-voltage cable outer metal sheath, characterized in that it comprises the following steps:

[0011] A. Current signal injection: The current injection module injects short-time test current into the outer metal sheath of the A, B, and C phase cables in a time-sharing manner;

[0012] B. Acquisition and preprocessing of current and voltage signals: Use current sensors and voltage sensors to obtain the current and voltage signals of any two phases of the outer metal sheath of the high-voltage cable respectively. The current and voltage signals are filtered by the filter module, and then the filtered data are transmitted to the AD converter for analog-to-digital conversion;

[0013] C. Acquisition and preprocessing of other sensor signals: The core current sensor, temperature sensor, humidity sensor, and anti-theft cutting sensor convert the measured analog signals into digital signals through AD converters;

[0014] D. Data transmission: The voltage, current, core current, temperature, humidity, and anti-theft cutting signal processed by the AD converter are transmitted to the main control chip STM32, processed by the main control chip and transmitted to the host computer by the data transmission module. The host computer displays the online monitoring results of the grounding defects of the outer metal sheath of the high-voltage cable;

[0015] E. Fault diagnosis: The main control chip STM32 performs data fusion processing, and the algorithm determines the specific defects of the outer metal sheath of the high-voltage cable.

[0016] A further improvement of the present invention is that in step A, the current injection module can output a DC-100kHz signal for injecting current into the A, B, and C phase loops of the outer metal sheath of the high-voltage cable, and the amplitude and frequency of the injected current are adaptive according to the connection status of the outer metal sheath of the high-voltage cable at site.

[0017] A further improvement of the present invention is that the amplitude and frequency of the current are adaptively controlled by closed-loop control, and the current sensor measures the current of the outer metal sheath of the high-voltage cable in real time, and feeds back the measured value to the PID controller. The PID controller calculates the control quantity based on the deviation between the feedback value and the target value, and then changes the output current amplitude and frequency related parameters through the current injection module to change the current size in the outer metal sheath of the cable, thereby reducing the deviation and finally stabilizing the current of the outer metal sheath of the cable near the target value.

[0018] A further improvement of the present invention is that a feedforward control link is provided in the PID controller, and the output of the controller is adjusted in advance according to known disturbances of the system or changes in input signals to compensate for the influence of the disturbances on the system.

[0019] A further improvement of the present invention is that in step B, the voltage sensor is based on the principle of resistance voltage division and is combined with a high-precision amplifier to ensure that the voltage information on the outer metal sheath of the high-voltage cable can be accurately collected. A current limiter is provided between the voltage sensor and the wire clamp to reduce the influence of the induced voltage of the cable metal sheath on the test equipment; the current sensor is based on the principle of electromagnetic induction and is combined with a high-precision amplifier to accurately measure the current information on the outer metal sheath of the high-voltage cable; the filtering module connects the current sensor, the voltage sensor, and the AD converter, and its function is to remove the power frequency interference of the electrical equipment around the device, the transient interference caused by the switching operation, and other radio interference.

[0020] The further improvement of the present invention is that: the main control chip STM32 is the core component in the device, realizing the functions of data processing and control, coordinating the work of various components, executing programs, communicating, and diagnosing device faults. The main control chip STM32 is connected to various sensors, alarm modules, data transmission modules, and current injection modules; the alarm module is composed of an LED lamp and a buzzer, and its function is to detect a grounding defect of the outer metal sheath of the high-voltage cable, and the alarm module starts the alarm; the data transmission module is composed of a wired or wireless network and an external network server, and its function is to transmit the signal processed by the main control chip STM32 to the external network server through a wired or wireless network, and then transmitted to the host computer by the external network server, and the host computer displays the grounding defect information of the outer metal sheath of the high-voltage cable and provides a human-computer interaction interface.

[0021] A further improvement of the present invention is that in step E, the algorithm is an improved neural network algorithm, and its diagnosis process is as follows:

[0022] A. The algorithm can diagnose the grounding defect of the outer metal sheath of the high-voltage cable. During the diagnosis process, the algorithm will first give a preliminary diagnosis result based on the level of fault impedance and fault characteristics. Then the system can diagnose through the neural network algorithm in STM32 to form the final diagnosis information;

[0023] B. The algorithm consists of three parts: input layer, middle layer and output layer. The input layer is the signal measured by the sensor, including current sensor, voltage sensor, core current sensor, temperature sensor, humidity sensor, anti-theft sensor; the output layer is the grounding defect type, including normal, construction process, production process, humid environment, rust corrosion failure, ant bite and rat bite, external force damage; the input layer and output layer are fixed, one layer is selected in the middle layer, and the connection line between layers corresponds to a different weight, which needs to be obtained through training; the algorithm is as follows:

[0024] Assume that the measured voltage signal, current signal, core current signal, temperature signal, humidity signal, and anti-theft cutting signal are U, I, and I respectively. n, T, W, S, the corresponding weights are t1, t2, t3, t4, t5, t6 respectively, then the final output f is:

[0025] f=t1U+t2I+t3I n +t3T+t5W+t6S;

[0026] C. Since the corresponding weights cannot be obtained immediately at the beginning, they need to be obtained through neural network learning. The learning process first needs to convert the sample data collected by each sensor through an AD converter, then extract the characteristic quantity of the sensor signal, and then use the training results for the grounding defect neural network to finally obtain the grounding defect diagnosis result;

[0027] D. The learning algorithm first initializes the weights and thresholds, then inputs random samples of the characteristic quantities of each sensor, calculates the output of the cable grounding defect type of the intermediate layer and the output layer, and ends the algorithm if the conditions are met. If the conditions are not met, the node error accuracy is calculated, and then the connection weights are modified to continue to judge whether the conditions are met. The calculation is repeated until the weights that meet the conditions are found;

[0028] E. Determine the weights corresponding to each branch of the neural network after learning. The information measured by the sensor is converted by the AD converter and transmitted to the main control chip STM32. The main control chip calculates and processes the weights obtained through the training through the algorithm, and finally transmits the calculation results to the host computer through the data transmission module.

[0029] An online monitoring system for grounding defects of a high-voltage cable outer metal sheath, the system comprising:

[0030] Current injection module: used to inject a section of DC current into the outer metal sheath A, B, C of the high-voltage cable and between any two phases. The current injection module is connected to the main control chip STM32;

[0031] PID control module: It is composed of a PID controller. The current sensor measures the current of the outer metal sheath of the high-voltage cable in real time and feeds the measured value back to the controller. The controller calculates the control amount according to the deviation between the feedback value and the target value, and then changes the output current amplitude and frequency related parameters by adjusting the current injection module to change the current size in the outer metal sheath of the cable, thereby reducing the deviation and finally stabilizing the current of the outer metal sheath of the cable near the target value.

[0032] Current sensor: Based on the principle of electromagnetic induction and equipped with a high-precision amplifier, it can accurately measure the tiny induced current information on the outer metal sheath of the high-voltage cable;

[0033] Voltage sensor: Based on the principle of resistance voltage division and equipped with a high-precision amplifier, it ensures that the voltage information on the outer metal sheath of the high-voltage cable can be accurately collected;

[0034] Filter module: used to remove power frequency interference from electrical equipment around the device, transient interference caused by switching operations, and other radio interference;

[0035] Current limiter: between the wire clamp and the voltage sensor, used to reduce the impact of the induced voltage of the cable metal sheath on the test equipment;

[0036] The first wire clamp and the second wire clamp are used to clamp any two phases of the outer metal sheath A, B, and C of the high-voltage cable to form electrical conduction;

[0037] AD converter: used to convert the analog signal after sensor measurement and preprocessing into a digital signal;

[0038] Main control chip STM32: It is the core component of the device, realizing the functions of data processing and control, coordinating the work of various components, executing programs, communication, and device fault diagnosis;

[0039] Alarm module: It is composed of LED light and buzzer. When the grounding defect of the metal sheath outside the high-voltage cable is detected, the alarm module will start the alarm.

[0040] The data acquisition module, the temperature sensor, the humidity sensor, the anti-theft cutting sensor, and the core wire current sensor are connected to the AD converter built into the main control chip STM32.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] 1. High-voltage cables can operate without power outages, enabling online monitoring and improving the safety and reliability of cable operation. They can detect various faults in the outer metal sheath of the cable in the first place, reducing the risk of major power accidents.

[0043] 2. There is no need for a large number of maintenance personnel to frequently monitor the outer metal sheath of the cable, which greatly reduces the cost and workload of power operation and maintenance.

[0044] 3. An adaptive algorithm is added to the current injection part. By adjusting the relevant parameters of the current injection module output, the deviation is reduced and the current of the cable outer metal sheath is stabilized near the target value.

[0045] 4. The algorithm has strong feature learning ability and good generalization ability, and can automatically extract useful features from a large amount of data. The algorithm automatically adjusts the internal weights to adapt to different tasks and environments, and can determine various defects in the metal sheath of the high-voltage cable, which helps maintenance personnel quickly locate and eliminate defects. Description of the drawings:

[0046] Figure 1 It is a block diagram of the online monitoring system;

[0047] Figure 2 Design a graph for the ground defect neural network;

[0048] Figure 3 This is a simplified diagram of the neural network implementation process for the grounding defect of the outer metal sheath of the cable;

[0049] Figure 4 This is a simplified diagram of the neural network training algorithm for cable outer metal sheath defects;

[0050] Figure 5 This is the overall diagram of the online monitoring system. Specific implementation method:

[0051] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The elements and features described in one embodiment of the present invention may be combined with the elements and features shown in one or more other embodiments. It should be noted that for the purpose of clarity, the representation and description of components and processes that are not related to the present invention and are known to those of ordinary skill in the art are omitted in the description. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0052] The present invention can work without power outage of the cable, and realizes online monitoring. Through the cooperation of current and voltage measurement module, single chip microcomputer and host computer, the equipment can quickly detect the fault when it occurs and facilitate the maintenance workers to remove the obstacle in time, reducing the risk of major power accidents. Current injection and sensor module: The current injection module can output a DC-100kHz signal, adaptively inject current into the outer metal sheath of the cable, and adjust the amplitude and frequency according to the on-site connection status. The voltage sensor and current sensor based on the principle of resistance voltage division are adopted, and the high-precision amplifier is used to ensure the accurate collection of the voltage and tiny induced current information on the outer metal sheath of the cable. The filter module is used to remove power frequency interference, transient interference and other radio interference. The algorithm in the present invention is similar to an improved neural network algorithm, which is used to diagnose the defects of the outer metal sheath of the cable, obtain weights through training and learning, and finally determine the defects of the outer metal sheath of the high-voltage cable. Fault impedance judgment is divided into three levels, and judgment is made according to different fault characteristics, including cable faults caused by production process, construction process, humid environment and external force damage, and their respective characteristics are described. The neural network structure consists of an input layer, an intermediate layer, and an output layer. The weights are determined through learning and training to realize fault diagnosis. The learning algorithm initializes weights and thresholds, inputs samples, calculates errors, modifies weights, and repeatedly calculates until a qualified weight is found, thereby finally determining the defects of the outer metal sheath of the high-voltage cable. The protection content of the present invention covers all components of the above technical solution, including monitoring methods, device structures, sensor technology, data processing algorithms, and neural network learning algorithms.

[0053] The present invention is further described below in conjunction with the accompanying drawings:

[0054] like Figure 1 As shown, an online monitoring system for grounding defects of the outer metal sheath of a high-voltage cable is provided, the system comprising:

[0055] Current injection module 1: used to inject a DC current into the outer metal sheath A, B, C of the high-voltage cable and between any two phases. Current injection module 1 is connected to the main control chip STM3215.

[0056] PID control module 2: It is composed of an improved PID controller. Its working principle is that the current sensor measures the current of the outer metal sheath of the high-voltage cable in real time, and feeds the measured value back to the controller. The controller calculates the control amount according to the deviation between the feedback value and the target value. Then, by adjusting the current injection module to change the output current amplitude, frequency and other related parameters, the current size in the outer metal sheath of the cable is changed, thereby reducing the deviation and finally stabilizing the current of the outer metal sheath of the cable near the target value.

[0057] The following improvements have been made based on the PID controller:

[0058] (1) Based on PID feedback control, a feedforward control link is added to adjust the controller output in advance according to the known disturbance of the system or the change of the input signal to compensate for the influence of the disturbance on the system. Feedforward PID control can improve the anti-interference ability and response speed of the system, enabling the system to track the change of the set value more quickly.

[0059] (2) When the error is small, PID control is used to ensure the control accuracy of the system; when the error exceeds a certain set limit, only PD control is used to avoid the accumulation of integral terms that may cause excessive overshoot in the system.

[0060] Current sensor 3: Based on the principle of electromagnetic induction and combined with a high-precision amplifier, it can accurately measure the tiny induced current information on the outer metal sheath of the high-voltage cable.

[0061] Voltage sensor 4: Based on the principle of resistance voltage division and equipped with a high-precision amplifier, it ensures that the voltage information on the outer metal sheath of the high-voltage cable can be accurately collected.

[0062] Filter module 5: used to remove power frequency interference from electrical equipment around the device, transient interference caused by switching operations, and other radio interference.

[0063] Current limiter 6: between the wire clamp and the voltage sensor, used to reduce the impact of the induced voltage of the cable metal sheath on the test equipment.

[0064] Wire clamps 7 and 8: used to clamp any two phases of the outer metal sheath A, B, C of the high-voltage cable to form electrical conduction.

[0065] AD converter 14: used to convert the analog signal measured and pre-processed by the sensor into a digital signal.

[0066] Main control chip STM3215: It is the core component of the device, realizing functions such as data processing and control, coordinating the work of various components, executing programs, communication, and device fault diagnosis. The main control chip STM32 is connected to various sensors, alarm modules, data transmission modules, and current injection modules; the alarm module is composed of LED lights and buzzers, and its function is to detect the grounding defect of the outer metal sheath of the high-voltage cable, and the alarm module starts the alarm; the data transmission module is composed of a wired or wireless network and an external network server, and its function is to transmit the signal processed by the main control chip STM32 to the external network server through a wired or wireless network, and then the external network server transmits it to the host computer, and the host computer displays the grounding defect information of the outer metal sheath of the high-voltage cable and provides a human-computer interaction interface.

[0067] Alarm module 16: It is composed of an LED light and a buzzer. Its function is to activate the alarm when a grounding defect of the outer metal sheath of the high-voltage cable is detected.

[0068] The data acquisition module 9, the temperature sensor 10, the humidity sensor 11, the anti-theft sensor 12, and the core current sensor 13 are connected to the AD converter built into the main control chip STM32.

[0069] like Figure 2 As shown in the figure, the neural network consists of three parts, namely the input layer, the middle layer, and the output layer. The input layer is the signal measured by the sensor, including current sensor, voltage sensor, core current sensor, temperature sensor, humidity sensor, and anti-theft sensor. The output layer is the grounding defect type, including normal, construction process, production process, humid environment, rust and corrosion failure, ant bite and rat bite, and external force damage. The neural network algorithm is as follows:

[0070] Assume that the measured voltage signal, current signal, core current signal, temperature, humidity, and anti-theft cutting data are U, I, and I respectively. n , T, W, S, the corresponding weights are t1, t2, t3, t4, t5, t6 respectively, then the final output f is:

[0071] f=t1U+t2I+t3I n +t4T+t5W+t6S

[0072] like Figure 3 As shown in the figure, since the corresponding weights cannot be obtained immediately at the beginning, they need to be obtained through neural network learning. The learning process first needs to pre-process the sample data collected by each sensor, then extract the characteristic quantity of the sensor signal, and then use the training results for the grounding defect neural network to finally obtain the grounding defect fault diagnosis result.

[0073] like Figure 4 As shown, the learning algorithm first initializes the weights and thresholds, then inputs random samples of each sensor, calculates the output of the cable grounding defect type of the intermediate layer and the output layer, ends the algorithm if the conditions are met, and calculates the node error accuracy if the conditions are not met, then modifies the connection weights and continues to judge whether the conditions are met, and repeats the calculation until the weights that meet the conditions are found.

[0074] like Figure 5As shown in the figure, the system includes three parts: terminal users, cloud applications, and field monitoring. The terminal user views the online monitoring results of the grounding defect of the outer metal sheath of the high-voltage cable sent by the main control chip STM32 to the host computer through the host computer. The field monitoring part includes the cable outer metal sheath grounding defect monitoring host, network port, network cable, wireless network, and the cloud application includes an external network server. The data transmission module consists of a network cable, a wireless network, and an external network server. Its function is to transmit the signal processed by the main control chip STM32 to the external network server through the wireless network, and then from the external network server to the host computer, and the host computer displays the grounding defect information of the outer metal sheath of the high-voltage cable.

[0075] The cable outer metal sheath grounding defect monitoring host is connected to the wireless network through the network port, and relies on the wireless network to connect to the terminal user through the external network server, transmits the final monitoring results to the terminal user, and displays the high-voltage cable outer metal sheath grounding defect information through the host computer.

[0076] A method for online monitoring of grounding defects of a high-voltage cable outer metal sheath, characterized in that it comprises the following steps:

[0077] A. Current signal injection: The current injection module injects short-time test current into the A, B, and C phase cable outer metal sheaths in time-sharing mode; the current injection module can output a DC-100kHz signal to inject current into the A, B, and C phase loops of the high-voltage cable outer metal sheath, and the amplitude and frequency of the injected current are adaptive according to the connection status of the high-voltage cable outer metal sheath on site. The current amplitude and frequency are adaptively controlled by closed-loop control. The current sensor measures the current of the high-voltage cable outer metal sheath in real time, and feeds the measured value back to the PID controller. The PID controller calculates the control quantity based on the deviation between the feedback value and the target value, and then changes the output current amplitude and frequency related parameters through the current injection module to change the current size in the cable outer metal sheath, thereby reducing the deviation and finally stabilizing the cable outer metal sheath current near the target value. The PID controller is provided with a feedforward control link, which adjusts the output of the controller in advance according to the known interference of the system or the change of the input signal to compensate for the influence of the interference on the system.

[0078] B. Acquisition and preprocessing of current and voltage signals: The current and voltage signals of any two phases of the outer metal sheath of the high-voltage cable are obtained by using a current sensor and a voltage sensor respectively. The current and voltage signals are filtered by a filtering module, and then the filtered data is transmitted to the AD converter for analog-to-digital conversion; the voltage sensor is based on the principle of resistance voltage division and is combined with a high-precision amplifier to ensure that the voltage information on the outer metal sheath of the high-voltage cable can be accurately collected. A current limiter is provided between the wire clamp and the voltage sensor and the wire clamp to reduce the impact of the induced voltage of the cable metal sheath on the test equipment; the current sensor is based on the principle of electromagnetic induction and is combined with a high-precision amplifier to accurately measure the current information on the outer metal sheath of the high-voltage cable; the filtering module connects the current sensor, the voltage sensor, and the AD converter, and its function is to remove the power frequency interference of the electrical equipment around the device, the transient interference caused by the switch operation, and other radio interference.

[0079] C. Acquisition and preprocessing of other sensor signals: The core current sensor, temperature sensor, humidity sensor, and anti-theft cutting sensor convert the measured analog signals into digital signals through AD converters;

[0080] D. Data transmission: The voltage, current, core current, temperature, humidity, and anti-theft cutting signal processed by the AD converter are transmitted to the main control chip STM32, processed by the main control chip and transmitted to the host computer by the data transmission module. The host computer displays the online monitoring results of the grounding defects of the outer metal sheath of the high-voltage cable;

[0081] E. Fault diagnosis: The main control chip STM32 performs data fusion processing, and the algorithm determines the specific defects of the outer metal sheath of the high-voltage cable.

[0082] The present invention studies a method and an online monitoring system for grounding defects of the outer metal sheath of a high-voltage cable. Compared with the traditional method, the online monitoring function can be realized. No power outage operation is required, which is more conducive to the needs of daily power life and production, and can also protect the life safety of maintenance workers to a greater extent. The specific effects are as follows:

[0083] 1. The equipment can work without power outages, realizing online monitoring and improving the safety and reliability of cable operation. It can detect various faults of the outer metal sheath of the cable in the first place, reducing the risk of major power accidents.

[0084] 2. There is no need for a large number of maintenance personnel to frequently monitor the outer metal sheath of the cable, which greatly reduces the cost and workload of power operation and maintenance.

[0085] 3. An adaptive algorithm is added to the current injection part to reduce the deviation by adjusting the relevant parameters of the power supply output, so that the current of the cable outer metal sheath is stabilized near the target value.

[0086] 4 The algorithm has strong feature learning ability and good generalization ability, and can automatically extract useful features from a large amount of data. The algorithm automatically adjusts the internal weights to adapt to different tasks and environments, and can determine various defects in the outer metal sheath of high-voltage cables, helping maintenance personnel to quickly locate and eliminate defects.

[0087] Finally, it should be noted that: although the present invention and its advantages have been described in detail above, it should be understood that various changes, substitutions and transformations can be made without exceeding the spirit and scope of the present invention as defined by the appended claims. Moreover, the scope of the present invention is not limited to the specific embodiments of the processes, devices, means, methods and steps described in the specification. It will be easily understood by those of ordinary skill in the art from the disclosure of the present invention that existing and future processes, devices, means, methods or steps that perform substantially the same functions as the corresponding embodiments described herein or obtain substantially the same results as the corresponding embodiments described herein can be used according to the present invention. Therefore, the appended claims are intended to include such processes, devices, means, methods or steps within their scope.

Claims

1. A method for online monitoring of grounding defects of the outer metal sheath of a high-voltage cable, characterized in that: The following steps are involved: A. Current signal injection: The current injection module injects short-time test current into the outer metal sheath of the A, B, and C phase cables in a time-sharing manner; B. Acquisition and preprocessing of current and voltage signals: Use current sensors and voltage sensors to obtain the current and voltage signals of any two phases of the outer metal sheath of the high-voltage cable respectively. The current and voltage signals are filtered by the filter module, and then the filtered data are transmitted to the AD converter for analog-to-digital conversion; C. Acquisition and preprocessing of other sensor signals: The core current sensor, temperature sensor, humidity sensor, and anti-theft cutting sensor convert the measured analog signals into digital signals through AD converters; D. Data transmission: The voltage, current, core current, temperature, humidity, and anti-theft cutting signal processed by the AD converter are transmitted to the main control chip STM32, processed by the main control chip and transmitted to the host computer by the data transmission module. The host computer displays the online monitoring results of the grounding defects of the outer metal sheath of the high-voltage cable; E. Fault diagnosis: The main control chip STM32 performs data fusion processing, and the algorithm determines the specific defects of the outer metal sheath of the high-voltage cable.

2. According to claim 1, a method for online monitoring of grounding defects of the outer metal sheath of a high-voltage cable is characterized by: In step A, the current injection module can output a DC-100kHz signal for injecting current into the A, B, and C phase loops of the outer metal sheath of the high-voltage cable. The amplitude and frequency of the injected current are adaptive according to the connection status of the outer metal sheath of the high-voltage cable at site.

3. According to claim 2, a method for online monitoring of grounding defects of the outer metal sheath of a high-voltage cable is characterized by: The current amplitude and frequency are adaptively controlled by closed-loop control. The current sensor measures the current of the outer metal sheath of the high-voltage cable in real time and feeds the measured value back to the PID controller. The PID controller calculates the control quantity based on the deviation between the feedback value and the target value, and then changes the output current amplitude and frequency related parameters through the current injection module to change the current size in the outer metal sheath of the cable, thereby reducing the deviation and finally stabilizing the current of the outer metal sheath of the cable near the target value.

4. According to claim 3, a method for online monitoring of grounding defects of the outer metal sheath of a high-voltage cable is characterized by: The PID controller is provided with a feedforward control link, which adjusts the output of the controller in advance according to known disturbances of the system or changes in input signals to compensate for the influence of the disturbances on the system.

5. According to claim 1, a method for online monitoring of grounding defects of the outer metal sheath of a high-voltage cable is characterized by: In step B, the voltage sensor is based on the principle of resistance voltage division and cooperates with a high-precision amplifier to ensure that the voltage information on the outer metal sheath of the high-voltage cable can be accurately collected. A current limiter is provided between the voltage sensor and the wire clamp to reduce the impact of the induced voltage of the cable metal sheath on the test equipment; the current sensor is based on the principle of electromagnetic induction and cooperates with a high-precision amplifier to accurately measure the current information on the outer metal sheath of the high-voltage cable; the filter module is connected to the current sensor, the voltage sensor, and the AD converter. Its function is to remove power frequency interference from electrical equipment around the device, transient interference caused by switching operations, and other radio interference.

6. The method for online monitoring of grounding defects of the outer metal sheath of a high-voltage cable according to claim 1, characterized in that: The main control chip STM32 is the core component of the device, which realizes the functions of data processing and control, coordination of the work of various components, execution of programs, communication, and device fault diagnosis. The main control chip STM32 is connected to various sensors, alarm modules, data transmission modules, and current injection modules; the alarm module is composed of an LED lamp and a buzzer, and its function is to start the alarm when a grounding defect of the outer metal sheath of the high-voltage cable is detected; the data transmission module is composed of a wired or wireless network and an external network server, and its function is to transmit the signal processed by the main control chip STM32 to the external network server through a wired or wireless network, and then the external network server transmits it to the host computer, and the host computer displays the grounding defect information of the outer metal sheath of the high-voltage cable and provides a human-computer interaction interface.

7. The method for online monitoring of grounding defects of the outer metal sheath of a high-voltage cable according to claim 1 is characterized by: In step E, the algorithm is an improved neural network algorithm, and its diagnosis process is as follows: A. The algorithm can diagnose the grounding defect of the outer metal sheath of the high-voltage cable. During the diagnosis process, the algorithm will first give a preliminary diagnosis result based on the level of fault impedance and fault characteristics. Then the system can diagnose through the neural network algorithm in STM32 to form the final diagnosis information; B. The algorithm consists of three parts: input layer, middle layer, and output layer. The input layer and output layer are fixed, and one middle layer is selected. The connection lines between layers correspond to different weights, which need to be obtained through training. The algorithm is as follows: Assume that the measured voltage signal, current signal, core current signal, temperature signal, humidity signal, and anti-theft cutting signal are U, I, and I respectively. n , T, W, S, the corresponding weights are t1, t2, t3, t4, t5, t6 respectively, then the final output f is: <h2 style=";text-align:left;direction:ltr">f = t1U + t2I + t3I<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> +t3T+t5W+t6S; C. Since the corresponding weights cannot be obtained immediately at the beginning, they need to be obtained through neural network learning. The learning process first needs to convert the sample data collected by each sensor through an AD converter, then extract the characteristic quantity of the sensor signal, and then use the training results for the grounding defect neural network to finally obtain the grounding defect diagnosis result; D. The learning algorithm first initializes the weights and thresholds, then inputs random samples of the characteristic quantities of each sensor, calculates the output of the cable grounding defect type of the intermediate layer and the output layer, and ends the algorithm if the conditions are met. If the conditions are not met, the node error accuracy is calculated, and then the connection weights are modified to continue to judge whether the conditions are met. The calculation is repeated until the weights that meet the conditions are found; E. Determine the weights corresponding to each branch of the neural network after learning. The information measured by the sensor is converted by the AD converter and transmitted to the main control chip STM32. The main control chip calculates and processes the weights obtained through the training through the algorithm, and finally transmits the calculation results to the host computer through the data transmission module.

8. An online monitoring system for grounding defects of the outer metal sheath of a high-voltage cable, characterized in that: The system includes: A current injection module (1): used to inject a section of direct current into the outer metal sheath A, B, C of the high-voltage cable and between any two phases, and the current injection module (1) is connected to the main control chip STM32 (15); PID control module (2): composed of a PID controller, a current sensor measures the current of the outer metal sheath of the high-voltage cable in real time, and feeds back the measured value to the controller. The controller calculates the control amount according to the deviation between the feedback value and the target value, and then changes the output current amplitude and frequency related parameters by adjusting the current injection module to change the current size in the outer metal sheath of the cable, thereby reducing the deviation and finally stabilizing the current of the outer metal sheath of the cable near the target value; Current sensor (3): Based on the principle of electromagnetic induction and combined with a high-precision amplifier, it can accurately measure the tiny induced current information on the outer metal sheath of the high-voltage cable; Voltage sensor (4): based on the principle of resistance voltage division and equipped with a high-precision amplifier, to ensure accurate acquisition of voltage information on the outer metal sheath of the high-voltage cable; Filter module (5): used to remove power frequency interference from electrical equipment around the device, transient interference caused by switch operation, and other radio interference; Current limiter (6): between the wire clamp and the voltage sensor, used to reduce the impact of the induced voltage of the cable metal sheath on the test equipment; The first wire clamp (7) and the second wire clamp (8) are used to clamp any two phases of the outer metal sheath A, B, C of the high-voltage cable to form electrical conduction; AD converter (14): used to convert the analog signal measured and pre-processed by the sensor into a digital signal; Main control chip STM32 (15): It is the core component of the device and realizes the functions of data processing and control, coordinating the work of various components, executing programs, communication, and device fault diagnosis; The alarm module (16) is composed of an LED light and a buzzer. When a grounding defect of the outer metal sheath of the high-voltage cable is detected, the alarm module starts an alarm. The data acquisition module (9), the temperature sensor (10), the humidity sensor (11), the anti-theft sensor (12), and the core wire current sensor (13) are connected to an AD converter (14) built into a main control chip STM32 (15).

Images