Medium-voltage cable grounding state monitoring method and system

Abstract

The invention relates to the technical field of medium-voltage cable grounding state monitoring, in particular to a medium-voltage cable grounding state monitoring method and system, and the method comprises the steps: obtaining target data through an acquisition device, transmitting the target data to a central processing system, and enabling the target data to comprise load current data and cable shielding layer grounding current; and analyzing the condition of the grounding system through the central processing system according to the target data, wherein the analysis of the condition of the grounding system comprises the step of evaluating the condition of the grounding system by establishing an equation set. The beneficial effects of the invention are that load current and shielding layer grounding current data of a cable line can be acquired in real time, and synchronization and analysis are carried out through the central processing system. The condition of the grounding system is evaluated by establishing an equation set based on the average period of the data of the intelligent electric meter, the load current of the cable section and the total grounding current, so that the fault type is accurately judged.

Description

Technical Field

[0001] The present invention relates to the technical field of medium voltage cable grounding status monitoring, and in particular to a medium voltage cable grounding status monitoring method and system. Background Art

[0002] With rapid economic and social development and rising urbanization, my country's electricity demand continues to grow, and so does the proportion of cables in the power system. Cable lines, as reliable links between energy and loads, are often difficult to directly observe and repair, requiring specialized methods to locate faults. New technologies are enabling condition monitoring of cable lines. These technologies can minimize the risk of failures and detect pre-fault conditions in advance, thereby avoiding prolonged power outages and potential electric shock hazards.

[0003] The grounding system is an important component of cable lines. Research on this system involves the grounding electrodes in high-voltage substations, the construction and optimization of the grounding system, and monitoring of the grounding system deep within the network and within the substation. However, existing technologies have significant drawbacks when monitoring the status of cable grounding systems:

[0004] Limited monitoring targets: Most monitoring technologies focus on monitoring the cable itself, lacking specialized monitoring methods for cable grounding systems. This limitation makes it difficult to detect grounding system degradation and faults in a timely manner.

[0005] Limited monitoring range: Existing technologies can usually only monitor a single or a few grounding systems, and can only monitor within a short distance, and cannot achieve simultaneous monitoring of multiple remote grounding systems.

[0006] Difficulty in implementation: Due to the large number and widespread distribution of grounding systems, effective monitoring of all of them is a significant challenge. Existing technologies are limited in monitoring scale and distance, making it difficult to meet practical application requirements.

[0007] These problems seriously restrict the comprehensive implementation of cable grounding system condition monitoring. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a method for monitoring the grounding status of a medium voltage cable, comprising acquiring target data through an acquisition device and transmitting the target data to a central processing system, wherein the target data includes load current data and cable shield grounding current;

[0010] The condition of the grounding system is analyzed according to the target data by the central processing system, wherein the analysis of the condition of the grounding system includes evaluating the condition of the grounding system by establishing a set of equations.

[0011] As a preferred solution of the medium voltage cable grounding status monitoring method of the present invention, wherein: the acquisition device includes a smart meter and a Rogowski coil, wherein the smart meter is installed on the low voltage side of the transformer, and the cable shielding layer is arranged in the middle of the measurement window of the Rogowski coil;

[0012] Smart meters are used to obtain real-time load current data of cable lines;

[0013] Rogowski coils are used to pick up the ground current in the cable shield.

[0014] As a preferred solution of the method for monitoring the grounding status of a medium-voltage cable of the present invention, the smart meter is used to obtain the load current data of the cable line in real time, including

[0015] The voltage and power data obtained by the smart meter are transmitted to the central processing system to calculate the current;

[0016] And according to Kirchhoff's law, the load current of the cable segment is recalculated.

[0017] As a preferred embodiment of the method for monitoring the grounding status of a medium voltage cable of the present invention, the condition of the grounding system is evaluated by establishing a set of equations, including:

[0018] A set of equations is established based on the average period of data obtained by the smart meter, the load current of the cable segment, and the total ground current obtained;

[0019] The share factor is obtained by solving the equation group, and the ground fault type is determined according to the change trend of the share factor.

[0020] As a preferred solution of the medium voltage cable grounding status monitoring method of the present invention, wherein: the condition of the grounding system is analyzed according to the target data by the central processing system, and further comprising:

[0021] Thermomechanical stress monitoring is used to determine the fault type of the last grounding system.

[0022] As a preferred solution of the method for monitoring the grounding status of a medium-voltage cable of the present invention, a maintenance strategy is formulated according to the status analysis result of the grounding system.

[0023] As a preferred solution of the method for monitoring the grounding status of a medium voltage cable of the present invention, wherein: formulating a maintenance strategy is a maintenance strategy formulated based on the health status of the grounding system;

[0024] The health of the grounding system is assessed through real-time or periodic monitoring.

[0025] In a second aspect, the present invention provides a medium voltage cable grounding status monitoring system, comprising: an acquisition module, configured to acquire target data through an acquisition device and transmit the target data to a central processing system, wherein the target data includes load current data and cable shield grounding current;

[0026] The analysis module is used to analyze the condition of the grounding system according to the target data through the central processing system, wherein the analysis of the condition of the grounding system includes evaluating the condition of the grounding system by establishing a set of equations.

[0027] In a third aspect, the present invention provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0028] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the above method when the computer program is executed by a processor.

[0029] Compared with the existing technology, the present invention has the following advantages: it can obtain the load current and shield grounding current data of the cable line in real time, and synchronize and analyze them through the central processing system. By establishing a set of equations based on the average cycle of smart meter data, the load current of the cable segment, and the total grounding current, the grounding system condition is evaluated, thereby accurately determining the type of fault. In addition, this method also considers the impact of environmental factors on the monitoring data, and further determines the fault type through thermomechanical stress monitoring. Ultimately, based on the analysis results, an optimized maintenance strategy is formulated to improve the safety and reliability of the power system and reduce operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a flow chart of the medium voltage cable grounding status monitoring method.

[0032] Figure 2 is an exemplary cable feeder diagram.

[0033] Figure 3 This is a diagram of the installation position of the Rogowski coil on the cable shield grounding system.

[0034] Figure 4 Figure 2 is a graph of Ircs as a function of Ipc. DETAILED DESCRIPTION

[0035] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0036] Example 1, reference Figures 1 to 4 , which is the first embodiment of the present invention, provides a method for improving the efficiency of short-term high-frequency energy storage, comprising:

[0037] S1. Acquire target data through an acquisition device and transmit the target data to a central processing system, wherein the target data includes load current data and cable shielding layer grounding current.

[0038] Furthermore, the data collection device includes a smart meter and a Rogowski coil, wherein the smart meter is installed on the low-voltage side of the transformer, and the cable shield is arranged in the middle of the measurement window of the Rogowski coil;

[0039] Smart meters are used to obtain real-time load current data of cable lines;

[0040] Rogowski coils are used to pick up the ground current in the cable shield.

[0041] It should be noted that in order to ensure that the smart meter acquisition is consistent with the grid's synchronization time, dedicated communication channels and network infrastructure are used for transmission. These measurement data are synchronized with GPS (Global Positioning System) time to ensure data synchronization.

[0042] It's also important to note that the cable shield must be centered within the Rogowski coil's measurement window, and the coil must be completely closed. Furthermore, all coils within a measurement system must maintain consistent mounting and winding orientation. Furthermore, the Rogowski coil's inner diameter must be larger than the outer diameter of the cable being measured, and the measurement window must be large enough to ensure the cable is centered.

[0043] It should be further explained that you can choose to Figure 3 The Rogowski coils are installed at positions A and B, ensuring measurement accuracy and minimizing measurement errors by placing the cable shield in the center of the coil's measurement window. Preferably, the installation position is point B, as this better ensures that the current from the cable shield is accurately coupled into the sensor, minimizing errors caused by incorrect positioning of the cable shield in the measurement window.

[0044] Furthermore, the smart meter is used to obtain the load current data of the cable line in real time, including

[0045] The voltage and power data obtained by the smart meter are transmitted to the central processing system to calculate the current;

[0046] And according to Kirchhoff's law, the load current of the cable segment is recalculated.

[0047] Preferably, recalculating the load current of the cable segment according to Kirchhoff's law helps to accurately obtain the actual load current of the cable segment.

[0048] S2. Analyzing the condition of the grounding system according to the target data through the central processing system, wherein analyzing the condition of the grounding system includes evaluating the condition of the grounding system by establishing a set of equations.

[0049] It should be noted that for a single-section cable line, the magnitude of the cable shield grounding current generally depends on: the cable layout, cable line parameters, particularly the cable shield cross-section, grounding system resistance, and cable line length. The longer the cable line, the greater the cable shield grounding current, Ircs. Ircs is higher for cables laid horizontally, and lower for cables laid in a zigzag pattern. This is because in the zigzag pattern, the magnetic fields generated by the cables almost completely ignore each other, while in the horizontal pattern, the negligence effect is smaller due to the large difference in coupling impedance between the cables. Experiments have shown that Ircs increases with increasing cable length; however, for longer cable lines, the current remains nearly constant. At the same time, Ircs decreases for higher grounding system resistances. The impact of cable line layout on grounding shield current is that even relatively minor changes in the layout can lead to an increase in Ircs.

[0050] For multi-segment cable runs: When analyzing a cable run consisting of two cable segments connected in series, ground system degradation in different cable segments produces different results. Ground system degradation closer to the measurement point has a greater impact on the ground shield current, Ircs, because it affects the current loops in more cable segments. The continuity of the cable ground system also has a certain impact on Ircs. When ground system continuity is disrupted, the ground system resistance increases, resulting in a decrease in the ground system current. The fault type presented also manifests as a decrease in the ground shield current amplitude; compared to ground point degradation, this fault occurs immediately.

[0051] Furthermore, simulations and actual measurements show that the correlation between the load current (expressed as the positive sequence current Ipc) and Ircs is very high. Based on the actual measurement results of a certain line section, Ircs is expressed as a function of Ipc on the xy Cartesian plane, as follows: Figure 3The measurements were taken under mild weather conditions (only brief, intermittent rainfall of less than an hour). In some severe weather conditions, the relationship between load current and Ircs may not be immediately apparent. The grounding system resistance can change significantly due to environmental conditions (i.e., rainfall or snowmelt). In the case of rainfall, it is relatively simple to correlate the grounding resistance change with rainfall, as the effects of rainfall can be observed shortly after the event. The effects of snowfall can be identified using information about snow and temperature—if the ambient temperature rises above 0°C after a snowfall, the grounding system resistance decreases, and therefore, the grounding current increases.

[0052] Furthermore, the condition of the grounding system is evaluated by establishing a set of equations, including,

[0053] An equation group is established based on the average period of data obtained by the smart meter, the load current of the cable segment, and the total ground current obtained. The more cable segments there are, the longer the equation group will be.

[0054] The share factor is obtained by solving the equation group, and the ground fault type is determined according to the change trend of the share factor. The share factor is obtained by solving the equation group using the least square method.

[0055] It should be noted that the change in the grounding system state affects the cable shield grounding current Ircs, and the load current has a high correlation with the grounding current. Figure 1 Taking the cable route shown as an example, the following equations are established:

[0056] I1 t1 ·RF r110 / 15_sL1 +I2 t1 ·RF r110 / 15_sL2 +I3 t1 ·RF r110 / 15_sL3 =I rcs_t1

[0057] I1 t2 ·RF r110 / 15_sL1 +I2 t2 ·RF r110 / 15_sL2 +I3 t2 ·RF r110 / 15_sL3 =I rcs_t2

[0058] I1 t3 ·RF r110 / 15_sL1 +I2 t3 ·RF r110 / 15_sL2 +I3 t3 ·RF r110 / 15_sL3 =I rcs_t3

[0059] Where t1, t2, and t3 are the averaging periods of the data recorded by the smart meter; RFr110 / 15_sL1, RFr110 / 15_sL2, and RFr110 / 15_sL3 are the share factors corresponding to the three cable segments; I1t, I2t, and I3t represent the load currents of each cable segment at different time points; and Ircs_t is the total ground current measured at these time points.

[0060] It is also important to note that the calculated share factors are correlated with the load current, and a trend line is plotted on the xy plane. The trend graph is observed in real time, and abnormal changes in the trend graph can be used to detect ground faults. If a significant trend change is observed, an alarm is generated. Alarm types include ground system degradation and cable joint damage. The number of share factors indicates the location of the anomaly. If only one share factor differs significantly, it can be determined that the cable joint is damaged. If multiple share factors differ significantly, it can be determined that ground system degradation is the cause of the anomaly.

[0061] Furthermore, the central processing system analyzes the condition of the grounding system based on the target data, including:

[0062] Thermomechanical stress monitoring is used to determine the fault type of the last grounding system.

[0063] It should be noted that when problems occur in the last grounding system and cable joint of the feeder, it is impossible to directly determine which type of fault it is, because the deterioration of the grounding system and the damage of the cable joint may produce similar results. Since the damage of the cable joint is related to the thermo-mechanical stress under high current conditions, thermo-mechanical stress monitoring is further used to determine the fault type of the last grounding system.

[0064] Furthermore, thermo-mechanical stress monitoring is performed by analyzing the event registers of digital protection relays.

[0065] It should be noted that the protection relay must be configured to record high-current events (such as phase-to-phase faults), store the current magnitude and duration, record the timestamp of the event, and have sufficient storage capacity. Whenever the current in the cable core exceeds a preset threshold, relevant information (such as current magnitude and duration) is stored in the relay's digital registers. Finally, the algorithm analyzes the Ircs_pre / post values ​​before and after the current event. If there is a significant change in Ircs, an alarm is issued: "Damaged cable joint." Otherwise, a grounding system fault is detected.

[0066] Furthermore, a maintenance strategy is formulated based on the grounding system condition analysis results.

[0067] Furthermore, the maintenance strategy is formulated based on the health status of the grounding system;

[0068] The health of the grounding system is assessed through real-time or periodic monitoring.

[0069] It should be noted that the grounding system health assessment is based on trend analysis of the share factor, monitoring of cable shield current distribution, and comparison with historical operating data. Maintenance priorities are determined based on health status: the criticality of the equipment is considered and the availability of maintenance resources is assessed. Maintenance activity scheduling: Prioritize areas experiencing significant abnormal changes based on the system's operating plan.

[0070] It should be further noted that during maintenance, professional technicians on-site will reinstall the damaged parts. After the maintenance is completed, the data before and after maintenance will be compared, the maintenance effect will be evaluated, and the maintenance results will be recorded to ensure the quality of the maintenance and repair.

[0071] In summary, the beneficial effect of the medium-voltage cable grounding status monitoring method of the present invention is that it can obtain the load current and shielding layer grounding current data of the cable line in real time, and synchronize and analyze them through the central processing system. By establishing a set of equations based on the average period of smart meter data, cable segment load current and total grounding current to evaluate the grounding system condition, the fault type can be accurately determined. In addition, this method also takes into account the impact of environmental factors on the monitoring data, and further determines the fault type through thermomechanical stress monitoring. Finally, based on the analysis results, an optimized maintenance strategy is formulated to improve the safety and reliability of the power system and reduce operating costs.

[0072] Embodiment 2 is a second embodiment of the present invention. This embodiment provides a medium voltage cable grounding status monitoring system, including an acquisition module for acquiring target data through an acquisition device and transmitting the target data to a central processing system, wherein the target data includes load current data and cable shield grounding current;

[0073] The analysis module is used to analyze the condition of the grounding system according to the target data through the central processing system, wherein the analysis of the condition of the grounding system includes evaluating the condition of the grounding system by establishing a set of equations.

[0074] Example 3 is the third embodiment of the present invention, which differs from the first two embodiments in that:

[0075] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the various embodiments of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0076] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0077] More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic devices), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0078] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0079] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for monitoring the grounding status of a medium voltage cable, characterized by: include, Acquire target data through an acquisition device and transmit the target data to a central processing system, wherein the target data includes load current data and cable shielding layer grounding current; The condition of the grounding system is analyzed according to the target data by the central processing system, wherein the analysis of the condition of the grounding system includes evaluating the condition of the grounding system by establishing a set of equations.

2. The method for monitoring the grounding status of a medium voltage cable according to claim 1, wherein: The collection device includes a smart meter and a Rogowski coil, wherein the smart meter is installed on the low-voltage side of the transformer, and the cable shielding layer is arranged in the middle of the measurement window of the Rogowski coil; The smart meter is used to obtain load current data of the cable line in real time; The Rogowski coil is used to obtain the ground current of the cable shield.

3. The method for monitoring the grounding status of a medium voltage cable according to claim 2, wherein: The smart meter is used to obtain the load current data of the cable line in real time, including The voltage and power data obtained by the smart meter are transmitted to the central processing system to calculate the current; And according to Kirchhoff's law, the load current of the cable segment is recalculated.

4. The method for monitoring the grounding status of a medium voltage cable according to claim 3, wherein: The condition of the grounding system is evaluated by establishing a set of equations, including: A set of equations is established based on the average period of data obtained by the smart meter, the load current of the cable segment, and the total ground current obtained; The share factor is obtained by solving the equation group, and the ground fault type is determined according to the change trend of the share factor.

5. The method for monitoring the grounding status of a medium voltage cable according to claim 4, wherein: The analyzing the condition of the grounding system according to the target data by the central processing system also includes: Thermomechanical stress monitoring is used to determine the fault type of the last grounding system.

6. The method for monitoring the grounding status of a medium voltage cable according to any one of claims 1 to 5, characterized in that: The method further includes formulating a maintenance strategy based on the condition analysis result of the grounding system.

7. The method for monitoring the grounding status of a medium voltage cable according to claim 6, wherein: The maintenance strategy is formulated based on the health status of the grounding system; The health status of the grounding system is evaluated through real-time or periodic monitoring.

8. A medium voltage cable grounding status monitoring system, characterized in that: include: An acquisition module is used to acquire target data through an acquisition device and transmit the target data to a central processing system, wherein the target data includes load current data and cable shielding layer grounding current; The analysis module is used to analyze the condition of the grounding system according to the target data through the central processing system, wherein the analysis of the condition of the grounding system includes evaluating the condition of the grounding system by establishing a set of equations.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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