A method for identifying power cable faults based on induced current

Abstract

The present invention provides a power cable fault identification method based on induced current, which belongs to the technical field of power cable fault prediction. The method includes recording data of the operating status when a short circuit fault occurs in the power cable, adding the recorded data of the operating status to the recorded data of the operating status when the short circuit fault occurred in the past, and obtaining the cable induced current value; determining the cause of the cable short circuit, including a single-phase ground short circuit fault and a two-phase ground short circuit fault; if the cause of the cable short circuit is a single-phase ground short circuit fault, the power system continues to operate; if the cause of the cable short circuit is a two-phase ground short circuit fault, the power system controls the circuit breaker to trip; and based on the data of the operating status recorded multiple times in the past when the short circuit fault occurred, predicting whether the cable is prone to short circuit faults. This method can accurately identify the cause of the short circuit fault and predict whether the power cable is prone to short circuit faults.

Description

Technical Field

[0001] The present invention relates to the technical field of power cable fault determination, and in particular to a power cable fault determination method based on induced current. Background Art

[0002] Diagnosing power cable anomalies is crucial for the stable operation of power systems. Due to the varying load rates, theoretical service lives, and operating environments of power cables, pre-diagnosis of power cable faults is generally difficult, and the aging mechanism of power cables is affected by a variety of factors. In related technologies, various measurement sensors and diagnostic algorithms have been gradually proposed, verified, and applied to address power cable fault pre-diagnosis. For example, there are high-frequency partial discharge detection systems for power cable aging diagnosis and diagnostic algorithms for power cable faults. However, these technologies do not provide a specific diagnosis of the cause of the cable fault, and subsequent treatment methods are not effective enough, resulting in reduced grid operating efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a power cable fault identification method based on induced current, which can accurately find out the cause of the short-circuit fault and predict whether the power cable is prone to short-circuit fault.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: a power cable fault identification method based on induced current, comprising the following contents:

[0005] When a short circuit fault occurs in the power cable, the operating status data at the time of the new short circuit fault is recorded, the recorded operating status data is added to the recorded operating status data at the time of the historical short circuit fault, and the cable induced current value is obtained;

[0006] Determine the cause of the cable short circuit based on the obtained cable induced current value. The causes of the cable short circuit include single-phase ground short circuit fault and two-phase ground short circuit fault;

[0007] If the cause of the cable short circuit is a single-phase ground short circuit fault, the power system continues to operate. If the cause of the cable short circuit is a two-phase ground short circuit fault, the power system controls the circuit breaker to trip.

[0008] Based on the data of multiple historical records of the operating status when short-circuit faults occurred, it is predicted whether the cable is prone to short-circuit faults.

[0009] In a preferred solution, when a short circuit occurs in a power cable, the recorded data includes the time when the short circuit occurs, the location where the short circuit occurs, various parameters of the power grid operation related to the short circuit, the environmental parameters when the short circuit occurs, and the parameters of the cable itself.

[0010] In a preferred solution, the parameters of the cable itself include the material of the cable, the service life of the cable, the length of the cable laid, the geometric dimensions of the cable, and the depth of the cable laid.

[0011] In a preferred solution, the method for determining the cause of a cable short circuit based on the cable induced current value is as follows: adjusting the capacity of the transformer corresponding to the location of the short circuit fault, obtaining the corresponding short circuit current values ​​when the transformer has different capacities, and if the maximum difference of all the obtained short circuit current values ​​is within the set threshold range, it is determined to be a single-phase ground short circuit fault; if the maximum difference of all the obtained short circuit current values ​​is outside the set threshold range, it is determined to be a two-phase ground short circuit fault.

[0012] In a preferred solution, if the cause of the cable short circuit is a single-phase ground short circuit fault, the power system continues to work. When the single-phase ground short circuit fault still exists after exceeding the set time range, the power system controls the circuit breaker to trip.

[0013] In a preferred solution, the process of predicting whether a cable is prone to short circuit failure is as follows:

[0014] The recorded data is normalized as eigenvalues, and the normalized eigenvalues ​​are clustered to obtain several cluster centers; the operating status of the power cable is monitored in real time, and based on the Euclidean distance value between the cluster position of the operating status at a certain time and place and a certain cluster center, it is judged whether the cable at this time and place is prone to short circuit failure.

[0015] In a preferred solution, based on the Euclidean distance between the cluster position of the operating status at a certain location at a certain moment and a certain cluster center, the rule for determining whether the cable at that location is prone to short circuit failure is as follows:

[0016] If the Euclidean distance between the cluster position of the operating status at a certain location at a certain moment and a certain cluster center is less than or equal to the set value, it is judged that the cable at this time and place is prone to short circuit fault and an early warning is issued;

[0017] If the Euclidean distance between the cluster position of the operating status at a certain location at a certain time and a certain cluster center is greater than the set value, but the similarity between the operating status and the operating status when a short circuit occurs is greater than the set similarity value, then it is judged that the cable at this time and location is prone to short circuit failure and an early warning is issued;

[0018] The remaining situations indicate that the cables at this time and location are not prone to short circuit failure.

[0019] In the preferred scheme, when recording the operating status data when a new short-circuit fault occurs, first determine which cluster the operating status belongs to, retrieve the operating status data of the cluster center, and compare the new operating status with the operating status of the cluster center for similarity. If there are the same eigenvalues, no recording is performed. If there are different eigenvalues, the difference between the two is recorded to complete the recording of the new operating status when a short-circuit fault occurs.

[0020] In a preferred solution, the similarity comparison includes a time similarity comparison, and the time similarity comparison includes three dimensions: whether it is a peak period, whether it is the same week, and whether it is the same month.

[0021] The present invention provides a method for determining power cable faults based on induced current, which has the following beneficial effects:

[0022] 1. The short-circuit current of a single-phase ground fault is unrelated to the transformer capacity, while the short-circuit current of a double-phase ground fault is related to the transformer capacity. Generally speaking, with other conditions remaining unchanged, the larger the transformer capacity, the greater the short-circuit current. Therefore, this method can determine whether it is a single-phase ground fault or a double-phase ground fault by detecting the short-circuit current at different transformer capacities. Taking different measures for different causes ensures the efficiency of power system operation.

[0023] 2. The characteristics of cable short-circuit faults are classified, and the current operation of the power system is predicted through historical faults. Timely warnings can be issued for possible cable short-circuit faults, further improving the stability of the power system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0025] Figure 1 This is a flow chart for determining the short-circuit cause of a short-circuit fault of the present invention;

[0026] Figure 2 This is a flow chart of the present invention for predicting whether a cable is prone to short circuit failure; DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] It should be understood that in various embodiments of the present invention, the size of the sequence number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0029] It should be understood that in the present invention, "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0030] It should be understood that in the present invention, "multiple" refers to two or more. "And / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "Contains A, B and C", "Contains A, B, C" means that A, B, and C are all included, "Contains A, B or C" means that one of A, B, and C is included, and "Contains A, B and / or C" means that any one, any two, or any three of A, B, and C are included.

[0031] The technical solution of the present invention is described in detail below with reference to specific embodiments. The embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0032] Combine Figure 1~Figure 2 The specific embodiments of the present invention are described in further detail.

[0033] Example:

[0034] like Figure 1 As shown in the figure, when a short circuit occurs due to a power cable fault, the process of determining the cause of the short circuit is as follows:

[0035] Step 1: The power fault monitoring system starts working to monitor whether the cable has a short circuit fault. If a short circuit fault occurs, the cable induced current value is obtained and the process goes to step 2. If no fault occurs, the power fault monitoring system continues to monitor the operation of the cable.

[0036] Step 2: Determine the cause of the cable short circuit based on the obtained cable induced current value. The causes of the cable short circuit include a single-phase ground short circuit fault and a two-phase ground short circuit fault.

[0037] The method for determining the cause of a cable short circuit based on the cable induced current value is as follows: adjust the capacity of the transformer corresponding to the location of the short circuit fault, obtain the corresponding short circuit current values ​​when the transformer has different capacities, and if the maximum difference of all the obtained short circuit current values ​​is within the set threshold range, it is determined to be a single-phase ground short circuit fault; if the maximum difference of all the obtained short circuit current values ​​is outside the set threshold range, it is determined to be a two-phase ground short circuit fault.

[0038] As shown in Tables 1 and 2, the short-circuit current of a single-phase ground fault has nothing to do with the capacity of the transformer; while the short-circuit current of a double-phase ground fault is related to the capacity of the transformer. Generally speaking, when other conditions remain unchanged, the larger the capacity of the transformer, the greater the short-circuit current.

[0039] Therefore, this method can determine whether it is a single-phase grounding short-circuit fault or a double-phase grounding short-circuit fault by detecting the magnitude of the short-circuit current at different transformer capacities, and then take corresponding measures.

[0040] Table 1 Relationship between short-circuit current and transformer capacity during single-phase ground fault

[0041] Transformer capacity (kVA) 200 250 315 400 500 630 800 Short-circuit current (A) 16.94 16.81 16.71 16.61 16.54 16.52 16.49

[0042] Table 2 Influence of transformer capacity on current flowing through power cable shielding layer during two-phase ground short circuit

[0043] Transformer capacity (kVA) 200 250 315 400 500 630 800 Short-circuit current (A) 325.24 403.68 503.34 625.55 761.88 852.97 1026.66

[0044] Step 3: If the cause of the cable short circuit is a single-phase ground short circuit fault, the power system continues to operate; if the cause of the cable short circuit is a two-phase ground short circuit fault, the power system controls the circuit breaker to trip.

[0045] For short-circuit faults caused by single-phase grounding, since one end of the power cable shield is grounded, the short-circuit current flows back to the power source through the cable sheath via the capacitance of the non-fault phase to ground, forming a loop. This means that the short-circuit current is the system capacitance current. The magnitude of the short-circuit current depends on parameters such as the line capacitance to ground and line length. Because a single-phase grounding has minimal impact on the entire power cable, the power system can continue to operate with the fault for a period of time. For short-circuit faults caused by double-phase grounding, the short-circuit current flows from one faulty phase through the cable sheath, the grounding resistance, the ground, the grounding resistance, and the cable sheath, returning to the other faulty phase. The magnitude of the short-circuit current is primarily affected by the grounding resistance and the leakage reactance of the power source, as well as other factors such as the line parameters. Because a double-phase grounding significantly impacts the entire power cable, the power system should control the short-circuit protection by tripping the short-circuit controller upon confirmation of a double-phase grounding fault to protect the entire system.

[0046] During specific operation, if the cause of the cable short circuit is a single-phase ground short circuit fault, the power system continues to work. When the single-phase ground short circuit fault still exists after exceeding the set time range, which can be between 0.05 and 0.1S, the power system controls the circuit breaker to trip. That is, if the single-phase ground short circuit fault is still not eliminated within the set time range, the circuit breaker needs to trip to protect the entire power system.

[0047] Example 2:

[0048] Predicting whether a cable is prone to short circuit failure includes the following steps:

[0049] When a short circuit fault occurs in the power cable, data of the operating status at the time of the new short circuit fault is recorded, and the recorded data of the operating status is added to the recorded data of the operating status at the time of the short circuit fault that occurred in the past.

[0050] The recorded data includes the time when the short circuit fault occurred, the location of the short circuit fault, various parameters of the power grid operation related to the short circuit fault when the short circuit fault occurred, the environmental parameters when the short circuit fault occurred, and the parameters of the cable itself.

[0051] The parameters of the cable itself include the material of the cable, the service life of the cable, the length of the cable laid, the geometric dimensions of the cable and the depth of the cable laid.

[0052] Based on the historical data of the operating status when short-circuit faults occurred, the cable is predicted to be prone to short-circuit faults. The specific process is as follows:

[0053] The recorded data is normalized as eigenvalues, and the normalized eigenvalues ​​are clustered to obtain several cluster centers.

[0054] The power fault monitoring system monitors the operating status of power cables in real time. Based on the Euclidean distance between the cluster location of the operating status at a certain time and location and a certain cluster center, it determines whether the cable at that time and location is prone to short circuit faults. The specific judgment rules are as follows:

[0055] If the Euclidean distance between the cluster position of the operating status at a certain location at a certain moment and a certain cluster center is less than or equal to the set value, it is judged that the cable at this time and place is prone to short circuit fault and an early warning is issued;

[0056] If the Euclidean distance between the cluster position of the operating status at a certain location at a certain time and a certain cluster center is greater than the set value, but the similarity between the operating status and the operating status when a short circuit occurs is greater than the set similarity value, then it is judged that the cable at this time and location is prone to short circuit failure and an early warning is issued;

[0057] The remaining situations indicate that the cables at this time and location are not prone to short circuit failure.

[0058] By predicting the current operation of the power system through historical faults, it is possible to issue timely warnings for possible cable short-circuit faults, further improving the stability of the power system operation. In this method, the operating status of the short-circuit faults that occurred in the past is recorded. The recorded data are all factors affecting the occurrence of short-circuit faults. Therefore, this method clusters the characteristic values, and each cluster center is a characteristic of a cable short-circuit fault. Since the power fault monitoring system can obtain the real-time operating status of the power system in real time, a cluster analysis is performed on the existing operating status. If the Euclidean distance between the cluster position of the operating status and a certain cluster center is less than or equal to the set value, it can be judged that the cable is prone to failure at this time.

[0059] Preferably, Figure 2 As shown, when recording the operating status data when a new short-circuit fault occurs, first determine which cluster the operating status belongs to, retrieve the operating status data of the cluster center, and compare the new operating status with the operating status of the cluster center for similarity. If there are identical eigenvalues, no recording is performed. If there are different eigenvalues, the difference between the two is recorded to complete the recording of the new operating status when a short-circuit fault occurs.

[0060] The similarity comparison includes a time similarity comparison, and the time similarity comparison includes three dimensions: whether it is a peak period, whether it is the same week, and whether it is the same month. In the time similarity comparison, the date cannot be used as a comparison because the dates will not be the same. Therefore, the time similarity comparison needs to be performed based on periodically repeated features, such as whether it is a peak period, whether it is the same week, and whether it is the same month. In specific implementation, the similarity can also have other similarity comparisons, such as operating parameters, location, environment, etc.

[0061] This data recording method can save storage space for records and clearly understand the classification of operating status and the differences between cluster centers, which is convenient for subsequent optimization research.

[0062] All the running status data are first clustered and grouped, ensuring that the data within each group is similar. Since the data within each group is highly similar, only one benchmark data needs to be selected. Within a cluster, the benchmark data is generally the data at the cluster center, and its attributes such as data type, data time, data assignment, and data lineage relationship are recorded. Since the remaining data are highly similar to the benchmark data, only the difference between all data and the benchmark data needs to be recorded. Compared with the existing technology that requires storing all data, the storage space is greatly reduced. At the same time, this method also improves the speed and efficiency of running status data search. For example, if all running status data within a certain range is to be found, the previous method is to traverse all running status data and select those that meet the range, which takes a long time. However, the data storage method of this method only needs to first find the benchmark data that meets the conditions, and then search for other data that meet the conditions based on the benchmark data. All running status data within a range can be quickly found, achieving rapid location of the required running status data and improving the speed and efficiency of the search.

[0063] Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the specific calculation is divided into different functional modules to complete all or part of the functions described above.

[0064] In the embodiments provided herein, it should be understood that the structures and methods described can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For example, the division of modules or units is merely a logical functional division. In actual implementation, other division methods may be used. For example, multiple units or components may be combined or integrated into another structure, or some features may be ignored or not implemented.

[0065] Units described as separate components may or may not be physically separate, and components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple places. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0066] In addition, the functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated units may be implemented in the form of hardware or software functional units.

[0067] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application is essentially 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, which is stored in a storage medium and includes several instructions for enabling a device (which can be a single-chip microcomputer, chip, etc.) or a processor (processor) to execute all or part of the steps of the various embodiments of the present application. 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.

[0068] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A method for identifying power cable faults based on induced current, characterized in that: Includes the following: When a short circuit fault occurs in the power cable, the operating status data at the time of the new short circuit fault is recorded, the recorded operating status data is added to the recorded operating status data at the time of the historical short circuit fault, and the cable induced current value is obtained; The cause of the cable short circuit is determined based on the obtained cable induced current value. The causes of the cable short circuit include a single-phase ground short circuit fault and a two-phase ground short circuit fault. The method for determining the cause of the cable short circuit based on the cable induced current value is as follows: the capacity of the transformer corresponding to the location of the short circuit fault is adjusted, and the corresponding short circuit current values ​​when the transformer has different capacities are obtained. If the maximum difference of all the obtained short circuit current values ​​is within a set threshold range, it is determined to be a single-phase ground short circuit fault. If the maximum difference of all the obtained short circuit current values ​​is outside the set threshold range, it is determined to be a two-phase ground short circuit fault. If the cause of the cable short circuit is a single-phase ground short circuit fault, the power system continues to operate. If the cause of the cable short circuit is a two-phase ground short circuit fault, the power system controls the circuit breaker to trip. Based on the historical data of the operating status when short-circuit faults occurred, the cable is predicted to be prone to short-circuit faults. The process of predicting whether the cable is prone to short-circuit faults is as follows: The recorded data is normalized as eigenvalues, and the normalized eigenvalues ​​are clustered to obtain several cluster centers. The operating status of the power cable is monitored in real time. Based on the Euclidean distance between the cluster position of the operating status at a certain time and location and a certain cluster center, it is determined whether the cable at this time and location is prone to short circuit faults. The rules are as follows: If the Euclidean distance between the cluster position of the operating status at a certain location at a certain moment and a certain cluster center is less than or equal to the set value, it is judged that the cable at this time and place is prone to short circuit fault and an early warning is issued; If the Euclidean distance between the cluster position of the operating status at a certain location at a certain time and a certain cluster center is greater than the set value, but the similarity between the operating status and the operating status when a short circuit occurs is greater than the set similarity value, then it is judged that the cable at this time and location is prone to short circuit failure and an early warning is issued; The remaining situations indicate that the cables at this time and location are not prone to short circuit failure.

2. A method for determining power cable faults based on induced current according to claim 1, characterized in that: When a short circuit occurs in a power cable, the recorded data includes the time and location of the short circuit, various parameters of the power grid operation related to the short circuit, environmental parameters at the time of the short circuit, and parameters of the cable itself.

3. A method for determining power cable faults based on induced current according to claim 2, characterized in that: The parameters of the cable include the material of the cable, the service life of the cable, the length of the cable, the geometric dimensions of the cable, and the depth of the cable.

4. The method for determining power cable faults based on induced current according to claim 1, characterized in that: If the cause of the cable short circuit is a single-phase ground short circuit fault, the power system continues to work. When the single-phase ground short circuit fault still exists after exceeding the set time range, the power system controls the circuit breaker to trip.

5. The method for determining power cable faults based on induced current according to claim 1, characterized in that: When recording data on the operating status when a new short-circuit fault occurs, first determine which cluster the operating status belongs to, retrieve the operating status data of the cluster center, and compare the new operating status with the operating status of the cluster center for similarity. If there are identical eigenvalues, no record is made; if there are different eigenvalues, the difference between the two is recorded to complete the record of the new operating status when a short-circuit fault occurs.

6. A method for determining power cable faults based on induced current according to claim 5, characterized in that: The similarity comparison includes time similarity comparison, and the time similarity comparison includes three dimensions: whether it is a peak period, whether it is the same week, and whether it is the same month.

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