A method and system for selecting a small current grounding line based on data window translation judgment

Abstract

The present invention discloses a method and system for selecting a small current grounding line based on data window translation discrimination. The method includes: determining the zero-sequence current sequence of each line in the current data window for the n alternative lines, and calculating the quality index based on the sum of the absolute values ​​of the zero-sequence current sequence; calculating the direction index based on the correlation of the zero-sequence current sequence of each line in the current data window; comprehensively calculating the comprehensive grounding line selection index of the line by combining the quality index and the direction index; if the comprehensive grounding line selection index of any line in the current data window exceeds the set value, the line with the largest number of times determined as the maximum comprehensive grounding line selection index in the set value C0 data windows before the current data window is selected as the grounding fault line. The present invention is completely based on the original zero-sequence current data, ensures the authenticity of fault discrimination, and can flexibly set the length of the time window and the number of repeated discriminations according to the needs of line selection, thereby improving the accuracy of the method for grounding line selection of distribution networks in different situations.

Description

Technical Field

[0001] The present invention belongs to the field of electric power safety, and in particular relates to a small current grounding line selection method and system based on data window translation discrimination. Background Art

[0002] A ground fault will generate an arc, which will be extinguished and reignited repeatedly. The overvoltage amplitude of the non-fault phase can rise to 3.5 times that of the normal situation. Considering the arc extinguishing when the high-frequency current of the cable passes through zero, the overvoltage can even be as high as 4 to 7 times, which can cause cumulative damage to the equipment operation.

[0003] The traditional distribution network uses the neutral point grounding method through the arc suppression coil to reduce the residual current of the fault, reduce the amplitude and rising speed of the voltage recovery at the fault point, and can automatically eliminate the instantaneous grounding fault and improve the reliability of power supply. However, the arc suppression coil cannot compensate for the fault active current and harmonic current. As the scale of the distribution network system increases, the active residual current also increases, and the fault arc extinguishing ability of the arc suppression coil is increasingly limited. Therefore, the line selection of small current grounding has become a key focus of the distribution network. However, the accuracy of the line selection of small current grounding faults cannot meet the requirements at present. The distribution network dispatching still uses the traditional manual trial line selection method to select the fault line, and the fault arc often appears. Therefore, it is necessary to quickly identify the single-phase grounding fault of the distribution network through the small current grounding line selection method, provide guidance for the dispatching personnel to quickly handle the fault, and improve the reliability of power supply. Summary of the invention

[0004] The technical problem to be solved by the present invention is as follows: In view of the above-mentioned problems in the prior art, a method and system for selecting a small current grounding line based on data window translation judgment is provided. The present invention can analyze the zero-sequence voltage and zero-sequence current data to judge the grounding fault line according to the characteristics of the grounding fault and the current status of the acquisition of fault data, and provide decision support for online scheduling. The present invention is completely based on the original zero-sequence current data to ensure the authenticity of the fault judgment, and can flexibly set the length of the time window and the number of repeated judgments according to the needs of line selection, thereby improving the accuracy of the method for grounding line selection of distribution networks in different situations.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for selecting a small current grounding line based on data window translation discrimination, comprising:

[0007] 1) For the n candidate lines, determine the zero-sequence current sequence of each line in the current data window;

[0008] 2) Calculate the quality index based on the sum of the absolute values ​​of the zero-sequence current sequences of each line in the current data window; and calculate the direction index based on the correlation of the zero-sequence current sequences of each line in the current data window;

[0009] 3) The quality index and direction index are combined to calculate the comprehensive grounding line selection index of the line;

[0010] 4) If the comprehensive grounding line selection index of any line in the current data window exceeds the set value, the line with the largest number of times determined as the comprehensive grounding line selection index in the set value C0 data windows before the current data window is selected as the grounding fault line.

[0011] Optionally, the calculation function expression of the quality index in step 2) is:

[0012]

[0013] In the above formula, S ka represents the quality index of any line k, S k represents the absolute value sum of the zero-sequence current sequence of line k in the time window, S i It represents the sum of the absolute values ​​of the zero-sequence current sequence of any line i within the time window, and n is the total number of alternative lines.

[0014] Optionally, the calculation function expression of the sum of the absolute values ​​of the zero-sequence current sequence of the line k in the time window is:

[0015] S k =∑|I k |

[0016] In the above formula, S k It represents the absolute value sum of the zero-sequence current sequence of line k in the time window, I k Represents the zero-sequence current sequence of line k in the time window.

[0017] Optionally, the step of calculating the direction index in step 2) includes:

[0018] 2.1) Calculate the correlation between any two of the n lines, and construct a matrix of the correlation between all two lines to obtain an n×n order correlation matrix R [n×n] ;

[0019] 2.2) For the correlation matrix R [n×n] Sum the columns, then set the positive elements to 1 and the negative elements to -1, and get the 1×n order correlation sequence P [1×n] ;

[0020] 2.3) Calculate the direction index of line k according to the following formula:

[0021] P ka =exp(-3×(P kb -1) 2 )

[0022] In the above formula, Pka represents the direction index of any line k, exp is an exponential function with the natural constant e as the base, P kb To represent the correlation sequence P [1×n] Zhong and P k Different number of elements, P k is the correlation sequence P [1×n] The element value corresponding to line k in .

[0023] Optionally, the calculation function expression of the comprehensive grounding line selection index in step 3) is:

[0024]

[0025] In the above formula, Z ka represents the comprehensive grounding line selection index of any line k, exp is an exponential function with the natural constant e as the base, S ka represents the quality index of any line k, P ka Represents the direction index of any line k.

[0026] Optionally, before step 1), the following steps are also included:

[0027] S1) Real-time monitoring of zero-sequence voltage;

[0028] S2) judging whether the zero-sequence voltage starting condition is met, if so, starting the zero-sequence voltage, and jumping to step 1); otherwise, jumping to step S1);

[0029] Optionally, in step S2), when jumping to step 1), the count value c of the counter of the data window is initialized to 1; step 4) includes:

[0030] 4.1) Determine whether the comprehensive grounding line selection index of any line in the current data window exceeds the set value. If not, jump to step S1); otherwise, jump to the next step;

[0031] 4.2) Determine whether the count value k of the counter of the data window exceeds the set value C0. If not, add 1 to the count value k of the counter of the data window, move the current data window back by one step and update to obtain a new current data window, and jump to step 1); otherwise, jump to the next step;

[0032] 4.3) Count the number of times that the comprehensive grounding line selection index of each line in the set value C0 data windows before the current data window is determined to be the maximum value, and determine the line with the largest number of times that the comprehensive grounding line selection index is determined to be the maximum value as the grounding fault line.

[0033] Optionally, the step size is 1.

[0034] In addition, the present invention also provides a small current grounding line selection system based on data window translation discrimination, including an interconnected microprocessor and a memory, wherein the microprocessor is programmed or configured to execute the steps of the aforementioned small current grounding line selection method based on data window translation discrimination.

[0035] In addition, the present invention also provides a computer-readable medium, in which a computer program is stored. The computer program is used to be executed by a microprocessor to implement the steps of the aforementioned small current grounding line selection method based on data window translation judgment.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] 1. The present invention can analyze the zero-sequence voltage and zero-sequence current data according to the characteristics of the ground fault and the current status of the acquisition of fault data to determine the ground fault line, and provide decision support for online scheduling.

[0038] 2. The present invention is completely based on the original zero-sequence current data to ensure the authenticity of fault identification, and can flexibly set the length of the time window and the number of repeated identifications according to the needs of line selection, thereby improving the accuracy of the method for grounding line selection in distribution networks under different conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the basic flow of the method of the embodiment of the present invention.

[0040] Figure 2 Detailed flowchart of the method of the embodiment of the present invention.

[0041] Figure 3 The bus zero-sequence voltage recording (above) and six line zero-sequence current recordings (below) in an embodiment of the present invention are shown.

[0042] Figure 4 It is a curve showing the change of the calculation results of the bus zero-sequence voltage startup and six-line grounding line selection index in the embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0044] like Figure 1 As shown, the small current grounding line selection method based on data window translation judgment in this embodiment includes:

[0045] 1) For the n candidate lines, determine the zero-sequence current sequence of each line in the current data window;

[0046] 2) Calculate the quality index based on the sum of the absolute values ​​of the zero-sequence current sequences of each line in the current data window; and calculate the direction index based on the correlation of the zero-sequence current sequences of each line in the current data window;

[0047] 3) The quality index and direction index are combined to calculate the comprehensive grounding line selection index of the line;

[0048] 4) If the comprehensive grounding line selection index of any line in the current data window exceeds the set value, the line with the largest number of times determined as the comprehensive grounding line selection index in the set value C0 data windows before the current data window is selected as the grounding fault line, where the set value C0 is a constant parameter, and the value is 60 in this embodiment.

[0049] In this embodiment, the quality index is calculated based on the sum of the absolute values ​​of the zero-sequence current sequences of each line in the current data window. The index is obtained by summing the absolute values ​​of the zero-sequence current sequences of each line in the data window and calculating the summation result on this basis. Specifically, the calculation function expression of the quality index in step 2) is:

[0050]

[0051] In the above formula, S ka represents the quality index of any line k, S k represents the absolute value sum of the zero-sequence current sequence of line k in the time window, S i represents the sum of the absolute values ​​of the zero-sequence current sequences of any line i in the time window, and n is the total number of alternative lines. The above formula can be used to extract the mass proportion of all line zero-sequence current sequences of line k in the time window. In this embodiment, the calculation function expression of the sum of the absolute values ​​of the zero-sequence current sequences of line k in the time window is:

[0052] S k =∑|I k |

[0053] In the above formula, S k It represents the absolute value sum of the zero-sequence current sequence of line k in the time window, I k represents the zero-sequence current sequence of line k in the time window. For n lines, assume that the zero-sequence current data sequences in their time windows are I1, I2, ...I n , the length of each sequence corresponds to the width of the time window.

[0054] In this embodiment, the direction index is calculated based on the correlation of the zero-sequence current sequences of each line in the current data window. The index is obtained by calculating the correlation coefficient of the zero-sequence current sequence of each line in the data window, and then calculating the correlation matrix on this basis. Specifically, the calculation step of the direction index in step 2) of this embodiment includes:

[0055] 2.1) Calculate the correlation between any two of the n lines, and construct a matrix of the correlation between all two lines to obtain an n×n order correlation matrix R [n×n] ;

[0056] 2.2) For the correlation matrix R [n×n] Sum the columns, then set the positive elements to 1 and the negative elements to -1, and get the 1×n order correlation sequence P [1×n] ;

[0057] 2.3) Calculate the direction index of line k according to the following formula:

[0058] P ka =exp(-3×(P kb -1) 2 )

[0059] In the above formula, P ka It represents the direction index of any line k. exp is an exponential function with the natural constant e as the base. The resolution of the direction index can be effectively improved by processing with this exponential function. kb P is the correlation degree sequence [1×n] Zhong and P k Different number of elements, P k is the correlation sequence P [1×n] The element value corresponding to line k in .

[0060] The comprehensive grounding line selection index of the line calculated by comprehensively calculating the quality index and the direction index can be selected in a desired manner according to the needs. For example, the calculation function expression of the comprehensive grounding line selection index in step 3) of this embodiment is:

[0061]

[0062] In the above formula, Z ka It represents the comprehensive grounding line selection index of any line k, and exp is an exponential function with the natural constant e as the base. The exponential function is also used to further improve the resolution of the line selection index. ka represents the quality index of any line k, P ka Represents the direction index of any line k.

[0063] See also Figure 2 , before step 1) of this embodiment, the following steps are also included:

[0064] S1) Real-time monitoring of zero-sequence voltage;

[0065] S2) judging whether the zero-sequence voltage starting condition is met (such as starting when it exceeds 20V), if so, starting the zero-sequence voltage and jumping to step 1); otherwise, jumping to step S1);

[0066] When jumping to step 1) in step S2), the count value c of the counter of the initialization data window is 1, see Figure 2 , step 4) of this embodiment includes:

[0067] 4.1) Determine whether the comprehensive grounding line selection index of any line in the current data window (one cycle before the current moment) exceeds the set value (the value in this embodiment is 0.8, which can be selected according to needs). If not, jump to step S1); otherwise, jump to the next step;

[0068] 4.2) Determine whether the count value c of the counter of the data window exceeds the set value C0 (in this embodiment, the value of C0 is 60, which can be selected according to needs). If not, add 1 to the count value c of the counter of the data window, move the current data window back by one step and update to obtain a new current data window, and jump to step 1); otherwise, jump to the next step;

[0069] 4.3) Count the number of times that the comprehensive grounding line selection index of each line in the set value C0 data windows before the current data window is determined to be the maximum value, and determine the line with the largest number of times that the comprehensive grounding line selection index is determined to be the maximum value as the grounding fault line.

[0070] When the current data window is shifted back by one step, the step size can be set as needed. For example, as an optional implementation, the step size in this embodiment is 1, which can realize continuous processing of zero-sequence current sequences. By shifting the data window, the time window number data can be updated for the above process and repeated small current grounding line selection index calculations can be performed. Finally, the line with the most occurrences of the maximum value of the index result in the repeated small current grounding line selection index calculation process is determined as the grounding fault line.

[0071] The following will take the actual ground fault waveform data that occurred at a substation as an example to illustrate the implementation process of the method of this embodiment. The substation has six outgoing lines. The zero-sequence voltage and zero-sequence current waveforms when a ground fault occurs are as follows: Figure 3 As shown, each curve in the figure represents a different line condition.

[0072] Analysis of the zero-sequence voltage shows that its amplitude begins to exceed 30V at 41.6ms (30V is set as the zero-sequence voltage start setting in this embodiment). As for the grounding line selection index, the calculation results of the grounding line selection index for each zero-sequence current sequence are as follows: Figure 4As shown. It can be seen that before the zero-sequence voltage starts, only the comprehensive grounding line selection index represented by line a obviously exceeds that of other lines, but its comprehensive grounding line selection index is only about 0.65, which does not meet the line selection judgment condition (exceeding 0.8). After 38.9ms, the comprehensive grounding line selection index of the line represented by curve b begins to obviously exceed that of other lines, and quickly exceeds 0.8 and reaches about 1, while the comprehensive grounding line selection indexes of other lines are all less than 0.2. Therefore, as the time window after the start-up shifts backward, the line corresponding to curve b can continue to meet the grounding line selection criterion, so it can be determined as the grounding fault line this time.

[0073] In summary, the method of this embodiment extracts the zero-sequence current sequence of each line of the required length data window for analysis based on the zero-sequence voltage start-up. On the one hand, the absolute cumulative value of the zero-sequence current of each line in the data window is calculated, and the quality index of the small current grounding line selection is calculated based on this; on the other hand, the correlation of the zero-sequence current sequence of each line in the data window is calculated, and the direction index of the small current grounding line selection is calculated based on this. Finally, the quality index and the direction index are integrated to obtain the final small current grounding line selection index. Through the translation of the data window, the time window number data of the above process can be updated and the small current grounding line selection index calculation can be repeated. Finally, according to the repeated calculation of the small current grounding line selection index, the line with the maximum number of times the maximum value of the index result appears is determined as the grounding fault line. According to the results of the grounding line selection, the reference results of fault discrimination can be directly provided for the dispatching operation. On this basis, the dispatching personnel can accurately handle the grounding fault, improve the efficiency of accident handling, shorten the duration of the fault, and improve the power supply reliability of the power system.

[0074] In addition, this embodiment also provides a small current grounding line selection system based on data window translation judgment, including a microprocessor and a memory connected to each other, and the microprocessor is programmed or configured to execute the steps of the aforementioned small current grounding line selection method based on data window translation judgment.

[0075] In addition, this embodiment further provides a computer-readable medium, in which a computer program is stored. The computer program is used to be executed by a microprocessor to implement the steps of the aforementioned small current grounding line selection method based on data window translation judgment.

[0076] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the functions in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0077] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for selecting a small current grounding line based on data window translation discrimination, characterized in that: include: 1) For alternative n lines, determine the zero-sequence current sequence of each line in the current data window; 2) Calculate the quality index based on the sum of the absolute values ​​of the zero-sequence current sequences of each line in the current data window; and calculating the direction index based on the correlation of the zero-sequence current sequences of each line in the current data window; 3) Calculate the comprehensive grounding line selection index of the line by combining the quality index and the direction index; 4) If the comprehensive grounding line selection index of any line in the current data window exceeds the set value, the line with the largest number of times of being determined as the comprehensive grounding line selection index in the set value C0 data windows before the current data window is selected as the ground fault line; The calculation function expression of the quality index in step 2) is: In the above formula, S ka Indicates any line k quality indicators, S k Indicates line k The sum of the absolute values ​​of the zero-sequence current sequence within the time window, S i Indicates any line i The sum of the absolute values ​​of the zero-sequence current sequence within the time window, n is the total number of alternative routes; The calculation steps of the directional indicator in step 2) include: 2.1) Calculation n The correlation between any two lines in the lines, and the correlation between all two lines to build a matrix, get n × n The correlation matrix of R [n×n] ; 2.2) Correlation Matrix R [n×n] Sum the columns, then set the positive elements to 1 and the negative elements to -1, to get 1× n The correlation degree sequence of P [1×n] ; 2.3) Calculate the line according to the following formula k Directional indicators: In the above formula, P ka Indicates any line k , exp is an exponential function with the natural constant e as the base. P kb To represent the correlation sequence P [1×n] Zhongyu P k Different number of elements, P k is the correlation sequence P [1×n] Corresponding lines k The element value of The calculation function expression of the comprehensive grounding line selection index in step 3) is: In the above formula, Z ka Indicates any line k The comprehensive grounding line selection index, exp is an exponential function with the natural constant e as the base, S ka Indicates any line k quality indicators, P ka Indicates any line k direction indicator.

2. The method for selecting a small current grounding line based on data window translation discrimination according to claim 1 is characterized in that: The line k The calculation function expression of the sum of the absolute values ​​of the zero-sequence current sequence within the time window is: In the above formula, S k Indicates line k The sum of the absolute values ​​of the zero-sequence current sequence within the time window, I k Indicates line k Zero-sequence current sequence within the time window.

3. The method for selecting a small current grounding line based on data window translation discrimination according to claim 1 is characterized in that: Step 1) also includes: S1) Real-time monitoring of zero-sequence voltage; S2) determines whether the zero-sequence voltage starting condition is met, if so, the zero-sequence voltage is started, and then jumps to step 1); otherwise, jumps to step S1).

4. The method for selecting a small current grounding line based on data window translation discrimination according to claim 3 is characterized in that: In step S2), when jumping to step 1), the count value c of the counter of the data window is initialized to 1; step 4) includes: 4.1) Determine whether the comprehensive grounding line selection index of any line in the current data window exceeds the set value. If not, jump to step S1); otherwise, jump to the next step; 4.2) Determine whether the count value c of the counter of the data window exceeds the set value C0. If not, add 1 to the count value c of the counter of the data window, move the current data window back by one step and update it to obtain a new current data window, and jump to step 1); otherwise, jump to the next step; 4.3) Count the number of times that the comprehensive grounding line selection index of each line in the set value C0 data windows before the current data window is determined to be the maximum value, and determine the line with the largest number of times that the comprehensive grounding line selection index is determined to be the maximum value as the grounding fault line.

5. The method for selecting a small current grounding line based on data window translation discrimination according to claim 4 is characterized in that: The step size is 1.

6. A low current grounding line selection system based on data window translation discrimination, comprising a microprocessor and a memory connected to each other, characterized in that: The microprocessor is programmed or configured to execute the steps of the method for selecting a small current grounding line based on data window translation discrimination as described in any one of claims 1 to 5.

7. A computer-readable medium having a computer program stored therein, characterized in that: The computer program is used to be executed by a microprocessor to implement the steps of the small current grounding line selection method based on data window translation judgment as described in any one of claims 1 to 5.

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