Fault line selection method based on phase current fundamental frequency jitter, medium and terminal

Abstract

The invention is applicable to the technical field of intelligent power grids, and relates to a fault line selection method based on phase current fundamental frequency jitter, a medium and a terminal, comprising the following steps: S10, when a power grid data acquisition and monitoring control system reports a substation bus grounding warning signal, a dispatcher checks three-phase voltage telemetry data of a substation bus, and sends the substation bus grounding warning signal to the medium; determining that the grounding phenomenon is a single-phase grounding fault; s20, exporting current data of all outgoing lines under the fault bus, selecting sampling data of a plurality of cycles before the fault moment and sampling data of a plurality of cycles after the fault moment, respectively calculating phase current fundamental frequency jitter values of each branch line, and sorting the phase current fundamental frequency jitter values from large to small; s30, determining the branch line of the first sequence, and observing whether the bus grounding alarm signal disappears or not while trying to open the line switch; and S40, if the grounding fault does not disappear, continuing to pull open the subsequently ranked lines until the alarm signal disappears. According to the invention, the judgment accuracy and fault processing efficiency of fault line selection of the power distribution network are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of smart grids, and in particular relates to a fault line selection method, a medium and a terminal based on phase current fundamental frequency jitter. Background Art

[0002] Research on automatic fault identification technology for distribution networks is fundamental to ensuring the safe and reliable operation of smart distribution networks and is of great practical significance. For a long time, research on automatic fault identification technology for distribution networks has primarily encompassed fault line selection, segment location, and fault distance measurement. Fault line selection is the foundation of the other two, and its high accuracy must be guaranteed. Although numerous fault line selection methods have been proposed and applied in the field, the actual results have been less than ideal. Difficulties include: unclear fault characteristics; weak steady-state fault currents in single-phase grounding in low-current grounding systems; and transient fault signals, while larger in amplitude than steady-state signals, are short-lived. The impact of unstable fault arcs: in field single-phase grounding faults, arc grounding, especially intermittent arc grounding, lacks a stable ground current (including injected current) signal. Furthermore, the length and number of substations fluctuate frequently. These factors contribute to the low accuracy and fault handling efficiency of existing fault line selection methods.

[0003] The patent with announcement number CN106370961B provides a method for selecting the line of a small current grounding fault in a substation based on capacitor load injection. A small current grounding fault line selection master device is installed in the substation, and a capacitor load injection device is installed on each section of the busbar; a load mutation sampling device is installed on the downstream side of each 10kV outgoing line switch of the substation; if no fault is detected, the capacitor load is in a disconnected state; if a small current grounding fault occurs, the capacitor load is controlled to be injected in phases, and the capacitor load is withdrawn after a certain period of time. At the same time, each load mutation sampling device sends the load mutation value of each phase of each feeder in the time period to the fault line selection master device, and the fault line selection master device selects the fault line according to the principle of the maximum fault phase mutation value. This patent uses small current grounding to achieve fault line selection, and the fault characteristics are not obvious, which will lead to low judgment accuracy, and has the same disadvantages as the existing technology.

[0004] Therefore, how to improve the accuracy of fault line selection and fault handling efficiency in distribution network is an urgent problem to be solved by people in this technical field. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a fault line selection method based on the fundamental frequency jitter of the phase current, so as to solve the problems of low judgment accuracy and fault handling efficiency in the existing technology of fault line selection in the distribution network; in addition, the present invention also provides a fault line selection medium and terminal based on the fundamental frequency jitter of the phase current.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for fault line selection based on phase current fundamental frequency jitter, comprising the following steps:

[0008] S10. When the power grid data acquisition and monitoring control system reports a substation busbar grounding warning signal, the dispatcher checks the three-phase voltage telemetry data of the substation busbar and confirms that the grounding phenomenon is a single-phase grounding fault;

[0009] S20. Derive current data for all outgoing lines under the faulty busbar, select sampling data for a number of cycles before and after the fault, calculate the fundamental frequency jitter value of the phase current for each branch line, and sort the data in descending order.

[0010] S30, determining the branch line where the first sort is located, attempting to open the line switch, and observing whether the busbar grounding alarm signal disappears;

[0011] S40: If the ground fault does not disappear, continue to open the subsequent ranked lines until the alarm signal disappears.

[0012] Furthermore, assume that each of the L branch lines under the busbar is equipped with a current parameter sensor for phases A, B, and C, which is used to obtain and report the current value at each outgoing line, denoted as I l,p ,l=1,2,...,L,p=1,2,3.

[0013] Furthermore, in step S20, sampling data of 6 cycles before the fault moment and 10 cycles after the fault moment are selected, and the time length of each cycle is 20 milliseconds.

[0014] Furthermore, in step S20, the specific steps for calculating the phase current fundamental frequency jitter value are as follows:

[0015] S201. Assume that the current sampling signals of 16 cycles of L branches and 3L transmission lines before and after the fault are recorded as:

[0016]

[0017] S202, analyzing the sampled signal of each line in a sliding window manner, wherein the window size is N=M / 8 sampling points and the number of points for each sliding is V=M / 512;

[0018] S203, calculating the values ​​of the window segment signals at the base frequency points in step S202 one by one, assuming the value of one segment is:

[0019]

[0020] Then the signal S l,p,t The value Y at the fundamental frequency l,p,t The calculation method is as follows:

[0021]

[0022] S204, Y in step S203 l,p,t Perform differential calculation and find the absolute value to obtain the first-order differential absolute value signal Θ l,p,t ,t=1,2,...,(MN) / V, then perform differential calculation to obtain the second-order differential signal Ω l,p,t ,t=1,2,...,(MN) / V-1;

[0023] S205, calculate the maximum jitter value △ of the current signal of each line branch at the fundamental frequency point l ,l=1,2,...,L.

[0024] Furthermore, in step S205, the calculation method is as follows:

[0025]

[0026] Compared with the prior art, the fault line selection method, medium, and terminal based on phase current fundamental frequency jitter provided by the present invention have at least the following beneficial effects:

[0027] Existing fault line selection methods have low accuracy and fault handling efficiency. The present invention has a simple process and convenient operation. After a single-phase grounding fault occurs in the distribution network, the method analyzes the variation characteristics of the phase current signals of each branch line at the 50Hz fundamental frequency point and uses maximum jitter to achieve fault line selection. The MATLAB Simulink fault model simulation results and actual field application results show that the present invention is applicable to distribution networks using different grounding methods, can effectively improve the accuracy of fault line selection and fault handling efficiency, and enhance the power supply reliability index of the distribution network, and has practical engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the scheme of the present invention, a brief introduction is given below to the figures required for use in the description of the embodiments. Obviously, the figures described below are some embodiments of the present invention. For ordinary technicians in this field, other figures can be obtained based on these figures without paying any creative work.

[0029] Figure 1 A flow chart of a fault line selection method based on phase current fundamental frequency jitter provided by an embodiment of the present invention;

[0030] Figure 2This is a diagram of an equivalent circuit analysis model for a single-phase ground fault in a distribution network in the prior art;

[0031] Figure 3 A schematic diagram of a signal segmentation method based on a sliding window in a fault line selection method based on phase current fundamental frequency jitter provided by an embodiment of the present invention;

[0032] Figure 4 A diagram of a 10 kV line grounding fault simulation model based on the MATLAB platform in a fault line selection method based on phase current fundamental frequency jitter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0035] The present invention provides a fault line selection method based on phase current fundamental frequency jitter, which is applied to the transmission network fault identification process in a 10kV distribution system. The fault line selection method based on phase current fundamental frequency jitter includes the following steps:

[0036] S10. When the power grid data acquisition and monitoring control system reports the substation bus grounding warning signal, the dispatcher checks the three-phase voltage telemetry data of the substation bus to confirm that the grounding phenomenon is a single-phase grounding fault; S20. Export the current data of all outgoing lines under the faulty bus, select the sampling data of several cycles before the fault moment and several cycles after the fault moment, calculate the phase current fundamental frequency jitter value of each branch route respectively, and sort them from large to small; S30. Determine the first ranked branch line, try to open the line switch, and observe whether the bus grounding alarm signal disappears; S40. If the grounding fault has not disappeared, continue to open the subsequent ranked lines until the alarm signal disappears.

[0037] The present invention effectively improves the judgment accuracy of distribution network fault line selection and the fault processing efficiency.

[0038] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0039] The present invention provides a fault line selection method based on phase current fundamental frequency jitter, which is applied to the fault identification process of the transmission network in a 10kV distribution system. Figure 2 As shown in the figure, E A , E B and E C Represents the potential of the three-phase winding of the transformer, N is the neutral point of the transformer winding, U A 、U B 、U C Indicates the bus three-phase voltage, L i represents the i-th distribution branch line, C l,p and G l,p is the ground capacitance and load admittance of the p-th phase line of the l-th branch (l=1,2,..,L,p=1,2,3), Z L is the adjustable inductance of the arc suppression coil, K is the ground fault point, R d The transition resistance of the grounding point, switches S1 and S2 respectively represent the switching of the neutral point of the transformer winding between low resistance grounding and arc suppression coil grounding. If both switches are disconnected, it means that the neutral point of the distribution network sampling is not grounded, and the closing of switch S3 indicates that a single-phase grounding fault occurs in the line. Figures 1 to 4 In this embodiment, the distribution network adopts a power grid data acquisition and monitoring control system (SCADA) that integrates the "four remote" functions for power dispatchers, which can obtain and automatically analyze the power grid telemetry data in real time. Figure 2 For example, assume that each of the L branch lines under the busbar is equipped with a current parameter sensor for phase A / B / C, which can obtain and report the current value at each outgoing line, recorded as I l,p ,l=1,2,...,L,p=1,2,3, combined Figures 1 to 3 In this embodiment, the fault line selection method based on phase current fundamental frequency jitter includes the following steps:

[0040] S10. When the power grid supervisory control and data acquisition (SCADA) system reports a substation bus grounding warning signal, the dispatcher checks the three-phase voltage telemetry data of the substation bus and confirms that the grounding phenomenon is a single-phase grounding fault.

[0041] S20, export the current data I of all outgoing lines under the fault bus l,p ,l=1,2,...,L,p=1,2,3, select the sampling data of 6 cycles before the fault moment and 10 cycles after the fault moment, a total of 16 cycles (the duration of one cycle is 20 milliseconds), and calculate the phase current fundamental frequency jitter value △ of each branch line separately l,l=1,2,...,L and sort from large to small.

[0042] Specifically, in this embodiment, the phase current fundamental frequency jitter value △ l ,l=1,2,...,LThe specific calculation steps are as follows:

[0043] S201. Assume that there are L branches, a total of 3L transmission lines. The current sampling signals of 16 cycles before and after the fault are recorded as:

[0044]

[0045] S202. Analyze the sampling signals of each line in step S201 in a sliding window manner, where the window size is N = M / 8 (2 cycles, 40 milliseconds, and the minimum frequency resolution is 25 Hz) sampling points, and the number of points for each sliding is V = M / 512 (1 / 32 cycle).

[0046] S203, calculate the values ​​of the window segmented signals at the base frequency (50 Hz) in step S202 one by one, and assume that the value of a segmented signal is:

[0047]

[0048] Then the signal S l,p,t The value Y at the fundamental frequency (50Hz) l,p,t The calculation method is as follows:

[0049]

[0050] S204: Perform differential calculation on the signal of step S203, and then calculate the absolute value to obtain the first-order differential absolute value signal θ l,p,t ,t=1,2,...,(MN) / V, that is:

[0051] Θ l,p,t =|Y l,p,t+1 -Y l,p,t |,t=1,2,...,(MN) / V;

[0052] Then perform differential calculation on the above formula to obtain the second-order differential signal Ω l,p,t ,t=1,2,...,(MN) / V-1, that is:

[0053] Ω l,p,t =Θ l,p,t+1 -Θ l,p,t ,t=1,2,...,(MN) / V-1;

[0054] S205. Finally, calculate the maximum jitter value of the current signal of each line branch at the base frequency point (50Hz)l ,l=1,2,...,L, the calculation method is as follows:

[0055]

[0056] where △ l ,l=1,2,...,L is essentially the maximum energy of the second-order differential signal of the three-phase line current signal of the first line branch.

[0057] S30: Determine the branch line where the first sort is located, try to open the line switch, and observe whether the busbar grounding alarm signal disappears.

[0058] S40: If the ground fault does not disappear, continue to open the subsequent ranked lines until the alarm signal disappears.

[0059] The fault line selection method based on phase current fundamental frequency jitter provided by the embodiment of the present invention has a basic principle: when there is no fault, although there is a certain asymmetry in the three-phase currents of each line branch, the change of the current signal at the fundamental frequency point is stable and steady. Both theoretical analysis and test results show that when there is no fault, most of the energy of the current waveform of each line in the distribution network is concentrated at the fundamental frequency point (50Hz), that is, the time domain waveform tends to a 50Hz sine wave. At this time, its signal change at the fundamental frequency point is relatively stable, so the element values ​​of the corresponding second-order differential signal tend to 0. When a ground fault occurs, it can be considered that a nonlinear time-varying load is suddenly connected to the fault line, the grid current suddenly changes, and all the capacitive currents of the line flow to the fault line through the grounding point. The three-phase current values ​​of the fault branch change greatly, while the three-phase current values ​​of the non-fault branch change very little. Therefore, based on the above physical characteristics, since the 50Hz fundamental frequency signal is the main frequency point of the AC signal, its faulty branch line will also experience violent jitter after the fault occurs. Therefore, by calculating the energy value of the second-order differential signal of each branch phase current signal at this frequency point, the line with the maximum value is found. This line is most likely the branch line where the fault occurs.

[0060] In this embodiment, Figure 4 As shown in the figure, a single-phase grounding fault simulation model of a 10kV distribution network is built using MATLAB. Three branch line outgoing lines are set up, and different neutral point grounding methods can be connected as needed, including no grounding, low-resistance grounding, and arc suppression coil grounding. The operating parameters of different branches can also be configured in the simulation, including line length, load level, etc.

[0061] Computer simulations were performed a total of 1,000 times, with different line parameters configured for each simulation. The line location of the grounding fault and related fault parameters were also different. Statistical data showed that under different neutral point grounding methods and different line and fault parameters, the branch line where the fault point was located was ranked first in the ranking 998 times, and ranked second in the remaining 2 times. To further verify the performance of the algorithm on actual lines, 100 single-phase grounding fault sample recordings that occurred in the Xinjiang Uygur Autonomous Region power grid in the past two years were selected for example verification. The fault line judgment results obtained by this algorithm are completely consistent with the conclusions reported by on-site line fault troubleshooting personnel. The results of computer simulation and field data verification show that the present invention can effectively improve the efficiency of power dispatchers in handling single-phase grounding faults, improve the power supply reliability index of the power supply enterprise's distribution network, and has economic benefits and engineering promotion value.

[0062] An embodiment of the present invention further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, any one of the methods in the embodiment is implemented.

[0063] An embodiment of the present invention further provides an electronic terminal, comprising: a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory, so that the terminal executes any one of the methods in this embodiment.

[0064] Regarding the computer-readable storage medium in this embodiment, those skilled in the art will appreciate that all or part of the steps in the aforementioned method embodiments can be implemented using hardware associated with the computer program. The aforementioned computer program can be stored in a computer-readable storage medium. When executed, the program performs the steps in the aforementioned method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0065] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication with each other. The memory is used to store computer programs, the communication interface is used for communication, and the processor and the transceiver are used to run computer programs so that the electronic terminal executes the various steps of the above method.

[0066] The fault line selection method, medium, and terminal based on the fundamental frequency jitter of the phase current described in the above embodiment are compared with the prior art, and the judgment accuracy and fault handling efficiency of the existing fault line selection method are relatively low. The present invention has a simple process and is easy to operate. After a single-phase grounding fault occurs in the distribution network, the fault line selection is achieved by analyzing the change characteristics of the phase current signal of each branch line at the 50Hz fundamental frequency point and utilizing the maximum jitter. The MATLAB Simulink fault model simulation results and the actual application effects on site show that the present invention is applicable to distribution networks using different grounding methods, can effectively improve the accuracy of fault line selection and fault handling efficiency, and improve the power supply reliability index of the distribution network, and has practical engineering application value.

[0067] Obviously, the embodiments described above are only preferred embodiments of the present invention, rather than all embodiments. The preferred embodiments of the present invention are given in the accompanying drawings, but they do not limit the patent scope of the present invention. The present invention can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Although the present invention has been described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned specific embodiments, or to make equivalent replacements for some of the technical features therein. Any equivalent structure made using the contents of the present invention specification and drawings, directly or indirectly used in other related technical fields, is also within the scope of patent protection of the present invention.

Claims

1. A fault line selection method based on phase current fundamental frequency jitter, characterized in that: The following steps are involved: S10. When the power grid data acquisition and monitoring control system reports a substation busbar grounding warning signal, the dispatcher checks the three-phase voltage telemetry data of the substation busbar and confirms that the grounding phenomenon is a single-phase grounding fault; S20. Derive current data for all outgoing lines under the faulty busbar, select sampling data for a number of cycles before and after the fault, calculate the fundamental frequency jitter value of the phase current for each branch line, and sort the data in descending order; S30, determining the branch line where the first sort is located, attempting to open the line switch, and observing whether the busbar grounding alarm signal disappears; S40: If the ground fault does not disappear, continue to open the subsequent ranked lines until the alarm signal disappears.

2. The fault line selection method based on phase current fundamental frequency jitter according to claim 1 is characterized in that: Assume that each of the L branch lines under the busbar is equipped with current parameter sensing devices for phases A, B, and C, which are used to obtain and report the current values ​​at their respective outlets, denoted as I l,p ,l=1,2,...,L,p=1,2,3.

3. The fault line selection method based on phase current fundamental frequency jitter according to claim 1 is characterized in that: In step S20, sampling data of 6 cycles before the fault moment and 10 cycles after the fault moment are selected, and the time length of each cycle is 20 milliseconds.

4. The fault line selection method based on phase current fundamental frequency jitter according to claim 3 is characterized in that: In step S20, the specific steps for calculating the phase current fundamental frequency jitter value are as follows: S201. Assume that the current sampling signals of 16 cycles of L branches and 3L transmission lines before and after the fault are recorded as: S202, analyzing the sampled signal of each line in a sliding window manner, wherein the window size is N=M / 8 sampling points and the number of points for each sliding is V=M / 512; S203, calculating the values ​​of the window segment signals at the base frequency points in step S202 one by one, assuming the value of one segment is: Then the signal S l,p,t The value Y at the fundamental frequency l,p,t The calculation method is as follows: S204, Y in step S203 l,p,t Perform differential calculation and find the absolute value to obtain the first-order differential absolute value signal Θ l,p,t ,t=1,2,...,(MN) / V, then perform differential calculation to obtain the second-order differential signal Ω l,p,t ,t=1,2,...,(MN) / V-1; S205, calculate the maximum jitter value △ of the current signal of each line branch at the fundamental frequency point l ,l=1,2,...,L.

5. The fault line selection method based on phase current fundamental frequency jitter according to claim 4 is characterized in that: In step S205, the calculation method is as follows:

6. A computer-readable storage medium, characterized in that The storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

7. An electronic terminal, characterized in that: include: processor and memory; The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory, so that the terminal performs the method according to any one of claims 1 to 5.

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