Power distribution network fault analysis method based on wide-area overcurrent comparison

Abstract

The application discloses a power distribution network fault analysis method based on wide-area overcurrent comparison, which comprises the following steps: arranging collecting devices in a power distribution network line to collect three-phase currents of the line and calculate current variation; when the collecting devices detect a short-circuit fault sequence, the three-phase current variation is transmitted to a data analysis master station; the data analysis master station judges a short-circuit fault type according to a first current value threshold, a second current value threshold and a current sudden change effective value of each collecting point; and judges a short-circuit fault occurrence section according to a third current threshold.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power technology, and in particular to a power distribution network fault analysis method based on wide-area overcurrent comparison. BACKGROUND

[0002] The power distribution network is an important part of the power system. With the rapid development of smart grids and the uncertain access of a large number of distributed power sources, the fault information of the power distribution network is becoming more and more complex, and the accurate and rapid analysis of faults is becoming more and more difficult. In order to ensure the highly intelligent operation of the power distribution network, it is necessary to monitor the feeder operation data in real time, to give timely warning of abnormal situations, and to quickly locate and handle faults. Therefore, line fault indicators and feeder terminals and other devices are usually installed in the power distribution network to record the operation of the power distribution network. In the prior art, the methods for fault location generally need to manually extract the recording wave characteristics, and then use the characteristics to identify and locate the grounding fault. For example, CN103728532 discloses a method for collecting zero sequence voltage 3U0 and zero sequence current 3I0 by using a power distribution automation feeder terminal, performing a series of processes on 3U0 and 3I0 and extracting characteristics, and then using a fault determination rule set by artificial experience to locate the fault section in combination with multiple power distribution automation feeder terminals. CN104101812 discloses a fault detection and positioning method and system for a small-current grounding power distribution network. The system master station extracts the transient signals of the zero sequence voltage and the zero sequence current from the recording waves at multiple points in the power distribution network, calculates the characteristic values and the similarity of the waveforms at each position, and determines the suspected fault area according to the single-point characteristic values and the correlation characteristic values.

[0003] According to the fault location method provided in the prior art, the fault type and the fault location are determined mainly based on the detection of the zero sequence voltage and the zero sequence current of the fault recording wave. This method cannot determine the reverse power supply in the power distribution network. When the user-side reverse power supply occurs in the power distribution line, the existing technical solution does not compare the size of the sudden change current at the fault moment, but analyzes and locates the section based on the fault information sent by the intelligent device. When the fault section is located only by using this technical solution, the fault section positioning may be inaccurate or incorrect. SUMMARY

[0004] The present application provides a method for identifying and locating short-circuit faults in a medium-voltage power distribution network, which solves the problem of inaccurate or incorrect short-circuit fault section positioning caused by reverse power supply in the power distribution network. By reasonably setting the current sudden change value, the fault information sent by the intelligent device is comprehensively analyzed to identify whether the short-circuit fault exists in the reverse power supply, and the short-circuit fault section is accurately located.

[0005] To achieve the above technical purpose, the present application provides a power distribution network fault analysis method based on wide-area overcurrent comparison, which comprises:

[0006] Collecting points are arranged at different physical positions in a distribution network line, collecting devices are arranged at the collecting points, and the collecting devices collect three-phase currents flowing through the collecting points;

[0007] The collecting devices also calculate current variation amounts of the three-phase currents according to fixed time intervals, and the fixed time intervals are determined according to the number of cycles of the current waveform signals;

[0008] The collecting devices judge whether a short-circuit fault sequence appears in the current waveform signals according to a short-circuit current mutation threshold and a short-circuit current duration threshold; when the collecting devices in the topology of the distribution network line detect the short-circuit fault sequence, the collecting devices of all the collecting points upload the three-phase current variation amounts to a data analysis master station;

[0009] The data analysis master station calculates current mutation effective values of each collecting point according to the three-phase current variation amounts uploaded by the collecting devices;

[0010] The data analysis master station judges the short-circuit fault types of each collecting point according to a first current value threshold, a second current value threshold and the current mutation effective value of each collecting point; the first current value threshold is a measurement error value of the collecting devices in a short-circuit current working state, and the second current value threshold is greater than or equal to the short-circuit current mutation threshold;

[0011] The data analysis master station compares the current mutation effective values of each collecting point in the distribution network topology along a power transmission direction one by one according to the first current value threshold I th1 , the second current value threshold I th2 , the third current threshold I th3 and the current mutation effective value of each collecting point to judge a short-circuit fault occurrence section; the third current threshold is a measurement error value of the collecting devices in a normal current working state.

[0012] In one embodiment, for the collecting device of the Kth collecting point, the current mutation effective value ΔI(K) is set as:

[0013] ;

[0014] If , and , it is indicated that the Kth point is a three-phase short-circuit fault;

[0015] If , , , and , it is indicated that the Kth point is an AB two-phase short-circuit fault;

[0016] If , , , and , it is indicated that the Kth point is an AC two-phase short-circuit fault;

[0017] If , , , and , it is indicated that the Kth point is a BC two-phase short-circuit fault;

[0018] If , , , and , it is indicated that the Kth point is an A-phase single-phase short-circuit fault;

[0019] If , , , and , it is indicated that the Kth point is a B-phase single-phase short-circuit fault;

[0020] If , , , and , it is indicated that the Kth point is a C-phase single-phase short-circuit fault;

[0021] In an embodiment, let the current mutation effective value be ΔI(K). Then there is:

[0022] If ΔI(K)-ΔI(K+1)≤I th1 , and ΔI(K)>I th2 , it is indicated that the fault is after the K+1th collection point. At this time, the above current mutation effective value judgment needs to be continued for the next collection point.

[0023] If ΔI(K)-ΔI(K+1)>I th1 , and ΔI(K)>I th2 , ΔI(K+1)>I th3 , it is indicated that the reverse power transmission occurs between the Kth collection point and the K+1th collection point.

[0024] If ΔI(K)-ΔI(K+1)>I th1 , and ΔI(K)>I th2 , ΔI(K+1)≤I th3 , it is indicated that the fault occurs between the Kth collection point and the K+1th collection point.

[0025] In an embodiment, the short-circuit current mutation threshold is not less than 150A, and the short-circuit current duration threshold T is not less than 3s.

[0026] In one embodiment, the number of cycles is 1 cycle, 4 cycles or 6 cycles.

[0027] Compared with the prior art, one or more embodiments of the present application can have the following advantages:

[0028] In the present application, the collection of the current value change value for each collection point can effectively analyze the position of the reverse sending electricity in the power transmission line, so as to effectively exclude the reverse sending electricity state from the short circuit fault analysis in the short circuit fault analysis, thereby improving the positioning analysis accuracy of the short circuit fault.

[0029] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the structure specifically pointed out in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, which together with the application embodiments, serve to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0031] Figure 1 is a schematic diagram of the power distribution network line topology of the present application setting collection points and collection devices;

[0032] Figure 2 is a flowchart of the fault analysis method of the present application;

[0033] Figure 3 is a current waveform schematic diagram of the short circuit fault sequence of the present application;

[0034] Figure 4 is a flowchart of the short circuit fault type analysis process of the present application;

[0035] Figure 5 is a flowchart of the short circuit fault positioning analysis process of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings.

[0037] As Figure 1 is a power distribution network line physical topology schematic diagram of the present embodiment, according to Figure 2 is a flowchart of the power distribution network fault positioning method based on wide-area overcurrent comparison of the present embodiment. The fault positioning method of the present embodiment includes:

[0038] First, data collection points are set up at different physical locations in the power distribution network line, and data collection equipment is set up at the data collection points. The data collection equipment collects the three-phase current of the line flowing through the data collection point, thereby realizing real-time monitoring of the three-phase current of the line at the data collection point. The data collection equipment can be, for example, a fault indicator, an FTU, or a DTU.

[0039] The data acquisition device collects the three-phase current of the line in real time and calculates the current change of the three-phase current according to a fixed time interval, which is determined by the number of cycles in the current waveform signal. Depending on the amount of data to be processed, one cycle, four cycles, six cycles, or more cycles can be selected. Using one cycle as the time interval is equivalent to integrating the current signal within each cycle and comparing the effective current values ​​between consecutive cycles to obtain the current change. Using four cycles as the time interval means integrating the current signal every four cycles and comparing the effective current values ​​of the first four cycles with the effective current values ​​of the last four cycles to obtain the current change. This process continues for other numbers of cycles.

[0040] The changes in phase A current, phase B current, and phase C current are denoted as ΔI. A (K), ΔI B (K), ΔI C (K), where K represents the data acquisition device at the Kth acquisition point along the power transmission direction of the distribution network. The change in phase A current ΔI... A (K), Change in phase B current ΔI B (K) and C phase current change

[0041] ΔI C The formula for calculating (K) is as follows:

[0042]

[0043] Where t1 represents the start time of the previous cycle in which the current integration operation was performed, and t2 represents the start time of the current cycle in which the current integration operation is performed.

[0044] When the data acquisition devices in the distribution network topology detect a short-circuit fault sequence, all data acquisition devices at all acquisition points upload the three-phase current changes to the data analysis master station, that is, upload the A-phase current change ΔI. A (K), Change in phase B current ΔI B (K) and C-phase current change ΔI C(K). At this point, all acquisition devices in the distribution network need to upload the three-phase current change. That is, acquisition devices that have not measured the short-circuit fault sequence also need to upload the current change value at the time of the short-circuit fault sequence. This is because only by acquiring the current value status of all acquisition points in the distribution line topology can the acquisition devices of the outgoing line back-feeding status after the short-circuit fault point be excluded, thereby achieving the purpose of more accurately locating the fault section.

[0045] like Figure 3 As shown, the short-circuit fault sequence refers to a situation where the line current value changes from the normal current value to the short-circuit fault current value, the short-circuit current lasts for a period of time, and then changes to a state of zero current during power outage. In the short-circuit fault sequence, when the line current value changes from the normal current value to the short-circuit fault current value, the sudden change in current exceeds the short-circuit current sudden change threshold I. th0 Furthermore, the duration of the short-circuit current exceeds the short-circuit current duration threshold T. According to the State Grid Corporation of China's alarm indicator parameters for short-circuit faults, the short-circuit current sudden change threshold I... th0 The current should be greater than 150A, and the short-circuit current duration threshold T should be no less than 3 seconds. In practical applications, the above-mentioned short-circuit current sudden change threshold I... th0 The specific value of the short-circuit current duration threshold T can be adjusted adaptively according to engineering needs.

[0046] After receiving the three-phase current changes uploaded by the acquisition devices from all acquisition points, the main data analysis station locates the fault type and fault section based on the uploaded current data.

[0047] like Figure 4 The diagram shown illustrates the fault type determination process in this embodiment. For the data acquisition device at the Kth acquisition point, the effective value of its current surge ΔI(K) is set as follows:

[0048]

[0049] Simultaneously set the first current value threshold I th1 Second current threshold I th2 .

[0050] if ,and If so, it indicates that point K is a three-phase short-circuit fault;

[0051] if , , ,and This indicates that point K is a two-phase short-circuit fault (A and B).

[0052] if , , ,and This indicates that point K is a two-phase AC short-circuit fault;

[0053] if , , ,and This indicates that point K is a two-phase short-circuit fault (BC).

[0054] if , , ,and If so, it means that point K is a single-phase short-circuit fault of phase A;

[0055] if , , ,and If so, it indicates that point K is a single-phase short-circuit fault of phase B;

[0056] if , , ,and If so, it indicates that point K is a single-phase short-circuit fault of phase C;

[0057] Wherein, the setting of the first current value threshold I th1 The value is the measurement error of the acquisition device under short-circuit current operating conditions, and the second current value threshold I is... th2 The value is higher than or equal to the short-circuit current surge threshold I. th0 .

[0058] like Figure 5 The diagram shown is a flowchart illustrating the fault location and determination process in this embodiment.

[0059] Set the third current threshold I th3 The effective value ΔI(K) of the current surge at each sampling point in the distribution network topology is compared sequentially along the transmission direction. The third current threshold I... th3 The value is the measurement error value of the acquisition device under normal current operating conditions.

[0060] If ΔI(K)-ΔI(K+1)≤I th1 And ΔI(K)>I th2 If the fault occurs after the (K+1)th sampling point, then it is necessary to continue judging the effective value of the current sudden change at the next sampling point.

[0061] If ΔI(K)-ΔI(K+1)>I th1 And ΔI(K)>I th2 ΔI(K+1)>Ith3 This indicates that reverse power transmission has occurred between the Kth and K+1th sampling points.

[0062] ΔI(K)-ΔI(K+1)>I th1 And ΔI(K)>I th2 ΔI(K+1)≤I th3 If the fault occurs between the Kth and (K+1)th data collection points, then the fault can be located in the distribution network physical section between the Kth and (K+1)th data collection points.

[0063] The above description is merely a specific implementation example of the present invention, and the scope of protection of the present invention is not limited thereto. Any modifications or substitutions made to the present invention by those skilled in the art within the technical specifications described herein should be within the scope of protection of the present invention.

Claims

1. A power distribution network fault analysis method based on wide-area overcurrent comparison, characterized by, The method comprises: Arranging collection points at different physical positions in a distribution network line, arranging collection devices at the collection points, the collection devices collecting three-phase currents flowing through the collection points; The collection devices further calculate current variation of the three-phase currents according to fixed time intervals, the fixed time intervals being determined by the number of cycles of the current waveform signals; The collection devices judge whether a short-circuit fault sequence appears in the current waveform signals according to a short-circuit current mutation threshold and a short-circuit current duration threshold; when the collection devices in the topology of the distribution network line detect the short-circuit fault sequence, the collection devices of all the collection points upload the three-phase current variations to a data analysis master station; The data analysis master station calculates current mutation effective values of each collection point according to the three-phase current variations uploaded by the collection devices; The data analysis master station judges the short-circuit fault type of each collection point according to a first current value threshold, a second current value threshold and the current mutation effective values of each collection point; the first current value threshold is a measurement error value of the collection devices in a short-circuit current working state, and the second current value threshold is greater than or equal to the short-circuit current mutation threshold; The data analysis master station compares the current mutation effective value of each collection point in the power distribution network topology along the power transmission direction one by one according to the first current value threshold I th1 , the second current value threshold I th2 , the third current threshold I th3 , and the current mutation effective value of each collection point to determine the short-circuit fault occurrence section; the third current threshold is the measurement error value of the collection device under the normal current working state. For the collection device of the Kth collection point, the current mutation effective value ΔI(K) is set as: ； If , and , it indicates that the Kth point is a three-phase short-circuit fault; If , , , and , it indicates that the Kth point is a short-circuit fault of the AB two-phase. If , , , and , it indicates that the Kth point is an AC two-phase short-circuit fault. If , , , and , it indicates that the Kth point is a short-circuit fault of the BC two-phase. If , , , and , it indicates that the Kth point is a single-phase short-circuit fault of phase A. If , , , and , it indicates that the Kth point is a single-phase short-circuit fault of phase B. If , , , and , it indicates that the Kth point is a C-phase single-phase short circuit fault.

2. The power distribution network fault analysis method of claim 1, wherein, Judging the short-circuit fault occurrence section comprises: If ΔI(K) - ΔI(K+1)≤I th1 , and ΔI(K) > I th2 , it means that the fault is after the K+1th acquisition point, and the above-mentioned current mutation effective value judgment needs to be continued for the next acquisition point. If ΔI(K) - ΔI(K+1) > I th1 , and ΔI(K) > I th2 , ΔI(K+1) > I th3 , it indicates that reverse current flow occurs between the Kth acquisition point and the K+1th acquisition point. If ΔI(K) - ΔI(K+1) > I th1 , and ΔI(K) > I th2 , ΔI(K+1) ≤ I th3 , it indicates that the fault occurs between the Kth and K+1th acquisition points.

3. The power distribution network fault analysis method of claim 1, wherein, The short-circuit current mutation threshold is not less than 150 A, and the short-circuit current duration threshold T is not less than 3 s.

4. The power distribution network fault analysis method of claim 1, wherein, The number of cycles is 1 cycle, 4 cycles or 6 cycles.

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