Power distribution network line protection method and system, medium and electronic equipment

Abstract

The invention provides a power distribution network line protection method and system, a medium and electronic equipment, and relates to the technical field of power distribution network protection, and the method comprises the steps: obtaining the voltage data of each preset station within a preset time period before and after an abnormal signal occurs, so as to determine the positive sequence voltage break variable of each preset station, taking the preset site corresponding to the maximum value in the positive sequence voltage break variables as an abnormal site; obtaining the current data of each line connected with the abnormal site within a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence current break variable of each line, and taking the line corresponding to the maximum value in the positive sequence current break variable as an abnormal line; the current apparent power of the abnormal line is obtained by combining the positive sequence current break variable corresponding to the abnormal line and the positive sequence voltage break variable of the abnormal site; and according to the current apparent power, judging whether the abnormal line has a fault or not. According to the invention, the problem that the fault line cannot be accurately judged and locked in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network protection, and in particular to a distribution network line protection method, system, medium and electronic equipment. Background Art

[0002] With the massive access of various distributed power sources such as photovoltaic, wind power, and small hydropower to the distribution network, the existing distribution network line protection technology faces huge challenges. Due to the auxiliary and external effects of distributed power sources, the protection range of the original three-stage current protection of the distribution network has changed significantly, resulting in a significant decrease in the reliability of the three-stage current protection, causing problems such as false protection, refusal to operate, and excessive delay in operation. At the same time, due to the existence of unmeasurable branches, current differential protection has completely lost its application premise.

[0003] Since distribution network disconnections and short-line grounding faults often occur due to lightning strikes, the power supply department is unable to detect the fault in time, so the fault exists for a long time and becomes a major hidden danger to personal safety.

[0004] Therefore, an effective distribution network line protection method is urgently needed to make up for the shortcomings of three-stage line protection in the new power system with widespread access to distributed power sources, so as to avoid the problem of being unable to accurately judge and lock the faulty line. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a distribution network line protection method, system, medium and electronic equipment, which solve the problem in the prior art that the faulty line cannot be accurately determined and locked.

[0006] At least one embodiment of the present invention provides a distribution network line protection method, comprising:

[0007] After the distribution network detects an abnormal electrical signal, the voltage data of each preset site in a preset time period before and after the abnormal signal occurs is obtained to determine the positive sequence voltage mutation amount of each preset site, and the preset site corresponding to the maximum value of each positive sequence voltage mutation amount is taken as the abnormal site;

[0008] Obtaining current data of each line connected to the abnormal site within a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence current mutation of each line, and taking the line corresponding to the maximum value of each positive sequence current mutation as the abnormal line;

[0009] Combining the positive sequence current mutation amount corresponding to the abnormal line and the positive sequence voltage mutation amount at the abnormal site, the current apparent power of the abnormal line is obtained;

[0010] Determining whether the abnormal line is faulty according to the current apparent power;

[0011] If it is determined that the abnormal line is faulty, the driving line protection device is activated; if it is determined that the abnormal line is not faulty, the driving line protection device is locked.

[0012] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0013] The method firstly utilizes the positive sequence voltage mutation amount of each preset station before and after the abnormal signal occurs to lock the abnormal station connected to the abnormal line, and then utilizes the positive sequence current mutation amount of each line connected to the abnormal station before and after the abnormal signal to lock the fault line.

[0014] The line protection method provided by the present invention successfully avoids the problem of incorrect protection action caused by unmeasurable branches, such as signal disturbance and the problem of false triggering of line protection device action, and has extremely strong reliability. It can significantly improve the accuracy of identifying faulty lines and solve the problem that traditional three-stage current protection and current differential protection cannot be applied due to unmeasurable branches. At the same time, the method of the present invention has low requirements on the computing power of the protection device, taking into account both effectiveness and practicality, and has strong engineering practical value.

[0015] In a distribution network line protection method provided by one embodiment of the present invention, the step of obtaining voltage data of each preset station in a preset time period before and after an abnormal signal occurs to determine a positive sequence voltage mutation amount of each preset station includes:

[0016] Acquire the first initial voltage waveform data of each preset site one power frequency cycle before the abnormal signal occurs, and the second initial voltage waveform data of each preset site one power frequency cycle after the abnormal signal occurs;

[0017] filtering each of the first initial voltage waveform data to obtain a plurality of first voltage waveform data, and filtering each of the second initial voltage waveform data to obtain a plurality of second voltage waveform data;

[0018] For any preset site, the positive sequence voltage mutation amount of the preset site is determined according to the first voltage waveform data and the second voltage waveform data of the preset site.

[0019] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0020] By collecting the first initial voltage waveform data of the power frequency cycle before the abnormal signal occurs, and the second initial voltage waveform data of the power frequency cycle after the abnormal signal occurs, the positive sequence voltage mutation amount of each preset site can be calculated to provide a basis for the judgment of subsequent abnormal sites.

[0021] In a distribution network line protection method provided by one embodiment of the present invention, the first initial voltage waveform data is filtered according to the following formula:

[0022]

[0023] Where N represents the order of the filter; fc is the cutoff frequency; u a (k),u b (k) and u c (k) represents the first initial voltage waveform data; u a F (k),u b F (k) and u c F (k) is represented as the first voltage waveform data.

[0024] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0025] The above filtering method has stronger filtering capability and better adaptability than the prior art when used for filtering power frequency voltage or current.

[0026] In a distribution network line protection method provided by one embodiment of the present invention, determining the positive sequence voltage mutation amount of the preset site according to the first voltage waveform data and the second voltage waveform data of the preset site includes:

[0027] Determine a first voltage effective value of the preset site according to the first voltage waveform data, and obtain a first positive sequence voltage component amplitude of the preset site according to the first voltage effective value;

[0028] Determine a second voltage effective value of the preset site according to the second voltage waveform data, and obtain a second positive sequence voltage component amplitude of the preset site according to the second voltage effective value;

[0029] The positive-sequence voltage mutation amount of the preset site is determined according to the difference between the first positive-sequence voltage component amplitude and the second positive-sequence voltage component amplitude.

[0030] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0031] By calculating the calculated first positive-sequence voltage component amplitude and the second positive-sequence voltage component amplitude, and then subtracting the first positive-sequence voltage component amplitude from the second positive-sequence voltage component amplitude, the positive-sequence voltage mutation amount corresponding to the preset site can be accurately obtained.

[0032] In a distribution network line protection method provided in one embodiment of the present invention, the first voltage effective value of the preset site is determined according to the first voltage waveform number according to the following formula:

[0033]

[0034] Among them, U a , U b and U c Expressed as the first voltage effective value.

[0035] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0036] Through the above formula, the first voltage effective value of the preset site can be easily obtained according to the first voltage waveform number.

[0037] In a distribution network line protection method provided by one embodiment of the present invention, judging whether the abnormal line is faulty according to the current apparent power includes:

[0038] Obtaining the minimum apparent power of the abnormal line under a preset minimum operating mode;

[0039] In combination with the minimum apparent power and the current apparent power, it is determined whether the abnormal line is faulty.

[0040] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0041] By comparing the minimum apparent power with the current apparent power, and based on the difference ratio between the two, it is possible to quickly determine whether the corresponding abnormal line is faulty or just disturbed.

[0042] In a distribution network line protection method provided by one embodiment of the present invention, the obtaining of the minimum apparent power of the abnormal line under a preset minimum operating mode includes:

[0043] Acquire a third current effective value of the abnormal line under a preset minimum operation mode, and a third voltage effective value of the abnormal site under a preset minimum operation mode;

[0044] The minimum apparent power is determined according to the third current effective value and the third voltage effective value.

[0045] The technical solution disclosed in the present invention has at least the following beneficial effects:

[0046] Through the above method, the minimum apparent power of the corresponding line can be quickly obtained to facilitate the subsequent judgment of whether a fault occurs.

[0047] At least one embodiment of the present invention further provides a power distribution network line protection system, comprising:

[0048] The abnormal site judgment module, after the distribution network detects an abnormal electrical signal, obtains the voltage data of each preset site in a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence voltage mutation amount of each preset site, and takes the preset site corresponding to the maximum value of each positive sequence voltage mutation amount as the abnormal site;

[0049] The abnormal line judgment module obtains the current data of each line connected to the abnormal site within a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence current mutation of each line, and takes the line corresponding to the maximum value of each positive sequence current mutation as the abnormal line;

[0050] The apparent power calculation module obtains the current apparent power of the abnormal line by combining the positive sequence current mutation amount corresponding to the abnormal line and the positive sequence voltage mutation amount of the abnormal site;

[0051] A judgment module, judging whether the abnormal line is faulty according to the current apparent power;

[0052] The protection module drives the circuit protection device to operate if it is determined that the abnormal circuit is faulty, and drives the circuit protection device to lock if it is determined that the abnormal circuit is not faulty.

[0053] The present invention also provides a computer-readable storage medium, in which instructions are stored. When the instructions are executed on a terminal device, the terminal device executes a distribution network line protection method as described above.

[0054] The present invention also provides an electronic device, comprising a memory, a processor, and a program stored in the memory and running on the processor, wherein the processor implements a distribution network line protection method as described above when executing the program. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a flow chart of a method for protecting a line in a distribution network;

[0056] Figure 2 This is the structural diagram of the 10kV distribution network;

[0057] Figure 3 It is the A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L1 when F1 fails;

[0058] Figure 4 This is the A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L1 after filtering when F1 fails;

[0059] Figure 5 It is the A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L1 when F2 fault occurs;

[0060] Figure 6 This is the A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L1 after filtering when F2 fault occurs;

[0061] Figure 7 It is a structural diagram of a distribution network line protection system. DETAILED DESCRIPTION

[0062] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0063] The present invention provides a method for protecting a power distribution network line. Figure 1 As shown, including:

[0064] After the distribution network detects an abnormal electrical signal, the voltage data of each preset site in a preset time period before and after the abnormal signal occurs is obtained to determine the positive sequence voltage mutation amount of each preset site, and the preset site corresponding to the maximum value of each positive sequence voltage mutation amount is taken as the abnormal site;

[0065] Obtaining current data of each line connected to the abnormal site within a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence current mutation of each line, and taking the line corresponding to the maximum value of each positive sequence current mutation as the abnormal line;

[0066] Combining the positive sequence current mutation amount corresponding to the abnormal line and the positive sequence voltage mutation amount at the abnormal site, the current apparent power of the abnormal line is obtained;

[0067] Determining whether the abnormal line is faulty according to the current apparent power;

[0068] If it is determined that the abnormal line is faulty, the driving line protection device is activated; if it is determined that the abnormal line is not faulty, the driving line protection device is locked.

[0069] The method firstly utilizes the positive sequence voltage mutation amount of each preset station before and after the abnormal signal occurs to lock the abnormal station connected to the abnormal line, and then utilizes the positive sequence current mutation amount of each line connected to the abnormal station before and after the abnormal signal to lock the fault line.

[0070] The line protection method provided by the present invention successfully avoids the problem of incorrect protection action caused by unmeasurable branches, such as signal disturbance and the problem of false triggering of line protection device action, and has extremely strong reliability. It can significantly improve the accuracy of identifying faulty lines and solve the problem that traditional three-stage current protection and current differential protection cannot be applied due to unmeasurable branches. At the same time, the method of the present invention has low requirements on the computing power of the protection device, taking into account both effectiveness and practicality, and has strong engineering practical value.

[0071] Specifically, in the above method:

[0072] After the distribution network detects an abnormal electrical signal, the voltage data of each preset site in a preset time period before and after the abnormal signal occurs is obtained to determine the positive sequence voltage mutation amount of each preset site, including: using a primary and secondary fusion switch to obtain the first initial voltage waveform data of each preset site in a power frequency cycle before the abnormal signal occurs, and the second initial voltage waveform data of a power frequency cycle after the abnormal signal occurs. The preset site referred to in this article is actually a substation or a switch station, wherein the sampling rate f m The sampling data of one power frequency cycle before and after the fault, that is, 20ms, is saved to obtain the voltage and current waveform arrays with an array length of 20. The voltage waveform arrays of the three phases A, B, and C of each switch station or substation are [u a ]、[u b ]、[u c ], the current waveform arrays of the three phases of lines A, B, and C are [i a ]、[i b ]、[i c Any element in the above array can be used a (i) u b (i) u c (i) a (i) b (i) c (i) indicates.

[0073] Filtering and denoising each of the first initial voltage waveform data to obtain a plurality of first voltage waveform data, and filtering and denoising each of the second initial voltage waveform data to obtain a plurality of second voltage waveform data;

[0074] The first initial voltage waveform data or the second initial voltage waveform data is filtered according to the following formula:

[0075]

[0076] Wherein, N represents the order of the filter, which is 1000 in this embodiment; fc is the cutoff frequency, which indicates the highest frequency allowed to pass in the signal, and is 80 Hz; ua (k),u b (k) and u c (k) represents the first initial voltage waveform data or the second initial voltage waveform data collected by the primary and secondary fusion switch; u a F (k),u b F (k) and u c F (k) is represented as the corresponding first voltage waveform data or second voltage waveform data;

[0077] The above filtering method has stronger filtering capability and better adaptability than the prior art when used to filter power frequency voltage or current.

[0078] Determine a first voltage effective value of the preset site according to the first voltage waveform data, and obtain a first positive sequence voltage component amplitude of the preset site according to the first voltage effective value;

[0079] Determine a second voltage effective value of the preset site according to the second voltage waveform data, and obtain a second positive sequence voltage component amplitude of the preset site according to the second voltage effective value;

[0080] The first voltage effective value or the second voltage effective value of the preset site is determined according to the first voltage waveform data or the second voltage waveform data according to the following formula:

[0081]

[0082] Among them, U a , U b and U c Expressed as a first voltage effective value or a second voltage effective value;

[0083] For the convenience of subsequent description, in the following text, U a , U b , U c are the first voltage effective values ​​of phases A, B, and C before the abnormal signal; I a ,I b ,I c They are the first effective current value of the three phases A, B, and C before the abnormal signal; the second effective voltage value and the second effective current value of the three phases A, B, and C after the abnormal signal, recorded as U' a , U' b , U' c , I' a , I' b , I' c .

[0084] The positive sequence voltage mutation amount of the preset site is determined according to the difference between the first positive sequence voltage component amplitude and the second positive sequence voltage component amplitude, wherein the calculation method of the first positive sequence voltage component amplitude and the second positive sequence voltage component amplitude is as follows:

[0085]

[0086] U1 represents the amplitude of the first positive sequence voltage component. Similarly, the amplitude of the second positive sequence voltage component can be calculated to be U'1.

[0087] Then, the positive sequence voltage mutation ΔU1 of the preset site is:

[0088] ΔU1=U1-U'1

[0089] In order to distinguish the positive sequence voltage mutation of each switch station or substation, the positive sequence voltage mutation can be assigned a serial number subscript, for example, the positive sequence voltage mutation of the mth switch station or substation is marked as ΔU 1-m Similarly, the positive sequence current mutation of the mth line is marked as ΔI 1-m .

[0090] By calculating the calculated first positive-sequence voltage component amplitude and the second positive-sequence voltage component amplitude, and then subtracting the first positive-sequence voltage component amplitude from the second positive-sequence voltage component amplitude, the positive-sequence voltage mutation amount corresponding to the preset site can be accurately obtained.

[0091] For any preset site, the positive sequence voltage mutation amount of the preset site is determined according to the first voltage waveform data and the second voltage waveform data of the preset site. By collecting the first initial voltage waveform data of a power frequency cycle before the abnormal signal occurs and the second initial voltage waveform data of a power frequency cycle after the abnormal signal occurs, the positive sequence voltage mutation amount of each preset site can be calculated to provide a basis for the subsequent judgment of abnormal sites;

[0092] Then, the preset site corresponding to the maximum value of each positive sequence voltage mutation is taken as the abnormal site, that is:

[0093] The above steps can be specifically understood as, after obtaining the positive sequence voltage mutation amount of each switch station or substation, forming an array [ΔU 1-1 ,ΔU 1-2 ,…,ΔU 1-m ], the positive sequence voltage mutation can be sorted and the switch station or substation with the largest positive sequence voltage mutation can be found:

[0094] N U =index{max[ΔU 1-1 ,ΔU 1-2 ,…,ΔU 1-m ]}

[0095] In the above formula: N U The subscript number of the switch station or substation with the largest positive sequence voltage mutation.

[0096] Then N U The corresponding switch station or substation is the switch station or substation connected to the faulty line. According to the above criteria, the switch station or substation connected to the faulty line can be immediately locked.

[0097] Subsequently, the current data of each line connected to the abnormal site within a preset time period before and after the abnormal signal occurs is obtained to determine the positive sequence current mutation of each line, and the line corresponding to the maximum value of each positive sequence current mutation is taken as the abnormal line.

[0098] Similarly, the processing steps for the positive sequence current mutation are the same as those for the positive sequence voltage mutation, including:

[0099] The first initial current waveform data of each line connected to each abnormal site in one power frequency cycle before the abnormal signal occurs and the second initial current waveform data of each power frequency cycle after the abnormal signal occurs are obtained.

[0100] filtering each of the first initial current waveform data to obtain a plurality of first current waveform data, and filtering each of the second initial current waveform data to obtain a plurality of second current waveform data;

[0101] The first initial current waveform data or the second initial current waveform data is filtered according to the following formula:

[0102]

[0103] Where N represents the order of the filter; fc is the cutoff frequency; i a (k), i b (k), i c (k) is represented as the first initial current waveform data or the second initial current waveform data; represented as first current waveform data or second current waveform data;

[0104] Determine a first current effective value of the preset station according to the first current waveform data, and obtain a first positive sequence current component amplitude of the preset station according to the first current effective value;

[0105] Determine a second current effective value of the preset station according to the second current waveform data, and obtain a second positive sequence current component amplitude of the preset station according to the second current effective value;

[0106] The first current effective value or the second current effective value of the preset station is determined according to the first current waveform data or the second current waveform data according to the following formula:

[0107]

[0108] Among them, I a ,I b ,I c Expressed as the first current effective value.

[0109] According to the difference between the amplitude of the first positive sequence current component and the amplitude of the second positive sequence current component, the positive sequence current mutation amount of each line is determined, wherein:

[0110]

[0111] I1 represents the amplitude of the positive sequence current component before the fault;

[0112] By calculating the calculated first positive-sequence current component amplitude and the second positive-sequence current component amplitude, and then subtracting the first positive-sequence current component amplitude from the second positive-sequence current component amplitude, the positive-sequence current mutation amount corresponding to each line can be accurately obtained.

[0113] After locking the substation connected to the abnormal line, the positive sequence current mutations of each line of the switch station or substation are sorted, and the line corresponding to the maximum value of the positive sequence current mutation of each line is taken as the abnormal line, that is:

[0114] After determining the switch station or substation to which the abnormal line is connected, the positive sequence current mutation of each line connected to it is immediately obtained to form an array [ΔI 1-1 ,ΔI 1-2 ,…,ΔI 1-m ], and sort the positive sequence current mutation of the switch station or substation, and find the switch station or substation with the largest positive sequence current mutation:

[0115] N I =index{max[ΔI 1-1 ,ΔI 1-2 ,…,ΔI 1-m ]}

[0116] In the above formula: N I The subscript represents the line with the largest positive sequence current mutation.

[0117] Then N I The corresponding line is the abnormal line. According to the above criteria, the abnormal line can be locked immediately.

[0118] Combined with the positive sequence current mutation corresponding to the abnormal line and the positive sequence voltage mutation at the abnormal site, the current apparent power of the abnormal line is obtained according to the following formula:

[0119] S f =U f I f

[0120] Among them, U f Expressed as positive sequence voltage mutation, I f Expressed as the positive sequence current mutation, S f > Table 1. shows 1S as the current apparent power;

[0121] The determining whether the abnormal line is faulty according to the current apparent power comprises: obtaining the minimum apparent power of the abnormal line under a preset minimum operation mode, that is, obtaining the third current effective value of the abnormal line under the preset minimum operation mode, and the third voltage effective value of the abnormal station under the preset minimum operation mode;

[0122] According to the third current effective value and the third voltage effective value, the minimum apparent power is determined according to the following formula:

[0123] S=UI

[0124] Wherein, S represents the minimum apparent power, U represents the third effective value of voltage of the abnormal line under the preset minimum operation mode, and I represents the third effective value of current of the abnormal line under the preset minimum operation mode.

[0125] Combining the minimum apparent power and the current apparent power, judging whether the abnormal line is faulty according to the following formula;

[0126] S f >>01..11SS, protection action;

[0127] S f >≤1.01.S1S, protection lock;

[0128] If it is judged that the abnormal line is faulty, the line protection device is driven to operate; if it is judged that the abnormal line is not faulty, the line protection device is driven to lock, that is, the maximum value of the voltage positive sequence mutation amount obtained after sorting is multiplied by the maximum value of the current positive sequence mutation amount, and the calculation result is compared with the apparent power transmitted under the minimum operating mode of the line to form a fault judgment criterion to prevent the power system disturbance from causing the line protection to malfunction.

[0129] This method first uses the positive sequence voltage mutation before and after the abnormal signal of each switch station or substation to lock the substation connected to the abnormal line, and then uses the positive sequence current mutation before and after the abnormality of each line to lock the abnormal line. This new line protection method successfully avoids the problem of incorrect protection action caused by unmeasurable branches and has extremely strong reliability. It can significantly improve the accuracy of identifying abnormal lines and solve the problem that traditional three-stage current protection and current differential protection cannot be applied due to unmeasurable branches. At the same time, this method has low requirements on the computing power of the protection device, takes into account both effectiveness and practicality, and has strong engineering practical value.

[0130] The following is explained in conjunction with specific embodiments:

[0131] Select Figure 2 The typical 10kV distribution network shown is taken as the research object.

[0132] 1) The system power supply is 110kV, the frequency is 50Hz, and the base capacity is 100MVA.

[0133] 2) The voltage level of the distribution network is 10kV; all lines are overhead lines, with line lengths of L1 = 11km, L2 = 12km, L3 = 8km, L4 = 13km, L5 = 14km, L6 = 8km, L7 = 7km, L8 = 9km, L9 = 13km, L 10 =10km; line resistance r=0.17027Ω / km, line reactance x=0.3364Ω / km; the DG dedicated line is connected to the midpoint of line L3.

[0134] 3) The DG capacities are as follows: wind power DG1 capacity is 3MW, and photovoltaic DG2 capacity is 1MW.

[0135] 4) Loads 1, 2, 3, and 4 are 3MW, 2MW, 2MW, and 1MW respectively.

[0136] 5) F1 and F2 represent two typical fault points, 2 km from the end of line L3 and 2 km from the end of line L4. 10 2km from the beginning.

[0137] The adaptability of the distribution network line protection method based on positive sequence mutation quantity sorting is analyzed in combination with specific scenarios.

[0138] Embodiment 1: A metallic two-phase short circuit fault is set at F1 to examine the action of each line protection.

[0139] Step 1: After the abnormality occurs, the voltage and current waveform data of one power frequency cycle before and after the abnormality of each switch station or substation are collected in real time by using the primary and secondary fusion switch, and the collected voltage and current data are filtered and denoised to obtain the filtered three-phase voltage and current waveform data array;

[0140] Specifically, step 1: after an abnormality occurs, the primary and secondary fusion switch collects the three-phase voltage and current waveform data of the distribution line in real time, with a sampling rate of 1kHz, and saves the sampling data of one power frequency cycle before and after the abnormality, that is, 20ms each, to obtain the voltage and current waveform arrays with an array length of 20 each. The A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L1 are as follows: Figure 3 shown.

[0141] Step 2: De-noise the three-phase voltage waveforms collected by each switch station or substation and the three-phase current waveforms of each line. The filtered A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L3 are as follows: Figure 4 shown.

[0142] Step 2: Use the filtered voltage and current waveform data of one cycle before and after the abnormality to calculate the positive sequence voltage and current amplitudes before and after the abnormality. The positive sequence voltage and current amplitude after the abnormality minus the positive sequence voltage and current amplitude before the abnormality is the positive sequence mutation of voltage and current.

[0143] The positive sequence voltage mutation of each switch station or substation is shown in Table 1; the positive sequence current mutation of each line is shown in Table 2.

[0144]

[0145] Table 1 Positive sequence voltage mutation of each switch station or substation when F1 is abnormal

[0146]

[0147] Table 2 The positive sequence current mutation of each line when F1 is abnormal

[0148] Step 3: Sort the positive sequence voltage mutations of each switch station or substation, where the switch station or substation with the largest positive sequence voltage mutation is the switch station or substation connected to the abnormal line;

[0149] From Table 1, we can see that the positive sequence voltage mutation of BUS3 is the largest, which is 2.34kV. Therefore, we can know that:

[0150] N U =index{max[ΔU 1-1 ,ΔU 1-2 ,ΔU 1-3 ,ΔU 1-4 ,ΔU 1-5 ]}=3

[0151] The switch station or substation corresponding to BUS3 is the switch station or substation connected to the abnormal line.

[0152] Step 4: After locking the substation connected to the abnormal line, sort the positive sequence current mutations of each line of the switch station or substation, and the line with the largest positive sequence current mutation is the abnormal line;

[0153] The lines connected to BUS3 are L3, L6, L7, and L10. As shown in Table 2, the positive sequence current mutation of L3 is the largest.

[0154] N I =index{max[ΔI 1-1 ,ΔI 1-2 ,…,ΔI 1-m ]}=3

[0155] Then the line corresponding to L3 is the abnormal line.

[0156] Step 5: Multiply the maximum value of the voltage positive sequence mutation obtained after sorting by the maximum value of the current positive sequence mutation, and compare the calculated result with the apparent power transmitted under the minimum operating mode of the line to form an abnormality judgment criterion to prevent the power system disturbance from causing false operation of the line protection.

[0157] Step 1: After determining the abnormal line, first obtain the apparent power of the line in the minimum operation mode. That is, obtain N I The effective value of the line current I of the corresponding line and N in the minimum operation mode U The corresponding switch station or substation line voltage effective value U. By calculation, it can be obtained that the apparent power S under the minimum operation mode is 7.32MVA.

[0158] Step 2: Obtain the positive sequence current mutation value I of the corresponding line under abnormal state f And the positive sequence voltage mutation U of the switch station or substation corresponding to the abnormal state f The current apparent power S can be obtained by calculation: f = > 31..11S3MVA.

[0159] Step 3: Compare the current apparent power after the abnormality with the apparent power under the minimum operation mode. Obviously, S f >>01..11SS, it can be considered that the line is faulty and the protection should be activated immediately.

[0160] Embodiment 2: A metallic two-phase short circuit fault is set at F2 to examine the action of each line protection.

[0161] Step 1: After the abnormality occurs, the voltage and current waveform data of one power frequency cycle before and after the abnormality of each switch station or substation are collected in real time by using the primary and secondary fusion switch, and the collected voltage and current data are filtered and denoised to obtain the filtered three-phase voltage and current waveform data array;

[0162] The specific steps are as follows: Step 1: After an abnormality occurs, the primary and secondary fusion switch collects the three-phase voltage and current waveform data of the distribution line in real time, with a sampling rate of 1kHz, and saves the sampling data of one power frequency cycle before and after the abnormality, that is, 20ms each, to obtain a voltage and current waveform array with an array length of 20. The A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L3 are as follows: Figure 5 shown.

[0163] Step 2: De-noise the three-phase voltage waveforms collected by each switch station or substation and the three-phase current waveforms of each line. The filtered A-phase voltage waveform of bus BUS1 and the A-phase current waveform of line L1 are as follows: Figure 6 shown.

[0164] Step 2: Use the filtered voltage and current waveform data of one cycle before and after the abnormality to calculate the positive sequence voltage and current amplitudes before and after the abnormality. The positive sequence voltage and current amplitude after the abnormality minus the positive sequence voltage and current amplitude before the abnormality is the positive sequence mutation of voltage and current.

[0165] The calculated positive sequence voltage mutation of each switch station or substation is shown in Table 3; the positive sequence current mutation of each line is shown in Table 4.

[0166]

[0167] Table 3F2 abnormality of each switch station or substation positive sequence voltage mutation

[0168]

[0169] Table 4: Sudden changes in positive sequence current of each line when F2 is abnormal

[0170] Step 3: Sort the positive sequence voltage mutations of each switch station or substation, where the switch station or substation with the largest positive sequence voltage mutation is the switch station or substation connected to the abnormal line;

[0171] From Table 3, we can see that the positive sequence voltage mutation of BUS3 is the largest, which is 2.12kV. Therefore, we can know that:

[0172] N U =index{max[ΔU 1-1 ,ΔU 1-2 ,ΔU 1-3 ,ΔU 1-4,ΔU 1-5 ]}=3

[0173] The switch station or substation corresponding to BUS3 is the switch station or substation connected to the abnormal line.

[0174] Step 4: After locking the switch station or substation connected to the abnormal line, sort the positive sequence current mutations of each line of the switch station or substation, and the line with the largest positive sequence current mutation is the abnormal line;

[0175] It can be seen from Table 4 that the positive sequence current mutation of line L10 is the largest, which is 1.21kA. From this data, it can be seen that:

[0176] N I =index{max[ΔI 1-1 ,ΔI 1-2 ,…,ΔI 1-m ]}=10

[0177] Then the line corresponding to line L10 is the abnormal line. According to the above criteria, the abnormal line can be immediately locked.

[0178] Step 5: Multiply the maximum value of the voltage positive sequence mutation obtained after sorting by the maximum value of the current positive sequence mutation, and compare the calculated result with the apparent power transmitted under the minimum operating mode of the line to form an abnormality judgment criterion to prevent the power system disturbance from causing false operation of the line protection.

[0179] Step 1: After determining the abnormal line, first obtain the apparent power of the line in the minimum operation mode. That is, obtain N I The effective value of the line current I of the corresponding line and N in the minimum operation mode U The corresponding switch station or substation line voltage effective value U. By calculation, it can be obtained that the apparent power S under the minimum operation mode is 1.21MVA.

[0180] Step 2: Obtain the positive sequence current mutation value I of the corresponding line under abnormal state f And the positive sequence voltage mutation U of the switch station or substation corresponding to the abnormal state f .

[0181] Step 3: Compare the current apparent power after the abnormality with the apparent power under the minimum operation mode. Obviously, S f >>01..11SS, it can be considered that the line is faulty and the protection should be activated immediately.

[0182] In summary, this embodiment verifies the correctness and superiority of the present invention. A distribution network line protection method based on positive sequence mutation quantity sorting perfectly solves the three-stage current protection error and refusal problem caused by distributed power access, greatly improves the response speed of distribution network line protection, and has great advantages and engineering practical value when dealing with the line protection dilemma caused by unmeasurable branches.

[0183] The present invention also provides a power distribution network line protection system, please refer to Figure 7 As shown, including:

[0184] The abnormal site judgment module, after the distribution network detects an abnormal electrical signal, obtains the voltage data of each preset site in a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence voltage mutation amount of each preset site, and takes the preset site corresponding to the maximum value of each positive sequence voltage mutation amount as the abnormal site;

[0185] The abnormal line judgment module obtains the current data of each line connected to the abnormal site within a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence current mutation of each line, and takes the line corresponding to the maximum value of each positive sequence current mutation as the abnormal line;

[0186] The apparent power calculation module obtains the current apparent power of the abnormal line by combining the positive sequence current mutation amount corresponding to the abnormal line and the positive sequence voltage mutation amount of the abnormal site;

[0187] A judgment module, judging whether the abnormal line is faulty according to the current apparent power;

[0188] The protection module drives the circuit protection device to operate if it is determined that the abnormal circuit is faulty, and drives the circuit protection device to lock if it is determined that the abnormal circuit is not faulty.

[0189] Furthermore, the abnormal line judgment module also includes:

[0190] Acquire the first initial voltage waveform data of each preset site one power frequency cycle before the abnormal signal occurs, and the second initial voltage waveform data of each preset site one power frequency cycle after the abnormal signal occurs;

[0191] filtering each of the first initial voltage waveform data to obtain a plurality of first voltage waveform data, and filtering each of the second initial voltage waveform data to obtain a plurality of second voltage waveform data;

[0192] For any preset site, the positive sequence voltage mutation amount of the preset site is determined according to the first voltage waveform data and the second voltage waveform data of the preset site.

[0193] Furthermore, the abnormal line judgment module filters the first initial voltage waveform data according to the following formula:

[0194]

[0195] Where N represents the order of the filter; fc is the cutoff frequency; u a (k),u b (k) and u c (k) represents the first initial voltage waveform data; u a F (k),u b F (k) and u c F (k) is represented as the first voltage waveform data.

[0196] Furthermore, the abnormal line judgment module also includes:

[0197] Determine a first voltage effective value of the preset site according to the first voltage waveform data, and obtain a first positive sequence voltage component amplitude of the preset site according to the first voltage effective value;

[0198] Determine a second voltage effective value of the preset site according to the second voltage waveform data, and obtain a second positive sequence voltage component amplitude of the preset site according to the second voltage effective value;

[0199] The positive-sequence voltage mutation amount of the preset site is determined according to the difference between the first positive-sequence voltage component amplitude and the second positive-sequence voltage component amplitude.

[0200] Furthermore, the abnormal line judgment module determines the first voltage effective value of the preset site according to the first voltage waveform number according to the following formula:

[0201]

[0202] Among them, U a , U b and U c Expressed as the first voltage effective value.

[0203] Furthermore, the judgment module specifically includes:

[0204] Obtaining the minimum apparent power of the abnormal line under a preset minimum operating mode;

[0205] In combination with the minimum apparent power and the current apparent power, it is determined whether the abnormal line is faulty.

[0206] Furthermore, the judgment module specifically includes:

[0207] Acquire a third current effective value of the abnormal line under a preset minimum operation mode, and a third voltage effective value of the abnormal site under a preset minimum operation mode;

[0208] The minimum apparent power is determined according to the third current effective value and the third voltage effective value.

[0209] The present invention also provides a computer-readable storage medium, in which instructions are stored. When the instructions are executed on a terminal device, the terminal device executes a distribution network line protection method as described above.

[0210] The present invention also provides an electronic device, comprising a memory, a processor, and a program stored in the memory and running on the processor, wherein the processor implements a distribution network line protection method as described above when executing the program.

[0211] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0212] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0213] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A distribution network line protection method, characterized in that: include: After the distribution network detects an abnormal electrical signal, the voltage data of each preset site in a preset time period before and after the abnormal signal occurs is obtained to determine the positive sequence voltage mutation amount of each preset site, and the preset site corresponding to the maximum value of each positive sequence voltage mutation amount is taken as the abnormal site; Obtaining current data of each line connected to the abnormal site within a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence current mutation of each line, and taking the line corresponding to the maximum value of each positive sequence current mutation as the abnormal line; Combining the positive sequence current mutation amount corresponding to the abnormal line and the positive sequence voltage mutation amount at the abnormal site, the current apparent power of the abnormal line is obtained; Determining whether the abnormal line is faulty according to the current apparent power; If it is determined that the abnormal line is faulty, the driving line protection device is activated; if it is determined that the abnormal line is not faulty, the driving line protection device is locked.

2. A distribution network line protection method according to claim 1, characterized in that: The step of obtaining voltage data of each preset station in a preset time period before and after the abnormal signal occurs to determine the positive sequence voltage mutation amount of each preset station includes: Acquire the first initial voltage waveform data of each preset site one power frequency cycle before the abnormal signal occurs, and the second initial voltage waveform data of one power frequency cycle after the abnormal signal occurs; filtering each of the first initial voltage waveform data to obtain a plurality of first voltage waveform data, and filtering each of the second initial voltage waveform data to obtain a plurality of second voltage waveform data; For any preset site, the positive sequence voltage mutation amount of the preset site is determined according to the first voltage waveform data and the second voltage waveform data of the preset site.

3. A distribution network line protection method according to claim 2, characterized in that: The first initial voltage waveform data is filtered according to the following formula: Where N represents the order of the filter; fc is the cutoff frequency; u a (k) and u b (k) and u c (k) represents the first initial voltage waveform data; u a F (k) and u b F (k) and u c F (k) is represented as the first voltage waveform data.

4. A distribution network line protection method according to claim 3, characterized in that: Determining the positive sequence voltage mutation amount of the preset site according to the first voltage waveform data and the second voltage waveform data of the preset site includes: Determine a first voltage effective value of the preset site according to the first voltage waveform data, and obtain a first positive sequence voltage component amplitude of the preset site according to the first voltage effective value; Determine a second voltage effective value of the preset site according to the second voltage waveform data, and obtain a second positive sequence voltage component amplitude of the preset site according to the second voltage effective value; The positive-sequence voltage mutation amount of the preset site is determined according to the difference between the first positive-sequence voltage component amplitude and the second positive-sequence voltage component amplitude.

5. A distribution network line protection method according to claim 4, characterized in that: The first voltage effective value of the preset station is determined according to the first voltage waveform number according to the following formula: Among them, U a , U b and U c Expressed as the first voltage effective value.

6. A distribution network line protection method according to claim 1, characterized in that: The determining, based on the current apparent power, whether the abnormal line is faulty includes: Obtaining the minimum apparent power of the abnormal line under a preset minimum operating mode; In combination with the minimum apparent power and the current apparent power, it is determined whether the abnormal line is faulty.

7. A distribution network line protection method according to claim 6, characterized in that: The obtaining of the minimum apparent power of the abnormal line in a preset minimum operation mode includes: Acquire a third current effective value of the abnormal line under a preset minimum operation mode, and a third voltage effective value of the abnormal site under a preset minimum operation mode; The minimum apparent power is determined according to the third current effective value and the third voltage effective value.

8. A distribution network line protection system, characterized in that: include: The abnormal site judgment module, after the distribution network detects an abnormal electrical signal, obtains the voltage data of each preset site in a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence voltage mutation amount of each preset site, and takes the preset site corresponding to the maximum value of each positive sequence voltage mutation amount as the abnormal site; The abnormal line judgment module obtains the current data of each line connected to the abnormal site within a preset time period before and after the abnormal signal occurs, so as to determine the positive sequence current mutation of each line, and takes the line corresponding to the maximum value of each positive sequence current mutation as the abnormal line; The apparent power calculation module obtains the current apparent power of the abnormal line by combining the positive sequence current mutation amount corresponding to the abnormal line and the positive sequence voltage mutation amount of the abnormal site; A judgment module, judging whether the abnormal line is faulty according to the current apparent power; The protection module drives the circuit protection device to operate if it is determined that the abnormal circuit is faulty, and drives the circuit protection device to lock if it is determined that the abnormal circuit is not faulty.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores instructions, and when the instructions are executed on a terminal device, the terminal device executes a distribution network line protection method as described in any one of claims 1 to 7.

10. An electronic device comprising a memory, a processor, and a program stored in the memory and running on the processor, characterized in that: When the processor executes the program, a distribution network line protection method as described in any one of claims 1 to 7 is implemented.

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