A fault direction determination method and system based on voltage and current changes

Abstract

The application discloses a fault direction distinguishing method and system based on voltage and current change amount, and belongs to the technical field of power system relay protection. The method comprises the following steps: when a fault occurs at the outlet of a new energy power source station on one side of a sending line, three-phase measured voltages and currents before and after the fault at the protection installation site are obtained; the voltage and current change amounts of each phase and the voltage change amounts between each phase are calculated; the impedance voltage drop change amounts between each phase and each phase at the protection installation site to the system side are constructed; the measured voltage after the fault is brought into the phase selection criterion to determine the fault phase; the correlation coefficient of the voltage change amount waveform and the impedance voltage drop change amount waveform of the fault phase is calculated; and the waveform correlation coefficient is brought into the preset criterion to distinguish the outlet fault direction. The criterion provided by the application is suitable for the grid connection scene of a double-fed type and an inverter type new energy power source station through a sending line, and can effectively solve the problem that the positive sequence voltage polarization direction element cannot correctly judge the internal and external faults when an outlet fault occurs, thereby ensuring reliable action.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, and in particular to a fault direction determination method and system based on voltage and current changes. Background Technology

[0002] The increasing proportion of renewable energy sources in power systems has led to a gradual increase in the level of power electronics in these systems. However, the fault characteristics of renewable energy sources, such as weak feedforward, high harmonics and frequency deviation, and system impedance instability, as well as the complex electromagnetic and control response processes, make the fault characteristics of renewable energy AC grid-connected systems significantly different from those of traditional power systems.

[0003] When a fault occurs near the outlet of the AC transmission line of a new energy power plant, the fault characteristics of the new energy power source will make it difficult for traditional positive sequence voltage polarization direction components to accurately determine the fault direction, which seriously threatens the safe and stable operation of the power system. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the present invention provides a fault direction discrimination method based on voltage and current changes, which can solve the problem of malfunction or failure to operate of traditional positive sequence voltage polarization direction elements.

[0006] To address the aforementioned technical problems, this invention provides the following technical solution: a fault direction determination method based on voltage and current changes, comprising: when a fault occurs at a certain outlet of a new energy power station's transmission line, acquiring the three-phase measured voltage and current at the current side protection installation point for a period of time before the fault, and the three-phase measured voltage and current at the protection installation point after the fault; calculating the voltage change of each phase, the voltage change between each phase, and the current change of each phase based on the measured voltage and current of each phase at the protection installation point before and after the fault; constructing the voltage drop change of each phase and the voltage drop change between each phase from the protection installation point to the system side potential based on line parameters, system impedance parameters, and the current changes of each phase; inputting the measured voltage of each phase and the voltage between each phase at the protection installation point after the fault into the phase selection criterion to determine the fault type and phase; selecting an appropriate data window to calculate the waveform correlation coefficient of the voltage change of the fault phase and the voltage drop change of the fault phase, as input to the outlet fault direction determination criterion; and inputting the waveform correlation coefficient into a preset criterion to determine the direction of the outlet fault.

[0007] As a preferred embodiment of the fault direction determination method based on voltage and current changes described in this invention, the voltage changes between each phase include those calculated using the formula for the protection of the new energy power station side.

[0008]

[0009] in, This represents the change in voltage of each phase at the protection installation location. This represents the measured voltage of each phase at the protection installation location at time t after the fault. Represented as tT before the fault w1 Protect the measured voltage of each phase at the installation location at all times;

[0010] For system-side protection, it is represented as follows:

[0011]

[0012] in, This represents the change in voltage of each phase at the system-side protection installation location. Let T be the measured voltage of each phase at the protection installation point at time t after the fault, and tT be the voltage before the fault. w1 Always protect the measured voltage of each phase at the installation location.

[0013] Calculate the phase-to-phase voltage change at the new energy side protection installation location using the formula.

[0014]

[0015] Calculate the phase-to-phase voltage change at the system-side protection installation location using the formula.

[0016]

[0017] in,

[0018] In a preferred embodiment of the fault direction determination method based on voltage and current changes described in this invention, the current changes in each phase are expressed as follows:

[0019]

[0020] in, This represents the change in current of each phase at the protection installation point on the new energy power station side. This represents the measured current at the protection installation point at time t after the fault. Represented as tT before the fault w1 Protect the measured current at the installation location at all times;

[0021] For system-side protection, it is represented as follows:

[0022]

[0023] in, This represents the change in current of each phase at the system-side protection installation location. This represents the measured current at the protection installation point at time t after the fault. Before the fault tT w1 The current measured at the protection installation location at all times;

[0024] T w1 It is a pre-set fixed time window, which should be an integer multiple of 20ms of one cycle duration, and time t should satisfy 0 ≤ tt. f ≤T w1 It should be at the fault time t f T after w1 Inside.

[0025] As a preferred embodiment of the fault direction determination method based on voltage and current changes described in this invention, the voltage drop changes of each phase impedance include those constructed using formulas for the protection of new energy power stations.

[0026]

[0027] in, L represents the change in voltage drop across the total impedance from the protection installation point at the renewable energy power station to the system-side potential. L L N R L R N These are the total inductance of the transmitting line, the equivalent inductance of the system, the total resistance of the transmitting line, and the equivalent resistance of the system, respectively.

[0028] For system-side protection, it is constructed using formulas.

[0029]

[0030] in, This is the change in voltage drop across the total impedance from the system-side protection installation point to the system-side potential.

[0031] Calculate the change in interphase withstand voltage drop at the protection installation point on the new energy side.

[0032]

[0033] Calculate the change in phase impedance voltage drop at the protection installation point on the system side.

[0034]

[0035] As a preferred embodiment of the fault direction discrimination method based on voltage and current changes described in this invention, the phase selection criterion includes calculating the phase voltage and phase-to-phase voltage amplitude at the protection installation points on both sides of the line after a fault using the following instantaneous value integration algorithm.

[0036]

[0037] in, These are the instantaneous values ​​of the phase voltage and phase-to-phase voltage at the protection installation location, respectively. These represent the phase voltage amplitude and phase-to-phase voltage amplitude at the protection installation location, respectively, t f The fault occurs at time N, which is the number of protection sampling points within one power frequency cycle, and Δt is the sampling interval.

[0038] Let U dset For a low voltage threshold, if min(U) is satisfied ab U bc U ca ) dest If the voltage amplitude is low, it is determined to be a phase-to-phase fault, and the two phases corresponding to the minimum phase-to-phase voltage amplitude are identified as the faulty phases; otherwise, it is determined to be a single-phase fault, and the phase corresponding to the minimum phase voltage amplitude is identified as the faulty phase.

[0039] As a preferred embodiment of the fault direction discrimination method based on voltage and current changes described in this invention, the waveform correlation coefficients for calculating the fault phase voltage change and the fault phase impedance voltage drop change include, for a single-phase fault, the fault phase voltage change Δu for new energy side protection, is... m (t) should be taken Change in impedance voltage drop of the fault phase Δu m ′(t) should be taken For system-side protection, the voltage change Δu of the fault phase is... n (t) should be taken Change in impedance voltage drop of the fault phase Δu' n (t) should be taken If it is a two-phase fault, for the protection on the new energy side, the voltage change Δu of the faulted phase is... m (t) should be taken Change in impedance voltage drop of the fault phase Δu′ m (t) should be taken For system-side protection, the voltage change Δu of the fault phase is... n (t) should be taken Change in impedance voltage drop of the fault phase Δu' n (t) should be taken

[0040] Calculate the correlation coefficients of the waveforms showing the change in fault phase voltage and the change in fault phase impedance voltage drop on both sides of the protection system. For the new energy side protection, the time window tT is used. w2 The waveform sequence U of the voltage change of the fault phase on the new energy side up to time t m ={Δu m (tT w2 ​+1),…,Δu m (t-1),Δu m The waveform sequence U of (t)} and the change in impedance voltage drop m '={Δu m '(tT w2 +1),…,Δu m '(t-1),Δu m Arrange the elements in '(t)} in ascending order to obtain the new sequence X = {x1, x2, ..., x}. n} and Y = {y1, y2, ..., y n}. The sequence U m Each element Δu m (tT w2 Let the corresponding position of +i in X be a. i This yields the sequence A = {a1, a2, ..., a...} n}; The sequence U m Each element Δu within ' m '(tT w2 The corresponding position of +i in Y is denoted as b. i This yields the sequence B = {b1, b2, ..., b}. n Subtracting each element from sequence A from sequence B yields sequence D = {d1, d2, ..., d...} n}={a1-b1,a2-b2,…,a n -b n Substitute each value in sequence D into the Spearman rank correlation coefficient formula: By performing calculations, the time window tT can be obtained. w2 The waveform correlation coefficient r of the voltage change and impedance drop change of the fault phase on the new energy side up to time t M (t), where n is the time window T w2 The number of corresponding sampling points.

[0041] For system-side protection, the time window tT w2 The waveform sequence U of the change in the system-side protection fault phase voltage up to time t n ={Δu n (tT w2 +1),…,Δu n (t-1),Δu n The values ​​of (t)} and the change in impedance voltage drop U n '={Δu n '(tT w2 +1),…,Δu n '(t-1),Δu nBy processing '(t)} according to the above steps, the time window tT can be obtained. w2 The waveform correlation coefficient r of the voltage change and impedance drop change of the system-side protection fault phase within time t. N (t).

[0042] As a preferred embodiment of the fault direction discrimination method based on voltage and current changes described in this invention, the method for discerning the direction of an exit fault includes selecting an appropriate time window T. w3 For the protection of new energy power stations, the time window [tT] w3 ,t]inner r M (t) continuously satisfies r M (t)>r Mset If the condition is met, a reverse exit fault is considered to have occurred; otherwise, a forward exit fault is considered to have occurred, where r Mset For the protection waveform correlation coefficient of the new energy power station side, the time window [tT] is the set value. For the system-side protection, the time window is [tT]. w3 ,t]inner r N (t) continuously satisfies r N (t)>r Nset If the condition is met, a forward exit fault is considered to have occurred; otherwise, a reverse exit fault is considered to have occurred, where r Nset This is the setting value for the correlation coefficient of the protection waveform on the system side.

[0043] Another objective of this invention is to provide a fault direction discrimination system based on voltage and current changes. This system comprises: a data acquisition module that accurately acquires three-phase voltage and current data before and after a fault, ensuring the integrity and accuracy of the basic data for subsequent analysis, thus aiding in fault analysis and judgment; a change calculation module that accurately calculates voltage and current changes to provide detailed fault characteristic information, providing reliable data support for subsequent impedance construction; an impedance construction module that constructs impedance voltage drop changes based on specific line and system parameters and current changes, ensuring accurate reflection of the electrical characteristics of the fault point during fault discrimination, thus improving the accuracy of the discrimination; a fault phase selection module that accurately determines the fault type and fault phase based on post-fault voltage data and phase selection criteria, ensuring the accuracy of the data used to calculate waveform correlation coefficients; a data selection module that selects an appropriate data window and calculates waveform correlation coefficients, ensuring the validity and accuracy of the input data for the criteria, thus improving the reliability of fault direction discrimination; and a direction determination module that accurately determines the direction of the fault at the exit point based on waveform correlation coefficients and preset criteria, facilitating timely implementation of correct protection and control measures and ensuring the safe operation of the system.

[0044] As a preferred embodiment of the fault direction discrimination system based on voltage and current changes described in this invention, it includes: a data acquisition module, a change calculation module, an impedance construction module, a fault phase selection module, a data selection module, and a direction determination module.

[0045] The data acquisition module acquires the three-phase measured voltage and current at the current protection installation location for a period of time before the fault occurs, and the three-phase measured voltage and current at the protection installation location after the fault occurs, when a fault occurs at a certain outlet of the transmission line of a new energy power station.

[0046] The change calculation module calculates the voltage change of each phase, the voltage change between each phase, and the current change of each phase based on the measured voltage and current of each phase before and after the fault at the protection installation location.

[0047] The impedance construction module constructs the phase impedance voltage drop variation and interphase impedance voltage drop variation between the protection installation point and the system side potential based on the line parameters, system impedance parameters, and phase current variation.

[0048] The fault identification module takes the measured voltages of each phase and the phase-to-phase voltage at the protection installation point after the fault and inputs them into the phase selection criteria to determine the fault type and phase.

[0049] The data selection module selects an appropriate data window and calculates the waveform correlation coefficients of the fault phase voltage change and the fault phase impedance voltage drop change, which serve as inputs for the outlet fault direction criterion.

[0050] The direction determination module inputs the waveform correlation coefficient into a preset criterion to determine the direction of the exit fault.

[0051] A computer device includes a memory and a processor, the memory storing a computer program, characterized in that, when the processor executes the computer program, it implements the steps of any one of the fault direction discrimination methods based on voltage and current changes.

[0052] A computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of any one of the methods in the fault direction determination method based on voltage and current changes.

[0053] The beneficial effects of the present invention are as follows: The criterion proposed in the present invention is applicable to the transmission line scenarios of doubly-fed new energy power sources and inverter-type new energy power sources. It can effectively solve the problem that the positive sequence voltage polarization direction element cannot correctly judge the fault inside and outside the zone when an output fault occurs in the AC grid-connected scenario of new energy power units. It is beneficial to the reliable operation of the AC grid-connected system of new energy power units under the condition of output fault. Attached Figure Description

[0054] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of a new energy power station transmission system structure provided by an embodiment of the present invention, which is based on a fault direction discrimination method for voltage and current changes.

[0056] Figure 2 In one embodiment of the present invention, a fault direction determination method based on voltage and current changes is provided. A fault occurs at the reverse outlet F1 of the transmission line system of a new energy power plant. The system-side protection uses the phase ratio result of existing positive-sequence voltage polarization direction elements. 21ms after the fault, the phase ratio result enters the protection operation range, causing maloperation of the system-side protection.

[0057] Figure 3 This invention provides a fault direction discrimination method based on voltage and current changes. A fault occurs at the reverse outlet F1 of the transmission line system side of an inverter-type new energy power plant. The diagram compares the changes in the fault phase voltage and impedance voltage drop of the system-side protection.

[0058] Figure 4 In one embodiment of the present invention, a fault direction discrimination method based on voltage and current changes is provided. A fault occurs at the reverse outlet F1 of the transmission line system of an inverter-type new energy power plant. The system-side protection uses the waveform correlation coefficient r calculated by the method of the present invention. N (t).

[0059] Figure 5 This is a comparison diagram of the voltage change and impedance voltage drop of the fault phase protected by the system side when a fault occurs at the forward outlet F2 of the transmission line system of an inverter-type new energy power plant, which is a fault direction discrimination method based on voltage and current changes, according to an embodiment of the present invention.

[0060] Figure 6 In one embodiment of the present invention, a fault direction discrimination method based on voltage and current changes is provided. A fault occurs at the positive outlet F2 of the transmission line system of an inverter-type new energy power plant. The system-side protection uses the waveform correlation coefficient r calculated by the method of the present invention. N (t).

[0061] Figure 7This invention provides a fault direction determination method based on voltage and current changes. A fault occurs at the positive outlet F3 on the new energy side of the transmission line of an inverter-type new energy power plant, which is a fault on the new energy side. The graph compares the changes in the fault phase voltage and the changes in the impedance voltage drop of the protection on the new energy side.

[0062] Figure 8 An embodiment of the present invention provides a fault direction discrimination method based on voltage and current changes. A fault occurs at the positive outlet F3 on the renewable energy side of the transmission line of an inverter-type renewable energy power plant. The renewable energy side protection uses the waveform correlation coefficient r calculated by the method of the present invention. M (t).

[0063] Figure 9 This invention provides a fault direction discrimination method based on voltage and current changes. A fault occurs at the reverse outlet F4 on the new energy side of the transmission line of an inverter-type new energy power plant. The graph compares the change in fault phase voltage and the change in impedance voltage drop of the protection on the new energy side.

[0064] Figure 10 An embodiment of the present invention provides a fault direction discrimination method based on voltage and current changes. A fault occurs at the reverse outlet F4 on the renewable energy side of the transmission line of an inverter-type renewable energy power plant. The renewable energy side protection uses the waveform correlation coefficient r calculated by the method of the present invention. M (t).

[0065] Figure 11 This is a comparison diagram of the voltage change and impedance voltage drop change of the fault phase protected by the system side when a fault occurs at the reverse outlet F1 of the transmission line system of a doubly fed new energy power station based on a fault direction discrimination method based on voltage and current changes, according to an embodiment of the present invention.

[0066] Figure 12 In one embodiment of the present invention, a fault direction discrimination method based on voltage and current changes is provided for a doubly fed new energy power plant. A fault occurs at the reverse outlet F1 of the transmission line system side of the power plant. The system-side protection uses the waveform correlation coefficient r calculated by the method of the present invention. N (t).

[0067] Figure 13 This is a comparison diagram of the voltage change and impedance voltage drop of the fault phase protected by the system side when a fault occurs at the positive outlet F2 of the transmission line system of a doubly fed new energy power station based on a fault direction discrimination method based on voltage and current changes, as provided in an embodiment of the present invention.

[0068] Figure 14In one embodiment of the present invention, a fault direction discrimination method based on voltage and current changes is provided for a doubly fed new energy power plant. A fault occurs at the positive outlet F2 of the transmission line system side of the power plant. The system-side protection uses the waveform correlation coefficient r calculated by the method of the present invention. N (t).

[0069] Figure 15 This is a comparison diagram of the voltage change and impedance voltage drop of the fault phase protected by the new energy side protection when a fault occurs at the positive outlet F3 of the new energy side of the doubly fed new energy power station transmission line, which is a fault direction discrimination method based on voltage and current changes, provided in one embodiment of the present invention.

[0070] Figure 16 An embodiment of the present invention provides a fault direction discrimination method based on voltage and current changes. A fault occurs at the positive outlet F3 on the renewable energy side of the transmission line of a doubly fed renewable energy power plant. The renewable energy side protection uses the waveform correlation coefficient r calculated by the method of the present invention. M (t).

[0071] Figure 17 This is a comparison diagram of the voltage change and impedance voltage drop change of the fault phase protected by the new energy side protection when a fault occurs at the reverse outlet F4 of the new energy side of the doubly fed new energy power station transmission line, which is a fault direction discrimination method based on voltage and current changes, according to an embodiment of the present invention.

[0072] Figure 18 In one embodiment of the present invention, a fault direction discrimination method based on voltage and current changes is provided for a doubly fed renewable energy power plant where a fault occurs at the reverse outlet F4 on the renewable energy side of the transmitting line. The renewable energy side protection uses the waveform correlation coefficient r calculated by the method of the present invention. M (t). Detailed Implementation

[0073] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0074] Example 1

[0075] Reference Figure 1 -- Figure 18 This is the first embodiment of the present invention, which provides a fault direction determination method based on voltage and current changes, including:

[0076] S1: When a fault occurs at a certain outlet of the transmission line of a new energy power station, obtain the three-phase measured voltage and current at the protection installation point on that side for a period of time before the fault, and the three-phase measured voltage and current at the protection installation point after the fault.

[0077] It should be noted that a typical schematic diagram of a new energy power plant's transmission system structure is shown below. Figure 1 As shown, the phase ratio results of maloperation caused by faults outside the region using existing positive sequence voltage polarization direction elements are as follows: Figure 2 As shown.

[0078] S2: Based on the measured voltage and current of each phase before and after the fault at the protection installation location, calculate the voltage change of each phase, the voltage change between each phase, and the current change of each phase.

[0079] It should be noted that the calculation involves the voltage changes of each phase. For the protection of new energy power plants, the formula is used. Calculation, where To protect against voltage variations in each phase at the installation location, The measured voltage of each phase at the protection installation point at time t after the fault. Before the fault tT w1 Constantly measure the phase voltage at the installation location. For system-side protection, use the formula... Calculation, where This refers to the change in voltage of each phase at the system-side protection installation point. The measured voltage of each phase at the protection installation point at time t after the fault. Before the fault tT w1 Always protect the measured voltage of each phase at the installation location.

[0080] Furthermore, according to the formula Calculate the phase-to-phase voltage variation at the protection installation point on the new energy side. According to the formula Calculate the phase-to-phase voltage variation at the protection installation point on the system side.

[0081] Calculate the changes in current for each phase. The calculation method is similar to that for the current in each phase; for the protection of the renewable energy power station side, the formula is used. Calculation, where This refers to the change in current of each phase at the protection installation point on the new energy power station side. The measured current at the protection installation point at time t after the fault. Before the fault tT w1 Constantly monitor the measured current at the installation location. For system-side protection, use the formula... Calculation, where This refers to the change in current of each phase at the system-side protection installation point. The measured current at the protection installation point at time t after the fault. Before the fault tT w1 The current is measured at the protection installation location at all times.

[0082] T in the above formula w1 It is a pre-set fixed time window, which should be an integer multiple of 20ms of one cycle duration, and time t should satisfy 0 ≤ tt. f ≤T w1 That is, it should be at the fault time t f T after w1 Within. In this example, T w1 Take 40ms. The voltage changes of the fault phase under various fault scenarios involved in this example are as follows: Figure 3 , 5 As shown in 7, 9, 11, 13, 15, and 17.

[0083] S3: Based on the line parameters, system impedance parameters, and changes in current of each phase, construct the changes in impedance voltage drop of each phase and the changes in impedance voltage drop between each phase from the protection installation point to the system side potential.

[0084] It should be noted that the voltage drop variation of each phase impedance is constructed. For the protection of the new energy power station side, the formula is used. To construct, where L represents the change in voltage drop across the total impedance from the protection installation point at the renewable energy power station to the system-side potential. L L N R L R N These are the total inductance of the outgoing line, the equivalent inductance of the system, the total resistance of the outgoing line, and the equivalent resistance of the system, respectively. For system-side protection, the formula is used. To construct, where It represents the change in voltage drop across the total impedance from the system-side protection installation point to the system-side potential.

[0085] Furthermore, according to the formula Calculate the change in interphase impedance voltage drop at the new energy side protection installation location. According to the formula Calculate the change in interphase impedance voltage drop at the protection installation point on the calculation system side. The changes in fault phase impedance voltage drop under various fault scenarios involved in this example are as follows: Figure 3 , 5 As shown in 7, 9, 11, 13, 15, and 17.

[0086] S4: Input the measured voltages of each phase and the phase-to-phase voltage at the protection installation point after the fault into the phase selection criteria to determine the fault type and phase.

[0087] It should be noted that the following instantaneous value integration algorithm is used to calculate the phase voltage and phase-to-phase voltage amplitude at the protection installation points on both sides of the line after a fault: in, These are the instantaneous values ​​of the phase voltage and phase-to-phase voltage at the protection installation location, respectively. These are the phase voltage amplitude and phase-to-phase voltage amplitude at the protection installation location, respectively. t f The fault time is N, the number of protection sampling points within one power frequency cycle is N, and the sampling interval is Δt.

[0088] Let U dset This is a low voltage threshold. If min(U) is satisfied... ab U bc U ca ) < U dset If the voltage amplitude is low, it is determined to be a phase-to-phase fault, and the two phases corresponding to the minimum phase-to-phase voltage amplitude are identified as the faulty phases; otherwise, it is determined to be a single-phase fault, and the phase corresponding to the minimum phase voltage amplitude is identified as the faulty phase.

[0089] S5: Select an appropriate data window and calculate the waveform correlation coefficients of the fault phase voltage change and the fault phase impedance voltage drop change as inputs for the outlet fault direction criterion.

[0090] It should be noted that the voltage change and impedance drop change of the fault phase at the protection installation points on both sides are determined based on the phase selection results of S4. If it is a single-phase fault, for the new energy side protection, the voltage change Δu of the fault phase... m (t) should be taken Change in impedance voltage drop of the fault phase Δu m '(t) should be taken For system-side protection, the voltage change Δu of the fault phase is... n (t) should be taken Change in impedance voltage drop of the fault phase Δu n '(t) should be taken If it is a two-phase fault, for the protection on the new energy side, the voltage change Δu of the faulted phase is... m (t) should be taken Change in impedance voltage drop of the fault phase Δu m '(t) should be taken For system-side protection, the voltage change Δu of the fault phase is... n (t) should be taken Change in impedance voltage drop of the fault phase Δu n '(t) should be taken

[0091] Calculate the correlation coefficients of the waveforms showing the change in fault phase voltage and the change in fault phase impedance voltage drop on both sides of the protection system. For the new energy side protection, the time window tT is used. w2 The waveform sequence U of the voltage change of the fault phase on the new energy side up to time t m ={Δu m (tT w2 +1),…,Δu m (t-1),Δu m The waveform sequence U of (t)} and the change in impedance voltage drop m '={Δu m '(tT w2 +1),…,Δu m '(t-1),Δu m Arrange the elements in '(t)} in ascending order to obtain the new sequence X = {x1, x2, ..., x}. n} and Y = {y1, y2, ..., y n}. The sequence U m Each element Δu m (tT w2 Let the corresponding position of +i in X be a. i This yields the sequence A = {a1, a2, ..., a...} n}; The sequence U m Each element Δu within ' m '(tT w2 The corresponding position of +i in Y is denoted as b. i This yields the sequence B = {b1, b2, ..., b}. n Subtracting each element from sequence A from sequence B yields sequence D = {d1, d2, ..., d...} n}={a1-b1,a2-b2,…,a n -b n Substitute each value in sequence D into the Spearman rank correlation coefficient formula: By performing calculations, the time window tT can be obtained. w2 The waveform correlation coefficient r of the voltage change and impedance drop change of the fault phase on the new energy side up to time t M (t), where n is the time window T w2 The number of corresponding sampling points.

[0092] Similarly, for system-side protection, the time window tT w2 The waveform sequence U of the change in the system-side protection fault phase voltage up to time t n ={Δu n (tT w2 +1),…,Δu n (t-1),Δun The values ​​of (t)} and the change in impedance voltage drop U n '={Δu n '(tT w2 +1),…,Δu n '(t-1),Δu n By processing '(t)} according to the above steps, the time window tT can be obtained. w2 The waveform correlation coefficient r of the voltage change and impedance drop change of the system-side protection fault phase within time t. N (t). In this example, T w2 Take 5ms. The waveform correlation coefficients calculated for various fault scenarios involved in this example are as follows: Figure 4 , 6 As shown in numbers 8, 10, 12, 14, 16, and 18.

[0093] S6: Substitute the waveform correlation coefficient into the preset criteria to determine the direction of the exit fault.

[0094] It should be noted that choosing an appropriate time window T w3 For the protection of new energy power stations, the time window [tT] w3 ,t]inner r M (t) continuously satisfies r M (t)>r Mset If the condition is met, a reverse exit fault is considered to have occurred; otherwise, a forward exit fault is considered to have occurred, where r... Mset This is the setting value for the waveform correlation coefficient of the new energy power station side protection. For system-side protection, the time window [tT] is... w3 ,t]inner r N (t) continuously satisfies r N (t)>r Nset If the condition is met, a forward exit fault is considered to have occurred; otherwise, a reverse exit fault is considered to have occurred, where r... Nset This is the setting value for the correlation coefficient of the system-side protection waveform. In this example, T... w3 Take 10ms, r Mset Take 0.2, r Nset Take 0.2.

[0095] Compared with the prior art, the technical solution conceived in this invention, based on the changes in voltage and current before and after a fault, proposes a method for determining the fault direction at the outlet of an AC transmission line of a new energy power plant. This method can effectively solve the problem that the positive sequence voltage polarization direction element cannot accurately determine the fault direction when a fault occurs at the outlet of a transmission line of a new energy power plant.

[0096] Example 2

[0097] The second embodiment of the present invention differs from the first embodiment in that:

[0098] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0099] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0100] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0101] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0102] Example 3

[0103] This is a third embodiment of the present invention, which provides a fault direction discrimination system based on voltage and current changes, characterized in that it includes: a data acquisition module, a change calculation module, an impedance construction module, a fault phase selection module, a data selection module, and a direction determination module;

[0104] The data acquisition module acquires the three-phase measured voltage and current at the current protection installation location for a period of time before the fault occurs, and the three-phase measured voltage and current at the protection installation location after the fault occurs, when a fault occurs at a certain outlet of the transmission line of a new energy power station.

[0105] The change calculation module calculates the voltage change of each phase, the voltage change between each phase, and the current change of each phase based on the measured voltage and current of each phase before and after the fault at the protection installation location.

[0106] The impedance construction module constructs the phase impedance voltage drop variation and interphase impedance voltage drop variation between the protection installation point and the system side potential based on the line parameters, system impedance parameters, and phase current variation.

[0107] The fault identification module takes the measured voltages of each phase and the phase-to-phase voltage at the protection installation point after the fault and inputs them into the phase selection criteria to determine the fault type and phase.

[0108] The data selection module selects an appropriate data window and calculates the waveform correlation coefficients of the fault phase voltage change and the fault phase impedance voltage drop change, which serve as inputs for the outlet fault direction criterion.

[0109] The direction determination module inputs the waveform correlation coefficient into a preset criterion to determine the direction of the exit fault.

[0110] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A fault direction discrimination method based on voltage current variation, characterized in that: Comprising, When the fault occurs at one side of the new energy power station sending-out line, the three-phase measured voltage and current of the protection installation at the current side within a period of time before the fault and the three-phase measured voltage and current of the protection installation after the fault are obtained; According to the measured voltage and current of each phase before and after the fault at the protection installation, the voltage variation of each phase, the voltage variation between phases, and the current variation of each phase are calculated; According to the line parameters, the system impedance parameters, and the current variation of each phase, the impedance voltage drop variation of each phase and the impedance voltage drop variation between phases between the protection installation and the system side potential are constructed; The measured voltage and the voltage between phases of each phase after the fault at the protection installation are brought into the phase selection criterion to determine the fault type and phase; The waveform correlation coefficient of the fault phase voltage variation and the fault phase impedance voltage drop variation is calculated as the input of the exit fault direction criterion by selecting a suitable data window; The waveform correlation coefficient is brought into the preset criterion to determine the direction of the exit fault; The waveform correlation coefficient of the fault phase voltage variation and the fault phase impedance voltage drop variation includes, if it is single-phase fault, for new energy side protection, fault phase voltage variation Δu m (t) should take The fault phase impedance voltage drop variation Δu m '(t) should take For system side protection, fault phase voltage variation Δu n (t) should take The fault phase impedance voltage drop variation Δu' n (t) should take If it is two-phase fault, for new energy side protection, fault phase voltage variation Δu m (t) should take The fault phase impedance voltage drop variation Δu' m (t) should take For system side protection, fault phase voltage variation Δu n (t) should take The fault phase impedance voltage drop variation Δu' n (t) should take Calculate the correlation coefficients of the fault phase voltage change waveform and the fault phase impedance voltage drop waveform for both protection sides. For the new energy side protection, the time window tT is used. w2 The waveform sequence U of the voltage change of the fault phase on the new energy side up to time t m ={Δu m (tT w2 +1),…,Δu m (t-1),Δu m The waveform sequence U of (t)} and the change in impedance voltage drop m '={Δu m '(tT w2 +1),…,Δu m '(t-1),Δu m Arrange the elements in '(t)} in ascending order to obtain the new sequence X = {x1, x2, ..., x}. n } and Y = {y1, y2, ..., y n }, sequence U m Each element Δu m (tT w2 Let the corresponding position of +i in X be a. i This yields the sequence A = {a1, a2, ..., a...} n }; The sequence U m Each element Δu within ' m '(tT w2 The corresponding position of +i in Y is denoted as b. i This yields the sequence B = {b1, b2, ..., b}. n Subtracting each element from sequence A from sequence B yields sequence D = {d1, d2, ..., d...} n }={a1-b1,a2-b2,…,a n -b n Substitute each value in sequence D into the Spearman rank correlation coefficient formula: Calculations are performed to obtain the time window tT. w2 The waveform correlation coefficient r of the voltage change and impedance drop change of the fault phase on the new energy side up to time t M (t), where n is the time window T w2 The number of corresponding sampling points; For system side protection, the waveform sequence U w2 = {Δu n (t-T w2 +1),…,Δu n (t-1),Δu n (t)} of the system side protection fault phase voltage variation and the value U n ' = {Δu n '(t-T w2 +1),…,Δu n '(t-1),Δu n '(t)} of the impedance voltage drop variation in the time window t-T w2 to t are processed to obtain the waveform correlation coefficient r N (t) of the system side protection fault phase voltage variation and the impedance voltage drop variation in the time window t-T w1 to t.

2. The fault direction discrimination method based on voltage and current variation according to claim 1, characterized in that: The voltage variation between phases includes, for the protection at the new energy station side, being calculated using a formula, wherein, represents the amount of change in each phase voltage at the protection installation site, represents each phase measured voltage at the protection installation site at time t after the fault, represents each phase measured voltage at the protection installation site at time t-T w1 before the fault; For the protection at the system side, being calculated using a formula, wherein, represents the variation of each phase voltage at the installation site of the protection system, is the measured voltage of each phase at the installation site of the protection system at time t after the fault, and w1 represents the measured voltage of each phase at the installation site of the protection system at time t-T before the fault. According to the formula, the new energy side protection installation place phase-to-phase voltage variation is calculated According to the formula, the system side protection installation place phase-to-phase voltage variation is calculated wherein 3. The fault direction discrimination method based on voltage and current variation according to claim 2, characterized in that: The current variation of each phase is calculated using a formula, wherein, represents the variation of each phase current at the installation site of the new energy field station protection, represents the measured current at the installation site of the protection at time t after the fault, represents the measured current at the installation site of the protection at time t-T w1 before the fault; For the protection at the system side, being calculated using a formula, wherein, represents the variation of each phase current at the protection installation site of the system side, represents the measured current at the protection installation site at time t after the fault, is the measured current at the protection installation site at time t-T w1 before the fault. T w1 is a pre-set fixed time window, which should be an integer multiple of a cycle length of 20 ms, and the time t satisfies 0≤t-t f ≤T w1 , which should be within T w1 after the fault time t f .

4. The fault direction discrimination method based on voltage and current variation according to claim 3, characterized in that: The impedance voltage drop variation of each phase includes, for the protection at the new energy station side, being constructed using a formula, wherein, L is the total impedance from the installation site to the system potential, L L N R L R N is the total line inductance, the system equivalent inductance, the total line resistance, and the system equivalent resistance, respectively. For the protection at the system side, being constructed using a formula, wherein is the change in voltage drop across the total impedance from the system side protection mounting to the system side potential; The impedance voltage drop variation between phases at the protection installation at the new energy side is calculated, The impedance voltage drop variation between phases at the protection installation at the system side is calculated, 5. The fault direction discrimination method based on voltage and current variation according to claim 4, characterized in that: The phase selection criterion includes calculating the amplitude of the voltage of each phase and the voltage between phases at the protection installation at both sides of the line after the fault using the following instantaneous value integral algorithm, wherein, respectively the instantaneous value of the phase voltage and the phase-to-phase voltage at the installation, respectively the amplitude of the phase voltage and the phase-to-phase voltage at the installation, f is the fault time, N is the number of sampling points in one power frequency cycle, and Δt is the sampling interval. Let U dset be the low voltage threshold, if min(U ab , U bc , U ca ) < U dset , it is determined as inter-phase fault and the two phases corresponding to the minimum phase-to-phase voltage amplitude are determined as fault phases; otherwise, it is determined as single-phase fault and the phase corresponding to the minimum phase voltage amplitude is determined as fault phase.

6. The fault direction discrimination method based on voltage and current variation according to claim 5, characterized in that: The direction of the discriminated outlet fault includes selecting a suitable time window T w3 For new energy station side protection, the time window [t-T w3 ,t] r M (t) continuously satisfies r M (t)>r Mset , it is considered that a reverse outlet fault occurs; if it is not satisfied, it is considered that a positive outlet fault occurs, wherein r Mset is the setting value of the waveform correlation coefficient of the new energy station side protection, for system side protection, the time window [t-T w3 ,t] r N (t) continuously satisfies r N (t)>r Nset , it is considered that a positive outlet fault occurs; if it is not satisfied, it is considered that a reverse outlet fault occurs, wherein r Nset is the setting value of the waveform correlation coefficient of the system side protection.

7. A system for fault direction discrimination based on the change in voltage and current according to any one of claims 1-6, characterized by: Comprising, a data acquisition module, a variation calculation module, an impedance construction module, a fault phase selection module, a data selection module, and a direction determination module; The data acquisition module, when the fault occurs at one side of the new energy power station sending-out line, acquires the three-phase measured voltage and current of the protection installation at the current side within a period of time before the fault and the three-phase measured voltage and current of the protection installation after the fault; The variation calculation module calculates the voltage variation of each phase, the voltage variation between phases, and the current variation of each phase according to the measured voltage and current of each phase before and after the fault at the protection installation; The impedance construction module constructs the impedance voltage drop variation of each phase and the impedance voltage drop variation between phases between the protection installation and the system side potential according to the line parameters, the system impedance parameters, and the current variation of each phase; The fault phase selection module brings the measured voltage and the voltage between phases of each phase after the fault at the protection installation into the phase selection criterion to determine the fault type and phase; The data selection module calculates the waveform correlation coefficient of the fault phase voltage variation and the fault phase impedance voltage drop variation as the input of the exit fault direction criterion by selecting a suitable data window; The direction determination module brings the waveform correlation coefficient into the preset criterion to determine the direction of the exit fault.

8. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that, The processor executes the computer program to implement the steps of the method of any one of claims 1 to 6.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method of any one of claims 1 to 6.

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