Method for determining the decay time constant of the direct current component of single-phase earth fault short circuit current

Abstract

The single-phase ground fault short-circuit current DC component decay time constant determination method provided in the application can be regarded as the simultaneous occurrence of three faults, i.e., single-phase ground fault of a generator side node, disconnection of a line connecting the generator side node and a grid side node, and single-phase ground fault of the grid side node when detecting that a single-phase ground short-circuit fault occurs at a generator access node. Therefore, the positive sequence network, the negative sequence network and the zero sequence network of the generator side and the grid side can be constructed according to the current single-phase ground short-circuit fault, and the port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network can be determined. In this way, the short-circuit current DC component of the generator side and the grid side can be calculated according to the port voltage and the port boundary condition, and then the curve fitting tool is used to fit the short-circuit current DC component of the generator side and the grid side into an exponential function, and the short-circuit current DC component decay time constant of the generator access node is determined through the exponential function.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power transmission, and particularly relates to a single-phase grounding fault short-circuit current DC component decay time constant determination method and device, a storage medium and a computer device. BACKGROUND

[0002] At present, for a simple circuit of a branch, the short-circuit current DC component decay time constant of the branch is the ratio of the inductance L and the resistance R of the branch, that is, L / R. For a complex network of multiple branches, when the short-circuit current DC component decay time constant of a node is calculated by using the equivalent frequency method, there is an error, which depends on the difference between the impedance amplitudes of the branches, the difference between the inductance and resistance, that is, the greater the difference between the impedance amplitudes of the branches and the greater the difference between the resistance and the inductance, the lower the accuracy of the calculation result. In essence, it can be understood that the greater the difference between the amplitudes of the short-circuit current DC components of the branches and the greater the difference between the decay time constants, the greater the error of the comprehensive decay time constant calculated by using the equivalent frequency method.

[0003] For a generator access point, that is, a power plant node, since the DC component decay time constant of the branch in which the synchronous generator and the transformer are connected in series is much larger than that of the line and the load in the power grid (the L / R of the two types of elements themselves is extremely large, about 500-600 ms), therefore, there is a large error when the short-circuit current DC component decay time constant of the power plant node is directly calculated by using the equivalent frequency method. Therefore, when a three-phase short-circuit fault occurs at the generator access node, the target power grid can be divided into two branches of a generator side branch and a power grid side branch with the power plant node as a sub-network point, then the equivalent frequency method is used to calculate the short-circuit current DC component amplitudes provided by the power grid side branch and the generator side branch and the self-impedances of the power grid side and the generator side under the equivalent frequency, after the short-circuit current DC components provided by the power grid side branch and the generator side branch are obtained, the CFTOOL curve fitting tool of the MATLAB software is used to fit the short-circuit current DC components of the generator side branch and the power grid side branch, and thus the short-circuit current DC component decay time constant of the generator access node can be obtained. However, compared with the three-phase grounding short-circuit fault, when a single-phase grounding short-circuit fault occurs at the generator access node, the generator side and the power grid side are connected through the non-fault phase, and the two branches are not completely decoupled, so the original sub-network and curve fitting method is no longer applicable. SUMMARY

[0004] The present application aims to at least solve one of the above technical defects, and particularly aims to solve the technical defect that the original calculation method of the short-circuit current DC component decay time constant of the generator access node when a three-phase short-circuit fault occurs at the generator access node is not applicable when a single-phase grounding short-circuit fault occurs at the generator access node, resulting in a large error of the calculation result.

[0005] The application provides a single-phase ground fault short-circuit current DC component decay time constant determination method, which comprises the following steps:

[0006] When a single-phase ground short-circuit fault of a generator access node is detected, a positive sequence network, a negative sequence network and a zero sequence network of the generator side and the grid side in the single-phase ground short-circuit fault are constructed;

[0007] The port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network are determined;

[0008] The short-circuit current DC component of the generator side and the grid side is determined according to the port voltage and the port boundary condition of each fault port;

[0009] After the short-circuit current DC component of the generator side and the grid side is fitted into an exponential function by using a curve fitting tool, the short-circuit current DC component decay time constant of the generator access node is determined by the exponential function.

[0010] Optionally, the determination of the port voltage of the fault port in the positive sequence network, the negative sequence network and the zero sequence network comprises the following steps:

[0011] The positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance of the fault port in the positive sequence network, the negative sequence network and the zero sequence network are determined;

[0012] The port voltage of each fault port is determined according to the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance.

[0013] Optionally, the determination of the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network comprises the following steps:

[0014] The positive sequence voltage and the positive sequence current, the negative sequence voltage and the negative sequence current, and the zero sequence voltage and the zero sequence current of the fault port in the positive sequence network, the negative sequence network and the zero sequence network are determined;

[0015] The port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network is determined according to the relationship among the positive sequence voltage, the negative sequence voltage and the zero sequence voltage of each fault port, and the relationship among the positive sequence current, the negative sequence current and the zero sequence current.

[0016] Optionally, the determination of the short-circuit current DC component of the generator side and the grid side according to the port voltage and the port boundary condition of each fault port comprises the following steps:

[0017] determine initial amplitudes of the DC components of the short circuit current of the generator side and the grid side according to the port voltage and the port boundary condition of each fault port;

[0018] determine the comprehensive self-impedance of the generator side and the grid side at a certain frequency by using the equivalent frequency method;

[0019] calculate the DC components of the short circuit current of the generator side and the grid side according to the initial amplitudes of the DC components of the short circuit current of the generator side and the grid side and the comprehensive self-impedance at a certain frequency.

[0020] The application further provides a device for determining the decay time constant of the DC component of the single-phase ground fault short circuit current, comprising:

[0021] a network construction module, configured to construct the positive sequence network, the negative sequence network and the zero sequence network of the generator side and the grid side when a single-phase ground short circuit fault occurs at the generator access node;

[0022] a port characteristic determination module, configured to determine the port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network;

[0023] a DC component calculation module, configured to determine the DC components of the short circuit current of the generator side and the grid side according to the port voltage and the port boundary condition of each fault port;

[0024] a decay time constant determination module, configured to determine the decay time constant of the DC component of the short circuit current of the generator access node by fitting the DC components of the short circuit current of the generator side and the grid side into an exponential function by using a curve fitting tool.

[0025] Optionally, the port characteristic determination module comprises:

[0026] a first characteristic determination module, configured to determine the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance of the fault port in the positive sequence network, the negative sequence network and the zero sequence network;

[0027] a port voltage determination module, configured to determine the port voltage of each fault port according to the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance.

[0028] Optionally, the port characteristic determination module further comprises:

[0029] a second characteristic determination module, configured to determine the positive sequence voltage and the positive sequence current, the negative sequence voltage and the negative sequence current, and the zero sequence voltage and the zero sequence current of the fault port in the positive sequence network, the negative sequence network and the zero sequence network.

[0030] a port boundary condition determining module configured to determine a port boundary condition of the faulted port in the positive sequence network, the negative sequence network and the zero sequence network according to a relationship among the positive sequence voltage, the negative sequence voltage and the zero sequence voltage of each faulted port, and a relationship among the positive sequence current, the negative sequence current and the zero sequence current.

[0031] Optionally, the DC component calculating module comprises:

[0032] an initial amplitude calculating module configured to determine an initial amplitude of the short-circuit current DC component of the generator side and the grid side according to the port voltage of each faulted port and the port boundary condition;

[0033] a comprehensive self-impedance calculating module configured to determine a comprehensive self-impedance of the generator side and the grid side at a specific frequency by using an equivalent frequency method;

[0034] a DC component calculating sub-module configured to calculate the short-circuit current DC component of the generator side and the grid side according to the initial amplitude of the short-circuit current DC component of the generator side and the grid side and the comprehensive self-impedance of the generator side and the grid side at the specific frequency.

[0035] The application further provides a storage medium having computer readable instructions stored therein, and the computer readable instructions, when executed by one or more processors, cause the one or more processors to perform the steps of the single-phase ground fault short-circuit current DC component decay time constant determination method according to any one of the above embodiments.

[0036] The application further provides a computer device comprising one or more processors and a memory.

[0037] The memory has computer readable instructions stored therein, and the computer readable instructions, when executed by the one or more processors, perform the steps of the single-phase ground fault short-circuit current DC component decay time constant determination method according to any one of the above embodiments.

[0038] As can be seen from the above technical solutions, the embodiments of the application have the following advantages:

[0039] The single-phase grounding fault short-circuit current direct-current component decay time constant determination method provided by the application can be regarded as the simultaneous occurrence of three faults, i.e., the single-phase grounding short circuit of the generator side node, the disconnection of the line connecting the generator side node and the grid side node, and the single-phase grounding short circuit of the grid side node, when detecting the single-phase grounding short circuit fault of the generator access node. Therefore, the positive sequence network, the negative sequence network and the zero sequence network of the generator side and the grid side can be constructed according to the current single-phase grounding short circuit fault, and the port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network can be determined. In this way, the short-circuit current direct-current component of the generator side and the grid side can be calculated according to the port voltage and the port boundary condition, and then the short-circuit current direct-current component decay time constant of the generator access node can be determined by using the exponential function to fit the short-circuit current direct-current component of the generator side and the grid side into an exponential function. The process not only can quickly measure the short-circuit current direct-current component decay time constant, but also can reduce the error, so that the finally obtained short-circuit current direct-current component decay time constant is more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0041] Figure 1 A flowchart of a single-phase grounding fault short-circuit current direct-current component decay time constant determination method provided by an embodiment of the application is shown in the figure.

[0042] Figure 2 A target grid structure diagram when a single-phase fault occurs (taking the A-phase grounding short circuit as an example) provided by an embodiment of the application is shown in the figure.

[0043] Figure 3 A structure diagram of the positive sequence network, the negative sequence network and the zero sequence network of the fault network provided by an embodiment of the application is shown in the figure.

[0044] Figure 4 A structure diagram of a single-phase grounding fault short-circuit current direct-current component decay time constant determination device provided by an embodiment of the application is shown in the figure.

[0045] Figure 5 An internal structure diagram of a computer device provided by an embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0046] With reference to the drawings and embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0047] When a three-phase short-circuit fault occurs at the generator access node, the target power grid can be divided into two branches, i.e., a generator-side branch and a power grid-side branch, with the power plant node as a sub-network point. Then, the equivalent frequency method is used to calculate the short-circuit current DC component amplitude provided by the power grid-side branch and the generator-side branch and the self-impedance of the power grid-side and the generator-side under the equivalent frequency. After obtaining the short-circuit current DC component provided by the power grid-side branch and the generator-side branch, the CFTOOL curve fitting tool of the MATLAB software is used to fit the short-circuit current DC component of the generator-side branch and the power grid-side branch, so as to obtain the short-circuit current DC component decay time constant of the generator access node. However, compared with the three-phase ground fault, when a single-phase ground fault occurs at the generator access node, the generator-side and the power grid-side are connected through the non-fault phase, and the two branches are not completely decoupled, so the original sub-network and curve fitting method is no longer applicable. Based on this, the technical solutions are provided as follows:

[0048] In one embodiment, as shown in Figure 1 , Figure 1 a flowchart of a single-phase ground fault short-circuit current DC component decay time constant determination method provided by the embodiments of the present application is shown; the present application provides a single-phase ground fault short-circuit current DC component decay time constant determination method, which can include the following steps:

[0049] S110: When a single-phase ground short-circuit fault is detected at the generator access node, the positive sequence network, the negative sequence network and the zero sequence network of the generator-side and the power grid-side under the single-phase ground short-circuit fault are constructed.

[0050] In this step, when a single-phase ground short-circuit fault is detected at the generator access node, it can be regarded as the simultaneous occurrence of three faults, i.e., single-phase ground short-circuit at the generator-side node, disconnection of the line connecting the generator-side and the power grid-side nodes, and single-phase ground short-circuit at the power grid-side node. Therefore, the positive sequence network, the negative sequence network and the zero sequence network of the generator-side and the power grid-side can be constructed according to this situation.

[0051] Illustratively, as shown in Figure 2 , Figure 3 , Figure 2 a target power grid structure diagram when a single-phase fault occurs (taking A-phase ground short-circuit as an example) is provided by the embodiments of the present application, Figure 3The structure schematic diagram of the positive sequence network, the negative sequence network and the zero sequence network of the fault network provided by the embodiment of the present application; when Figure 2 A single-phase short-circuit fault occurs at the generator access node in the above formula, it can be regarded as the simultaneous occurrence of three faults, i.e., single-phase ground short-circuit of the generator side node, disconnection of the line connecting the generator side and the grid side node, and single-phase ground short-circuit of the grid side node, at this time, the positive sequence network, the negative sequence network and the zero sequence network shown in Figure 3 can be constructed, wherein Z 1_1 , Z 1_2 and Z 1_0 are the positive, negative and zero sequence self-impedances of the generator side respectively, Z 2_1 , Z 2_2 and Z 2_0 are the positive, negative and zero sequence self-impedances of the grid side respectively, and nodes 1 and 2 are the fault ports. As can be seen from the positive, negative and zero sequence networks, the generator side and the grid side are decoupled due to the single-phase disconnection fault, therefore, the fault port voltage equation can be written according to this, and the short-circuit current of the generator side and the grid side can be calculated by using the complex fault solving method.

[0052] S120: determining the port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network.

[0053] In this step, after the positive sequence network, the negative sequence network and the zero sequence network of the generator side and the grid side in the single-phase ground short-circuit fault are constructed by S110, since the generator side and the grid side are decoupled due to the single-phase disconnection fault, the positive sequence voltage, the negative sequence voltage and the zero sequence voltage of each fault port can be determined according to the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance of each fault port in the positive sequence network, the negative sequence network and the zero sequence network, and the port voltage of each fault port is constituted.

[0054] Further, after the positive sequence current, the negative sequence current and the zero sequence current, and the positive sequence voltage, the negative sequence voltage and the zero sequence voltage of each fault port are measured, the port boundary condition of each fault port can be determined according to the relationship between the positive sequence current, the negative sequence current and the zero sequence current, and the relationship between the positive sequence voltage, the negative sequence voltage and the zero sequence voltage, and the short-circuit current direct current component of the generator side and the grid side is determined according to the port voltage and the port boundary condition.

[0055] S130: determining the short-circuit current direct current component of the generator side and the grid side according to the port voltage and the port boundary condition of each fault port.

[0056] In this step, after determining the port voltage and port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network through S120, the application can determine the short-circuit current DC component of the generator side and the grid side according to the port voltage and the port boundary condition of each fault port, and calculate the short-circuit current DC component decay time constant of the generator access node based on this.

[0057] In a specific implementation, the application can first determine the initial amplitude of the short-circuit current DC component of the generator side and the grid side according to the port voltage and the port boundary condition of each fault port, and then use the initial amplitude to calculate the short-circuit current DC component of the generator side and the grid side.

[0058] S140: After fitting the short-circuit current DC component of the generator side and the grid side into an exponential function using a curve fitting tool, the short-circuit current DC component decay time constant of the generator access node is determined by the exponential function.

[0059] In this step, after determining the short-circuit current DC component of the generator side and the grid side through S130, a curve fitting tool can be used to fit the short-circuit current DC component of the generator side and the grid side into an exponential function, so that the short-circuit current DC component decay time constant of the generator access node can be extracted from the exponential function.

[0060] It can be understood that compared with the working current of the transmission line, the short-circuit current of the system is very large, and when the line or busbar has a short-circuit fault, the magnetic flux of the inductive element in the system cannot change suddenly at the moment of short-circuit, so there will be a DC component in the short-circuit current, and the maximum value of the DC component must be equal to the absolute value of the change amount of the short-circuit current periodic component. When the system has a short-circuit fault at t0, the DC component i DC It can be expressed in the form of a simple exponential function as follows: Where, i DC is the DC component of the fault current at the fault moment t0, t is the time after the short-circuit fault, and τ is the DC component decay time constant of the grid.

[0061] Based on this, the application can use the CFTOOL curve fitting tool in the MATLAB software to fit the short-circuit current DC component of the generator side and the grid side into an exponential function In this way, the value of τ in the exponential function can be determined, and the short-circuit current DC component decay time constant of the generator access node can be determined.

[0062] In the above embodiment, when a single-phase ground fault of the generator access node is detected, it can be considered that the single-phase ground fault of the generator side node, the disconnection of the line connecting the generator side node and the grid side node, and the single-phase ground fault of the grid side node occur simultaneously, so the positive sequence network, the negative sequence network and the zero sequence network of the generator side and the grid side can be constructed according to the current single-phase ground fault, and the port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network are determined, so that the short-circuit current direct current component of the generator side and the grid side can be calculated according to the port voltage and the port boundary condition, and then the short-circuit current direct current component of the generator access node can be determined by fitting the short-circuit current direct current component of the generator side and the grid side into an exponential function by using a curve fitting tool, so that the short-circuit current direct current component decay time constant of the generator access node can be quickly measured, and the error can be reduced, so that the short-circuit current direct current component decay time constant obtained finally is more accurate.

[0063] In one embodiment, determining the port voltage of the fault port in the positive sequence network, the negative sequence network and the zero sequence network in S120 can include:

[0064] S121: determining the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance of the fault port in the positive sequence network, the negative sequence network and the zero sequence network.

[0065] S122: determining the port voltage of each fault port according to the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance.

[0066] In this embodiment, when determining the port voltage of the fault port in the positive sequence network, the negative sequence network and the zero sequence network, the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance of the fault port in the positive sequence network, the negative sequence network and the zero sequence network can be determined first, and then the fault port voltage equation can be written according to the positive sequence current, the negative sequence current, the zero sequence current, the initial voltage at the fault moment and the mutual impedance of each fault port, so that the port voltage of each fault port can be obtained.

[0067] Illustratively, the fault ports of the generator side single-phase short circuit, the disconnection of the line connecting the generator side and the grid side, and the grid side single-phase short circuit can be F1, F2 and F3 respectively, and the fault port voltage equation is:

[0068]

[0069]

[0070]

[0071] wherein, V F1 (1), V F1 (2), V F1 (0), V F2 (1), V F2 (2), V F2 (0), V F3 (1), V F3 (2), V F3 (0) are positive, negative and zero sequence voltages of faulted port F1, F2, F3, respectively; I F1 (1), I F1 (2), I F1 (0), I F2 (1), I F2 (2), I F2 (0), I F3 (1), I F3 (2), I F3 (0) are positive, negative and zero sequence currents of faulted port F1, F2, F3, respectively. are initial voltages of faulted port F1, F2, F3 at fault instant; Z FxFy (1), Z FxFy (2), Z FxFy (0) are mutual impedances between port x and y.

[0072] In addition, the matrix in formula (1) of the present application satisfies:

[0073]

[0074]

[0075]

[0076]

[0077] wherein, V0 is initial voltage of faulted port of power plant access node at fault instant.

[0078] In one embodiment, determining the port boundary condition of the faulted port in the positive sequence network, the negative sequence network and the zero sequence network in S120 can comprise:

[0079] S123: determining the positive sequence voltage and positive sequence current, the negative sequence voltage and negative sequence current, and the zero sequence voltage and zero sequence current of the faulted port in the positive sequence network, the negative sequence network and the zero sequence network.

[0080] S124: Determine the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network according to the relationship between the positive sequence voltage, the negative sequence voltage and the zero sequence voltage of each fault port, and the relationship between the positive sequence current, the negative sequence current and the zero sequence current.

[0081] In this embodiment, when calculating the short-circuit current DC component of the generator side and the grid side, not only the port voltage of each fault port is needed, but also the port boundary condition of each fault port, so that the short-circuit current DC component of the generator side and the grid side can be determined under the boundary condition.

[0082] Specifically, the application can first determine the positive sequence voltage and the positive sequence current, the negative sequence voltage and the negative sequence current, and the zero sequence voltage and the zero sequence current of the fault port in the positive sequence network, the negative sequence network and the zero sequence network, and then determine the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network according to the relationship between the positive sequence voltage, the negative sequence voltage and the zero sequence voltage of each fault port, and the relationship between the positive sequence current, the negative sequence current and the zero sequence current. The specific port boundary condition is as follows:

[0083] I F1 (1) = I F1 (2) = I F1 (0)

[0084] V F1 (1) + V F1 (2) + V F1 (0) = 0

[0085] I F2 (1) + I F2 (2) + I F2 (0) = 0

[0086] V F2 (1) = V F2 (2) = V F2 (0)

[0087] I F3 (1) = I F3 (2) = I F3 (0)

[0088] V F3 (1) + V F3 (2) + V F3 (0) = 0 (3)

[0089] It can be derived that the single-phase ground short-circuit current at the access node of the power plant satisfies the following formula:

[0090]

[0091] The accuracy of the single-phase ground fault equivalent fault model is verified.

[0092] In one embodiment, determining the direct current component of the short circuit current of the generator side and the grid side according to the port voltage of each fault port and the port boundary condition in S130 can include:

[0093] S131: determining the initial amplitude of the direct current component of the short circuit current of the generator side and the grid side according to the port voltage of each fault port and the port boundary condition.

[0094] S132: determining the comprehensive self-impedance of the generator side and the grid side at a specific frequency by using the equivalent frequency method.

[0095] S133: calculating the direct current component of the short circuit current of the generator side and the grid side according to the initial amplitude of the direct current component of the short circuit current of the generator side and the grid side and the comprehensive self-impedance at the specific frequency.

[0096] In the embodiment, when determining the direct current component of the short circuit current of the generator side and the grid side according to the port voltage of each fault port and the port boundary condition, the initial amplitude of the direct current component of the short circuit current of the generator side and the grid side can be determined according to the port voltage of each fault port and the port boundary condition, then the comprehensive self-impedance of the generator side and the grid side at a specific frequency is determined by using the equivalent frequency method, and finally the direct current component of the short circuit current of the generator side and the grid side is calculated according to the initial amplitude of the direct current component of the short circuit current of the generator side and the grid side and the comprehensive self-impedance at the specific frequency.

[0097] In a specific implementation, the initial amplitude I dc1 of the direct current component of the short circuit current of the generator side and the initial amplitude I dc2 of the direct current component of the short circuit current of the grid side can be obtained by formula (1) and formula (3) as follows:

[0098]

[0099]

[0100] Then, the comprehensive self-impedance Z1 and Z2 of the generator side and the grid side at a specific frequency f are obtained by using the equivalent frequency method as follows:

[0101]

[0102]

[0103] Finally, the expressions of the generator-side short-circuit current DC component I1(t) and the grid-side short-circuit current DC component I2(t) can be obtained from the formula (7) and the formula (8) respectively as follows:

[0104]

[0105]

[0106] It can be understood that, in the equivalent frequency method calculation, the expression of the short-circuit current DC component is as follows:

[0107]

[0108] wherein τ is a DC component decay time constant, and the expression thereof is f c is the equivalent frequency, X ffc is the equivalent frequency f c is the reactance value of the equivalent self-impedance of the short-circuit point, R ffc is the equivalent frequency f c is the resistance value of the equivalent self-impedance of the short-circuit point, I" k is the short-circuit current AC component effective value, and the expression thereof is U N is the fault node reference voltage, Z ff is the fault node self-impedance, and c is the voltage coefficient.

[0109] Since the DC component decay speed in the actual short-circuit current changes with time, the equivalent frequency f c of the decay time constant can be selected according to the product of the reference frequency f(50hZ) and the time t, i.e., the cycle, as shown in the following table:

[0110] f · t <1 <2.5 <5 <12.5 fc / f 0.27 0.15 0.092 0.055

[0111] Table 1 is the equivalent frequency method value selection

[0112] Through the table and the time t after the short-circuit fault starts and the reference frequency f, the specific frequency when the equivalent frequency method is used can be determined, and then the equivalent frequency method is used to determine the comprehensive self-impedance of the generator side and the grid side at the specific frequency.

[0113] The single-phase ground fault short-circuit current DC component decay time constant determination device provided by the embodiments of the present application is described below, and the single-phase ground fault short-circuit current DC component decay time constant determination device described below can be correspondingly referred to the single-phase ground fault short-circuit current DC component decay time constant determination method described above.

[0114] In one embodiment, as shown in Figure 4 Figure 4 ​A structural schematic diagram of a single-phase ground fault short-circuit current direct current component decay time constant determination device provided by an embodiment of the present application; the present application also provides a single-phase ground fault short-circuit current direct current component decay time constant determination device, which comprises a network construction module 210, a port characteristic determination module 220, a direct current component calculation module 230 and a decay time constant determination module 240, and specifically comprises the following:

[0115] The network construction module 210 is used for constructing the positive sequence network, the negative sequence network and the zero sequence network of the generator side and the power grid side when a single-phase ground short-circuit fault occurs at the generator access node.

[0116] The port characteristic determination module 220 is used for determining the port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network.

[0117] The direct current component calculation module 230 is used for determining the short-circuit current direct current component of the generator side and the power grid side according to the port voltage and the port boundary condition of each fault port.

[0118] The decay time constant determination module 240 is used for fitting the short-circuit current direct current component of the generator side and the power grid side into an exponential function by using a curve fitting tool, and determining the short-circuit current direct current component decay time constant of the generator access node through the exponential function.

[0119] In the above embodiment, when a single-phase ground short-circuit fault is detected at the generator access node, it can be regarded as the simultaneous occurrence of three faults, i.e., single-phase ground short-circuit of the generator side node, disconnection of the line connecting the generator side node and the power grid side node, and single-phase ground short-circuit of the power grid side node. Therefore, the positive sequence network, the negative sequence network and the zero sequence network of the generator side and the power grid side can be constructed according to the current single-phase ground short-circuit fault, and the port voltage and the port boundary condition of the fault port in the positive sequence network, the negative sequence network and the zero sequence network can be determined. In this way, the short-circuit current direct current component of the generator side and the power grid side can be calculated according to the port voltage and the port boundary condition, and then the curve fitting tool is used to fit the short-circuit current direct current component of the generator side and the power grid side into an exponential function, and the short-circuit current direct current component decay time constant of the generator access node is determined through the exponential function. This process not only can quickly measure the short-circuit current direct current component decay time constant, but also can reduce the error, so that the finally obtained short-circuit current direct current component decay time constant is more accurate.

[0120] In one embodiment, the port characteristic determination module comprises:

[0121] a first characteristic determining module, configured to determine positive sequence currents, negative sequence currents, zero sequence currents, initial voltages at a fault moment, and mutual impedances of the fault ports in the positive sequence network, the negative sequence network, and the zero sequence network;

[0122] a port voltage determining module, configured to determine port voltages of the fault ports according to the positive sequence currents, the negative sequence currents, the zero sequence currents, the initial voltages at the fault moment, and the mutual impedances.

[0123] In one embodiment, the port characteristic determining module further comprises:

[0124] a second characteristic determining module, configured to determine positive sequence voltages and positive sequence currents, negative sequence voltages and negative sequence currents, and zero sequence voltages and zero sequence currents of the fault ports in the positive sequence network, the negative sequence network, and the zero sequence network;

[0125] a port boundary condition determining module, configured to determine port boundary conditions of the fault ports in the positive sequence network, the negative sequence network, and the zero sequence network according to relationships among the positive sequence voltages, the negative sequence voltages, and the zero sequence voltages of the fault ports, and relationships among the positive sequence currents, the negative sequence currents, and the zero sequence currents.

[0126] In one embodiment, the DC component calculating module comprises:

[0127] an initial amplitude calculating module, configured to determine initial amplitudes of the DC components of the short circuit currents of the generator side and the grid side according to the port voltages of the fault ports and the port boundary conditions;

[0128] a comprehensive self-impedance calculating module, configured to determine comprehensive self-impedances of the generator side and the grid side at a specific frequency by using an equivalent frequency method;

[0129] a DC component calculating submodule, configured to calculate the DC components of the short circuit currents of the generator side and the grid side according to the initial amplitudes of the DC components of the short circuit currents of the generator side and the grid side and the comprehensive self-impedances of the generator side and the grid side at the specific frequency.

[0130] In one embodiment, the present application further provides a storage medium, wherein the storage medium stores computer readable instructions, and the computer readable instructions are executed by one or more processors to make the one or more processors perform steps of the single-phase grounding fault short circuit current DC component decay time constant determining method according to any one of the above embodiments.

[0131] In one embodiment, the present application further provides a computer device, comprising one or more processors and a memory.

[0132] The memory stores computer readable instructions which, when executed by the one or more processors, perform the steps of the single-phase ground fault short circuit current direct component decay time constant determination method of any of the above embodiments.

[0133] As shown schematically, Figure 5 Figure 5 An internal structure schematic diagram of a computer device is provided in the embodiments of the present application. The computer device 300 can be provided as a server. Referring to Figure 5 , the computer device 300 includes a processing assembly 302, which further includes one or more processors, and a memory resource represented by a memory 301 for storing instructions, such as application programs, executable by the processing assembly 302. The application programs stored in the memory 301 can include one or more than one module each corresponding to a set of instructions. In addition, the processing assembly 302 is configured to execute the instructions to perform the single-phase ground fault short circuit current direct component decay time constant determination method of any of the above embodiments.

[0134] The computer device 300 can further include a power supply assembly 303 configured to perform power management of the computer device 300, a wired or wireless network interface 304 configured to connect the computer device 300 to a network, and an input output (I / O) interface 305. The computer device 300 can operate based on an operating system stored in the memory 301, such as Windows Server TM, Mac OS X TM, Unix TM, Linux TM, Free BSD TM, or the like.

[0135] Those skilled in the art can understand that Figure 5 the structure shown in the above is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. The specific computer device can include more or less components than those shown in the figure, or combine certain components, or have a different component arrangement.

[0136] ​Finally, it should be noted that the terms "first", "second", and the like, herein do not denote any order, quantity, combination, or importance, but rather are used to distinguish one element from another, and are not intended to denote the presence of any such actual relationship or order. Moreover, the terms "include", "have", or any other variant thereof are intended to encompass non-exclusive inclusions, such that processes, methods, articles, or apparatuses that comprise a list of elements are not required to comprise only those elements in the list, but can include other elements not expressly listed, or also include elements inherent in such processes, methods, articles, or apparatuses. Without additional restrictions, an element preceded by "comprises... a" does not exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the stated element.

[0137] The various embodiments in the specification are described in progressive order with each embodiment building on one or more of the previous embodiments, however the order of the embodiments presented is not intended to be construed as a requirement or limitation for these embodiments. Any one or more of the embodiments described herein are possible embodiments, which can be combined with each other in any way. The same reference numerals in different drawings represent the same or similar elements.

[0138] The above description of disclosed embodiments provides enabling teaching for a person skilled in the art to implement or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of determining a decay time constant of a direct current component of a single-phase earth fault short circuit current, characterized in that, The method comprises: when detecting that a single-phase ground fault occurs at a generator access node, constructing a positive sequence network, a negative sequence network and a zero sequence network of the generator side and the grid side in the single-phase ground fault; determining port voltages and port boundary conditions of fault ports in the positive sequence network, the negative sequence network and the zero sequence network; determining a direct current component of a short circuit current of the generator side and the grid side according to the port voltages and the port boundary conditions of each fault port; after fitting the direct current component of the short circuit current of the generator side and the grid side into an exponential function by using a curve fitting tool, determining a decay time constant of the direct current component of the short circuit current of the generator access node through the exponential function; the determination of the port voltages of the fault ports in the positive sequence network, the negative sequence network and the zero sequence network comprises: determining positive sequence currents, negative sequence currents, zero sequence currents, initial voltages at a fault moment and mutual impedances of the fault ports in the positive sequence network, the negative sequence network and the zero sequence network; determining the port voltages of each fault port according to the positive sequence currents, the negative sequence currents, the zero sequence currents, the initial voltages at the fault moment and the mutual impedances.

2. The method of determining the decay time constant of the direct current component of single-phase earth fault short circuit current according to claim 1, characterized in that, the determination of the port boundary conditions of the fault ports in the positive sequence network, the negative sequence network and the zero sequence network comprises: determining positive sequence voltages and positive sequence currents, negative sequence voltages and negative sequence currents, zero sequence voltages and zero sequence currents of the fault ports in the positive sequence network, the negative sequence network and the zero sequence network; determining the port boundary conditions of the fault ports in the positive sequence network, the negative sequence network and the zero sequence network according to relationships among the positive sequence voltages, the negative sequence voltages and the zero sequence voltages of each fault port, and relationships among the positive sequence currents, the negative sequence currents and the zero sequence currents.

3. The method of claim 1, wherein the time constant is determined by: ###0001### where: I is the DC component of the single-phase-to-ground fault short circuit current; and V is the voltage of the power system. the determination of the direct current component of the short circuit current of the generator side and the grid side according to the port voltages and the port boundary conditions of each fault port comprises: determining initial amplitudes of the direct current component of the short circuit current of the generator side and the grid side according to the port voltages and the port boundary conditions of each fault port; determining comprehensive self-impedances of the generator side and the grid side at a specific frequency by using an equivalent frequency method; calculating the direct current component of the short circuit current of the generator side and the grid side according to the initial amplitudes of the direct current component of the short circuit current of the generator side and the grid side and the comprehensive self-impedances at the specific frequency.

4. An apparatus for determining a direct current component decay time constant of a single-phase earth fault short circuit current, characterized in that comprise: a network construction module configured to, when detecting that a single-phase ground fault occurs at a generator access node, construct a positive sequence network, a negative sequence network and a zero sequence network of the generator side and the grid side in the single-phase ground fault; a port characteristic determination module configured to determine port voltages and port boundary conditions of fault ports in the positive sequence network, the negative sequence network and the zero sequence network; a direct current component calculation module configured to determine a direct current component of a short circuit current of the generator side and the grid side according to the port voltages and the port boundary conditions of each fault port; a decay time constant determination module configured to determine a short-circuit current DC component decay time constant of the generator access node by fitting the short-circuit current DC components of the generator side and the grid side into an exponential function after fitting the short-circuit current DC components of the generator side and the grid side into the exponential function using a curve fitting tool; the port characteristic determination module comprises: a first characteristic determination module configured to determine positive sequence currents, negative sequence currents, zero sequence currents, initial voltages at the fault instant, and mutual impedances of the fault ports in the positive sequence network, the negative sequence network, and the zero sequence network; a port voltage determination module configured to determine port voltages of the fault ports according to the positive sequence currents, the negative sequence currents, the zero sequence currents, the initial voltages at the fault instant, and the mutual impedances.

5. The single-phase earth fault short circuit current direct component decay time constant determination device according to claim 4, characterized in that the port characteristic determination module further comprises: a second characteristic determination module configured to determine positive sequence voltages and positive sequence currents, negative sequence voltages and negative sequence currents, zero sequence voltages and zero sequence currents of the fault ports in the positive sequence network, the negative sequence network, and the zero sequence network; a port boundary condition determination module configured to determine port boundary conditions of the fault ports in the positive sequence network, the negative sequence network, and the zero sequence network according to relationships among the positive sequence voltages, the negative sequence voltages, and the zero sequence voltages of the fault ports, and relationships among the positive sequence currents, the negative sequence currents, and the zero sequence currents.

6. The single-phase earth fault short circuit current direct component decay time constant determination device according to claim 4, characterized in that the DC component calculation module comprises: an initial amplitude calculation module configured to determine initial amplitudes of the short-circuit current DC components of the generator side and the grid side according to the port voltages of the fault ports and the port boundary conditions; a comprehensive self-impedance calculation module configured to determine comprehensive self-impedances of the generator side and the grid side at a specific frequency using an equivalent frequency method; a DC component calculation submodule configured to calculate the short-circuit current DC components of the generator side and the grid side according to the initial amplitudes of the short-circuit current DC components of the generator side and the grid side and the comprehensive self-impedances of the generator side and the grid side at the specific frequency.

7. A storage medium characterized by: The storage medium has computer readable instructions stored therein, and the computer readable instructions, when executed by one or more processors, cause the one or more processors to perform the steps of the single-phase ground fault short-circuit current DC component decay time constant determination method according to any one of claims 1 to 3.

8. A computer device, comprising: comprise: one or more processors, and a memory; The memory has computer readable instructions stored therein, and the computer readable instructions, when executed by the one or more processors, perform the steps of the single-phase ground fault short-circuit current DC component decay time constant determination method according to any one of claims 1 to 3.

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