Method for determining the short-circuit current resistance of a circuit breaker and device for determining the same

Abstract

This application provides a method and apparatus for determining the short-circuit current withstand capability of a circuit breaker. The method includes: performing equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches, and determining the relative time variation of the DC component of the short-circuit current under different impedance parameters to determine a multi-dimensional fault space; determining the node impedance matrix of the power grid based on the node admittance matrix, and determining the node self-impedance based on the node impedance matrix; performing frequency correction on the node admittance matrix to obtain an equivalent node admittance matrix at the equivalent frequency, and determining a first relationship based on the equivalent node admittance matrix; determining a second relationship based on the node self-impedance and the first relationship, and determining a target relationship based on the second relationship and the fault space; determining a target attenuation time constant based on the target relationship, and determining whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the target attenuation time constant is greater than a predetermined value.

Description

Technical Field

[0001] This application relates to the field of power grid technology, and more specifically, to a method for determining the short-circuit current withstand capability of a circuit breaker, a device for determining the short-circuit current withstand capability of a circuit breaker, a computer-readable storage medium, and an electronic device. Background Technology

[0002] The slower decay of the DC component of the short-circuit current will increase the DC component content of the short-circuit impact current, the total short-circuit current, and the interrupting current required by the circuit breaker. This poses a severe challenge to whether some circuit breakers with very small interrupting capacity margins in the power grid can interrupt the short-circuit current in a timely manner as required by the configuration, and creates hidden dangers for the safe operation of the system.

[0003] Currently, domestic attention to short-circuit current calculation mainly focuses on the calculation of the periodic component of the short-circuit current. In practical engineering applications, the DC component of the short-circuit current and its attenuation are not given due attention, and there has been a lack of simple and practical engineering methods and tools for calculating the attenuation of the DC component. Summary of the Invention

[0004] The main objective of this application is to provide a method, apparatus, computer-readable storage medium, and electronic device for determining the short-circuit current withstand capability of a circuit breaker, so as to at least solve the problem that the low calculation accuracy of the DC component of the short-circuit current in the prior art leads to inaccurate judgment of the short-circuit current withstand capability of the circuit breaker.

[0005] To achieve the above objectives, according to one aspect of this application, a method for determining the short-circuit current withstand capability of a circuit breaker is provided, comprising: performing equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches, and using the impedance parameters of each equivalent branch as variables to determine the relative time variation of the DC component of the short-circuit current under different impedance parameters, obtaining multiple curves, the boundaries of the multiple curves constituting a multi-dimensional fault space, wherein the equivalent branch is the Thevenin equivalent circuit corresponding to the branch; determining the node impedance matrix of the power grid based on the node admittance matrix, and determining the node self-impedance based on the node impedance matrix; and performing... Frequency correction is performed to obtain the equivalent node admittance matrix at the equivalent frequency. Based on the equivalent node admittance matrix, the correspondence between the equivalent node self-impedance and the equivalent frequency is determined to obtain a first relationship. Based on the node self-impedance and the first relationship, the correspondence between the DC component of the short-circuit current and the equivalent frequency is determined to obtain a second relationship. Based on the second relationship and the fault space, a target relationship is determined, which is the relationship between the DC component of the short-circuit current and time. Based on the target relationship, a target attenuation time constant is determined. Based on whether the target attenuation time constant is greater than a predetermined value, it is determined whether the circuit breaker's short-circuit current withstand capability is insufficient.

[0006] Optionally, the node admittance matrix is ​​frequency-corrected to obtain an equivalent node admittance matrix at the equivalent frequency, and the correspondence between the equivalent node self-impedance and the equivalent frequency is determined based on the equivalent node admittance matrix to obtain a first relationship. This includes: correcting the node admittance matrix using the equivalent frequency method to obtain the equivalent node admittance matrix; determining the equivalent node impedance matrix based on the equivalent node admittance matrix; and determining the first relationship based on the equivalent node impedance matrix.

[0007] Optionally, based on the node self-impedance and the first relationship, the correspondence between the DC component of the short-circuit current and the equivalent frequency is determined to obtain a second relationship, including: based on the first relationship, the correspondence between the decay time constant and the equivalent frequency is calculated to obtain a third relationship; and based on the node self-impedance and the third relationship, the second relationship is determined.

[0008] Optionally, determining the target relationship based on the second relationship and the fault space includes: processing the fault space using a pattern search algorithm to determine the DC component of the short-circuit current corresponding to the point with the highest data density in the fault space as the first DC component of the short-circuit current; substituting the first DC component of the short-circuit current into the second relationship to obtain a fourth relationship, the fourth relationship being the correspondence between the optimal frequency of the power grid and the time, the optimal frequency being the equivalent frequency corresponding to the first DC component of the short-circuit current; and determining the target relationship based on the fourth relationship.

[0009] Optionally, determining the target relationship based on the fourth relationship includes: determining the correspondence between the node admittance matrix corresponding to the optimal frequency and the time based on the fourth relationship to obtain a fifth relationship; determining the correspondence between the equivalent node self-impedance corresponding to the optimal frequency and the time based on the fifth relationship to obtain a sixth relationship; and substituting the sixth relationship into the input impedance method calculation formula to obtain the target relationship.

[0010] Optionally, the impedance parameters include resistance and reactance. Using the impedance parameters of each equivalent branch as variables, the change of the DC component of the short-circuit current relative to time under different impedance parameters is determined to obtain multiple curves. This includes: obtaining the resistance and reactance of each equivalent branch, and determining the impedance as Z = R + JωL based on the resistance and reactance, where Z represents the impedance, R represents the resistance, L represents the reactance, ω represents the angular frequency of the power grid, and J represents the imaginary unit; using each resistance and reactance as variables, multiple curves are obtained.

[0011] Optionally, the variable satisfies a predetermined condition, wherein the ratio of the impedances of any two equivalent branches is in the range of 0.01 to 100, and the ratio of the real part to the imaginary part of the impedance is in the range of 0.01 to 3.

[0012] Optionally, determining whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the target attenuation time constant is greater than a predetermined value includes: if the target attenuation time constant is greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability does not meet the actual requirements; if the target attenuation time constant is not greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability meets the actual requirements.

[0013] According to another aspect of this application, a device for determining the short-circuit current withstand capability of a circuit breaker is provided, comprising a processing unit, a first determining unit, a second determining unit, a third determining unit, and a fourth determining unit. The processing unit performs equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each equivalent branch as variables, it determines the relative time variation of the DC component of the short-circuit current under different impedance parameters, obtaining multiple curves. The boundaries of these curves constitute a multi-dimensional fault space, and each equivalent branch is a Thevenin equivalent circuit corresponding to that branch. The first determining unit is used to determine the node impedance matrix of the power grid based on the node admittance matrix, and to determine the node self-impedance based on the node impedance matrix. The second determining unit is used to perform frequency correction on the node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and to determine the correspondence between the equivalent node self-impedance and the equivalent frequency based on the equivalent node admittance matrix, thus obtaining a first relationship; the third determining unit is used to determine the correspondence between the DC component of the short-circuit current and the equivalent frequency based on the node self-impedance and the first relationship, thus obtaining a second relationship, and to determine a target relationship based on the second relationship and the fault space, wherein the target relationship is the relationship between the DC component of the short-circuit current and the time; the fourth determining unit is used to determine a target attenuation time constant based on the target relationship, and to determine whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the target attenuation time constant is greater than a predetermined value.

[0014] According to another aspect of this application, a computer-readable storage medium is provided, the computer-readable storage medium including a stored program, wherein, when the program is executed, it controls the device in which the computer-readable storage medium is located to perform any of the methods for determining the short-circuit current withstand capability of a circuit breaker.

[0015] According to another aspect of this application, an electronic device is provided, comprising: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including a method for performing a method for determining the short-circuit current withstand capability of any of the circuit breakers described herein.

[0016] Applying the technical solution of this application, the method for determining the short-circuit current withstand capability of the circuit breaker firstly involves equivalent processing of each branch of the power grid before the fault point, resulting in multiple equivalent branches. Using the impedance parameters of each equivalent branch as variables, the relative time variation of the DC component of the short-circuit current under different impedance parameters is determined, resulting in multiple curves. The boundaries of these curves constitute a multi-dimensional fault space, and each equivalent branch is the Thevenin equivalent circuit corresponding to that branch. Next, based on the node admittance matrix of the power grid, the node impedance matrix of the power grid is determined, and based on the node impedance matrix, the node self-impedance is determined. Finally, frequency correction is applied to the node admittance matrix. The method first determines the fault space, then determines the correspondence between the short-circuit current DC component and the equivalent frequency (i.e., the second relationship), and finally determines the target attenuation time constant based on whether the target attenuation time constant is greater than a predetermined value to determine whether the circuit breaker's short-circuit current withstand capability is insufficient. This method first determines the fault space, then determines the correspondence between the short-circuit current DC component and the equivalent frequency (i.e., the second relationship), and determines the relationship between the short-circuit current DC component and the time based on the second relationship and the fault space (i.e., the target relationship). This method calculates the short-circuit current DC component with high accuracy, resulting in a high-accuracy target attenuation time constant, thus solving the problem of inaccurate judgment of the circuit breaker's short-circuit current withstand capability due to the low calculation accuracy of the short-circuit current DC component in the prior art. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 A hardware block diagram of a mobile terminal for performing a method for determining the short-circuit current withstand capability of a circuit breaker, according to an embodiment of this application, is shown.

[0019] Figure 2A flowchart illustrating a method for determining the short-circuit current withstand capability of a circuit breaker according to an embodiment of this application is shown.

[0020] Figure 3 A schematic diagram of a power system network structure according to an embodiment of this application is shown;

[0021] Figure 4 A schematic diagram of the equivalent circuit structure of a power system network structure according to an embodiment of this application is shown;

[0022] Figure 5 A structural block diagram of a device for determining the short-circuit current withstand capability of a circuit breaker according to an embodiment of this application is shown.

[0023] The above figures include the following reference numerals:

[0024] 102. Processor; 104. Memory; 106. Transmission device; 108. Input / output device. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] As described in the background section, the low accuracy of calculating the DC component of short-circuit current in the prior art leads to inaccurate judgment of the short-circuit current withstand capability of circuit breakers. To solve the above problems, embodiments of this application provide a method for determining the short-circuit current withstand capability of circuit breakers, a device for determining the short-circuit current withstand capability of circuit breakers, a computer-readable storage medium, and an electronic device.

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0030] The methods and embodiments provided in this application can be executed on a mobile terminal, computer terminal, or similar computing device. Taking running on a mobile terminal as an example, Figure 1 This is a hardware structure block diagram of a mobile terminal for a method of determining the short-circuit current withstand capability of a circuit breaker according to an embodiment of the present invention. Figure 1 As shown, a mobile terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 (which may include, but is not limited to, a microprocessor MCU or a programmable logic device FPGA, etc.) and a memory 104 for storing data are also shown. The mobile terminal may further include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that... Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the mobile terminal described above. For example, the mobile terminal may also include components that are more... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown.

[0031] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the method for determining the short-circuit current withstand capability of a circuit breaker in this embodiment of the invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, thereby implementing the above-described method. The memory 104 may include high-speed random access memory and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the mobile terminal via a network. Examples of the aforementioned networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof. The transmission device 106 is used to receive or send data via a network. Specific examples of the aforementioned networks may include wireless networks provided by the mobile terminal's communication provider. In one example, the transmission device 106 includes a network interface controller (NIC), which can be connected to other network devices via a base station to communicate with the Internet. In one example, the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0032] This embodiment provides a method for determining the short-circuit current withstand capability of a circuit breaker operating on a mobile terminal, computer terminal, or similar computing device. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0033] Figure 2 This is a flowchart illustrating a method for determining the short-circuit current withstand capability of a circuit breaker according to an embodiment of this application. Figure 2 As shown, the method includes the following steps:

[0034] Step S201: Perform equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each of the above equivalent branches as variables, determine the change of the DC component of the short-circuit current relative to time under different impedance parameters to obtain multiple curves. The boundaries of the multiple curves constitute a multidimensional fault space. The above equivalent branches are the Thevenin equivalent circuits corresponding to the above branches.

[0035] Specifically, each branch is processed to obtain multiple equivalent branches. The fault space is constructed by the impedance parameters of the equivalent branches, making the fault space more comprehensive.

[0036] In practical applications, for arbitrary faults and short-circuit faults in complex systems, the network structure is as follows: Figure 3 As shown, where f is the faulty node, Figure 3 A number of branches greater than 2 indicates a bus short circuit, while a number equal to 2 indicates a line short circuit. If the external circuit is completely equivalent, the transient characteristics of the DC component cannot be characterized. Although completely equivalent external circuits can accurately calculate the initial value of the DC component of the short-circuit current, the decay time constant is actually composed of the superposition of many components with different decay time constants, as shown in the following formula: Here, T1, T2, and T3 represent the short-circuit current decay time constants, and i1, i2, and i3 represent the initial values ​​of the DC component of the short-circuit current. Using a single decay time constant introduces system errors, which are particularly significant in systems with large impedance ratio differences. To improve the calculation accuracy of traditional methods and reduce system errors, i1, i2, and i3 can be calculated independently. k1 i k2 and i k3 Methods such as these improve computational accuracy by performing Thevenin equivalents on each branch and describing each branch separately. Taking a three-branch circuit as an example, its equivalent circuit is as follows: Figure 4 As shown, for Figure 4 The equivalent circuit model shown is used to write the differential equation expression. Substituting the boundary conditions, and according to the calculation method of the DC component of the short-circuit current in "Power System Analysis", the following can be obtained:

[0037]

[0038] Where R1, R2, R3, X1, X2, and X3 are the equivalent impedances of each branch, and U n T1, T2, and T3 represent the system nominal voltage, and T1, T2, and T3 are the attenuation time constants of each branch, respectively. However, due to the complexity of power grid structures, traditional methods for calculating the input impedance of complex networks cannot calculate the equivalent impedance of each branch at the fault point individually. Therefore, the national standard adopts the equivalent frequency method to reduce this error.

[0039] The aforementioned impedance parameters include resistance and reactance. To reduce the error in the calculation method of input impedance for complex networks, in step S201, the impedance parameters of each of the aforementioned equivalent branches are used as variables to determine the relative time variation of the DC component of the short-circuit current under different impedance parameters, resulting in multiple curves. This can be achieved by: obtaining the resistance and reactance of each of the aforementioned equivalent branches, and determining the impedance as Z = R + JωL based on the resistance and reactance, where Z represents the impedance, R represents the resistance, L represents the reactance, ω represents the angular frequency of the power grid, and J represents the imaginary unit; using each of the aforementioned resistances and reactances as variables, multiple curves are obtained.

[0040] In one alternative embodiment, the aforementioned variables satisfy predetermined conditions, namely, the ratio of the impedances of any two equivalent branches is in the range of 0.01 to 100, and the ratio of the real part to the imaginary part of the impedance is in the range of 0.01 to 3. The real part of the impedance is R, and the imaginary part of the impedance is X = ωL.

[0041] In practical applications, the equivalent impedances R1, R2, R3, X1, X2, and X3 of each branch are used as variables to plot the aforementioned fault space with a fixed step size. Each variable satisfies the following conditions: the ratio of the impedances of any two equivalent branches is between 0.01 and 100, and the ratio of the real to imaginary parts of the impedances is between 0.01 and 3. Based on these constraints, assuming R1 = 1, a series of DC component curves of the short-circuit current that meet the requirements can be plotted with a fixed step size, thereby constructing the fault space S = [R1, R2, R3, X1, X2, X3, I...]. DC [(t)], where I DC (t) is the DC component curve of the short-circuit current under the corresponding parameters.

[0042] Step S202: Determine the node impedance matrix of the power grid based on the node admittance matrix of the power grid, and determine the node self-impedance based on the node impedance matrix.

[0043] Specifically, any power network topology can be described using a node admittance matrix.

[0044] Power system networks are generally described using nodal admittance matrices, and their basic form is as follows:

[0045]

[0046] Matrix Y is called the nodal admittance matrix, and its diagonal elements Y ii The self-admittance of node i is called the self-admittance, and its value is equal to the sum of the admittances of all branches connected to node i; the off-diagonal element Y ij This is called the admittance between node i and node j, and its value is equal to the negative of the admittance of the branch connected between node i and node j. If there is no direct branch between node i and node j, then Y... ij = 0. Therefore, any power network topology can be described using the node admittance matrix. The admittance expression can be written as:

[0047]

[0048] Among them, R ij Let X be the branch resistance between node i and node j. ij Let be the branch reactance between node i and node j, ω represent the angular frequency, and J represent the imaginary unit. Inverting the node admittance matrix yields the node impedance matrix Z, where Z is the diagonal element of Z. iiThe node self-impedance is called node i.

[0049] Step S203: Perform frequency correction on the above node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and determine the correspondence between the equivalent node self-impedance and the above equivalent frequency based on the above equivalent node admittance matrix to obtain the first relationship.

[0050] Specifically, frequency correction is applied to the above-mentioned node admittance matrix to reduce system error.

[0051] In one alternative approach, the node admittance matrix is ​​frequency-corrected to obtain an equivalent node admittance matrix at the equivalent frequency. Based on the equivalent node admittance matrix, the correspondence between the equivalent node self-impedance and the equivalent frequency is determined to obtain a first relationship. This includes: correcting the node admittance matrix using the equivalent frequency method to obtain the equivalent node admittance matrix; determining the equivalent node impedance matrix based on the equivalent node admittance matrix; and determining the first relationship based on the equivalent node impedance matrix.

[0052] Calculate the nodal admittance matrix after correction using the equivalent frequency method, i.e., the equivalent nodal admittance matrix Y. equ Its diagonal element Y equii The self-admittance of node i is called the self-admittance, and its value is equal to the sum of the admittances of all branches connected to node i; the off-diagonal element Y equij This is called the admittance between node i and node j, and its value is equal to the negative of the admittance of the branch connected between node i and node j. If there is no direct branch between node i and node j, then Y... equij = 0. Therefore, any power network topology can be described using the node admittance matrix. The admittance expression can be written as:

[0053]

[0054] Among them, X equij ω is the branch reactance between node i and node j after correction using the equivalent frequency method. equ The equivalent frequency is ω. equ Treating it as a variable, we obtain the equivalent nodal admittance matrix Y. equ Regarding the equivalent frequency ω equ Relationship Y equij (ω equ Inverting the equivalent nodal admittance matrix yields the equivalent nodal impedance matrix Z. equ Z equ diagonal element Z equii This is called the equivalent node self-impedance of node i. Z equii It's actually about the equivalent frequency ω of the variable. equ function Z equii (ωequ Z equii (ω equ This is the first relationship mentioned above.

[0055] Step S204: Based on the above node self-impedance and the above first relationship, determine the correspondence between the above short-circuit current DC component and the above equivalent frequency to obtain the second relationship, and determine the target relationship based on the above second relationship and the above fault space. The target relationship is the relationship between the above short-circuit current DC component and the above time.

[0056] Specifically, based on the input impedance method calculation formula, the second relationship can be determined according to the above node self-impedance and the above first relationship.

[0057] In one alternative approach, the correspondence between the DC component of the short-circuit current and the equivalent frequency is determined based on the aforementioned node self-impedance and the aforementioned first relationship, thereby obtaining a second relationship. This includes: calculating the correspondence between the attenuation time constant and the aforementioned equivalent frequency based on the aforementioned first relationship, thereby obtaining a third relationship; and determining the aforementioned second relationship based on the aforementioned node self-impedance and the aforementioned third relationship.

[0058] In practical applications, based on the input impedance method calculation formula, the DC component of the short-circuit current calculated by the input impedance method at the corresponding fault point f can be written as a function of the equivalent frequency and time t, as follows:

[0059]

[0060] Among them, V f In order to use the equivalent voltage source voltage, Z ff The input impedance of the fault node f is T. equ The attenuation time constant after correction using the equivalent frequency method is calculated using the following formula:

[0061]

[0062] The above formula is the third relationship. Substituting this third relationship into the function of the DC component of the short-circuit current with respect to the equivalent frequency and time t, we can see that the DC component of the short-circuit current calculated by the actual input impedance method is a function of the equivalent frequency and time t, i.e., i dc (t,ω equ ), i dc (t,ω equ This is the second relationship.

[0063] To obtain the optimal frequency curve using the equivalent frequency method, it is necessary to search for the point with the highest density in the solution space and plot the time-domain curve. In one alternative approach, determining the target relationship based on the aforementioned second relationship and the aforementioned fault space includes: processing the fault space using a pattern search algorithm to determine the DC component of the short-circuit current corresponding to the point with the highest data density in the fault space as the first DC component of the short-circuit current; substituting the first DC component of the short-circuit current into the aforementioned second relationship to obtain a fourth relationship, which is the correspondence between the optimal frequency of the power grid and the aforementioned time, and the optimal frequency is the equivalent frequency corresponding to the first DC component of the short-circuit current; and determining the target relationship based on the aforementioned fourth relationship.

[0064] In one alternative approach, determining the target relationship based on the fourth relationship includes: determining the correspondence between the node admittance matrix corresponding to the optimal frequency and the time based on the fourth relationship, thus obtaining the fifth relationship; determining the correspondence between the equivalent node self-impedance corresponding to the optimal frequency and the time based on the fifth relationship, thus obtaining the sixth relationship; and substituting the sixth relationship into the input impedance method calculation formula to obtain the target relationship.

[0065] Specifically, by using a pattern search algorithm to process the aforementioned fault space, the Meanshift clustering algorithm can be used to find the densest data location within the fault space. The basic principle of the algorithm is as follows:

[0066] For a d-dimensional Euclidean space X, with n sample points (i = 1, ..., n), arbitrarily select a point x in the space, let k(x) represent the Gaussian kernel function in that space, and k(x) be the contour function corresponding to the kernel function. R d The probability density estimate of point x in space is:

[0067]

[0068] Among them, S k It is a high-dimensional region with radius h, in x i k sample points are located in S k Within the region; c is the normalization constant of the Gaussian kernel function. The direction of the densest data in space can be found by taking the gradient with respect to the probability density.

[0069]

[0070] in:

[0071]

[0072]

[0073] Where g(x) = -k'(x), if and only if m h,G(X)≤ε, the probability density gradient is 0, pointing to the position where the data is most dense, and ε is the error threshold.

[0074]

[0075] The above formula is the algorithm's position update function, where p is the number of iterations. When the distance change reaches a threshold, the algorithm converges; otherwise, it returns to the above iterative process.

[0076] In practical applications, let the following equation be satisfied at time t0:

[0077] I DC (t0)-i dc (w best ,t0)=0,

[0078] Among them, I DC (t0) represents the DC component of the short-circuit current in the input impedance method optimization model at time t0, i dc (ω best ω is the optimal frequency at time t0. best Calculate the optimal frequency ω at time t0 based on the DC component of the short-circuit current. best By changing the time step by step, the optimal frequency curve can be plotted in a fixed step. The DC component curve of the short-circuit current is plotted, and the equivalent nodal admittance matrix under the optimal frequency optimization method is corrected and calculated as follows:

[0079]

[0080] For the equivalent nodal admittance matrix Y bestij Inverse the equation to obtain the equivalent nodal impedance matrix Z. best Z best diagonal element Z bestii This is called the equivalent node self-impedance after optimal frequency correction for node i. Based on the input impedance method calculation formula, the DC component calculation curve of the short-circuit current at the corresponding network fault node f using the proposed optimization method can be written as follows:

[0081]

[0082] Among them, I dc (t) represents the target relationship described above.

[0083] Step S205: Based on the above target relationship, determine the target attenuation time constant, and determine whether the circuit breaker's ability to withstand short-circuit current is insufficient based on whether the above target attenuation time constant is greater than a predetermined value.

[0084] Specifically, the DC component of the short-circuit current and the decay time constant have a significant impact on the evaluation of short-circuit current data.

[0085] In practical applications, with the development of ultra-high voltage (UHV) projects, in order to reduce transmission losses, the capacity of generators and transformers has gradually increased, and the resistance of transmission lines has further decreased. This leads to an increasingly larger reactance-resistivity ratio of the equivalent system at the short-circuit point, and consequently, an increased DC component decay time constant. The impact of the DC component of the short-circuit current on the power grid is becoming increasingly prominent. Under short-circuit faults, the decay rate of the DC component of the short-circuit current slows down, and its impact on the actual breaking capacity of circuit breakers becomes increasingly significant. Therefore, only by accurately calculating the decaying DC component of the short-circuit current over time on each circuit breaker branch connected to the short-circuit node can a valid basis be provided for verifying the breaking capacity of the circuit breakers. Specifically, the breaking current of a circuit breaker refers to the maximum instantaneous current that the circuit breaker can safely and reliably separate from the fault area in the power grid. When overload, short circuit, or other faults occur, the higher the breaking current, the faster the device can cut off the fault current, protecting the equipment and personnel. The larger the decay time constant, the smaller the coefficient for calculating the breaking current value, and the slower the device cuts off the fault current. Therefore, the more accurate the calculation of the decay time constant, the more accurately it can be determined whether the circuit breaker's ability to withstand short-circuit current is insufficient.

[0086] To accurately determine whether the short-circuit current withstand capability of a circuit breaker meets actual requirements, one option involves determining whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the target attenuation time constant is greater than a predetermined value. This includes: if the target attenuation time constant is greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability does not meet actual requirements; and if the target attenuation time constant is not greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability meets actual requirements.

[0087] Specifically, the aforementioned predetermined value can be the standard time constant for the decay of the short-circuit current of the circuit breaker. Based on the above target relationship, the target decay time constant can be obtained as follows:

[0088]

[0089] Through the above embodiments, the fault space is first determined, and then the correspondence between the DC component of the short-circuit current and the equivalent frequency is determined, i.e., the second relationship. Based on the second relationship and the fault space, the relationship between the DC component of the short-circuit current and the aforementioned time is determined, i.e., the target relationship. This method calculates the DC component of the short-circuit current with high accuracy, thereby obtaining a high-accuracy target attenuation time constant. This solves the problem in the prior art where the calculation accuracy of the DC component of the short-circuit current is low, leading to inaccurate judgment of the circuit breaker's ability to withstand short-circuit current.

[0090] This application also provides a device for determining the short-circuit current withstand capability of a circuit breaker. It should be noted that this device can be used to execute the method for determining the short-circuit current withstand capability of a circuit breaker provided in this application. This device is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0091] The following describes the device for determining the short-circuit current withstand capability of a circuit breaker provided in the embodiments of this application.

[0092] Figure 5 This is a schematic diagram of a device for determining the short-circuit current withstand capability of a circuit breaker according to an embodiment of this application. Figure 5 As shown, the device includes a processing unit 10, a first determining unit 20, a second determining unit 30, a third determining unit 40, and a fourth determining unit 50, wherein:

[0093] The aforementioned processing unit 10 is used to perform equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each of the aforementioned equivalent branches as variables, it determines the change of the DC component of the short-circuit current relative to time under different impedance parameters, and obtains multiple curves. The boundaries of the multiple curves constitute a multidimensional fault space. The aforementioned equivalent branches are Thevenin equivalent circuits corresponding to the aforementioned branches.

[0094] Specifically, each branch is processed to obtain multiple equivalent branches. The fault space is constructed by the impedance parameters of the equivalent branches, making the fault space more comprehensive.

[0095] In practical applications, for arbitrary faults and short-circuit faults in complex systems, the network structure is as follows: Figure 3 As shown, where f is the faulty node, Figure 3 A number of branches greater than 2 indicates a bus short circuit, while a number equal to 2 indicates a line short circuit. If the external circuit is completely equivalent, the transient characteristics of the DC component cannot be characterized. Although completely equivalent external circuits can accurately calculate the initial value of the DC component of the short-circuit current, the decay time constant is actually composed of the superposition of many components with different decay time constants, as shown in the following formula: Here, T1, T2, and T3 represent the short-circuit current decay time constants, and i1, i2, and i3 represent the initial values ​​of the DC component of the short-circuit current. Using a single decay time constant introduces system errors, which are particularly significant in systems with large impedance ratio differences. To improve the calculation accuracy of traditional methods and reduce system errors, i1, i2, and i3 can be calculated independently. k1 i k2and i k3 Methods such as these improve computational accuracy by performing Thevenin equivalents on each branch and describing each branch separately. Taking a three-branch circuit as an example, its equivalent circuit is as follows: Figure 4 As shown, for Figure 4 The equivalent circuit model shown is used to write the differential equation expression. Substituting the boundary conditions, and according to the calculation method of the DC component of the short-circuit current in "Power System Analysis", the following can be obtained:

[0096]

[0097] Where R1, R2, R3, X1, X2, and X3 are the equivalent impedances of each branch, and U n T1, T2, and T3 represent the system nominal voltage, and T1, T2, and T3 are the attenuation time constants of each branch, respectively. However, due to the complexity of power grid structures, traditional methods for calculating the input impedance of complex networks cannot calculate the equivalent impedance of each branch at the fault point individually. Therefore, the national standard adopts the equivalent frequency method to reduce this error.

[0098] The aforementioned impedance parameters include resistance and reactance. To reduce the error in the calculation method of input impedance for complex networks, the aforementioned processing unit includes an acquisition module and a first processing module. The acquisition module is used to acquire the resistance and reactance of each of the aforementioned equivalent branches, and determine the impedance as Z = R + JωL based on the resistance and reactance, where Z represents the impedance, R represents the resistance, L represents the reactance, ω represents the angular frequency of the aforementioned power grid, and J represents the imaginary unit. The first processing module is used to obtain multiple of the aforementioned curves using each of the aforementioned resistances and reactances as variables.

[0099] In one alternative embodiment, the aforementioned variables satisfy predetermined conditions, namely, the ratio of the impedances of any two equivalent branches is in the range of 0.01 to 100, and the ratio of the real part to the imaginary part of the impedance is in the range of 0.01 to 3. The real part of the impedance is R, and the imaginary part of the impedance is X = ωL.

[0100] In practical applications, the equivalent impedances R1, R2, R3, X1, X2, and X3 of each branch are used as variables to plot the aforementioned fault space with a fixed step size. Each variable satisfies the following conditions: the ratio of the impedances of any two equivalent branches is between 0.01 and 100, and the ratio of the real to imaginary parts of the impedances is between 0.01 and 3. Based on these constraints, assuming R1 = 1, a series of DC component curves of the short-circuit current that meet the requirements can be plotted with a fixed step size, thereby constructing the fault space S = [R1, R2, R3, X1, X2, X3, I...]. DC [(t)], where I DC (t) is the DC component curve of the short-circuit current under the corresponding parameters.

[0101] The first determining unit 20 is used to determine the node impedance matrix of the power grid based on the node admittance matrix of the power grid, and to determine the node self-impedance based on the node impedance matrix.

[0102] Specifically, any power network topology can be described using a node admittance matrix.

[0103] Power system networks are generally described using nodal admittance matrices, and their basic form is as follows:

[0104]

[0105] Matrix Y is called the nodal admittance matrix, and its diagonal elements Y ii The self-admittance of node i is called the self-admittance, and its value is equal to the sum of the admittances of all branches connected to node i; the off-diagonal element Y ij This is called the admittance between node i and node j, and its value is equal to the negative of the admittance of the branch connected between node i and node j. If there is no direct branch between node i and node j, then Y... ij = 0. Therefore, any power network topology can be described using the node admittance matrix. The admittance expression can be written as:

[0106]

[0107] Among them, R ij Let X be the branch resistance between node i and node j. ij Let be the branch reactance between node i and node j, ω represent the angular frequency, and J represent the imaginary unit. Inverting the node admittance matrix yields the node impedance matrix Z, where Z is the diagonal element of Z. ii The node self-impedance is called node i.

[0108] The second determining unit 30 performs frequency correction on the above-mentioned node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and determines the correspondence between the equivalent node self-impedance and the above-mentioned equivalent frequency based on the above-mentioned equivalent node admittance matrix to obtain the first relationship.

[0109] Specifically, frequency correction is applied to the above-mentioned node admittance matrix to reduce system error.

[0110] In one alternative embodiment, the second determining unit includes a second processing module, a first determining module, and a second determining module. The second processing module is used to correct the node admittance matrix using the equivalent frequency method to obtain the equivalent node admittance matrix. The first determining module is used to determine the equivalent node impedance matrix based on the equivalent node admittance matrix. The second determining module is used to determine the first relationship based on the equivalent node impedance matrix.

[0111] Calculate the nodal admittance matrix after correction using the equivalent frequency method, i.e., the equivalent nodal admittance matrix Y. equ Its diagonal element Y equii The self-admittance of node i is called the self-admittance, and its value is equal to the sum of the admittances of all branches connected to node i; the off-diagonal element Y equij This is called the admittance between node i and node j, and its value is equal to the negative of the admittance of the branch connected between node i and node j. If there is no direct branch between node i and node j, then Y... equij = 0. Therefore, any power network topology can be described using the node admittance matrix. The admittance expression can be written as:

[0112]

[0113] Among them, X equij ω is the branch reactance between node i and node j after correction using the equivalent frequency method. equ The equivalent frequency is ω. equ Treating it as a variable, we obtain the equivalent nodal admittance matrix Y. equ Regarding the equivalent frequency ω equ Relationship Y equij (ω equ Inverting the equivalent nodal admittance matrix yields the equivalent nodal impedance matrix Z. equ Z equ diagonal element Z equii This is called the equivalent node self-impedance of node i. Z equii It's actually about the equivalent frequency ω of the variable. equ function Z equii (ω equ Z equii (ω equ This is the first relationship mentioned above.

[0114] The third determining unit 40 determines the correspondence between the DC component of the short-circuit current and the equivalent frequency based on the node self-impedance and the first relationship, obtains the second relationship, and determines the target relationship based on the second relationship and the fault space. The target relationship is the relationship between the DC component of the short-circuit current and the time.

[0115] Specifically, based on the input impedance method calculation formula, the second relationship can be determined according to the above node self-impedance and the above first relationship.

[0116] In one alternative embodiment, the third determining unit includes a calculation module and a third determining module. The calculation module is used to calculate the correspondence between the attenuation time constant and the equivalent frequency based on the first relationship, thereby obtaining the third relationship. The third determining module is used to determine the second relationship based on the node self-impedance and the third relationship.

[0117] In practical applications, based on the input impedance method calculation formula, the DC component of the short-circuit current calculated by the input impedance method at the corresponding fault point f can be written as a function of the equivalent frequency and time t, as follows:

[0118]

[0119] Among them, V f In order to use the equivalent voltage source voltage, Z ff The input impedance of the fault node f is T. equ The attenuation time constant after correction using the equivalent frequency method is calculated using the following formula:

[0120]

[0121] The above formula is the third relationship. Substituting this third relationship into the function of the DC component of the short-circuit current with respect to the equivalent frequency and time t, we can see that the DC component of the short-circuit current calculated by the actual input impedance method is a function of the equivalent frequency and time t, i.e., i dc (t,ω equ ), i dc (t,ω equ This is the second relationship.

[0122] To obtain the optimal frequency curve using the equivalent frequency method, it is necessary to search for the point with the highest density in the solution space and plot the time-domain curve. In one optional scheme, the third determining unit includes a third processing module, a fourth processing module, and a fourth determining module. The third processing module is used to process the fault space using a pattern search algorithm to determine the DC component of the short-circuit current corresponding to the point with the highest data density in the fault space as the first DC component of the short-circuit current. The fourth processing module is used to substitute the first DC component of the short-circuit current into the second relation to obtain a fourth relation, which is the correspondence between the optimal frequency of the power grid and the time, and the optimal frequency is the equivalent frequency corresponding to the first DC component of the short-circuit current. The fourth determining module is used to determine the target relation based on the fourth relation.

[0123] In one alternative embodiment, the fourth determining module includes a first determining submodule, a second determining submodule, and a processing submodule. The first determining submodule is used to determine the correspondence between the node admittance matrix corresponding to the optimal frequency and the time based on the fourth relationship, thus obtaining a fifth relationship. The second determining submodule is used to determine the correspondence between the equivalent node self-impedance corresponding to the optimal frequency and the time based on the fifth relationship, thus obtaining a sixth relationship. The processing submodule is used to substitute the sixth relationship into the input impedance method calculation formula to obtain the target relationship.

[0124] Specifically, by using a pattern search algorithm to process the aforementioned fault space, the Meanshift clustering algorithm can be used to find the densest data location within the fault space. The basic principle of the algorithm is as follows:

[0125] For a d-dimensional Euclidean space X, with n sample points (i = 1, ..., n), arbitrarily select a point x in the space, let k(x) represent the Gaussian kernel function in that space, and k(x) be the contour function corresponding to the kernel function. R d The probability density estimate of point x in space is:

[0126]

[0127] Among them, S k It is a high-dimensional region with radius h, in x i k sample points are located in S k Within the region; c is the normalization constant of the Gaussian kernel function. The direction of the densest data in space can be found by taking the gradient with respect to the probability density.

[0128]

[0129] in:

[0130]

[0131]

[0132] Where g(x) = -k'(x), if and only if m h,G (X)≤ε, the probability density gradient is 0, pointing to the position where the data is most dense, and ε is the error threshold.

[0133]

[0134] The above formula is the algorithm's position update function, where p is the number of iterations. When the distance change reaches a threshold, the algorithm converges; otherwise, it returns to the above iterative process.

[0135] In practical applications, let the following equation be satisfied at time t0:

[0136] I DC (t0)-i dc (w best ,t0)=0,

[0137] Among them, I DC (t0) represents the DC component of the short-circuit current in the input impedance method optimization model at time t0, i dc (ω best ω is the optimal frequency at time t0. best Calculate the optimal frequency ω at time t0 based on the DC component of the short-circuit current. bestBy changing the time step by step, the optimal frequency curve can be plotted in a fixed step. The DC component curve of the short-circuit current is plotted, and the equivalent nodal admittance matrix under the optimal frequency optimization method is corrected and calculated as follows:

[0138]

[0139] For the equivalent nodal admittance matrix Y bestij Inverse the equation to obtain the equivalent nodal impedance matrix Z. best Z best diagonal element Z bestii This is called the equivalent node self-impedance after optimal frequency correction for node i. Based on the input impedance method calculation formula, the DC component calculation curve of the short-circuit current at the corresponding network fault node f using the proposed optimization method can be written as follows:

[0140]

[0141] Among them, I dc (t) represents the target relationship described above.

[0142] The fourth determining unit 50 is used to determine the target attenuation time constant according to the target relationship, and to determine whether the circuit breaker's ability to withstand short-circuit current is insufficient based on whether the target attenuation time constant is greater than a predetermined value.

[0143] Specifically, the DC component of the short-circuit current and the decay time constant have a significant impact on the evaluation of short-circuit current data.

[0144] In practical applications, with the development of ultra-high voltage (UHV) projects, in order to reduce transmission losses, the capacity of generators and transformers has gradually increased, and the resistance of transmission lines has further decreased. This leads to an increasingly larger reactance-resistivity ratio of the equivalent system at the short-circuit point, and consequently, an increased DC component decay time constant. The impact of the DC component of the short-circuit current on the power grid is becoming increasingly prominent. Under short-circuit faults, the decay rate of the DC component of the short-circuit current slows down, and its impact on the actual breaking capacity of circuit breakers becomes increasingly significant. Therefore, only by accurately calculating the decaying DC component of the short-circuit current over time on each circuit breaker branch connected to the short-circuit node can a valid basis be provided for verifying the breaking capacity of the circuit breakers. Specifically, the breaking current of a circuit breaker refers to the maximum instantaneous current that the circuit breaker can safely and reliably separate from the fault area in the power grid. When overload, short circuit, or other faults occur, the higher the breaking current, the faster the device can cut off the fault current, protecting the equipment and personnel. The larger the decay time constant, the smaller the coefficient for calculating the breaking current value, and the slower the device cuts off the fault current. Therefore, the more accurate the calculation of the decay time constant, the more accurately it can be determined whether the circuit breaker's ability to withstand short-circuit current is insufficient.

[0145] To accurately determine whether the circuit breaker's short-circuit current withstand capability meets actual requirements, in one optional embodiment, the fourth determining unit includes a fifth determining module and a sixth determining module. The fifth determining module is used to determine that the circuit breaker's short-circuit current withstand capability does not meet actual requirements if the target attenuation time constant is greater than the predetermined value. The sixth determining module is used to determine that the circuit breaker's short-circuit current withstand capability meets actual requirements if the target attenuation time constant is not greater than the predetermined value.

[0146] Specifically, the aforementioned predetermined value can be the standard time constant for the decay of the short-circuit current of the circuit breaker. Based on the above target relationship, the target decay time constant can be obtained as follows:

[0147]

[0148] Through the above embodiments, the fault space is first determined, and then the correspondence between the DC component of the short-circuit current and the equivalent frequency is determined, i.e., the second relationship. Based on the second relationship and the fault space, the relationship between the DC component of the short-circuit current and the aforementioned time is determined, i.e., the target relationship. The device calculates the DC component of the short-circuit current with high accuracy, thereby obtaining a high-accuracy target attenuation time constant. This solves the problem in the prior art where the calculation accuracy of the DC component of the short-circuit current is low, leading to inaccurate judgment of the circuit breaker's ability to withstand short-circuit current.

[0149] The aforementioned device for determining the short-circuit current withstand capability of the circuit breaker includes a processor and a memory. The aforementioned processing unit, the first determining unit, the second determining unit, the third determining unit, and the fourth determining unit are all stored as program units in the memory. The processor executes these program units stored in the memory to achieve the corresponding functions. All of the aforementioned modules are located in the same processor; alternatively, the aforementioned modules may be located in different processors in any combination.

[0150] The processor contains a kernel, which retrieves the corresponding program unit from memory. One or more kernels can be configured, and adjusting kernel parameters can address the problem in existing technologies where the low accuracy of calculating the DC component of short-circuit current leads to inaccurate judgment of the circuit breaker's short-circuit current withstand capability.

[0151] The memory may include non-permanent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0152] This invention provides a computer-readable storage medium including a stored program, wherein, when the program is executed, it controls the device containing the computer-readable storage medium to perform the method for determining the short-circuit current withstand capability of the circuit breaker.

[0153] Specifically, the methods for determining the short-circuit current withstand capability of a circuit breaker include:

[0154] Step S201: Perform equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each of the above equivalent branches as variables, determine the change of the DC component of the short-circuit current relative to time under different impedance parameters to obtain multiple curves. The boundaries of the multiple curves constitute a multidimensional fault space. The above equivalent branches are the Thevenin equivalent circuits corresponding to the above branches.

[0155] Specifically, each branch is processed to obtain multiple equivalent branches. The fault space is constructed by the impedance parameters of the equivalent branches, making the fault space more comprehensive.

[0156] Step S202: Determine the node impedance matrix of the power grid based on the node admittance matrix of the power grid, and determine the node self-impedance based on the node impedance matrix.

[0157] Specifically, any power network topology can be described using a node admittance matrix.

[0158] Step S203: Perform frequency correction on the above node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and determine the correspondence between the equivalent node self-impedance and the above equivalent frequency based on the above equivalent node admittance matrix to obtain the first relationship.

[0159] Specifically, frequency correction is applied to the above-mentioned node admittance matrix to reduce system error.

[0160] Step S204: Based on the above node self-impedance and the above first relationship, determine the correspondence between the above short-circuit current DC component and the above equivalent frequency to obtain the second relationship, and determine the target relationship based on the above second relationship and the above fault space. The target relationship is the relationship between the above short-circuit current DC component and the above time.

[0161] Specifically, based on the input impedance method calculation formula, the second relationship can be determined according to the above node self-impedance and the above first relationship.

[0162] Step S205: Based on the above target relationship, determine the target attenuation time constant, and determine whether the circuit breaker's ability to withstand short-circuit current is insufficient based on whether the above target attenuation time constant is greater than a predetermined value.

[0163] Specifically, the DC component of the short-circuit current and the decay time constant have a significant impact on the evaluation of short-circuit current data.

[0164] Optionally, the node admittance matrix is ​​frequency-corrected to obtain an equivalent node admittance matrix at the equivalent frequency, and the correspondence between the equivalent node self-impedance and the equivalent frequency is determined based on the equivalent node admittance matrix to obtain a first relationship. This includes: correcting the node admittance matrix using the equivalent frequency method to obtain the equivalent node admittance matrix; determining the equivalent node impedance matrix based on the equivalent node admittance matrix; and determining the first relationship based on the equivalent node impedance matrix.

[0165] Optionally, based on the above-mentioned node self-impedance and the above-mentioned first relationship, the correspondence between the above-mentioned short-circuit current DC component and the above-mentioned equivalent frequency is determined to obtain the second relationship, including: based on the above-mentioned first relationship, the correspondence between the attenuation time constant and the above-mentioned equivalent frequency is calculated to obtain the third relationship; based on the above-mentioned node self-impedance and the above-mentioned third relationship, the above-mentioned second relationship is determined.

[0166] Optionally, determining the target relationship based on the second relationship and the fault space includes: processing the fault space using a pattern search algorithm to determine the DC component of the short-circuit current corresponding to the point with the highest data density in the fault space as the first DC component of the short-circuit current; substituting the first DC component of the short-circuit current into the second relationship to obtain a fourth relationship, the fourth relationship being the correspondence between the optimal frequency of the power grid and the time, the optimal frequency being the equivalent frequency corresponding to the first DC component of the short-circuit current; and determining the target relationship based on the fourth relationship.

[0167] Optionally, the target relationship is determined based on the fourth relationship, including: determining the correspondence between the node admittance matrix and the time corresponding to the optimal frequency based on the fourth relationship, to obtain the fifth relationship; determining the correspondence between the equivalent node self-impedance and the time corresponding to the optimal frequency based on the fifth relationship, to obtain the sixth relationship; and substituting the sixth relationship into the input impedance method calculation formula to obtain the target relationship.

[0168] Optionally, the impedance parameters mentioned above include resistance and reactance. Using the impedance parameters of each of the above equivalent branches as variables, the change of the DC component of the short-circuit current relative to time under different impedance parameters is determined, resulting in multiple curves. This includes: obtaining the resistance and reactance of each of the above equivalent branches, with the relationship between impedance and resistance and reactance as follows: where represents the impedance, represents the resistance, represents the reactance, represents the angular frequency of the power grid, and represents the imaginary unit; using each of the above resistances and reactances as variables, multiple curves are obtained.

[0169] Optionally, the above variables satisfy predetermined conditions, wherein the ratio of the impedances of any two of the above equivalent branches is in the range of 0.01 to 100, and the ratio of the real part to the imaginary part of the impedance is in the range of 0.01 to 3.

[0170] Optionally, determining whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the target attenuation time constant is greater than the predetermined value includes: if the target attenuation time constant is greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability does not meet the actual requirements; if the target attenuation time constant is not greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability meets the actual requirements.

[0171] This invention provides a processor for running a program, wherein the program executes the method for determining the short-circuit current withstand capability of the circuit breaker.

[0172] Specifically, the methods for determining the short-circuit current withstand capability of a circuit breaker include:

[0173] Step S201: Perform equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each of the above equivalent branches as variables, determine the change of the DC component of the short-circuit current relative to time under different impedance parameters to obtain multiple curves. The boundaries of the multiple curves constitute a multidimensional fault space. The above equivalent branches are the Thevenin equivalent circuits corresponding to the above branches.

[0174] Specifically, each branch is processed to obtain multiple equivalent branches. The fault space is constructed by the impedance parameters of the equivalent branches, making the fault space more comprehensive.

[0175] Step S202: Determine the node impedance matrix of the power grid based on the node admittance matrix of the power grid, and determine the node self-impedance based on the node impedance matrix.

[0176] Specifically, any power network topology can be described using a node admittance matrix.

[0177] Step S203: Perform frequency correction on the above node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and determine the correspondence between the equivalent node self-impedance and the above equivalent frequency based on the above equivalent node admittance matrix to obtain the first relationship.

[0178] Specifically, frequency correction is applied to the above-mentioned node admittance matrix to reduce system error.

[0179] Step S204: Based on the above node self-impedance and the above first relationship, determine the correspondence between the above short-circuit current DC component and the above equivalent frequency to obtain the second relationship, and determine the target relationship based on the above second relationship and the above fault space. The target relationship is the relationship between the above short-circuit current DC component and the above time.

[0180] Specifically, based on the input impedance method calculation formula, the second relationship can be determined according to the above node self-impedance and the above first relationship.

[0181] Step S205: Based on the above target relationship, determine the target attenuation time constant, and determine whether the circuit breaker's ability to withstand short-circuit current is insufficient based on whether the above target attenuation time constant is greater than a predetermined value.

[0182] Specifically, the DC component of the short-circuit current and the decay time constant have a significant impact on the evaluation of short-circuit current data.

[0183] Optionally, the node admittance matrix is ​​frequency-corrected to obtain an equivalent node admittance matrix at the equivalent frequency, and the correspondence between the equivalent node self-impedance and the equivalent frequency is determined based on the equivalent node admittance matrix to obtain a first relationship. This includes: correcting the node admittance matrix using the equivalent frequency method to obtain the equivalent node admittance matrix; determining the equivalent node impedance matrix based on the equivalent node admittance matrix; and determining the first relationship based on the equivalent node impedance matrix.

[0184] Optionally, based on the above-mentioned node self-impedance and the above-mentioned first relationship, the correspondence between the above-mentioned short-circuit current DC component and the above-mentioned equivalent frequency is determined to obtain the second relationship, including: based on the above-mentioned first relationship, the correspondence between the attenuation time constant and the above-mentioned equivalent frequency is calculated to obtain the third relationship; based on the above-mentioned node self-impedance and the above-mentioned third relationship, the above-mentioned second relationship is determined.

[0185] Optionally, determining the target relationship based on the second relationship and the fault space includes: processing the fault space using a pattern search algorithm to determine the DC component of the short-circuit current corresponding to the point with the highest data density in the fault space as the first DC component of the short-circuit current; substituting the first DC component of the short-circuit current into the second relationship to obtain a fourth relationship, the fourth relationship being the correspondence between the optimal frequency of the power grid and the time, the optimal frequency being the equivalent frequency corresponding to the first DC component of the short-circuit current; and determining the target relationship based on the fourth relationship.

[0186] Optionally, the target relationship is determined based on the fourth relationship, including: determining the correspondence between the node admittance matrix and the time corresponding to the optimal frequency based on the fourth relationship, to obtain the fifth relationship; determining the correspondence between the equivalent node self-impedance and the time corresponding to the optimal frequency based on the fifth relationship, to obtain the sixth relationship; and substituting the sixth relationship into the input impedance method calculation formula to obtain the target relationship.

[0187] Optionally, the impedance parameters mentioned above include resistance and reactance. Using the impedance parameters of each of the above equivalent branches as variables, the change of the DC component of the short-circuit current relative to time under different impedance parameters is determined, resulting in multiple curves. This includes: obtaining the resistance and reactance of each of the above equivalent branches, with the relationship between impedance and resistance and reactance as follows: where represents the impedance, represents the resistance, represents the reactance, represents the angular frequency of the power grid, and represents the imaginary unit; using each of the above resistances and reactances as variables, multiple curves are obtained.

[0188] Optionally, the above variables satisfy predetermined conditions, wherein the ratio of the impedances of any two of the above equivalent branches is in the range of 0.01 to 100, and the ratio of the real part to the imaginary part of the impedance is in the range of 0.01 to 3.

[0189] Optionally, determining whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the target attenuation time constant is greater than the predetermined value includes: if the target attenuation time constant is greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability does not meet the actual requirements; if the target attenuation time constant is not greater than the predetermined value, determining that the circuit breaker's short-circuit current withstand capability meets the actual requirements.

[0190] This invention provides a device including a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, it performs at least the following steps:

[0191] Step S201: Perform equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each of the above equivalent branches as variables, determine the change of the DC component of the short-circuit current relative to time under different impedance parameters to obtain multiple curves. The boundaries of the multiple curves constitute a multidimensional fault space. The above equivalent branches are the Thevenin equivalent circuits corresponding to the above branches.

[0192] Step S202: Determine the node impedance matrix of the power grid based on the node admittance matrix of the power grid, and determine the node self-impedance based on the node impedance matrix.

[0193] Step S203: Perform frequency correction on the above node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and determine the correspondence between the equivalent node self-impedance and the above equivalent frequency based on the above equivalent node admittance matrix to obtain the first relationship.

[0194] Step S204: Based on the above node self-impedance and the above first relationship, determine the correspondence between the above short-circuit current DC component and the above equivalent frequency to obtain the second relationship, and determine the target relationship based on the above second relationship and the above fault space. The target relationship is the relationship between the above short-circuit current DC component and the above time.

[0195] Step S205: Based on the above target relationship, determine the target attenuation time constant, and determine whether the circuit breaker's ability to withstand short-circuit current is insufficient based on whether the above target attenuation time constant is greater than a predetermined value.

[0196] The devices mentioned in this article can be servers, PCs, tablets, mobile phones, etc.

[0197] This application also provides a computer program product, which, when executed on a data processing device, is suitable for executing an initialization program having at least the following method steps:

[0198] Step S201: Perform equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each of the above equivalent branches as variables, determine the change of the DC component of the short-circuit current relative to time under different impedance parameters to obtain multiple curves. The boundaries of the multiple curves constitute a multidimensional fault space. The above equivalent branches are the Thevenin equivalent circuits corresponding to the above branches.

[0199] Step S202: Determine the node impedance matrix of the power grid based on the node admittance matrix of the power grid, and determine the node self-impedance based on the node impedance matrix.

[0200] Step S203: Perform frequency correction on the above node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and determine the correspondence between the equivalent node self-impedance and the above equivalent frequency based on the above equivalent node admittance matrix to obtain the first relationship.

[0201] Step S204: Based on the above node self-impedance and the above first relationship, determine the correspondence between the above short-circuit current DC component and the above equivalent frequency to obtain the second relationship, and determine the target relationship based on the above second relationship and the above fault space. The target relationship is the relationship between the above short-circuit current DC component and the above time.

[0202] Step S205: Based on the above target relationship, determine the target attenuation time constant, and determine whether the circuit breaker's ability to withstand short-circuit current is insufficient based on whether the above target attenuation time constant is greater than a predetermined value.

[0203] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0204] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0205] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0206] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0207] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0208] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0209] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0210] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0211] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0212] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0213] 1) In the method for determining the short-circuit current withstand capability of the circuit breaker described in this application, firstly, the branches of the power grid before the fault point are equivalently processed to obtain multiple equivalent branches. Using the impedance parameters of each equivalent branch as variables, the relative time variation of the DC component of the short-circuit current under different impedance parameters is determined, resulting in multiple curves. The boundaries of these multiple curves constitute a multi-dimensional fault space, and the equivalent branches are the Thevenin equivalent circuits corresponding to these branches. Then, based on the node admittance matrix of the power grid, the node impedance matrix of the power grid is determined, and based on the node impedance matrix, the node self-impedance is determined. Finally, the node admittance matrix is ​​frequency corrected to obtain... The method first determines the fault space, then determines the correspondence between the short-circuit current DC component and the equivalent frequency (i.e., the second relationship), and finally determines the target attenuation time constant based on whether the target attenuation time constant is greater than a predetermined value to determine whether the circuit breaker's short-circuit current withstand capability is insufficient. This method first determines the fault space, then determines the correspondence between the short-circuit current DC component and the equivalent frequency (i.e., the second relationship), and then determines the relationship between the short-circuit current DC component and the time based on the second relationship and the fault space (i.e., the target relationship). This method has high accuracy in calculating the short-circuit current DC component, resulting in high accuracy in obtaining the target attenuation time constant. This solves the problem in the prior art where the low calculation accuracy of the short-circuit current DC component leads to inaccurate judgment of the circuit breaker's short-circuit current withstand capability.

[0214] 2) The device for determining the short-circuit current withstand capability of the circuit breaker described in this application includes a processing unit, a first determining unit, a second determining unit, a third determining unit, and a fourth determining unit. The processing unit performs equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each equivalent branch as variables, it determines the relative time variation of the DC component of the short-circuit current under different impedance parameters, resulting in multiple curves. The boundaries of these curves constitute a multi-dimensional fault space, and each equivalent branch is a Thevenin equivalent circuit corresponding to that branch. The first determining unit determines the node impedance matrix of the power grid based on the node admittance matrix, and determines the node self-impedance based on the node impedance matrix. The second determining unit... The unit is used to perform frequency correction on the above-mentioned node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and to determine the correspondence between the equivalent node self-impedance and the equivalent frequency based on the above-mentioned equivalent node admittance matrix, thereby obtaining a first relationship; the third determining unit is used to determine the correspondence between the above-mentioned short-circuit current DC component and the above-mentioned equivalent frequency based on the above-mentioned node self-impedance and the above-mentioned first relationship, thereby obtaining a second relationship, and to determine a target relationship based on the above-mentioned second relationship and the above-mentioned fault space, wherein the target relationship is the relationship between the above-mentioned short-circuit current DC component and the above-mentioned time; the fourth determining unit is used to determine a target attenuation time constant based on the above-mentioned target relationship, and to determine whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the above-mentioned target attenuation time constant is greater than a predetermined value. The device first determines the fault space, then determines the correspondence between the DC component of the short-circuit current and the equivalent frequency, i.e., the second relationship. Based on the second relationship and the fault space, it determines the relationship between the DC component of the short-circuit current and the aforementioned time, i.e. the target relationship. The device calculates the DC component of the short-circuit current with high accuracy, thus obtaining a high-accuracy target decay time constant. This solves the problem in the prior art where the calculation accuracy of the DC component of the short-circuit current is low, leading to inaccurate judgment of the circuit breaker's ability to withstand short-circuit current.

[0215] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for determining the short-circuit current withstand capability of a circuit breaker, characterized in that, include: The power grid is processed by equivalent processing of each branch before the fault point to obtain multiple equivalent branches. The impedance parameters of each equivalent branch are used as variables to determine the change of the DC component of the short-circuit current relative to time under different impedance parameters, resulting in multiple curves. The boundaries of the multiple curves constitute a multidimensional fault space. The equivalent branch is the Thevenin equivalent circuit corresponding to the branch. Based on the node admittance matrix of the power grid, determine the node impedance matrix of the power grid, and based on the node impedance matrix, determine the node self-impedance; The node admittance matrix is ​​frequency corrected to obtain the equivalent node admittance matrix at the equivalent frequency. Based on the equivalent node admittance matrix, the correspondence between the equivalent node self-impedance and the equivalent frequency is determined to obtain the first relationship. Based on the node self-impedance and the first relationship, the correspondence between the DC component of the short-circuit current and the equivalent frequency is determined to obtain the second relationship. Based on the second relationship and the fault space, a target relationship is determined, wherein the target relationship is the relationship between the DC component of the short-circuit current and the time. Based on the target relationship, a target attenuation time constant is determined, and based on whether the target attenuation time constant is greater than a predetermined value, it is determined whether the circuit breaker's ability to withstand short-circuit current is insufficient. The predetermined value is the standard time constant for the attenuation of the short-circuit current of the circuit breaker. Determining the target relationship based on the second relationship and the fault space includes: processing the fault space using a pattern search algorithm to determine the DC component of the short-circuit current corresponding to the point with the highest data density in the fault space as the first DC component of the short-circuit current; substituting the first DC component of the short-circuit current into the second relationship to obtain a fourth relationship, the fourth relationship being the correspondence between the optimal frequency of the power grid and the time, the optimal frequency being the equivalent frequency corresponding to the first DC component of the short-circuit current; and determining the target relationship based on the fourth relationship.

2. The method according to claim 1, characterized in that, The node admittance matrix is ​​frequency corrected to obtain the equivalent node admittance matrix at the equivalent frequency. Based on the equivalent node admittance matrix, the correspondence between the equivalent node self-impedance and the equivalent frequency is determined to obtain a first relationship, including: The nodal admittance matrix is ​​corrected using the equivalent frequency method to obtain the equivalent nodal admittance matrix; Based on the equivalent node admittance matrix, determine the equivalent node impedance matrix; The first relationship is determined based on the equivalent node impedance matrix.

3. The method according to claim 1, characterized in that, Based on the node self-impedance and the first relationship, the correspondence between the DC component of the short-circuit current and the equivalent frequency is determined, resulting in a second relationship, including: Based on the first relationship, the correspondence between the decay time constant and the equivalent frequency is calculated, thus obtaining the third relationship; The second relationship is determined based on the node self-impedance and the third relationship.

4. The method according to claim 1, characterized in that, Determining the target relation based on the fourth relation includes: Based on the fourth relationship, the correspondence between the node admittance matrix corresponding to the optimal frequency and the time is determined, thus obtaining the fifth relationship; Based on the fifth relationship, the correspondence between the equivalent node self-impedance and the time corresponding to the optimal frequency is determined, thus obtaining the sixth relationship; Substituting the sixth relationship into the input impedance method calculation formula, the target relationship is obtained.

5. The method according to claim 1, characterized in that, The impedance parameters include resistance and reactance. Using the impedance parameters of each equivalent branch as variables, the change of the DC component of the short-circuit current relative to time under different impedance parameters is determined, resulting in multiple curves, including: Obtain the resistance and reactance of each equivalent branch, and determine the impedance based on the resistance and reactance. ,in, This represents the impedance. This indicates the resistance. Indicates the reactance, This represents the angular frequency of the power grid. Indicates the imaginary part; Using the resistance and reactance of each of the aforementioned parameters as variables, multiple curves are obtained.

6. The method according to claim 5, characterized in that, The variables satisfy predetermined conditions, wherein the ratio of the impedances of any two equivalent branches is in the range of 0.01 to 100, and the ratio of the real part to the imaginary part of the impedance is in the range of 0.01 to 3.

7. The method according to any one of claims 1 to 6, characterized in that, Determining whether the circuit breaker's short-circuit current withstand capability is insufficient based on whether the target attenuation time constant is greater than a predetermined value includes: If the target decay time constant is greater than the predetermined value, it is determined that the circuit breaker's short-circuit current withstand capability does not meet the actual requirements. If the target decay time constant is not greater than the predetermined value, the circuit breaker's ability to withstand short-circuit current is determined to meet actual requirements.

8. A device for determining the short-circuit current withstand capability of a circuit breaker, characterized in that, include: The processing unit is used to perform equivalent processing on each branch of the power grid before the fault point to obtain multiple equivalent branches. Using the impedance parameters of each equivalent branch as variables, it determines the change of the DC component of the short-circuit current relative to time under different impedance parameters, and obtains multiple curves. The boundaries of the multiple curves constitute a multi-dimensional fault space. The equivalent branch is the Thevenin equivalent circuit corresponding to the branch. The first determining unit is used to determine the node impedance matrix of the power grid based on the node admittance matrix of the power grid, and to determine the node self-impedance based on the node impedance matrix. The second determining unit is used to perform frequency correction on the node admittance matrix to obtain the equivalent node admittance matrix at the equivalent frequency, and to determine the correspondence between the equivalent node self-impedance and the equivalent frequency based on the equivalent node admittance matrix to obtain the first relationship. The third determining unit is used to determine the correspondence between the DC component of the short-circuit current and the equivalent frequency based on the node self-impedance and the first relationship, to obtain the second relationship, and to determine the target relationship based on the second relationship and the fault space, wherein the target relationship is the relationship between the DC component of the short-circuit current and the time. The fourth determining unit is used to determine the target attenuation time constant according to the target relationship, and to determine whether the circuit breaker's ability to withstand short-circuit current is insufficient based on whether the target attenuation time constant is greater than a predetermined value, wherein the predetermined value is the standard time constant for the attenuation of the short-circuit current of the circuit breaker. The third determining unit includes a third processing module, a fourth processing module, and a fourth determining module. The third processing module processes the fault space using a pattern search algorithm to determine the DC component of the short-circuit current corresponding to the point with the highest data density in the fault space as the first DC component of the short-circuit current. The fourth processing module substitutes the first DC component of the short-circuit current into the second relation to obtain a fourth relation, which is the correspondence between the optimal frequency of the power grid and the time, where the optimal frequency is the equivalent frequency corresponding to the first DC component of the short-circuit current. The fourth determining module determines the target relation based on the fourth relation.

9. An electronic device, characterized in that, include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including a method for performing a method for determining the short-circuit current withstand capability of a circuit breaker as described in any one of claims 1 to 7.

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