Method and apparatus for identifying neutral line disconnection in current secondary circuit

Abstract

A method and apparatus for identifying a neutral line disconnection in a current secondary circuit. The method comprises: calculating a first braking current change amount of a busbar in a first calculation period and a second braking current change amount thereof in a second calculation period (S101); when the first braking current change amount is greater than a preset current change amount, calculating first fault current proportions respectively corresponding to at least two branches of a first phase of the busbar corresponding to the first braking current change amount, and second fault current proportions respectively corresponding to at least two branches of a second phase of the busbar corresponding to the second braking current change amount (S102); determining at least two ratios on the basis of the at least two first fault current proportions and the at least two second fault current proportions, and when any one of the at least two ratios is greater than a first preset ratio and the other ratio(s) among the at least two ratios is / are less than a second preset ratio, determining that a neutral line disconnection in a current secondary circuit has occurred to the branch corresponding to said one of the ratios (S103).

Description

Method and apparatus for identifying a broken neutral wire in a current secondary circuit

[0001] This application claims priority to Chinese Patent Application No. 202410914103.2, filed on July 8, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of power system fault identification technology, such as a method, apparatus, electronic device, and computer-readable medium for identifying a broken neutral wire in a current secondary circuit. Background Technology

[0003] In the event of a power supply system malfunction, the fault zero-sequence current needs to flow in the zero-sequence loop formed by the neutral line circuit. Because the neutral line of the secondary current loop is broken, the fault zero-sequence current cannot flow to the neutral line circuit and can only flow to the current loops of the non-faulty phases, thus creating a differential current in the non-faulty phases. Since the non-faulty phases mainly contain system load current, which has weak restraint, the resulting differential current may cause relay protection equipment to malfunction.

[0004] To prevent abnormal operation of relay protection equipment due to the impact of a broken neutral line in the secondary current circuit on current sampling during power supply system faults, a rapid and accurate identification of the neutral line in the secondary current circuit is necessary. Related technologies for determining the neutral line in the secondary current circuit utilize the difference between external zero-sequence current and self-generated zero-sequence current, as well as significant changes in neutral line voltage or current, to identify the neutral line. Alternatively, current criteria can be formed based on the changing characteristics of neutral line current, system-side neutral point grounding current, and third harmonic current on the line. Then, a voltage adaptation coefficient is introduced to improve the traditional neutral line offset voltage protection criteria, forming a voltage criterion. Finally, the current and voltage criteria are fused to jointly determine whether a neutral line breakage fault has occurred.

[0005] However, this application finds that the related technology requires configuring a neutral current or voltage channel for each bay for multi-bay relay protection equipment. With a fixed number of simulated channels, this reduces the number of connected bays, and when the current loop load imbalance is high, there are cases of misjudgment or missed judgment. Summary of the Invention

[0006] This application provides a method for identifying a broken neutral wire in a current secondary circuit.

[0007] The method may include: calculating the change in first braking current during a first calculation period of the busbar and the change in second braking current during a second calculation period; wherein the second calculation period is the next calculation period adjacent to the first calculation period; if the change in first braking current is greater than a preset change in current, calculating the proportion of first fault current corresponding to at least two branches of the first phase of the busbar corresponding to the change in first braking current, and calculating the proportion of second fault current corresponding to at least two branches of the second phase of the busbar corresponding to the change in second braking current; determining at least two ratios based on at least two first fault current ratios and at least two second fault current ratios, and if any one of the at least two ratios is greater than a first preset ratio, and the other ratios of the at least two ratios are less than a second preset ratio, determining that the neutral line of the secondary circuit of the branch corresponding to any ratio is disconnected.

[0008] According to some embodiments, calculating the change in the first braking current during a first calculation period and the change in the second braking current during a second calculation period may include: obtaining first current sampling values ​​corresponding to at least two branches corresponding to the bus during the initial calculation period, and calculating the initial bus protection braking current corresponding to the bus based on the first current sampling values; obtaining second current sampling values ​​corresponding to at least two branches corresponding to the bus during the first calculation period, and calculating the first bus protection braking current corresponding to the bus based on the second current sampling values; obtaining third current sampling values ​​corresponding to at least two branches corresponding to the bus during the second calculation period, and calculating the second bus protection braking current corresponding to the bus based on the third current sampling values; calculating the change in the first braking current based on the initial bus protection braking current and the first bus protection braking current; and calculating the change in the second braking current based on the first bus protection braking current and the second bus protection braking current.

[0009] According to some embodiments, the calculation formulas for the initial bus protection braking current, the first bus protection braking current, and the second bus protection braking current are as follows:

[0010] in, The current sampling value is n = 1, 2, 3...m, where n is the branch number, m is a positive integer, phi represents the phase, and r is the bus.

[0011] According to some embodiments, the formulas for calculating the change in the first braking current and the change in the second braking current are: ΔI r_phi_t =|I r_phi_t -I r_phi_(t-T) |

[0012] Among them, I r_phi_tFor the bus protection braking current in the current calculation period t, -I r_phi_(t-T) This is the bus protection braking current for the next calculation period T after the current calculation period t.

[0013] According to some embodiments, determining at least two ratios based on at least two first fault current ratios and at least two second fault current ratios may include: performing ratio processing on at least two first fault current ratios and at least two second fault current ratios based on the principle of performing ratio processing on the fault current ratios of branches with corresponding relationships, so as to obtain at least two ratios.

[0014] According to some embodiments, calculating the first fault current percentage corresponding to at least two branches of the first phase of the busbar, respectively, and calculating the second fault current percentage corresponding to at least two branches of the second phase of the busbar, respectively, can include: calculating the first current change corresponding to at least two branches of the first phase, calculating the second current change corresponding to at least two branches of the second phase; calculating the first fault current percentage based on the first current change corresponding to at least two branches, and calculating the second fault current percentage based on the second current change corresponding to at least two branches.

[0015] According to some embodiments, the formulas for calculating the first current change and the second current change are as follows:

[0016] in, Let be the current sample value of the branch corresponding to time t, and n be the branch number. The current sample value of the branch corresponding to time tT is the calculation period;

[0017] The formulas for calculating the proportion of the first fault current and the proportion of the second fault current are:

[0018] Where phi represents the phase, n is the branch number, T is the calculation period, and ΔI r_phi_t This represents the change in braking current.

[0019] This application provides a device for identifying a broken neutral wire in a current secondary circuit. The device may include: a braking current change calculation module, a fault current proportion calculation module, and a neutral wire breakage determination module, wherein...

[0020] The braking current change calculation module is configured to calculate the first braking current change in the first calculation cycle and the second braking current change in the second calculation cycle of the bus; wherein the second calculation cycle is the next calculation cycle adjacent to the first calculation cycle.

[0021] The fault current percentage calculation module is configured to calculate the first fault current percentage corresponding to at least two branches of the first phase of the busbar, respectively, when the first braking current change is greater than the preset current change, and to calculate the second fault current percentage corresponding to at least two branches of the second phase of the busbar, respectively, when the first braking current change is greater than the preset current change.

[0022] The neutral line disconnection determination module is configured to determine at least two ratios based on at least two first fault current ratios and at least two second fault current ratios, and to determine that the neutral line of the secondary circuit of the branch circuit corresponding to any ratio is disconnected if any ratio is greater than a first preset ratio and the other ratios of the at least two ratios are less than a second preset ratio.

[0023] According to some embodiments, the braking current change calculation module is configured to: obtain first current sampling values ​​corresponding to at least two branches corresponding to each busbar within an initial calculation period, and calculate the initial busbar protection braking current corresponding to each busbar based on the first current sampling values; obtain second current sampling values ​​corresponding to at least two branches corresponding to each busbar within the first calculation period, and calculate the first busbar protection braking current corresponding to each busbar based on the second current sampling values; obtain third current sampling values ​​corresponding to at least two branches corresponding to each busbar within a second calculation period, and calculate the second busbar protection braking current corresponding to each busbar based on the third current sampling values; calculate the first braking current change based on the initial busbar protection braking current and the first busbar protection braking current, and calculate the second braking current change based on the first busbar protection braking current and the second busbar protection braking current.

[0024] According to some embodiments, the calculation formulas for the initial bus protection braking current, the first bus protection braking current, and the second bus protection braking current are as follows:

[0025] in, The current sampling value is n = 1, 2, 3...m, which represents the branch number, m is a positive integer, phi represents the phase, and r is the bus.

[0026] According to some embodiments, the formulas for calculating the change in the first braking current and the change in the second braking current are: ΔI r_phi_t =|I r_phi_t -I r_phi_(t-T) |

[0027] Among them, I r_phi_t For the bus protection braking current in the current calculation period t, -I r_phi_(t-T) This is the bus protection braking current for the next calculation period T after the current calculation period t.

[0028] According to some embodiments, the neutral line disconnection determination module is configured to: perform ratio processing based on the fault current ratio of branches with corresponding relationships, and perform ratio processing on at least two first fault current ratios and at least two second fault current ratios to obtain at least two ratios.

[0029] According to some embodiments, the fault current percentage calculation module is configured to: calculate the first current change corresponding to at least two branches of the first phase, and calculate the second current change corresponding to at least two branches of the second phase; calculate the first fault current percentage based on the first current change corresponding to at least two branches, and calculate the second fault current percentage based on the second current change corresponding to at least two branches.

[0030] According to some embodiments, the formulas for calculating the first current change and the second current change are as follows:

[0031] in, Let be the current sample value of the branch at time t, and n be the branch. tT represents the sampled current value of the branch corresponding to the phase at time tT, where T is the calculation period;

[0032] The formulas for calculating the proportion of the first fault current and the proportion of the second fault current are:

[0033] Where phi represents the phase, n is the branch, t is the calculation period, and ΔI is the value of ΔI. r_phi_t This represents the change in braking current.

[0034] This application provides an electronic device that may include: a processor; and a memory storing a computer program, which, when executed by the processor, causes the processor to perform the above-described method.

[0035] This application provides a computer-readable medium, which adopts the following technical solution:

[0036] A computer-readable medium having a computer program stored thereon, which, when executed by a computer program processor, causes the processor to perform the above-described method.

[0037] According to the above embodiments provided in this application, a preset current change amount is set. When the first braking current change amount calculated in the first calculation cycle is greater than the preset current change amount, the first fault current ratio of each branch connected to the first phase corresponding to the first braking current change amount is calculated. In the second calculation cycle, the second fault current ratio of each branch connected to the second phase corresponding to the second braking current change amount is calculated. The first fault current ratio and the second fault current ratio are compared to obtain at least two ratios. Subsequently, when any ratio is greater than the first preset ratio and other ratios are less than the second preset ratio, it can be determined that the neutral line of the secondary circuit of the branch corresponding to any ratio is broken. This completes the breakage identification and reduces the probability of false positives or false negatives. Attached Figure Description

[0038] Figure 1 is a block diagram of the neutral wire disconnection identification method for current secondary circuits provided in the embodiments of this application;

[0039] Figure 2 is a schematic diagram of a single busbar connection provided in an embodiment of this application;

[0040] Figure 3 is a flowchart illustrating the neutral wire disconnection identification method for the current secondary circuit provided in this application embodiment;

[0041] Figure 4 is a block diagram of the neutral wire disconnection identification device for the current secondary circuit provided in the embodiment of this application;

[0042] Figure 5 is a schematic diagram of the device provided in an embodiment of this application.

[0043] Explanation of reference numerals in the attached figures: 40: Neutral line breakage identification device in the secondary current circuit; 401: Braking current change calculation module; 402: Fault current proportion calculation module; 403: Neutral line breakage judgment module; 50: Device; 501: Processor; 502: Bus; 503: Memory; 504: Transceiver. Detailed Implementation

[0044] The present application will be further described in detail below with reference to Figures 1-5.

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] In some embodiments, the neutral current loop is an important component of the current loop, providing a path for the current and forming a complete closed loop. Relay protection devices sample the current through the secondary current loop.

[0047] This application provides a method for identifying a broken neutral wire in a current secondary circuit, which can be executed by a device. This device can be an electronic device, a server, or a terminal device. The server can be a standalone physical server, a server cluster consisting of multiple physical servers, a distributed device, or a cloud server providing cloud computing services. The terminal device can be a computer, but is not limited to these. The terminal device and the server can be directly or indirectly connected via wired or wireless communication, and this application does not impose any limitations on this.

[0048] In some embodiments, the current secondary circuit neutral line breakage identification method provided in this application can be applied to the current secondary circuit neutral line breakage identification of three-phase circuits, and can also be applied to the current secondary circuit neutral line breakage identification of two-phase circuits. This application takes a three-phase circuit as an example for specific illustration.

[0049] Referring to Figure 1, a method for identifying a broken neutral wire in a current secondary circuit includes steps S101, S102, and S103, wherein...

[0050] S101, calculate the first braking current change in the first calculation cycle and the second braking current change in the second calculation cycle of the bus.

[0051] In some embodiments, the second calculation period is the next calculation period adjacent to the first calculation period; the first calculation period and the second calculation period are equal, and the setting of the first calculation period and the second calculation period can be based on the AC frequency. For example, the domestic AC frequency is 50 Hz, and the converted calculation period is 20 ms; the foreign AC frequency is 60 Hz, and the converted calculation period is 16.7 ms; the first braking current change and the second braking current change are the braking current changes of each phase of the bus.

[0052] In some embodiments, the busbar is a three-phase circuit, including phase A, phase B, and phase C; and each phase is connected to at least two branches, and the number of branches connected to each phase is equal and there is a one-to-one correspondence. For example, referring to Figure 2, phases A, B, and C are all connected to branch 1, branch 2, and branch 3. The current sampling device collects the current of each branch in real time, and the electronic device obtains the current sampling value of each branch from the current sampling device. The electronic device collects the current of each branch based on a calculation cycle, that is, it collects the current of each branch in the current calculation cycle at the end of each calculation cycle. The electronic device calculates the corresponding first braking current change based on the current sampling value of each branch collected in the first calculation cycle, and calculates the corresponding second braking current change based on the current sampling value of each branch collected in the second calculation cycle.

[0053] S102, when the change in the first braking current is greater than the preset change in current, calculate the proportion of the first fault current corresponding to at least two branches of the first phase of the busbar, which corresponds to the change in the first braking current, and calculate the proportion of the second fault current corresponding to at least two branches of the second phase of the busbar, which corresponds to the change in the second braking current.

[0054] In some embodiments, the preset current change can be subjectively set by a technician based on experience, wherein the preset current change can be set to 0.3In to 0.5In (In is the secondary rated value of the current transformer, 1A or 5A); the specific setting value of the preset current change is not specifically limited in this application embodiment. The first fault current ratio is the ratio of the current change of each branch in the first calculation period to the braking current change of its corresponding single phase; the second fault current ratio is the ratio of the current change of each branch in the second calculation period to the braking current change of its corresponding single phase.

[0055] In some embodiments, the electronic device compares the first braking current change calculated in each corresponding phase during the first calculation cycle with a preset current change to determine whether the first braking current change is greater than the preset current change. If the first braking current change in the first phase is greater than the preset current change, it indicates that at least one of the at least two branches connected to the first phase corresponding to the first braking current change has experienced a first-phase ground fault, and the other branches connected to it are supplying fault current to the grounding point. Subsequently, the electronic device calculates the current change corresponding to the at least two branches connected to the first phase during the first calculation cycle, and calculates the proportion of the first fault current corresponding to each branch based on the current change.

[0056] In some embodiments, when a first-phase ground fault occurs in a branch, the first-phase fault current can only form a fault current loop through the current loops of other phases, thus causing current faults in other phases as well. When fault currents occur in other phases, the change in braking current of those other phases will also change. Therefore, the electronic device can compare the second braking current change corresponding to the second phase calculated in the second calculation cycle with a preset current change to determine whether the second braking current change is greater than the preset current change. If the second braking current change of the second phase is greater than the preset current change, the electronic device calculates the current changes corresponding to at least two branches connected to the second phase within the second calculation cycle; and calculates the proportion of the second fault current corresponding to each branch based on these current changes; wherein, the second phase refers to all phases in the busbar other than the first phase.

[0057] S103, determine at least two ratios based on at least two first fault current ratios and at least two second fault current ratios, and if any one of the at least two ratios is greater than a first preset ratio, and the other ratios among the at least two ratios are less than a second preset ratio, determine that the neutral line of the secondary circuit of the branch generating circuit corresponding to any ratio is broken.

[0058] In some embodiments, the electronic device performs ratio processing on at least two calculated first fault current ratios and at least two second fault current ratios based on a preset ratio processing principle to obtain at least two ratios; wherein, the preset ratio processing principle is a principle based on the ratio processing of fault currents between branches that have a corresponding relationship.

[0059] Subsequently, the electronic device compares at least two ratios with a first preset ratio to determine if any of the at least two ratios is greater than the first preset ratio. If any of the at least two ratios is greater than the first preset ratio, the other ratios are compared with a second preset ratio to determine if the other ratio is less than the second preset ratio. If the other ratio is less than the second preset ratio, the neutral line of the secondary circuit of the branch circuit corresponding to that ratio is determined to be broken. This allows for the identification of a broken neutral line in the secondary circuit without the need for auxiliary judgment using neutral line current or voltage, and without being affected by unbalanced current circuit loads, thus reducing the probability of false positives or false negatives.

[0060] In some embodiments, at least two ratios are compared with a third preset ratio and a fourth preset ratio, respectively. If at least two ratios are greater than the third preset ratio and less than the fourth preset ratio, it is determined that no neutral line breakage has occurred in the secondary circuit of the branch corresponding to the at least two ratios.

[0061] In some embodiments, the first preset ratio, the second preset ratio, the third preset ratio, and the fourth preset ratio can be set subjectively by a technician based on experience. For example, the first preset ratio is greater than 1.6; the second preset ratio is less than 0.5; the third preset ratio is greater than 0.5 and less than 0.9; and the fourth preset ratio is greater than 1.2 and less than 1.6. The specific values ​​are not specifically limited in the embodiments.

[0062] In step S101, calculating the change in the first braking current during the first calculation period and the change in the second braking current during the second calculation period includes: obtaining the first current sampling values ​​corresponding to at least two branches of the busbar within the initial calculation period, and calculating the initial busbar protection braking current corresponding to the busbar based on the first current sampling values; obtaining the second current sampling values ​​corresponding to at least two branches of the busbar within the first calculation period, and calculating the first busbar protection braking current corresponding to the busbar based on the second current sampling values; obtaining the third current sampling values ​​corresponding to at least two branches of the busbar within the second calculation period, and calculating the second busbar protection braking current corresponding to the busbar based on the third current sampling values; calculating the change in the first braking current based on the initial busbar protection braking current and the first busbar protection braking current, and calculating the change in the second braking current based on the first busbar protection braking current and the second busbar protection braking current.

[0063] In some embodiments, at the end of the initial calculation cycle, the electronic device collects the first current sampling values ​​corresponding to at least two branches of the bus, and accumulates the first current sampling values ​​corresponding to at least two branches of the same phase to obtain the bus protection braking current corresponding to each of the initial calculation cycles.

[0064] At the end of the first calculation cycle, the electronic equipment collects the second current sampling values ​​corresponding to at least two branches of the busbar, and accumulates the second current sampling values ​​corresponding to at least two branches of the same phase to obtain the first busbar protection braking current corresponding to each of the first calculation cycles.

[0065] Subsequently, the electronic equipment subtracts the first bus protection braking current from the initial bus protection braking current and calculates the absolute value to obtain the corresponding change in the first braking current of each bus.

[0066] At the end of the second calculation cycle, the electronic equipment collects the third current sampling values ​​corresponding to at least two branches of each busbar, and accumulates the third current sampling values ​​corresponding to at least two branches of the same phase to obtain the corresponding second busbar protection braking current.

[0067] Subsequently, the electronic equipment subtracts the second bus protection braking current from the first bus protection braking current and calculates the absolute value to obtain the corresponding change in the second braking current of each bus.

[0068] In some embodiments, the calculation formulas for the initial bus protection braking current, the first bus protection braking current, and the second bus protection braking current are as follows:

[0069] in, The current sampling value is n = 1, 2, 3...m, where n is the branch number, m is a positive integer, phi represents the phase, and r is the bus.

[0070] In some embodiments, the formulas for calculating the change in the first braking current and the change in the second braking current are: ΔI r_phi_t =|I r_phi_t -I r_phi_(t-T) |

[0071] Among them, I r_phi_t For the bus protection braking current in the current calculation period t, -I r_phi_(t-T) This is the bus protection braking current for the next calculation period T after the current calculation period t.

[0072] In step S102, the calculation of the first fault current percentage corresponding to at least two branches of the first phase of the busbar, corresponding to the first braking current change, and the calculation of the second fault current percentage corresponding to at least two branches of the second phase of the busbar, corresponding to the second braking current change, includes: calculating the first current change corresponding to at least two branches of the first phase, and calculating the second current change corresponding to at least two branches of the second phase; calculating the first fault current percentage based on the first current change corresponding to at least two branches, and calculating the second fault current percentage based on the second current change corresponding to at least two branches.

[0073] In some embodiments, the electronic device performs subtraction and absolute value calculation on the first current sampling values ​​of at least two branches of each phase of the bus collected at the end of the initial calculation cycle and the second current sampling values ​​of at least two branches of each phase of the bus collected at the end of the first calculation cycle. The subtraction and absolute value calculation are performed based on the principle of subtracting and calculating the absolute value between current sampling values ​​of corresponding branches to obtain the first current change corresponding to at least two branches of each phase of the bus. This includes the first current change corresponding to at least two branches of the first phase. Subsequently, the electronic device compares the first current change corresponding to at least two branches of each phase with the first braking current change of its corresponding phase to obtain the first fault current percentage corresponding to at least two branches.

[0074] The electronic equipment performs subtraction and absolute value calculation on the second current sampling values ​​of at least two branches of each phase of the busbar collected at the end of the first calculation cycle and the third current sampling values ​​of at least two branches of each phase of the busbar collected at the end of the second calculation cycle. The subtraction and absolute value calculation are based on the principle of subtracting and calculating the absolute value between current sampling values ​​of branches with corresponding relationships, to obtain the second current change corresponding to at least two branches of each phase of the busbar. This includes the second current change corresponding to at least two branches of the second phase. Subsequently, the electronic equipment compares the first current change corresponding to at least two branches of each phase with the second braking current change of its corresponding phase to obtain the second fault current percentage corresponding to at least two branches.

[0075] In some embodiments, the formulas for calculating the first current change and the second current change are as follows:

[0076] in, Let be the current sample value of the branch corresponding to time t, and n be the branch number. tT represents the current sampling value of the branch at time tT, where T is the calculation period.

[0077] The formulas for calculating the proportion of the first fault current and the proportion of the second fault current are:

[0078] Where phi represents the phase, n is the branch number, t is the calculation period, and ΔI n_phi_t Let ΔI be the change in branch current at time t. r_phi_t Let t be the change in braking current of the branch at time t.

[0079] In some embodiments, referring to FIG2, the busbar is a three-phase circuit, including phase A, phase B, and phase C, and each phase is connected to branch 1, branch 2, and branch 3; the current acquisition device acquires the current of the three branches connected to each phase of the busbar in real time during each calculation cycle, and the electronic device obtains the current sampling value of the three branches connected to each phase from the current acquisition device. Where n = 1, 2, 3…m represents the branch number, m is a positive integer, i = A, B, C, and phi represents the phase; subsequently, the protective braking current I of each phase in the busbar is calculated. r_phi and the change in braking current ΔI r_phi_t The calculation formula is:

[0080] Among them, I r_phi_t For the bus protection braking current in the current calculation period t, -I r_phi_(t-T)This is the bus protection braking current for the next calculation period T after the current calculation period t.

[0081] Taking a phase-A ground fault in branch 3 as an example, when a phase-A ground fault occurs in branch 3, branch 1 and branch 2 provide fault current to the grounding point, and the change in the braking current of phase A is ΔI. r_A_t If the current change exceeds the preset amount, the electronic device calculates the current change ΔI corresponding to the three branches of phase A at the current time T1, which is the first timing cycle. n_A_T1 and the proportion of fault current K n_A_T1 The calculation formula is:

[0082] in This represents the sampled value of phase A current in branch at time T1. The value of the A-phase current of the branch at time T1-T is the sampled value, where T is the calculation period.

[0083] Since no neutral line break occurred in the secondary current circuit of branch 1 and branch 2, the fault current of phase A can only form a fault current circuit through the current circuits of phases B and C, resulting in fault currents in phases B and C respectively, and causing the change in the protective braking current ΔI of phases B and C. r_B_t and ΔI r_C_t The situation changes, and at this point, the electronic equipment can calculate the protective braking current ΔI for phases B and C. r_B_t and ΔI r_C_t The braking current change ΔI in phases B and C is compared with the preset current change. r_B_t and ΔI r_C_t If the current change exceeds the preset value, calculate the current change ΔI corresponding to the three branches of phase B at the current time T2, i.e., the second calculation cycle. n_B_T2 and the proportion of fault current K n_B_T2 The change in current ΔI in phase C n_C_T2 and the proportion of fault current K n_C_T2 The calculation formula is:

[0084] The proportion of phase B fault current calculated in the second calculation cycle of each branch, K n_B_T2 and the proportion of C-phase fault current K n_C_T2 The proportion K of phase A fault current calculated in the first calculation cycle of each branch n_A_T1 Compare them.

[0085] For branch 1 and branch 2, the B-phase and C-phase currents in the first calculation cycle are both load currents, and K can be considered as the load current for branch 1 and branch 2. 1_B_T2 K 1_C_T2 K 2_B_T2 K 2_C_T2 Close to 0.

[0086] For branch 3, during the second calculation cycle, the current changes in phases B and C are approximately equal to the braking current changes in phases B and C, i.e., K 3_B_T2 and K 3_C_T2 Approximately equal to 1, the proportion of the fault current in phase A of branch 3 calculated in the first calculation cycle is approximately equal to 0.5, and branch 3 satisfies... And branch 1 and branch 2 satisfy Therefore, it can be determined that the neutral wire of the secondary circuit of branch 3 is broken.

[0087] In some embodiments, referring to FIG3, the current sampling value I of the branch connected to the busbar is... d_phi The amount of braking current change ΔI of the phase that is greater than the differential starting current setting or the busbar is greater than the differential starting current setting. r_phi The starting current is greater than the braking current change setting, i.e., the preset current change, and (K m_phx / K m_phi )>K3 and (K m_phx / K m_phi If K < K4, it is determined that a break in the secondary current circuit of the branch is present; where K m_phx K represents the proportion of fault current. m_phi This represents the change in braking current.

[0088] This application provides a device for identifying a broken neutral wire in a current secondary circuit, which adopts the following technical solution;

[0089] Referring to Figure 4, a neutral wire disconnection identification device 40 for a current secondary circuit includes: a braking current change calculation module 401, a fault current proportion calculation module 402, and a neutral wire disconnection determination module 403.

[0090] The braking current change calculation module 401 is configured to calculate the first braking current change in the first calculation cycle and the second braking current change in the second calculation cycle of the bus; wherein the second calculation cycle is the next calculation cycle adjacent to the first calculation cycle.

[0091] The fault current percentage calculation module 402 is configured to calculate the first fault current percentage corresponding to at least two branches of the first phase of the busbar, respectively, when the first braking current change is greater than the preset current change, and to calculate the second fault current percentage corresponding to at least two branches of the second phase of the busbar, respectively, when the first braking current change is greater than the preset current change.

[0092] The neutral line disconnection determination module 403 is configured to determine at least two ratios based on at least two first fault current ratios and at least two second fault current ratios, and to determine that the neutral line of the secondary circuit of the branch generating circuit corresponding to any ratio is disconnected if any ratio is greater than a first preset ratio and the other ratios of the at least two ratios are less than a second preset ratio.

[0093] In some embodiments, the braking current change calculation module 401 is configured to: obtain first current sampling values ​​corresponding to at least two branches corresponding to each busbar within an initial calculation period, and calculate the initial busbar protection braking current corresponding to each busbar based on the first current sampling values; obtain second current sampling values ​​corresponding to at least two branches corresponding to each busbar within a first calculation period, and calculate the first busbar protection braking current corresponding to each busbar based on the second current sampling values; obtain third current sampling values ​​corresponding to at least two branches corresponding to each busbar within a second calculation period, and calculate the second busbar protection braking current corresponding to each busbar based on the third current sampling values; calculate the first braking current change based on the initial busbar protection braking current and the first busbar protection braking current, and calculate the second braking current change based on the first busbar protection braking current and the second busbar protection braking current.

[0094] In some embodiments, the calculation formulas for the initial bus protection braking current, the first bus protection braking current, and the second bus protection braking current are as follows:

[0095] in, The current sampling value is n = 1, 2, 3...m, which represents the branch number, m is a positive integer, phi represents the phase, and r is the bus.

[0096] According to some embodiments, the formulas for calculating the change in the first braking current and the change in the second braking current are: ΔI r_phi_t =|I r_phi_t -I r_phi_(t-T) |

[0097] Among them, I r_phi_t For the bus protection braking current in the current calculation period t, -I r_phi_(t-T) This is the bus protection braking current for the next calculation period T after the current calculation period t.

[0098] In some embodiments, the neutral line disconnection determination module 403 is configured to: perform ratio processing on at least two first fault current ratios and at least two second fault current ratios based on the principle of ratio processing of fault current ratios of branches with corresponding relationships, so as to obtain at least two ratios.

[0099] In some embodiments, the fault current percentage calculation module 402 is configured to: calculate the first current change corresponding to at least two branches of the first phase, and calculate the second current change corresponding to at least two branches of the second phase; calculate the first fault current percentage based on the first current change corresponding to at least two branches, and calculate the second fault current percentage based on the second current change corresponding to at least two branches.

[0100] In some embodiments, the formulas for calculating the first current change and the second current change are as follows:

[0101] in, Let be the current sample value of the branch at time t, and n be the branch. tT represents the sampled current value of the branch corresponding to the phase at time tT, where T is the calculation period;

[0102] The formulas for calculating the proportion of the first fault current and the proportion of the second fault current are:

[0103] Where phi represents the phase, n is the branch, t is the calculation period, and ΔI is the value of ΔI. r_phi_t This represents the change in braking current.

[0104] In some embodiments, the braking current change calculation module 401 may include logic circuits or be implemented by a central processing unit, digital signal processor or field programmable gate array included in an electronic device.

[0105] The fault current percentage calculation module 402 may include logic circuits or be implemented by a central processing unit, digital signal processor or field programmable gate array contained in electronic devices.

[0106] The neutral line disconnection detection module 403 may include logic circuits or be implemented by a central processing unit, digital signal processor or field programmable gate array contained in electronic devices.

[0107] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0108] This application discloses an electronic device, which includes: a processor; and a memory storing a computer program. When the computer program is executed by the processor, the processor performs the above-described method for identifying a broken neutral wire in a secondary current circuit.

[0109] For example, referring to FIG5, the device 50 shown in FIG5 includes a processor 501 and a memory 503. The processor 501 and the memory 503 are connected, for example, via a bus 502. Optionally, the device 50 may also include a transceiver 504. It should be noted that in practical applications, the transceiver 504 is not limited to one, and the structure of the device 50 does not constitute a limitation on the embodiments of this application.

[0110] Processor 501 may be a CPU (Central Processing Unit), a general-purpose processor, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in this application. Processor 501 may also be a combination that implements computational functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0111] Bus 502 may include a pathway for transmitting information between the aforementioned components. Bus 502 may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. Bus 502 may be divided into address bus, data bus, control bus, etc. For ease of illustration, only one thick line is used to represent it in Figure 5, but this does not indicate that there is only one bus or one type of bus.

[0112] The memory 503 may be a ROM (Read Only Memory) or other type of static storage device capable of storing static information and instructions, RAM (Random Access Memory) or other type of dynamic storage device capable of storing information and instructions, or an EEPROM (Electrically Erasable Programmable Read Only Memory), CD-ROM (Compact Disc Read Only Memory) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto.

[0113] The memory 503 is used to store application code that executes the solution of this application, and its execution is controlled by the processor 501. The processor 501 is used to execute the application code stored in the memory 503 to implement the content shown in the foregoing method embodiments.

[0114] The device shown in Figure 5 is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0115] This application discloses a computer-readable medium storing a computer program. When the computer program is executed by a processor, the processor performs the above-described method for identifying a broken neutral wire in a current secondary circuit.

[0116] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0117] The above are only some embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for identifying a broken neutral wire in a current secondary circuit, comprising: The first braking current change in the first calculation cycle and the second braking current change in the second calculation cycle of the busbar are calculated; wherein the second calculation cycle is the next calculation cycle adjacent to the first calculation cycle. When the change in the first braking current is greater than the preset change in current, calculate the proportion of the first fault current corresponding to at least two branches of the first phase of the busbar, which corresponds to the change in the first braking current, and calculate the proportion of the second fault current corresponding to at least two branches of the second phase of the busbar, which corresponds to the change in the second braking current. At least two ratios are determined based on at least two first fault current ratios and at least two second fault current ratios. If any one of the at least two ratios is greater than a first preset ratio, and the other ratios of the at least two ratios are less than a second preset ratio, it is determined that the neutral line of the secondary circuit of the branch generating circuit corresponding to any one ratio is broken.

2. The method according to claim 1, wherein, The first braking current change in the first calculation cycle and the second braking current change in the second calculation cycle of the busbar include: Obtain the first current sampling values ​​corresponding to at least two branches of the busbar within the initial calculation period, and calculate the initial busbar protection braking current corresponding to the busbar based on the first current sampling values. Obtain the second current sampling values ​​corresponding to at least two branches of each busbar within the first calculation cycle, and calculate the first busbar protection braking current corresponding to each busbar based on the second current sampling values. Obtain the third current sampling values ​​corresponding to at least two branches corresponding to each of the busbars within the second calculation period, and calculate the second busbar protection braking current corresponding to each of the busbars based on the third current sampling values. Based on the initial bus protection braking current and the first bus protection braking current, calculate the change in the first braking current; The change in the second braking current is calculated based on the first bus protection braking current and the second bus protection braking current.

3. The method according to claim 2, wherein, The calculation formulas for the initial bus protection braking current, the first bus protection braking current, and the second bus protection braking current are as follows: in, The current sampling value is n = 1, 2, 3...m, where n is the branch number, m is a positive integer, phi represents the phase, and r is the bus.

4. The method according to claim 2, wherein, The formulas for calculating the first and second braking current changes are: ΔI r_phi_t =|I r_phi_t -I r_phi_(t-T) | Among them, I r_phi_t I is the bus protection braking current for the current calculation period t. r_phi_(t-T) This is the bus protection braking current for the next calculation period T after the current calculation period t.

5. The method according to claim 1, wherein, The determination of at least two ratios based on at least two first fault current ratios and at least two second fault current ratios includes: Based on the principle of ratio processing of the fault current ratio of branches with corresponding relationships, the ratio of the at least two first fault current ratios and the at least two second fault current ratios are processed to obtain the at least two ratios.

6. The method according to any one of claims 1-5, wherein, The calculation of the first fault current percentage corresponding to at least two branches of the first phase of the busbar, corresponding to the first braking current change, and the calculation of the second fault current percentage corresponding to at least two branches of the second phase of the busbar, corresponding to the second braking current change, includes: Calculate the first current change corresponding to at least two branches of the first phase; Calculate the second current change corresponding to at least two branches of the second phase; The proportion of the first fault current is calculated based on the first current change corresponding to at least two branches respectively. The proportion of the second fault current is calculated based on the second current change corresponding to at least two branches.

7. The method according to claim 6, wherein, The formulas for calculating the first current change and the second current change are as follows: in, Let be the current sample value of the branch corresponding to time t, and n be the branch number. The current sample value of the branch corresponding to time tT is the calculation period; The formulas for calculating the proportion of the first fault current and the proportion of the second fault current are as follows: Where phi represents the phase, n is the branch number, t is the calculation period, and ΔI r_phi_t This represents the change in braking current.

8. A device for identifying a broken neutral wire in a current secondary circuit, comprising: The braking current change calculation module is configured to calculate the first braking current change in the first calculation cycle and the second braking current change in the second calculation cycle of the bus; wherein the second calculation cycle is the next calculation cycle adjacent to the first calculation cycle. The fault current percentage calculation module is configured to calculate, when the change in the first braking current is greater than the preset change in current, the first fault current percentage corresponding to at least two branches of the first phase of the busbar and corresponding to the change in the first braking current, and the second fault current percentage corresponding to at least two branches of the second phase of the busbar and corresponding to the change in the second braking current. The neutral line disconnection determination module is configured to determine at least two ratios based on at least two first fault current ratios and at least two second fault current ratios, and to determine that the neutral line of the secondary circuit of the branch generating circuit corresponding to any ratio is disconnected if any ratio is greater than a first preset ratio and the other ratios of the at least two ratios are less than a second preset ratio.

9. An electronic device, comprising: processor; A memory storing a computer program that, when executed by the processor, causes the processor to perform the method as described in any one of claims 1-7.

10. A computer-readable medium having a computer program stored thereon, which, when executed by a processor, causes the processor to perform the method of any one of claims 1-7.

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