Method and device for cross differential protection of a generator

Abstract

The application belongs to the technical field of generator protection, and particularly relates to a transverse difference protection method and a transverse difference protection device for a generator. The method comprises the following steps: obtaining branch current characteristic parameters of multiple parallel branches arranged for each phase of a generator stator; grouping the multiple parallel branches based on the branch current characteristic parameters to obtain multiple optimal groups, wherein each optimal group comprises part of the parallel branches in the multiple parallel branches; determining harmonic distortion information between the multiple optimal groups according to the branch current characteristic parameters of each part of the parallel branches in each optimal group; and performing a protection locking action in the case that the harmonic distortion information meets a harmonic locking condition, wherein the harmonic locking condition meeting indicates that there is an interference difference flow caused by excitation distortion, core saturation or rotor two-point grounding of the generator.

Description

Technical Field

[0001] This application belongs to the field of generator protection technology, and particularly relates to a differential protection method and device for a generator. Background Technology

[0002] In power systems, fault recorders are core devices for recording the operating status of the power grid and analyzing the causes of accidents. In the field of relay protection for large generator sets, internal faults such as stator winding inter-turn short circuits, parallel branch open circuits, and branch weld failures are frequent threats to the safety of the generator itself, easily leading to serious accidents such as winding burnout, core overheating, and unplanned unit shutdowns. Phase-splitting differential protection is the core main protection against in-phase inter-turn faults and branch faults in the generator stator. It effectively compensates for the technical shortcomings of longitudinal differential protection in identifying inter-turn faults and is widely used in large hydro-turbine and steam turbine generator sets with three or more branches per phase.

[0003] However, existing technologies for fault recorders in providing differential phase protection for generators suffer from issues such as maloperation and failure to operate, resulting in low overall sensitivity and operational reliability. Summary of the Invention

[0004] In view of this, the present application provides a differential protection method and a differential protection device for a generator to solve the problems of false tripping and failure to tripping in existing differential protection methods, resulting in low overall sensitivity and operational reliability.

[0005] A first aspect of this application provides a differential protection method for a generator, comprising: acquiring branch current characteristic parameters of each of the multiple parallel branches configured for each phase of the generator stator; grouping the multiple parallel branches based on the branch current characteristic parameters to obtain multiple optimal groups, wherein each optimal group includes a portion of the multiple parallel branches; determining harmonic distortion information between the multiple optimal groups according to the branch current characteristic parameters of each portion of the parallel branches in each optimal group; and performing a protection blocking action when the harmonic distortion information satisfies the harmonic blocking condition, wherein satisfying the harmonic blocking condition indicates that the generator has an interference differential current caused by excitation distortion, core saturation, or rotor two-point grounding.

[0006] According to an embodiment of this application, based on the branch current characteristic parameter, multiple parallel branches are grouped to obtain multiple optimal groups, including: enumerating the effective branches among the multiple parallel branches to obtain multiple grouping schemes, wherein the grouping scheme includes multiple initial groups, and each initial group includes a portion of the effective branches; and determining an optimal scheme from the multiple grouping schemes based on the branch current characteristic parameter, wherein the optimal scheme includes multiple optimal groups.

[0007] According to an embodiment of this application, determining the optimal scheme from multiple grouping schemes based on the branch current characteristic parameters includes: for any grouping scheme, generating an evaluation index for the grouping scheme based on the branch current characteristic parameters of each of the multiple effective branches in each initial group, wherein the evaluation index characterizes the degree of balance of the operating state of each effective branch within the same phase of the generator; and determining the optimal scheme from multiple grouping schemes based on the evaluation indexes of each grouping scheme.

[0008] According to an embodiment of this application, the branch current characteristic parameter includes the fundamental current phasor.

[0009] According to an embodiment of this application, generating an evaluation index for the grouping scheme based on the branch current characteristic parameters of each of the multiple effective branches in each initial group includes: for any initial group, determining the mean winding impedance based on the fundamental current phasor of each of the multiple effective branches in the initial group, and determining the branch equivalent impedance mean deviation of the grouping scheme based on the mean winding impedance of the multiple initial groups; determining the branch current amplitude deviation of the grouping scheme based on the fundamental current phasor of each of the multiple effective branches in each initial group; and performing a weighted summation of the branch equivalent impedance mean deviation and the branch current amplitude deviation to obtain the evaluation index of the grouping scheme.

[0010] According to an embodiment of this application, the branch current characteristic parameter includes the fundamental current phasor.

[0011] According to an embodiment of this application, determining the harmonic distortion information among multiple optimal groups based on the branch current characteristic parameters of each part of the parallel branch in each optimal group includes: determining the transverse differential current among multiple optimal groups based on the fundamental current phasor of each part of the parallel branch in each optimal group; extracting the fundamental differential current component and the harmonic differential current component from the differential current time domain waveform, wherein the differential current time domain waveform is constructed based on the transverse differential current at multiple times; and determining the harmonic distortion information based on the fundamental differential current component and the harmonic differential current component.

[0012] According to an embodiment of this application, the differential protection method further includes: determining a baseline balance threshold at the current moment based on the generator unit parameters and the unit load parameters at the current moment; generating abnormal alarm information when the fundamental differential current component meets the baseline balance threshold but does not meet the braking condition, wherein the harmonic distortion information is determined based on the fundamental differential current component.

[0013] According to an embodiment of this application, the differential protection method further includes: determining the negative-sequence active power of the generator based on the negative-sequence voltage phasor and negative-sequence current phasor of the generator; performing a protection blocking action when the negative-sequence active power is greater than a preset power threshold, wherein the negative-sequence active power being greater than the preset power threshold indicates an external fault of the generator where the negative-sequence power flows from the power grid to the generator; and performing a protection unlocking action when the negative-sequence active power is less than the preset power threshold, wherein the negative-sequence active power being less than the preset power threshold indicates an internal fault of the generator where the negative-sequence power flows from the generator to the power grid.

[0014] According to an embodiment of this application, the differential protection method further includes: determining a fundamental ratio braking condition based on the baseline balance threshold and the grouped composite current of each of the optimal groups; generating fault information when the fundamental differential current component satisfies the fundamental ratio braking condition, the harmonic distortion information does not satisfy the harmonic blocking condition, and the negative sequence active power is less than a preset power threshold, wherein the fault information indicates that the generator has a fault.

[0015] According to an embodiment of this application, the branch current characteristic parameter includes the fundamental current phasor.

[0016] According to an embodiment of this application, the differential protection method further includes: pairing multiple parallel branches in multiple optimal groups to obtain multiple pairing combinations, wherein each pairing combination includes one parallel branch in each optimal group; determining a phase-splitting differential current matrix based on the fundamental current phasor of each parallel branch in the pairing combination; determining a target combination from the multiple pairing combinations based on the phase-splitting differential current matrix, wherein the target combination includes multiple target branches; determining the phase-splitting differential current amplitude between the target branch and each associated branch for each target branch; and, if the phase-splitting differential current amplitude satisfies the fault identification condition, identifying the target branch as a fault branch and generating fault branch location information based on the fault branch.

[0017] A second aspect of this application provides a differential protection device for a generator, comprising: a parameter acquisition module for acquiring branch current characteristic parameters of each of the multiple parallel branches set for each phase of the generator stator; a branch grouping module for grouping the multiple parallel branches based on the branch current characteristic parameters to obtain multiple optimal groups, wherein each optimal group includes a portion of the multiple parallel branches; a distortion determination module for determining harmonic distortion information between the multiple optimal groups based on the branch current characteristic parameters of each portion of the parallel branches in each optimal group; and an action execution module for executing a protection blocking action when the harmonic distortion information satisfies the harmonic blocking condition, wherein satisfying the harmonic blocking condition indicates that the generator has an interference differential current caused by excitation distortion, core saturation, or rotor two-point grounding.

[0018] A third aspect of this application provides an electronic device, including: one or more processors; and a memory for storing one or more computer programs, wherein the one or more processors execute the one or more computer programs to implement the steps of the method described above.

[0019] A fourth aspect of this application provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implement the steps of the above-described method.

[0020] A fifth aspect of this application provides a computer program product, including a computer program or instructions, which, when executed by a processor, implement the steps of the above-described method.

[0021] Compared with the prior art, the beneficial effects of this application embodiment are as follows: by synchronously collecting the current of multiple parallel branches and obtaining accurate branch current characteristic parameters, and combining the characteristic parameters to achieve adaptive optimal grouping of parallel branches, the traditional manual grouping mode is abandoned, which effectively improves the fault identification capability and detection sensitivity of generator differential protection. At the same time, by accurately identifying the harmonic distortion information between the optimal groups and matching the harmonic blocking conditions to distinguish the real fault differential current from the interference differential current caused by excitation distortion, core saturation, and rotor two-point grounding, the problem of protection maloperation and failure to operate is effectively solved, and the overall sensitivity and operational reliability of generator differential protection are significantly improved. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart of a transverse differential protection method according to an embodiment of this application is shown; Figure 2 A flowchart illustrating the generation process of the optimal grouping in an embodiment of this application is shown; Figure 3 A flowchart of another embodiment of the transverse differential protection method of this application is shown; Figure 4 A flowchart of a transverse differential protection method according to another embodiment of this application is shown; Figure 5 A structural block diagram of a generator differential protection device according to an embodiment of this application is shown; Figure 6 A block diagram of an electronic device suitable for implementing the above-described method according to an embodiment of this application is shown. Detailed Implementation

[0024] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0026] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0028] As used in this specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [the described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [the described condition or event] is detected," or "in response to detection of [the described condition or event]."

[0029] Furthermore, in the description of this application, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] Currently, the traditional generator phase-splitting differential protection in the industry generally adopts a factory-fixed manual grouping technical solution, which mechanically divides the multi-branch windings of the same phase into two groups, and calculates the differential current by collecting the combined neutral point current of the two groups to achieve fault identification. The existing technologies have several inherent technical defects: First, the parallel branch windings of the generator have manufacturing tolerances, impedance differences, and uneven slot distribution. The fixed grouping method will generate a large inherent unbalanced differential current under normal unit load, external asymmetrical operating conditions, and excitation harmonic distortion. It can only avoid false tripping by raising the protection action setting value, resulting in the inability to identify minor inter-turn faults and weak branch open circuit faults, and the protection sensitivity is extremely low. Second, the traditional grouping logic is fixed. When a single branch is taken out for maintenance or the winding operating status changes, the original grouping structure completely fails. The protection device needs to be taken out of operation or the parameters need to be manually readjusted, resulting in extremely poor adaptability and automation. Third, the existing transverse differential protection is only configured with a single ratio braking or a simple floating threshold. It does not distinguish between interference conditions such as excitation distortion, rotor two-point grounding, and external short circuit. Under complex operating conditions, the protection will frequently maloperate or fail to operate. Fourth, the traditional solution only calculates the total differential current of the two groups and can only determine the faulty phase. It cannot accurately locate the specific faulty branch, which makes fault diagnosis time-consuming and maintenance inefficient. Existing improvements are limited to optimizing braking coefficients, adjusting fixed grouping ratios, and adding single harmonic blocking. They lack systematic innovation in grouping logic, braking architecture, fault location, and incomplete phase-splitting compensation, failing to address industry pain points such as the inability to balance sensitivity and reliability, poor adaptability to operating conditions, lack of fault location, and the existence of protection dead zones. With the large-scale commissioning of large-capacity, multi-branch generator units, the power grid's requirements for the sensitivity, reliability, automation, and full coverage of internal fault protection for generator units are continuously increasing. There is an urgent need to develop a multi-branch phase-splitting differential current protection scheme that can adapt to multi-branch structures, has strong anti-interference capabilities, can accurately locate faults, and eliminate protection dead zones.

[0031] In view of this, the present application provides a differential protection method and a differential protection device for a generator to solve the problems of false tripping and failure to tripping in existing differential protection methods, resulting in low overall sensitivity and operational reliability.

[0032] In this embodiment, by synchronously collecting the current of multiple parallel branches and obtaining accurate branch current characteristic parameters, and combining the characteristic parameters to achieve adaptive optimal grouping of parallel branches, the traditional manual grouping mode is abandoned, which effectively improves the fault identification capability and detection sensitivity of generator differential protection. At the same time, by accurately identifying the harmonic distortion information between the optimal groups and matching the harmonic blocking conditions to distinguish the real fault differential current from the interference differential current caused by excitation distortion, core saturation, and rotor two-point grounding, the problem of protection maloperation and failure to operate is effectively solved, and the overall sensitivity and operational reliability of generator differential protection are significantly improved.

[0033] Figure 1 A flowchart of a transverse differential protection method according to an embodiment of this application is shown.

[0034] Please see Figure 1 An embodiment of a generator differential protection method in this application may include steps S101 to S104: In step S101, for each of the multiple parallel branches set in each phase of the generator stator, the branch current characteristic parameters of each of the multiple parallel branches are obtained.

[0035] In step S102, based on the branch current characteristic parameters, multiple parallel branches are grouped to obtain multiple optimal groups, wherein each optimal group includes some of the parallel branches among the multiple parallel branches.

[0036] In step S103, the harmonic distortion information between multiple optimal groups is determined based on the branch current characteristic parameters of each part of the parallel branch in each optimal group.

[0037] In step S104, if the harmonic distortion information meets the harmonic blocking condition, the protection blocking action is performed. The meeting of the harmonic blocking condition indicates that the generator has excitation distortion, core saturation, or interference differential current caused by two-point grounding of the rotor.

[0038] This embodiment is applicable to operating scenarios where each phase of the generator stator has no less than three parallel branches. In this application, the branch current characteristic parameter can be the fundamental current phasor of each parallel branch. This parameter can accurately reflect the true operating current state of the parallel branches of the generator stator and is the core basis for conducting branch grouping and harmonic distortion information determination.

[0039] To accurately obtain the branch current characteristic parameters of multiple parallel branches of each phase of the generator stator, this embodiment independently configures current transformers (CTs) on the neutral point side of each parallel branch of the generator stator to synchronously collect the instantaneous operating data of the three-phase current of all parallel branches, providing raw data support for the subsequent extraction of the branch current characteristic parameters of each parallel branch.

[0040] To address the issues of noise interference and insufficient data accuracy in the raw current data collected on-site, this embodiment employs high-speed AD (Analog-to-Digital) synchronous sampling technology combined with a Fourier filtering algorithm to process the raw sampling data, eliminate invalid sampling noise, and accurately extract the fundamental current phasor of each branch current. The branch current characteristic parameters of each parallel branch can be the fundamental current phasor, thus constructing a complete and reliable multi-branch current sampling dataset, providing an accurate data foundation for subsequent parallel branch grouping calculations.

[0041] After obtaining the branch current characteristic parameters of each parallel branch, this embodiment groups multiple parallel branches based on the corresponding branch current characteristic parameters. This embodiment uses parallel branches operating normally under the same phase as the basic unit, combining the inherent rated winding impedance parameters of each branch with the load current amplitude and phase characteristics obtained from the fundamental current phasor under real-time operating conditions. Through a global binary combination traversal combined with a dual-index weighted optimization intelligent calculation method, it automatically completes the dynamic grouping of all parallel branches, obtaining multiple optimal groups. Each optimal group contains some parallel branches. The entire process requires no manual intervention to set grouping rules, and can adapt to different generator operating conditions.

[0042] After obtaining multiple optimal groups, this embodiment calculates and determines the harmonic distortion information between the multiple optimal groups based on the branch current characteristic parameters of each parallel branch in each optimal group. Specifically, this embodiment uses the third harmonic distortion ratio between groups as the harmonic distortion information. The setting threshold corresponding to the harmonic blocking condition can be set to 0.25–0.35. This embodiment uses 0.3 as a typical example for judgment: when the calculated third harmonic distortion ratio between the optimal groups is greater than 0.3, the harmonic distortion information is determined to meet the harmonic blocking condition. This condition indicates that the generator has excitation distortion, core saturation, or interference differential current caused by two-point grounding of the rotor. This embodiment immediately executes the protection blocking action.

[0043] According to the embodiments of this application, by synchronously collecting the current of multiple parallel branches and obtaining accurate branch current characteristic parameters, and combining the characteristic parameters to achieve adaptive optimal grouping of parallel branches, the traditional manual grouping mode is abandoned, which effectively improves the fault identification capability and detection sensitivity of generator differential protection. At the same time, by accurately identifying the harmonic distortion information between the optimal groups and matching the harmonic blocking conditions to distinguish the real fault differential current from the interference differential current caused by excitation distortion, core saturation, and rotor two-point grounding, the problem of protection maloperation and failure to operate is effectively solved, and the overall sensitivity and operational reliability of generator differential protection are significantly improved.

[0044] Figure 2 A flowchart illustrating the generation process of the optimal grouping in an embodiment of this application is shown.

[0045] According to an embodiment of this application, multiple parallel branches are grouped based on branch current characteristic parameters to obtain multiple optimal groups, including: enumerating the effective branches in the multiple parallel branches to obtain multiple grouping schemes, wherein the grouping scheme includes multiple initial groups, and each initial group includes a portion of the effective branches; and determining the optimal scheme from the multiple grouping schemes based on branch current characteristic parameters, wherein the optimal scheme includes multiple optimal groups.

[0046] This embodiment provides a specific implementation method for achieving optimal grouping of parallel branches based on branch current characteristic parameters. First, this embodiment performs effective branch screening, collecting all parallel branches of the generator currently in normal operation, removing invalid branches in maintenance, shutdown, or outage states, obtaining the set of effective branches at the current moment, constructing the corresponding effective branch sequence, and eliminating interference from invalid branches on the grouping calculation.

[0047] Reference Figure 2 After obtaining the effective branch sequence, in step S201 of this embodiment, a full-domain enumeration process without omission is carried out on all effective branches. For example, two groups are used to generate all feasible P1 and P2 two-grouping schemes. Each grouping scheme contains several initial groups, and each initial group contains some branches in the effective branch sequence, so as to achieve full coverage enumeration of all grouping possibilities without any branch omission.

[0048] After all grouping schemes have been enumerated and generated, this embodiment compares and filters all the enumerated grouping schemes based on the branch current characteristic parameters of each parallel branch, and selects the optimal scheme from among many grouping schemes. The multiple initial groups contained in the optimal scheme are the multiple optimal groups required, thus completing the adaptive optimal grouping configuration of the parallel branches.

[0049] According to the embodiments of this application, by first screening effective branches, then enumerating all grouping schemes in a binary combination across the entire domain, and then selecting the optimal grouping scheme based on the branch current characteristic parameters, the traditional fixed grouping logic is completely abandoned. It can adaptively adapt to complex working conditions such as single branch maintenance exit and winding operation status changes. There is no need for manual parameter resetting or shutdown of protection devices, which greatly improves the automation level and working condition adaptability of generator differential protection grouping configuration and ensures stable operation of protection devices throughout the entire process.

[0050] According to an embodiment of this application, determining the optimal scheme from multiple grouping schemes based on branch current characteristic parameters includes: for any grouping scheme, generating an evaluation index for the grouping scheme based on the branch current characteristic parameters of each effective branch in each initial group, wherein the evaluation index characterizes the degree of balance of the operating state of each effective branch within the same phase of the generator; and determining the optimal scheme from multiple grouping schemes based on the evaluation index of each grouping scheme.

[0051] This embodiment provides a detailed explanation of the specific process for selecting the optimal grouping scheme based on the characteristic parameters of branch current. (Refer to...) Figure 2 In this embodiment, after enumerating all feasible grouping schemes, in step S202, for any grouping scheme, the branch current characteristic parameters (e.g., fundamental current phasor) of all effective branches in each initial group within the grouping scheme are retrieved, and combined with the real-time operating parameters of each branch, the evaluation index of the corresponding grouping scheme is generated.

[0052] This embodiment specifically uses the comprehensive imbalance cost as the evaluation index. This evaluation index can accurately characterize the balance of the operating states of each effective branch within the same phase of the generator, and intuitively reflect the branch current balance effect of different grouping schemes.

[0053] In step S203, this embodiment uses a preset calculation formula. The evaluation metrics for all grouping schemes were iterated and compared, among which... This represents the combined imbalance cost of each grouping scheme. This embodiment selects the minimum combined imbalance cost. The corresponding grouping scheme, as the real-time optimal balanced grouping scheme, i.e. the optimal scheme, can ensure that the branch impedance consistency and current balance of each initial group reach the global optimum under the current operating conditions, and suppress the inherent unbalanced differential current of the generator to the greatest extent from a mathematical perspective.

[0054] Meanwhile, this embodiment can achieve adaptive dynamic optimization under operating conditions. The device polls and monitors the operating status of each parallel branch in real time. Once changes in operating conditions such as branch activation / deactivation or maintenance status switching are detected, the current effective branch sequence can be automatically refreshed, the global traversal and optimal group optimization process can be restarted, and the optimal group structure can be reconstructed in real time. The entire process is completed automatically without the need for manual modification of protection settings or the need for the protection device to be taken out of operation.

[0055] According to the embodiments of this application, by constructing an evaluation index characterizing the degree of branch operation balance, and combining the minimum comprehensive imbalance cost to screen the optimal grouping scheme, the traditional fixed mechanical grouping mode is replaced. This can achieve global balance of branch current and impedance under different operating conditions, suppress the inherent imbalance differential current of the generator from the source, effectively avoid the protection abnormal operation problem caused by the inherent differential current, and greatly improve the detection sensitivity and operation stability of the generator differential protection.

[0056] According to embodiments of this application, the branch current characteristic parameters include the fundamental current phasor.

[0057] According to an embodiment of this application, an evaluation index for a grouping scheme is generated based on the branch current characteristic parameters of each of the multiple effective branches in each initial group. This includes: for any initial group, determining the mean winding impedance based on the fundamental current phasors of each of the multiple effective branches within the initial group, and determining the branch equivalent impedance mean deviation of the grouping scheme based on the mean winding impedance of the multiple initial groups; determining the branch current amplitude deviation of the grouping scheme based on the fundamental current phasors of each of the multiple effective branches within each initial group; and performing a weighted summation of the branch equivalent impedance mean deviation and the branch current amplitude deviation to obtain the evaluation index for the grouping scheme.

[0058] This embodiment details the specific generation method of the evaluation index for the grouping scheme. The branch current characteristic parameter in this embodiment includes the fundamental current phasor. After completing the binary enumeration of effective branches to obtain each grouping scheme and the corresponding initial group, for each grouping scheme, an evaluation index is constructed from two dimensions: impedance balance and current balance, based on the fundamental current phasor of each effective branch within the initial group.

[0059] First, for any initial group, the mean winding impedance of the corresponding initial group is accurately calculated based on the fundamental current phasor of each effective branch within the group. Then, using the mean winding impedance of different initial groups, the deviation of the mean branch equivalent impedance between the two initial groups of this grouping scheme is calculated. ,in The value is the absolute difference between the average values ​​of the two sets of branch winding impedances. The calculation of the average deviation ΔZ of the branch equivalent impedance is shown in formula (1): (1) in, and These are the average values ​​of the winding impedances of the two initial groups S1 and each branch winding within S1, respectively, i.e., the average winding impedance.

[0060] Secondly, based on the fundamental current phasor of the effective branches within each initial group, the branch combined current magnitude of different initial groups is calculated. The branch current amplitude deviation of the grouping scheme is obtained by the absolute value of the difference between the two combined current magnitudes. As shown in formula (2): (2) in, Let i be the fundamental current phasor of the i-th effective parallel branch in the initial group S1. Let J be the fundamental current phasor of the j-th effective parallel branch in the initial group S1.

[0061] Based on this, the weighted summation of the mean deviation of the equivalent impedance of the branches and the amplitude deviation of the branch current is used to obtain the evaluation index of the grouping scheme. The calculation of the evaluation index is shown in formula (3): (3) in, As evaluation indicators, The impedance balancing weight has a value ranging from 0.4 to 0.6. The load current balancing weight has a value ranging from 0.4 to 0.6, and the two weighting coefficients satisfy the following conditions: The weights can be flexibly adjusted according to the actual operating conditions of the generator to meet the balance requirements of different operating scenarios.

[0062] This embodiment still uses the minimum cost selection logic, selecting from all binary search combinations, and then... The grouping scheme is used as the real-time optimal equalization grouping, so that the impedance consistency and current balance of the two branches under the current operating conditions reach the global optimum, and the inherent unbalanced differential current of the generator is suppressed to the maximum extent from a mathematical perspective.

[0063] According to the embodiments of this application, an evaluation index is constructed by weighted fusion of impedance and load current deviations, which realizes multi-branch adaptive equilibrium optimization grouping, completely replacing the traditional fixed mechanical grouping method. This effectively suppresses the inherent unbalanced differential current of the generator from the source, avoids protection misjudgment and maloperation caused by inherent differential current, and significantly improves the detection sensitivity and operating condition adaptability of generator differential protection.

[0064] According to embodiments of this application, the branch current characteristic parameters include the fundamental current phasor.

[0065] According to an embodiment of this application, harmonic distortion information among multiple optimal groups is determined based on the branch current characteristic parameters of each part of the parallel branch in each optimal group, including: determining the transverse differential current among multiple optimal groups based on the fundamental current phasor of each part of the parallel branch in each optimal group; extracting the fundamental differential current component and harmonic differential current component from the differential current time domain waveform, wherein the differential current time domain waveform is constructed based on the transverse differential current at multiple times; and determining harmonic distortion information based on the fundamental differential current component and harmonic differential current component.

[0066] This embodiment details the specific process for determining the harmonic distortion information between optimal groups. The branch current characteristic parameters in this embodiment include the fundamental current phasor. After completing the adaptive optimal grouping of the generator stator parallel branches, the branch composite current vectors of different optimal groups are calculated based on the fundamental current phasors of all parallel branches within each optimal group. The total transverse differential current of the generator is then constructed based on the two sets of branch composite current vectors. The transverse differential current used in this embodiment is shown in formula (4): (4) in, , These are the branch fundamental current vector sums for the two optimal groupings, P1 and P2, respectively. The total transverse differential current is calculated. Simultaneously, this embodiment traverses any two parallel branches under the same phase, calculating the split-phase differential current between each branch diagonally, forming a fully covered branch differential current dataset to ensure the integrity and comprehensiveness of the differential current data.

[0067] This embodiment continuously collects differential current data at multiple time points, and constructs a complete differential current time-domain waveform based on the multi-time sampling data. Then, a sliding window Fourier transform is applied to the differential current time-domain waveform, using the unit's power frequency of 50Hz as the reference frequency, to accurately extract the corresponding fundamental differential current component. This component has extremely high sensitivity to real internal faults such as generator stator inter-turn short circuits and branch open circuits, and is considered an effective fault characteristic component. Simultaneously, the third harmonic differential current component corresponding to 150Hz is extracted. This component is mainly caused by operating conditions such as generator core saturation, excitation distortion, rotor two-point grounding, and system voltage distortion, and is unrelated to real winding faults, thus belonging to interference characteristic components.

[0068] After completing the frequency domain component separation, this embodiment calculates the amplitude of the fundamental differential current component using formulas (5) and (6), respectively. Amplitude of the third harmonic differential current component : (5) (6) in, Characterizing the amplitude of the effective fault component of the fundamental wave in transverse differential current, The amplitude of the third harmonic interference component of the transverse differential current. These are the real and imaginary parts of the fundamental component, respectively. These are the real and imaginary parts of the third harmonic differential current component, respectively.

[0069] Finally, this embodiment combines the fundamental differential current component and the third harmonic differential current component to calculate the third harmonic distortion ratio as harmonic distortion information. Harmonic distortion information This provides accurate data for subsequent determination of harmonic blocking conditions, including harmonic distortion information. The calculation is shown in formula (7): (7) In harmonic distortion information When the interference differential current is determined to be caused by excitation distortion, core saturation, or rotor two-point grounding, an instantaneous protection interlocking action is executed. That is, the setting threshold corresponding to the harmonic blocking condition mentioned above.

[0070] According to the embodiments of this application, by acquiring the time-domain waveform and decoupling the frequency-domain components of the differential current, the effective fault fundamental component and the interference harmonic component can be accurately distinguished. Based on the two types of components, the harmonic distortion information can be calculated, which can accurately identify interference conditions such as excitation harmonic distortion, core saturation, and rotor two-point grounding, effectively distinguishing between real faults and interference anomalies, and providing strong support for the precise blocking and reliable operation of generator differential protection.

[0071] Figure 3 A flowchart of a transverse differential protection method according to another embodiment of this application is shown.

[0072] like Figure 3 As shown, the differential protection method further includes steps S301 to S302: In step S301, the baseline balance threshold at the current moment is determined based on the generator unit parameters and the unit load parameters at the current moment.

[0073] In step S302, if the fundamental differential current component meets the baseline balance threshold but does not meet the braking condition, an abnormal alarm message is generated, wherein the harmonic distortion information is determined based on the fundamental differential current component.

[0074] This embodiment, based on the previous embodiments, supplements the dynamic threshold determination and abnormal alarm process for generator differential protection. This embodiment combines the generator unit parameters and the current unit load parameters to calculate and determine the baseline balance threshold corresponding to the current operating condition in real time, achieving adaptive dynamic adjustment of the protection start threshold to adapt to the baseline imbalance characteristics of the generator under different load conditions.

[0075] In this embodiment, the baseline balance threshold is calculated using a dynamic floating adaptive threshold formula, as shown in formula (8): (8) in, This is the dynamic floating start threshold, i.e., the baseline balance threshold; This is the inherent maximum unbalanced differential current of the unit under no-load conditions, which is a fixed unit parameter. This is the current effective value of the unit load current, which is a real-time unit load parameter. The unloaded unbalanced reliability coefficient has a value range of 0.9 to 1.1. This is the load imbalance correction factor, with a value range of 0.05 to 0.1. The parameter can be flexibly matched according to the actual operating characteristics of the unit to ensure the accuracy of the threshold calculation.

[0076] In this embodiment, the required harmonic distortion information is calculated based on the fundamental differential current component, consistent with the frequency domain component extraction logic described above. During real-time monitoring, the extracted fundamental differential current component is continuously compared with the dynamically calculated baseline balance threshold. When the fundamental differential current component is detected to meet the baseline balance threshold (i.e., the fundamental differential current component is greater than the dynamic floating start threshold) and the current operating condition does not meet the protection braking conditions, generator abnormality alarm information is immediately generated, enabling effective identification and alerting of minor unit abnormalities and early fault conditions.

[0077] According to the embodiments of this application, a dynamic floating baseline balance threshold is constructed based on the inherent parameters of the generator unit and real-time load parameters to replace the traditional fixed threshold. This accurately adapts to the baseline imbalance characteristics of different load conditions. At the same time, an abnormal alarm identification logic is added on the basis of the protection blocking criterion to distinguish between protection blocking, protection braking and abnormal alarm conditions. This achieves full coverage identification of multiple conditions such as interference conditions, serious faults and early minor abnormalities. This makes up for the shortcomings of traditional differential protection, which only has tripping blocking function and no early warning capability, and further improves the comprehensiveness and safety of generator operation status monitoring.

[0078] like Figure 3 As shown, the differential protection method further includes steps S303 to S305: In step S303, the negative sequence active power of the generator is determined based on the negative sequence voltage phasor and negative sequence current phasor of the generator.

[0079] In step S304, if the negative sequence active power is greater than a preset power threshold, a protection blocking action is performed. Here, the negative sequence active power being greater than the preset power threshold indicates that the negative sequence power is flowing from the power grid to the generator due to an external generator fault.

[0080] In step S305, if the negative sequence active power is less than a preset power threshold, the protection lockout action is released. Here, the negative sequence active power being less than the preset power threshold indicates that the negative sequence power is flowing from the generator to the power grid due to an internal generator fault.

[0081] This embodiment, based on the aforementioned harmonic distortion blocking and dynamic threshold alarm, adds negative sequence power direction blocking discrimination logic to achieve accurate differentiation of fault areas. This embodiment collects generator terminal voltage and current data, accurately extracts the generator's negative sequence voltage phasor and negative sequence current phasor, and calculates the generator's real-time negative sequence active power based on these two types of phasor parameters, using this as the core basis for internal and external fault discrimination.

[0082] This embodiment uses the negative sequence active power standard calculation formula for calculation, as shown in formula (9): (9) in, This refers to the negative-sequence active power of the generator. This is the negative sequence voltage phasor at the generator terminals. This is the negative sequence current phasor of the generator. The rules for taking the real part of the result of an operation are as follows: The conjugate operation represents the current phasor.

[0083] This embodiment utilizes the positive and negative characteristics of negative-sequence active power, combined with a preset power threshold, to achieve fault type identification and protection logic linkage. In this embodiment, the preset power threshold is set to 0. When the calculated negative-sequence active power is greater than the preset power threshold, it is determined that the negative-sequence power flows from the grid to the generator. This condition belongs to an external fault of the generator caused by the grid side. At this time, the protection blocking action is immediately executed to avoid the unit's differential protection from malfunctioning due to external grid faults.

[0084] When the calculated negative sequence active power is less than the preset power threshold, it is determined that the negative sequence power flows from the generator to the power grid. This condition is an internal fault caused by an abnormality in the generator winding. At this time, the protection lockout action is released, and the fault identification and operation logic of the differential protection is opened to ensure that the protection can operate reliably and clear the fault in time when there is an internal fault.

[0085] According to the embodiments of this application, a negative sequence power direction blocking discrimination mechanism is added on the basis of harmonic distortion blocking and early abnormal alarm. The negative sequence active power flow direction accurately distinguishes between external grid faults and internal unit faults, forming a multi-level and multi-dimensional protection blocking discrimination system. This effectively avoids the problem of false blocking and false operation of protection caused by external faults, and further improves the fault discrimination accuracy and operational reliability of generator differential protection.

[0086] According to an embodiment of this application, the differential protection method further includes: determining the fundamental ratio braking condition based on the baseline balance threshold and the grouped synthetic current of each optimal group; generating fault information when the fundamental differential current component satisfies the fundamental ratio braking condition, the harmonic distortion information satisfies the harmonic blocking condition, and the negative sequence active power is less than a preset power threshold, wherein the fault information indicates that the generator has a fault.

[0087] This embodiment, based on the aforementioned dynamic baseline threshold, harmonic distortion discrimination, and negative sequence directional blocking, adds fundamental frequency ratio braking discrimination logic to construct a multi-layered composite linkage discrimination system, achieving accurate generator fault determination. Based on the calculated baseline balance threshold and combined with the group synthesis current corresponding to each optimal group, this embodiment calculates and determines the fundamental frequency ratio braking condition in real time, using this as the core braking threshold for internal fault discrimination.

[0088] In this embodiment, the braking current required for ratio braking is first calculated as shown in formula (10): (10) in, For braking current, , These are the effective values ​​of the combined current of the two optimal groups, respectively. Based on this, the final fundamental frequency action threshold, i.e., the fundamental frequency ratio braking condition, is calculated by combining the baseline balance threshold, as shown in formula (11): (11) in, This is the final fundamental frequency action threshold, i.e., the fundamental frequency ratio braking condition. The dynamic baseline balancing threshold. It is a ratio braking coefficient, with a value ranging from 0.3 to 0.6, which can effectively suppress the protection maloperation problem caused by large currents from external faults.

[0089] This embodiment uses a four-layer composite linkage braking logic to comprehensively determine the generator's operating status. Only when all three core conditions are met simultaneously is the generator determined to have a real internal fault and fault information generated. The specific comprehensive discrimination conditions are: the fundamental differential current component meets the fundamental ratio braking condition, the harmonic distortion information does not meet the harmonic blocking condition, and the negative sequence active power is less than the preset power threshold. The corresponding quantitative discrimination logic is shown in formula (12): (12) Specifically, This indicates that the current fundamental differential current exceeds the braking threshold, suggesting a genuine fault. The third harmonic distortion ratio does not reach the blocking threshold, thus excluding interference conditions such as excitation distortion, core saturation, and rotor two-point grounding. It represents the flow of negative sequence power from the generator to the power grid, eliminates asymmetrical short-circuit faults outside the power grid area, and achieves accurate fault identification through the linkage of three conditions.

[0090] According to the embodiments of this application, by adding a four-layer composite linkage braking discrimination logic, it can accurately distinguish five complex operating conditions: normal load imbalance, excitation harmonic distortion, rotor two-point grounding, external asymmetrical short circuit, and internal fault. It comprehensively covers various abnormal operating states of the unit, completely solves the industry problem of traditional differential protection being prone to false tripping or failure to trip under complex operating conditions, effectively balances the action sensitivity and operational reliability of generator differential protection, and greatly improves the overall performance and operating condition adaptability of unit fault protection.

[0091] Figure 4 A flowchart of a transverse differential protection method according to another embodiment of this application is shown.

[0092] According to embodiments of this application, the branch current characteristic parameters include the fundamental current phasor.

[0093] like Figure 4 As shown, the transverse differential protection method further includes steps S401 to S405: In step S401, multiple parallel branches in multiple optimal groups are paired to obtain multiple pairing combinations, wherein each pairing combination includes one parallel branch in each optimal group.

[0094] In step S402, the split-phase differential current matrix is ​​determined based on the fundamental current phasor of each parallel branch in the pairing combination.

[0095] In step S403, a target combination is determined from multiple pairing combinations based on the split phase differential flow matrix, wherein the target combination includes multiple target branches.

[0096] In step S404, for each target branch, the phase difference flow amplitude between the target branch and each associated branch is determined.

[0097] In step S405, if the amplitude of the split phase differential current meets the fault identification conditions, the target branch is identified as the fault branch, and fault branch location information is generated based on the fault branch.

[0098] This embodiment adds a precise fault branch location function based on the aforementioned differential protection discrimination logic. The branch current characteristic parameter in this embodiment includes the fundamental current phasor. After completing the adaptive optimal grouping of parallel branches, all parallel branches within multiple optimal groups are permuted and paired in pairs to generate all branch pairing combinations. Each pairing combination is taken from a single parallel branch of a different optimal group, achieving full coverage pairing of all effective branches in the same phase, without omission or duplication.

[0099] For each pairing combination, this embodiment calculates the phase-splitting differential current between branches in real time based on the fundamental current phasor of the two parallel branches within the pair, constructs a complete phase-splitting differential current matrix, and comprehensively records the differential current data between each pair of branches. The phase-splitting differential current calculation between each pair of branches is shown in formula (13): (13) in, For any two parallel branches x and y, the split-phase differential flow, , denoted as x and y, respectively, are the fundamental current phasors of the x-branch and y-branch. Under normal operating conditions, the currents of each parallel branch are balanced and consistent, and the amplitudes of all phase differential currents within the matrix are maintained within a very small inherent imbalance threshold range. The differential current amplitudes of each branch are basically the same, with no obvious extreme value differences.

[0100] When an internal fault occurs in the generator, the fundamental current phasor amplitude and phase of the faulty branch will be significantly distorted, while the operating parameters of the other normal branches remain basically stable. Based on this fault characteristic, this embodiment traverses the differential current amplitude of all paired combinations within the split-phase differential current matrix, selects the branch paired combination corresponding to the global maximum differential current amplitude, determines this paired combination as the target combination, and the corresponding two branches are the target branches.

[0101] Further differentiation was performed on the two target branches, and the amplitude values ​​of all paired differential flow involved by each target branch were statistically analyzed. If all paired differential flow amplitude values ​​involved by one target branch were at the highest level in the entire domain, while the remaining paired differential flow amplitude values ​​of the other target branch remained normal, then the branch with an overall high differential flow amplitude in the entire domain was determined to be the actual fault branch.

[0102] When the phase difference current amplitude of the target branch and each associated branch meets the preset fault identification conditions, the fault branch can be accurately located, the corresponding fault phase and specific fault branch number can be determined, and complete fault branch location information can be automatically generated and sent to the monitoring backend to complete the accurate fault location.

[0103] According to the embodiments of this application, by adding branch-to-branch differential current traversal calculation, matrix comparison and extreme value identification and positioning logic, the technical limitation of traditional generator differential protection that can only identify faulty phases is broken through. It can directly and accurately locate the specific faulty branch number, realizing the upgrade from "faulty phase discrimination" to "accurate faulty branch positioning", which greatly shortens the fault investigation and handling time and improves the efficiency and accuracy of generator fault operation and maintenance.

[0104] This embodiment provides a detailed explanation of the closed-loop logic for protection action output, fault data storage, and event recording, serving as the final execution and data archiving stage of this method. During unit operation, this method employs a real-time cyclic execution mechanism to continuously complete the entire logical operation process, including parallel branch current acquisition, effective branch screening, adaptive optimal grouping, differential current calculation, and multi-level braking and interlocking judgment, thereby achieving 24 / 7 real-time monitoring of the generator's operating status.

[0105] During real-time monitoring and judgment, the signal output logic for different operating conditions is executed in layers. When the system simultaneously meets all fault action conditions such as fundamental differential current exceeding the limit, no harmonic blocking, and no negative sequence directional blocking, it is determined that a real internal fault has occurred in the generator. After a fixed delay, the device stably outputs a trip action command to reliably disconnect the faulty equipment and prevent the fault from continuing to expand and causing damage to the unit.

[0106] When the operating condition only triggers the dynamic floating baseline balance threshold but does not reach the fault trip action standard, it is determined that the unit has an early minor abnormality or imbalance condition. The device does not output a trip command, but only outputs an abnormal alarm signal to the outside world, so as to realize early warning of hidden faults of the unit.

[0107] At the same time, the device has the function of full data synchronous storage and event recording. At the moment of triggering an alarm or protection action, it synchronously and completely stores core operating data such as waveform data of the fault period, differential current calculation data of each group, and accurate fault branch location information. It automatically completes the archiving and recording of fault events and alarm transmission to the operation and maintenance platform, forming a complete closed-loop protection logic of "monitoring-judgment-action-archiving".

[0108] According to the embodiments of this application, by setting up a hierarchical action output mechanism and real-time data storage and archiving logic, two types of operating conditions are distinguished: fault tripping and minor abnormality alarms. This ensures reliable protection operation during serious faults and prevents fault propagation, while also enabling early identification of early abnormal states of the unit, balancing unit operation safety and forward-looking maintenance. Simultaneously, relying on complete fault data storage capabilities, it provides detailed data support for subsequent fault tracing, operating condition analysis, and equipment maintenance optimization, adapting to the data interface and recording requirements of fault recorders, further enhancing the integrity and engineering practicality of the protection system.

[0109] In summary, this application presents a generator neutral point multi-branch split-phase differential intelligent protection method and system adapted to fault recorders. Compared with traditional fixed-group split-phase differential protection and single braking improvement technology, it integrates core innovative technologies such as multi-branch adaptive equalization grouping, four-layer composite braking criteria, and precise positioning of branch-to-branch differential current, and has comprehensive technical advantages in all aspects and at multiple levels.

[0110] This application completely replaces the traditional fixed mechanical grouping method by adopting a dual-dimensional adaptive balancing optimization grouping mode based on impedance and load current. This effectively suppresses the inherent unbalanced differential current of the unit from the source and significantly improves the sensitivity of protection actions. At the same time, relying on a four-layer composite linkage braking logic, it can accurately identify five complex operating conditions: normal load imbalance, excitation harmonic distortion, rotor two-point grounding, external asymmetrical short circuit, and internal fault. This completely solves the technical problem of traditional differential protection being prone to false tripping or failure to trip under complex operating conditions, achieving a balance between protection sensitivity and operational reliability.

[0111] This application boasts exceptional versatility and adaptability to various operating conditions, fully compatible with multi-branch generator sets including 3-branch, 4-branch, and 6-branch units, and accommodating multiple wiring configurations such as single neutral point and dual neutral point. The device automatically identifies changes in operating conditions such as branch maintenance, commissioning, and decommissioning, and reconstructs the optimal grouping in real time. No manual modification of protection settings or device parameters is required throughout the process, nor is it necessary to shut down the protection device for adjustment. This effectively adapts to diverse operating modes of the generator set, significantly reducing on-site maintenance workload and costs.

[0112] In addition, this application introduces a new branch-to-branch differential current traversal comparison and positioning mechanism, which breaks through the technical bottleneck of traditional protection that can only identify the fault phase. It can accurately output the specific fault branch number, realize the fine positioning of the fault point, effectively shorten the fault investigation and equipment handling time, significantly improve the efficiency of generator set fault operation and maintenance and the stability of power grid operation, and has extremely high engineering application value and promotion prospects.

[0113] Figure 5 A structural block diagram of a generator differential protection device according to an embodiment of this application is shown.

[0114] like Figure 5 As shown, the differential protection device for the generator can be applied to a fault recorder. The differential protection device 500 includes a parameter acquisition module 510, a branch grouping module 520, a distortion determination module 530, and an action execution module 540.

[0115] The parameter acquisition module 510 is used to acquire the branch current characteristic parameters of each of the multiple parallel branches set for each phase of the generator stator.

[0116] The branch grouping module 520 is used to group multiple parallel branches based on the branch current characteristic parameters to obtain multiple optimal groups, wherein each optimal group includes some of the parallel branches among the multiple parallel branches.

[0117] The distortion determination module 530 is used to determine the harmonic distortion information between multiple optimal groups based on the branch current characteristic parameters of each part of the parallel branch in each optimal group.

[0118] The action execution module 540 is used to perform protection blocking actions when the harmonic distortion information meets the harmonic blocking conditions. The harmonic blocking conditions indicate that the generator has excitation distortion, core saturation, or interference differential current caused by two-point grounding of the rotor.

[0119] According to the embodiments of this application, by synchronously collecting the current of multiple parallel branches and obtaining accurate branch current characteristic parameters, and combining the characteristic parameters to achieve adaptive optimal grouping of parallel branches, the traditional manual grouping mode is abandoned, which effectively improves the fault identification capability and detection sensitivity of generator differential protection. At the same time, by accurately identifying the harmonic distortion information between the optimal groups and matching the harmonic blocking conditions to distinguish the real fault differential current from the interference differential current caused by excitation distortion, core saturation, and rotor two-point grounding, the problem of protection maloperation and failure to operate is effectively solved, and the overall sensitivity and operational reliability of generator differential protection are significantly improved.

[0120] According to an embodiment of this application, the branch grouping module includes a grouping enumeration submodule and a scheme determination submodule.

[0121] The grouping enumeration submodule is used to enumerate the effective branches in multiple parallel branches to obtain multiple grouping schemes. Each grouping scheme includes multiple initial groups, and each initial group includes a portion of the effective branches.

[0122] The scheme determination submodule is used to determine the optimal scheme from multiple grouping schemes based on the branch current characteristic parameters. The optimal scheme includes multiple optimal groups.

[0123] According to an embodiment of this application, the scheme determination submodule includes an index determination unit and a scheme determination unit.

[0124] The index determination unit is used to generate evaluation indexes for any grouping scheme based on the branch current characteristic parameters of each effective branch in each initial group. The evaluation indexes characterize the degree of balance of the operating status of each effective branch in the same phase of the generator.

[0125] The scheme determination unit is used to determine the optimal scheme from multiple grouping schemes based on the evaluation indicators of each grouping scheme.

[0126] According to embodiments of this application, the branch current characteristic parameters include the fundamental current phasor.

[0127] According to an embodiment of this application, the index determination unit includes a first deviation subunit, a second deviation subunit, and an index determination subunit.

[0128] The first deviation sub-unit is used to determine the mean winding impedance based on the fundamental current phasor of each of the multiple effective branches within the initial group for any initial group, and to determine the branch equivalent impedance mean deviation of the grouping scheme based on the mean winding impedance of the multiple initial groups.

[0129] The second deviation sub-unit is used to determine the branch current amplitude deviation of the grouping scheme based on the fundamental current phasor of each of the multiple effective branches in each initial group.

[0130] The index determination sub-unit is used to perform a weighted summation of the mean deviation of the branch equivalent impedance and the deviation of the branch current amplitude to obtain the evaluation index of the grouping scheme.

[0131] According to embodiments of this application, the branch current characteristic parameters include the fundamental current phasor.

[0132] According to an embodiment of this application, the distortion determination module includes a differential current determination unit, a component extraction unit, and a distortion determination unit.

[0133] The differential current determination unit is used to determine the transverse differential current between multiple optimal groups based on the fundamental current phasor of each part of the parallel branch in each optimal group.

[0134] The component extraction unit is used to extract the fundamental differential current component and harmonic differential current component from the differential current time domain waveform, wherein the differential current time domain waveform is constructed based on the transverse differential current at multiple times.

[0135] The distortion determination unit is used to determine harmonic distortion information based on the fundamental differential current component and the harmonic differential current component.

[0136] According to an embodiment of this application, the differential protection device further includes a threshold determination module and an alarm generation module.

[0137] The threshold determination module is used to determine the baseline balance threshold at the current moment based on the generator unit parameters and the unit load parameters at the current moment.

[0138] The alarm generation module is used to generate abnormal alarm information when the fundamental differential current component meets the baseline balance threshold but does not meet the braking condition. The harmonic distortion information is determined based on the fundamental differential current component.

[0139] According to an embodiment of this application, the differential protection device further includes a power determination module, a lockout execution module, and a lockout release module.

[0140] The power determination module is used to determine the negative-sequence active power of the generator based on the negative-sequence voltage phasor and negative-sequence current phasor of the generator.

[0141] The interlocking execution module is used to perform protection interlocking actions when the negative sequence active power is greater than a preset power threshold. The negative sequence active power being greater than the preset power threshold indicates that the negative sequence power is flowing from the power grid to the generator due to an external generator fault.

[0142] The unlocking module is used to perform the unlocking action when the negative sequence active power is less than a preset power threshold. The negative sequence active power being less than the preset power threshold indicates that the negative sequence power is flowing from the generator to the grid due to an internal generator fault.

[0143] According to embodiments of this application, the differential protection device further includes a condition determination module and a fault generation module.

[0144] The condition determination module is used to determine the fundamental frequency ratio braking condition based on the baseline balance threshold and the grouped synthetic current of each optimal group.

[0145] The fault generation module is used to generate fault information when the fundamental differential current component meets the fundamental ratio braking condition, the harmonic distortion information does not meet the harmonic blocking condition, and the negative sequence active power is less than the preset power threshold. The fault information indicates that there is a fault in the generator.

[0146] According to embodiments of this application, the branch current characteristic parameters include the fundamental current phasor.

[0147] According to embodiments of this application, the differential protection device further includes a branch pairing module, a matrix generation module, a combination determination module, an amplitude determination module, and a fault location module.

[0148] The branch pairing module is used to pair multiple parallel branches in multiple optimal groups to obtain multiple pairing combinations, wherein each pairing combination includes one parallel branch in each optimal group.

[0149] The matrix generation module is used to determine the split-phase differential current matrix based on the fundamental current phasor of each parallel branch in the pairing combination.

[0150] The combination determination module is used to determine a target combination from multiple paired combinations based on the split phase differential flow matrix, wherein the target combination includes multiple target branches.

[0151] The amplitude determination module is used to determine the phase difference flow amplitude between the target branch and each associated branch for each target branch.

[0152] The fault location module is used to identify the target branch as the fault branch when the differential current amplitude of the split phase meets the fault identification conditions, and to generate fault branch location information based on the fault branch.

[0153] According to embodiments of this application, any multiple modules among the parameter acquisition module 510, branch grouping module 520, distortion determination module 530, and action execution module 540 can be merged into one module, or any one of these modules can be split into multiple modules. Alternatively, at least some of the functions of one or more of these modules can be combined with at least some of the functions of other modules and implemented in one module. According to embodiments of this application, at least one of the parameter acquisition module 510, branch grouping module 520, distortion determination module 530, and action execution module 540 can be at least partially implemented as hardware circuits, such as field-programmable gate arrays, programmable logic arrays, systems-on-a-chip, systems-on-a-substrate, systems-on-package, application-specific integrated circuits, or implemented in hardware or firmware by any other reasonable means of integrating or packaging circuits, or implemented in any one of the three implementation methods of software, hardware, and firmware, or in a suitable combination of any of these. Alternatively, at least one of the parameter acquisition module 510, branch grouping module 520, distortion determination module 530, and action execution module 540 can be at least partially implemented as a computer program module, which can perform corresponding functions when the computer program module is run.

[0154] Figure 6 A block diagram of an electronic device suitable for implementing the above-described method according to an embodiment of this application is shown.

[0155] like Figure 6 As shown, the electronic device 600 according to an embodiment of this application may refer to a fault recorder. The electronic device 600 includes a processor 601, which can perform various appropriate actions and processes according to a program stored in a read-only memory 602 or a program loaded from a storage portion 608 into a random access memory 603. The processor 601 may, for example, include a general-purpose microprocessor, an instruction set processor, and / or an associated chipset and / or a dedicated microprocessor. The processor 601 may also include onboard memory for caching purposes. The processor 601 may include a single processing unit or multiple processing units for executing different steps of the method flow according to an embodiment of this application.

[0156] Random access memory 603 stores various programs and data required for the operation of electronic device 600. Processor 601, read-only memory 602, and random access memory 603 are interconnected via bus 604. Processor 601 executes various steps of the method flow according to embodiments of this application by executing programs in read-only memory 602 and / or random access memory 603. It should be noted that the programs may also be stored in one or more memories other than read-only memory 602 and random access memory 603. Processor 601 may also execute various steps of the method flow according to embodiments of this application by executing programs stored in said one or more memories.

[0157] According to embodiments of this application, the electronic device 600 may further include an input / output interface 605, which is also connected to a bus 604. The electronic device 600 may also include one or more of the following components connected to the input / output interface 605: an input section 606 including a keyboard, mouse, etc.; an output section 607 including a cathode ray tube, liquid crystal display, etc., and a speaker, etc.; a storage section 608 including a hard disk, etc.; and a communication section 609 including a network interface card, such as a local area network card, modem, etc. The communication section 609 performs communication processing via a network such as the Internet. A drive 610 is also connected to the input / output interface 605 as needed. A removable medium 611, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed on the drive 610 as needed so that computer programs read from it can be installed into the storage section 608 as needed.

[0158] Embodiments of this application also provide a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments; or it may exist independently and not assembled into the device / apparatus / system. The computer-readable storage medium carries one or more programs, which, when executed, implement the method according to the embodiments of this application.

[0159] According to embodiments of this application, the computer-readable storage medium can be a non-volatile computer-readable storage medium, such as including but not limited to: portable computer disks, hard disks, random access memory, read-only memory, erasable programmable read-only memory, portable compact disk read-only memory, optical storage devices, magnetic storage devices, or any suitable combination thereof. In embodiments of this application, the computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. For example, according to embodiments of this application, the computer-readable storage medium may include the read-only memory 602 described above, and / or random access memory 603, and / or one or more memories other than read-only memory 602 and random access memory 603.

[0160] Embodiments of this application also include a computer program product comprising a computer program containing program code for performing the methods shown in the flowchart. When the computer program product is run on a computer system, the program code is used to cause the computer system to implement the methods provided in the embodiments of this application.

[0161] In one embodiment, the computer program may rely on a tangible storage medium such as an optical storage device or a magnetic storage device. In another embodiment, the computer program may also be transmitted and distributed in the form of signals over a network medium, and downloaded and installed via the communication section 609, and / or installed from the removable medium 611. The program code contained in the computer program can be transmitted using any suitable network medium, including but not limited to: wireless, wired, etc., or any suitable combination thereof.

[0162] In embodiments of this application, the computer program can be downloaded and installed from a network via communication section 609, and / or installed from removable medium 611. When the computer program is executed by processor 601, it performs the functions defined in the system of embodiments of this application. According to embodiments of this application, the systems, devices, apparatuses, modules, units, etc., described above can be implemented by computer program modules.

[0163] According to embodiments of this application, program code for executing the computer programs provided in the embodiments of this application can be written in any combination of one or more programming languages. Specifically, these computational programs can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. The program code can be executed entirely on the user's computing device, partially on the user's device, partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0164] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0165] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application.

Claims

1. A method for differential protection of a generator, characterized in that, include: For each of the multiple parallel branches set in each phase of the generator stator, the branch current characteristic parameters of each of the multiple parallel branches are obtained; Based on the branch current characteristic parameters, the multiple parallel branches are grouped to obtain multiple optimal groups, wherein each optimal group includes a portion of the parallel branches among the multiple parallel branches; Based on the branch current characteristic parameters of each part of the parallel branch in each optimal group, the harmonic distortion information among multiple optimal groups is determined; When the harmonic distortion information meets the harmonic blocking conditions, a protection blocking action is performed, wherein the meeting of the harmonic blocking conditions indicates that the generator has excitation distortion, core saturation, or interference differential current caused by two-point grounding of the rotor.

2. The transverse difference protection method according to claim 1, characterized in that, Based on the branch current characteristic parameters, the multiple parallel branches are grouped to obtain multiple optimal groups, including: The effective branches in the multiple parallel branches are grouped and enumerated to obtain multiple grouping schemes, wherein the grouping scheme includes multiple initial groups, and each initial group includes a portion of the effective branches; Based on the branch current characteristic parameters, an optimal scheme is determined from multiple grouping schemes, wherein the optimal scheme includes multiple optimal groupings.

3. The transverse difference protection method according to claim 2, characterized in that, Based on the branch current characteristic parameters, the optimal scheme is determined from multiple grouping schemes, including: For any of the grouping schemes, an evaluation index for the grouping scheme is generated based on the branch current characteristic parameters of each of the multiple effective branches in each initial group. The evaluation index characterizes the degree of balance of the operating states of each effective branch within the same phase of the generator. The optimal scheme is determined from the multiple grouping schemes based on the evaluation indicators of each of the grouping schemes.

4. The transverse difference protection method according to claim 3, characterized in that, The branch current characteristic parameters include the fundamental current phasor; The step of generating evaluation metrics for the grouping scheme based on the branch current characteristic parameters of each of the multiple effective branches in each initial group includes: For any of the initial groups, the mean value of the winding impedance is determined based on the fundamental current phasor of each of the multiple effective branches within the initial group, and the deviation of the mean value of the branch equivalent impedance of the grouping scheme is determined based on the mean value of the winding impedance of the multiple initial groups. The branch current amplitude deviation of the grouping scheme is determined based on the fundamental current phasor of each of the multiple effective branches within each initial group. The evaluation index of the grouping scheme is obtained by weighted summation of the mean deviation of the equivalent impedance of the branch and the amplitude deviation of the branch current.

5. The transverse difference protection method according to claim 1, characterized in that, The branch current characteristic parameters include the fundamental current phasor; The step of determining the harmonic distortion information among multiple optimal groups based on the branch current characteristic parameters of each parallel branch in each optimal group includes: Based on the fundamental current phasor of each part of the parallel branch in each optimal group, determine the transverse differential current between multiple optimal groups; The fundamental differential current component and harmonic differential current component are extracted from the differential current time domain waveform, wherein the differential current time domain waveform is constructed based on the transverse differential current at multiple times; The harmonic distortion information is determined based on the fundamental differential current component and the harmonic differential current component.

6. The transverse difference protection method according to claim 1, characterized in that, Also includes: Based on the generator unit parameters and the unit load parameters at the current moment, determine the baseline balance threshold at the current moment; If the fundamental differential current component satisfies the baseline balance threshold but does not meet the braking condition, an abnormal alarm message is generated, wherein the harmonic distortion information is determined based on the fundamental differential current component.

7. The transverse difference protection method according to claim 6, characterized in that, Also includes: The negative-sequence active power of the generator is determined based on the negative-sequence voltage phasor and negative-sequence current phasor of the generator. When the negative sequence active power is greater than a preset power threshold, a protection blocking action is performed, wherein the negative sequence active power being greater than the preset power threshold indicates that the negative sequence power is flowing from the power grid to the generator due to an external fault. If the negative sequence active power is less than the preset power threshold, the protection lockout action is executed, wherein the negative sequence active power being less than the preset power threshold indicates an internal generator fault in which negative sequence power flows from the generator to the power grid.

8. The transverse difference protection method according to claim 7, characterized in that, Also includes: Based on the baseline balance threshold, the fundamental frequency ratio braking condition is determined according to the grouped synthetic current of each of the optimal groups; When the fundamental differential current component satisfies the fundamental ratio braking condition, the harmonic distortion information does not satisfy the harmonic blocking condition, and the negative sequence active power is less than a preset power threshold, fault information is generated, wherein the fault information indicates that the generator has a fault.

9. The transverse difference protection method according to any one of claims 1 to 7, characterized in that, The branch current characteristic parameters include the fundamental current phasor; The method further includes: Pairing up the parallel branches in the multiple optimal groups yields multiple pairing combinations, wherein each pairing combination includes one of the parallel branches in each optimal group; Based on the fundamental current phasor of each parallel branch in the pairing combination, the phase-splitting differential current matrix is ​​determined; Based on the split phase differential flow matrix, a target combination is determined from a plurality of pairing combinations, wherein the target combination includes a plurality of target branches; For each target branch, determine the phase difference flow amplitude between the target branch and each associated branch; If the amplitude of the split-phase differential current meets the fault identification conditions, the target branch is identified as the fault branch, and fault branch location information is generated based on the fault branch.

10. A differential protection device for a generator, characterized in that, include: The parameter acquisition module is used to acquire the branch current characteristic parameters of each of the multiple parallel branches set for each phase of the generator stator. The branch grouping module is used to group multiple parallel branches based on the branch current characteristic parameters to obtain multiple optimal groups, wherein each optimal group includes a portion of the parallel branches among the multiple parallel branches; The distortion determination module is used to determine the harmonic distortion information among multiple optimal groups based on the branch current characteristic parameters of each part of the parallel branch in each optimal group; The action execution module is used to perform a protection blocking action when the harmonic distortion information meets the harmonic blocking condition, wherein the meeting of the harmonic blocking condition indicates that the generator has excitation distortion, core saturation or rotor two-point grounding caused by interference differential current.

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