Ground fault arc extinction and TVS fault identification method and system based on slot potential

Abstract

The present application belongs to the technical field of large-scale generator safety protection, and specifically discloses a ground fault arc extinguishing and TVS fault identification method and system based on slot potential. The present application calculates the fundamental slot potential and the third harmonic slot potential of each slot conductor by obtaining the fundamental and third harmonic voltages at the neutral point and the machine end of the generator. The actual fault location is further determined by matching with the ground fault potential, thereby realizing fault location at any position within the entire winding range, breaking through the limitations of traditional methods, and significantly improving the coverage of fault location. The present application calculates the ground transition resistance during ground fault and the ground transition resistance when stable after arc extinguishing is completed by using the voltage and current low-frequency components of the neutral point of the generator. By comparing the transition resistances in different states to determine the nature of the fault, it can accurately distinguish between transient faults and permanent faults, provide simple and effective fault identification, be easy to implement in engineering, and be able to quickly and accurately determine the nature of the fault.

Description

Technical Field

[0001] The present application belongs to the technical field of large generator safety protection, and more specifically, to a method and system for identifying ground fault arc suppression and TVS based on slot potential. Background Art

[0002] Single-phase grounding faults in the stator winding are one of the most common faults in large generators. When a single-phase grounding fault occurs in a generator's stator winding, existing arc suppression methods can be categorized as either passive or active, depending on whether an external injection device is required. Passive methods primarily involve grounding the neutral point via an arc suppression coil to compensate for the fault current. However, arc suppression coils can only compensate for single-frequency fault components and are unable to compensate for harmonic components in the fault current. Even after compensation, residual current remains high. Actual operating experience has shown that existing generator neutral-point grounding methods are unable to reliably suppress arcs in various fault scenarios. Active arc suppression methods use an external injection source to control the fault point voltage below the arc reignition voltage, theoretically preventing arc reignition. However, active arc suppression methods for generator stator grounding faults require a large-capacity inverter, which is bulky and expensive.

[0003] The existing compensation calculation method based on turn potential cannot achieve fault arc extinguishing at non-coil connection points, which limits the engineering application of the existing method.

[0004] Patent CN113777526A discloses a stator ground fault location method and system based on third harmonic potential distribution, including: S1. Taking the third harmonic slot potential as a unit, the third harmonic slot potential is calculated according to the third harmonic potential measured at the neutral point and the machine end, and the third harmonic potential of the faulty part winding is calculated according to the winding connection sequence and the third harmonic slot potential; S2. Based on the third harmonic equivalent circuit of the generator, a fault evaluation index is constructed in combination with the third harmonic potential; S3. Multiple reference points are preset in the fault phase, the fault evaluation index value of each reference point is calculated, the reference point with the smallest calculated value is regarded as the fault location, and the slot number where the fault is located is determined.

[0005] However, this patent only locates faults based on the third harmonic relationship. Although it has a certain degree of accuracy in some scenarios, it has the problem of multiple positioning solutions, and it is difficult to achieve a unique solution by relying solely on the third harmonic potential. In addition, the positioning method of this patent cannot be used to solve the dual-frequency fault potential, and has great limitations in the actual application of arc extinguishing technology. At the same time, the positioning technology of this patent cannot identify the nature of the fault, which may lead to delays in fault handling and cause serious damage to the generator. Summary of the Invention

[0006] In response to the defects of the existing technology, the purpose of this application is to provide a ground fault arc extinguishing and TVS fault identification method and system based on slot potential, aiming to solve the problem that the existing positioning technology cannot solve the dual-frequency fault potential and cannot realize the fault nature identification.

[0007] A first aspect of the present application relates to a ground fault arc extinguishing method based on slot potential, the arc extinguishing method comprising:

[0008] S1. Obtain the fundamental voltage and third harmonic voltage at the generator neutral point and generator terminal in real time during normal operation and after a ground fault.

[0009] S2. Calculate the fundamental slot potential amplitude of each stator slot conductor based on the fundamental voltage of the normal operating terminal and the neutral point, and calculate the third harmonic slot potential amplitude of each stator slot conductor based on the third harmonic voltage of the normal operating terminal and the neutral point;

[0010] S3. Using the fundamental slot potential amplitude and the stator slot conductor connection sequence, construct the fundamental fault potential expression with the fault location as the independent variable: , using the third harmonic slot potential amplitude and the stator slot conductor connection sequence, the third harmonic fault potential expression with the fault location as the independent variable is constructed , using the fundamental voltage of the generator neutral point after the ground fault and third harmonic voltage , calculate the intermediate variables A and B;

[0011] S4. Constructing the objective function , solve the fault location when the objective function is minimized, and then determine the fundamental fault potential value and the third harmonic fault potential value;

[0012] S5. The neutral point of the generator is grounded by a hybrid flexible grounding method to extinguish arc at the fault point; the hybrid flexible grounding method is as follows: the neutral point is grounded through an arc suppression coil, and a dual-frequency reverse fault potential is injected into the neutral point by an external dual-frequency active arc suppression device.

[0013] In some embodiments, the intermediate variables A and B are as follows:

[0014]

[0015] in, is the middle vector, and are the fundamental voltage and third harmonic voltage of the generator neutral point after the ground fault, Fault phase The third harmonic potential of the midpoint of the coil to the neutral point, is the third harmonic phase potential of the fault phase, represents an imaginary number, represents the angular frequency, Indicates the equivalent capacitance to ground of a single-turn coil of the fault phase, Indicates the equivalent capacitance to ground of each phase of the direct-connect system at the machine end. is the equivalent inductance of the winding, represents the capacitance of the generator stator winding to ground, is the total number of stator winding turns of the fault phase.

[0016] A second aspect of the present application relates to a fault identification method based on a transition resistor (TVS), the identification method comprising:

[0017] T1. A low-frequency power supply is injected into the neutral point of the generator, wherein the frequency of the low-frequency power supply is less than 50 Hz;

[0018] T2. Obtain the voltage and current at the generator neutral point during normal operation (the first moment), from the time the fault occurs to the time the ground fault arc is extinguished (the second moment), and the third moment of stabilization after arc extinguishing. Use Fourier transform to extract the low-frequency components of the voltage and current, which are consistent with the frequency of the low-frequency power supply.

[0019] T3. Calculate the ground impedance during normal operation by using the voltage and current low-frequency components of the neutral point at the first moment. , calculate the ground impedance during ground fault by using the voltage and current low-frequency components of the neutral point at the second moment , calculate the impedance to ground when arc extinction is complete and stable through the voltage and current low-frequency components of the neutral point at the third moment ,comprehensive and Calculate the ground transition resistance of the primary side of the generator stator winding when a ground fault occurs ,comprehensive and Calculate the ground transition resistance when the arc is extinguished and stable ;

[0020] T4. Identify the nature of the fault using the following rules:

[0021]

[0022] in, is the lower limit margin coefficient; is the upper margin coefficient.

[0023] In some embodiments, the arc extinguishing method as described in the first aspect is used to extinguish arc due to a fault.

[0024] In some embodiments, the impedance to ground The calculation formula is as follows:

[0025]

[0026] in, and are the low-frequency components of the voltage and current at the neutral point, is the middle CT ratio, is the voltage divider ratio.

[0027] In some embodiments, the ground transition resistor The calculation formula is as follows:

[0028]

[0029] in, is the middle CT ratio, is the voltage divider ratio.

[0030] In some embodiments, after determining the nature of the fault, if it is a transient ground fault and the arc is extinguished successfully, the externally attached voltage source is directly removed to restore the system to normal operation; if it is a permanent ground fault, the neutral point voltage is kept equal to the fault electromotive force amplitude, the ground fault current is suppressed, and the protection is activated after the load is transferred, and the generator is tripped smoothly; regardless of whether it is a transient ground fault or a permanent ground fault, the injection of external current is eventually stopped.

[0031] The third aspect of the present application relates to a ground fault arc extinguishing system based on slot potential, comprising: at least one memory for storing programs; at least one processor for entering the program stored in the memory, and when the program stored in the memory is entered, the processor is used to enter the arc extinguishing method as described in the first aspect.

[0032] The fourth aspect of the present application relates to a fault identification system based on a transition resistor TVS, comprising: at least one memory for storing a program; at least one processor for entering the program stored in the memory, and when the program stored in the memory is entered, the processor is used to enter the identification method as described in the second aspect.

[0033] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies:

[0034] (1) This application proposes a ground fault arc extinguishing method based on slot potential. By obtaining the fundamental and third harmonic voltages at the generator neutral point and the machine end, the fundamental slot potential and third harmonic slot potential of each slot conductor are calculated. The actual fault location is further determined by matching with the ground fault potential, achieving fault location at any position within the entire winding range, breaking through the limitations of traditional methods and significantly improving the coverage of fault location. Compared with CN113777526A, this application comprehensively considers the fundamental and third harmonic slot potentials, constructs expressions for the fundamental fault potential and third harmonic fault potential with the fault location as the independent variable, and constructs the objective function in combination with the matching conditions of the fault potential. The objective function value is minimized only when the true fault location is located. The farther from the true fault location, the larger the objective function value. By finding the fault location with the minimum objective function value, the accuracy and reliability of fault location are significantly improved, the possibility of misjudgment is reduced, and the overall performance of the system is enhanced. This method can adapt to various complex fault scenarios, including faults at coil connection points and non-coil connection points, enhancing the system's adaptability in complex fault scenarios and improving the robustness of fault location. This method accurately determines the fault location and fault potential, providing an accurate compensation basis for arc extinguishing. By injecting a dual-frequency reverse fault potential through a dual-frequency active arc extinguishing device, the fault current can be effectively suppressed, achieving reliable arc extinguishing throughout the entire winding range. This significantly improves the reliability and effectiveness of arc extinguishing, especially at non-coil connection points, which is significantly better than traditional methods. The hybrid flexible grounding method combines arc extinguishing coils and dual-frequency active devices. While ensuring arc extinguishing effectiveness, it reduces equipment cost and volume while improving arc extinguishing effectiveness, thereby enhancing the feasibility and cost-effectiveness of engineering applications.

[0035] (2) This application proposes a fault identification method based on a transition resistor TVS. The voltage and current low-frequency components of the generator neutral point are used to calculate the grounding transition resistance during a ground fault and the grounding transition resistance when the arc is extinguished and stabilized. The nature of the fault is determined by comparing the transition resistance in different states. This method can accurately distinguish between transient faults and permanent faults, and take corresponding treatment measures. For transient faults, the external voltage source is directly removed after successful arc extinguishing to restore the normal operation of the system. For permanent faults, the neutral point voltage is kept equal to the fault electromotive force amplitude, the grounding fault current is suppressed, and the generator is smoothly disconnected after the load is transferred. Targeted treatment measures are taken according to the nature of the fault, avoiding the risks brought by misjudgment and improving the safety and reliability of the system. This application provides simple and effective fault identification rules that are easy to implement in engineering, improve the practicality of fault identification and the convenience of engineering application, and can quickly and accurately determine the nature of the fault, providing strong support for system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1A flow chart of a ground fault arc extinguishing method based on slot potential provided in an embodiment of the present application.

[0037] Figure 2 A flow chart of a fault identification method based on a transition resistor TVS provided in an embodiment of the present application.

[0038] Figure 3 Schematic diagram of the hybrid flexible arc extinguishing effect based on slot potential provided in an embodiment of the present application, (a), (b), (c), and (d) correspond to the fault positions of 0.29375, 0.5, 0.79375, and the machine end, respectively.

[0039] Figure 4 A diagram showing the change pattern of transition resistance in a 500 ohm constant resistance model corresponding to a transient ground fault provided in an embodiment of the present application.

[0040] Figure 5 This is a diagram showing the change pattern of transition resistance in a 500 ohm constant resistance model corresponding to a permanent ground fault provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0042] First, the technical terms involved in the embodiments of this application are introduced.

[0043] Large generators: Generators with inherent ground capacitance current generally exceeding 20A.

[0044] TVS: Transient Voltage Suppression, transition resistor.

[0045] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0046] like Figure 1 As shown, the present application discloses a ground fault arc extinguishing method based on slot potential, the arc extinguishing method comprising:

[0047] S1. Obtain the fundamental voltage and third harmonic voltage at the neutral point and generator terminal in real time during normal operation and after a ground fault.

[0048] This application is not limited to the basis for determining whether a single-phase grounding fault occurs. Generally, the phase with the lowest voltage is used as the fault phase.

[0049] S2. Calculate the fundamental slot potential amplitude of each stator slot conductor based on the fundamental voltage at the normal operating terminal and the neutral point, and calculate the third harmonic slot potential amplitude of each stator slot conductor based on the third harmonic voltage at the normal operating terminal and the neutral point.

[0050] In some embodiments, in step S2, the fundamental wave slot potential amplitude of the slot conductor is The calculation formula is as follows:

[0051]

[0052] in, and are the fundamental voltages at the generator terminals and neutral point during normal operation, ∠ represents the phase angle sign, ~ Indicates the fundamental potential phase of each slot conductor, and artificially sets the reference 0 phase of the fundamental potential. , The total number of slot conductors in a branch of one phase of the stator winding

[0053] The third harmonic slot potential amplitude of the slot conductor The calculation formula is as follows:

[0054]

[0055] in, and are the third harmonic voltages at the generator terminal and neutral point during normal operation, Indicates the phase of the third harmonic potential of each slot conductor.

[0056] S3. Using the fundamental slot potential amplitude and the stator slot conductor connection sequence, construct the fundamental fault potential expression with the fault location as the independent variable: , using the third harmonic slot potential amplitude and the stator slot conductor connection sequence, the third harmonic fault potential expression with the fault location as the independent variable is constructed , using the fundamental voltage of the generator neutral point after the ground fault and third harmonic voltage , calculate the intermediate variables A and B.

[0057] In some embodiments, in step S3, the fundamental fault potential expression with the fault location as the independent variable is: The details are as follows:

[0058]

[0059] in, Indicates the fundamental fault potential of the fault phase of the generator stator winding, is the total number of slot conductors in a branch of one phase of the stator winding, is the fault location, Indicates that the fault occurs on the first slot conductor, and so on for other cases. is the fundamental wave slot potential amplitude of the slot conductor, ∠ represents the phase angle sign, ~ Indicates the fundamental potential phase of each slot conductor, and artificially sets the reference 0 phase of the fundamental potential. It represents the fundamental wave potential from the neutral point of the generator to the first slot conductor at the machine end, Before The vector sum of the fundamental potentials of the slot conductors, .

[0060] In some embodiments, in step S3, the third harmonic fault potential expression with the fault location as the independent variable is: The details are as follows:

[0061]

[0062] in, Indicates the third harmonic fault potential of the fault phase of the generator stator winding, is the total number of slot conductors in a branch of one phase of the stator winding, is the fault location, Indicates that the fault occurs on the first slot conductor, and so on for other cases. is the third harmonic slot potential amplitude of the slot conductor, ∠ represents the phase angle sign, Indicates the phase of the third harmonic potential of each slot conductor, and artificially sets the reference 0 phase of the third harmonic potential. It represents the third harmonic potential from the neutral point of the generator to the first slot conductor at the machine end. Before The vector sum of the third harmonic potential of the slot conductors, .

[0063] The fundamental voltage of the generator neutral point after a ground fault is used and third harmonic voltage , calculate the intermediate variables A and B as follows:

[0064]

[0065] in, is the middle vector, and are the fundamental voltage and third harmonic voltage of the generator neutral point after the ground fault, Fault phase The third harmonic potential of the midpoint of the coil to the neutral point, is the third harmonic phase potential of the fault phase, represents an imaginary number, represents the angular frequency, which is equal to , The power frequency is 50 Hz. Indicates the equivalent capacitance to ground of a single-turn coil of the fault phase, Indicates the equivalent capacitance to ground of each phase of the direct-connect system at the machine end. is the equivalent inductance of the winding, represents the capacitance of the generator stator winding to ground, is the total number of stator winding turns of the fault phase.

[0066] Calculated based on the number of slots, number of turns, slot pitch electrical angle, number of pole pairs and rated voltage of the generator stator winding , the calculation formula is as follows: =No. The third harmonic potential from the end of the coil to the neutral point + 1 / 2 The potential of the turns of the coil. It is the third harmonic potential of the winding from the machine end to the neutral point of the entire fault phase, which is calculated based on the parameters of the generator's stator winding, such as the number of slots, number of turns, slot pitch electrical angle, number of pole pairs, and rated voltage.

[0067] S4. Constructing the objective function , solve the fault location when the objective function is minimized, and then determine the fundamental fault potential value and the third harmonic fault potential value.

[0068] Assuming that the measured values are all accurate ideal values, only the fundamental wave and third harmonic potential of the winding corresponding to the real fault position meet the minimum objective function value, that is, only when the optimal objective function value of the conductor of the real fault slot is the minimum, the corresponding is the actual fault location. The further away from the actual fault location the optimal objective function value of the other slot conductors is, the larger the calculated value. This method allows for an accurate solution of the dual-frequency fault potential.

[0069] S5. The neutral point of the generator is grounded by a hybrid flexible grounding method to extinguish arc at the fault point; the hybrid flexible grounding method is as follows: the neutral point is grounded through an arc suppression coil, and a dual-frequency reverse fault potential is injected into the neutral point by an external dual-frequency active arc suppression device.

[0070] like Figure 2 As shown, the present application discloses a fault identification method based on a transition resistor TVS, the identification method comprising:

[0071] T1. A low-frequency power supply is injected into the neutral point of the generator, where the frequency of the low-frequency power supply is less than 50 Hz.

[0072] The low-frequency power supply in this embodiment is a 20 Hz current source.

[0073] T2. Obtain the voltage and current at the neutral point of the generator at the first moment of normal operation, the second moment after the fault occurs and before the start of ground fault arc extinction, and the third moment of stabilization after arc extinction is completed, and use Fourier transform to extract the low-frequency components of the voltage and current, which are consistent with the frequency of the low-frequency power supply.

[0074] like is the ground transition resistance converted to the secondary side, is the three-phase capacitive reactance of the generator converted to the secondary side, is the middle CT ratio, is the voltage divider ratio, is the secondary resistance of the grounding transformer, and The low-frequency voltage of the injection protection measurement can be obtained by injecting the internal resistance and internal potential of the power supply respectively. and low-frequency current The calculation formula is:

[0075]

[0076] Then we can conclude that: .

[0077] T3. Calculate the ground impedance during normal operation by using the voltage and current low-frequency components of the neutral point at the first moment. , calculate the ground impedance during ground fault by using the voltage and current low-frequency components of the neutral point at the second moment , calculate the impedance to ground when arc extinction is complete and stable through the voltage and current low-frequency components of the neutral point at the third moment ,comprehensive and Calculate the ground transition resistance of the primary side of the generator stator winding when a ground fault occurs ,comprehensive and Calculate the ground transition resistance when the arc is extinguished and stable .

[0078] Measure the normal operation and Calculated , and then measure the ground fault and Calculated Due to normal operation , when ground fault occurs , thus obtaining the secondary side transition resistance , then the primary side transition resistance .

[0079] In some embodiments, the impedance to ground The calculation formula is as follows:

[0080]

[0081] in, and are the low-frequency components of the voltage and current at the neutral point, is the middle CT ratio, is the voltage divider ratio.

[0082] In some embodiments, the ground transition resistor The calculation formula is as follows:

[0083]

[0084] in, is the middle CT ratio, is the voltage divider ratio.

[0085] T4. Identify the nature of the fault using the following rules:

[0086]

[0087] in, is the lower limit margin coefficient, the recommended value range is: 30< <100; is the upper limit margin coefficient, the recommended value range is: 1.2< <2.

[0088] In some embodiments, after determining the nature of the fault, if it is a transient ground fault and the arc is extinguished successfully, the externally attached voltage source is directly removed to restore the system to normal operation; if it is a permanent ground fault, the neutral point voltage is kept equal to the fault electromotive force amplitude, the ground fault current is suppressed, and the protection is activated after the load is transferred, and the generator is tripped smoothly; regardless of whether it is a transient ground fault or a permanent ground fault, the injection of external current is eventually stopped.

[0089] This application can perform hybrid flexible arc suppression on single-phase grounding faults in the generator stator and identify the nature of the fault, which is crucial for preventing equipment damage, avoiding accidental power outages, ensuring power supply reliability and protecting personal safety.

[0090] The effectiveness of the proposed modeling method is verified through simulation.

[0091] This example uses a one-phase, two-branch generator model with eight windings per branch as a prototype, establishing a quasi-distributed parameter model for simulation analysis. The generator has a capacity of 30 kVA, a rated voltage of 10.5 kV, and a rated current of 2.86 A. Each branch consists of eight coils connected in series, with one pole pair and 48 total slots, corresponding to a slot pitch of 7.5°. The stator winding-to-ground capacitance per phase is 0.397 μF, and the equivalent-to-ground capacitance per phase of the generator-side directly connected device is 0.405 μF. The analysis is based on the first branch of phase A.

[0092] To verify the arc extinguishing effect based on the slot potential analysis unit, a single-phase grounding fault with a transition resistance of 500Ω was set at 0.5° at the generator A phase coil connection and at the machine end; and at 0.29375° and 0.79375° at the non-coil connection at 0.2s. Figure 3 shown. Figure 3 In the figure, all generators adopt hybrid flexible grounding method, arc suppression coil grounding method corresponds to over-compensation, and the compensation degree is 10%. The active arc suppression device is put into operation at 0.24s. In the figure, (a), (b), (c), and (d) correspond to the fault positions at 0.29375, 0.5, 0.79375, and the machine end respectively. Among them, 0.29375 and 0.79375 are the fault positions at non-coil connection, and 0.5 and the machine end are the fault positions at coil connection. Indicates time in seconds, vertical axis Indicates the fault current in A. Figure 3 It can be seen that when the fault occurs at the non-coil connection of the winding, the arc extinguishing effect of the fault potential calculation method based on the slot potential as the analysis unit is better, and accurate and reliable arc extinguishing can also be achieved at the coil connection.

[0093] In the simulation model, a 500 ohm constant resistance model is used to simulate the ground fault resistance and verify the successful identification method of the fault arc extinction proposed in this application.

[0094] Assume that the single-phase ground fault starts at 0.2s, the transient fault lasts for 0.3s, and the hybrid flexible grounding method is used to extinguish the arc at the fault point at 0.4s. A 500 ohm constant resistance model is used to simulate the ground fault resistance. The transition resistance change waveform calculated according to the method of this application is as follows: Figure 4 The transition resistance measured in the constant resistance model is approximately 500 ohms when the fault occurs. After arc extinction stabilizes, the transition resistance amplitude measured is greater than 15,000 ohms, indicating that the fault is transient, verifying the effectiveness of this method.

[0095] Assuming that the single-phase ground fault starts at 0.2s and the permanent fault lasts for 1.3s, a hybrid flexible grounding method is used to extinguish the arc at the fault point at 0.4s. A 500 ohm constant resistance model is used to simulate the ground fault resistance. The transition resistance change waveform calculated according to the method of this application is as follows: Figure 5 The transition resistance measured in the constant resistance model is approximately 500 ohms when the fault occurs. After arc extinction stabilizes, the transition resistance amplitude measured is less than 600 ohms, indicating that the fault is a permanent fault, verifying the effectiveness of this method.

[0096] It is understandable that the detailed functional implementation of each of the above units / modules can be found in the introduction of the aforementioned method embodiment, and will not be repeated here.

[0097] It should be understood that the above-mentioned device is used to execute the method in the above-mentioned embodiment. The implementation principle and technical effect of the corresponding program module in the device are similar to those described in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method and will not be repeated here.

[0098] Based on the method in the above embodiment, the embodiment of the present application provides an electronic device / image signal generator / network device / transmitter / terminal / base station / industrial computer, which may include: a processor, a communication interface (Communications Interface), a memory (Memory), and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus. The processor can call the logic instructions in the memory to execute the method in the above embodiment.

[0099] In addition, the logical instructions in the above-mentioned memory can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application, or the part that contributes to the existing technology, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application.

[0100] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0101] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0102] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0103] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and storage medium can be located in an ASIC.

[0104] The above embodiments can be implemented in whole or in part using software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions. When loaded and executed on a computer, the computer program instructions fully or partially produce the processes or functions described in the embodiments of this application. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted via the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be magnetic media (e.g., floppy disk, hard disk, tape), optical media (e.g., DVD), or semiconductor media (e.g., solid-state drive (SSD)).

[0105] It will be understood that the various numerical numbers involved in the embodiments of the present application are merely distinctions for the convenience of description and are not intended to limit the scope of the embodiments of the present application.

[0106] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A ground fault arc extinguishing method based on slot potential, characterized in that: The arc fault extinguishing method includes: S1. Obtain the fundamental voltage and third harmonic voltage at the generator neutral point and generator terminal in real time during normal operation and after a ground fault. S2. Calculate the fundamental slot potential amplitude of each stator slot conductor based on the fundamental voltage of the normal operating terminal and the neutral point, and calculate the third harmonic slot potential amplitude of each stator slot conductor based on the third harmonic voltage of the normal operating terminal and the neutral point; S3. Using the fundamental slot potential amplitude and the stator slot conductor connection sequence, construct the fundamental fault potential expression with the fault location as the independent variable: , using the third harmonic slot potential amplitude and the stator slot conductor connection sequence, the third harmonic fault potential expression with the fault location as the independent variable is constructed , using the fundamental voltage of the generator neutral point after the ground fault and third harmonic voltage , calculate the intermediate variables A and B; The intermediate variables A and B are as follows: in, is the middle vector, and are the fundamental voltage and third harmonic voltage of the generator neutral point after the ground fault, Fault phase The third harmonic potential of the midpoint of the coil to the neutral point, is the third harmonic phase potential of the fault phase, represents an imaginary number, represents the angular frequency, Indicates the equivalent capacitance to ground of a single-turn coil of the fault phase, Indicates the equivalent capacitance to ground of each phase of the direct-connect system at the machine end. is the equivalent inductance of the winding, represents the capacitance of the generator stator winding to ground, is the total number of stator winding turns of the fault phase; S4. Constructing the objective function , solve the fault location when the objective function is minimized, and then determine the fundamental fault potential value and the third harmonic fault potential value; S5. The neutral point of the generator is grounded by a hybrid flexible grounding method to extinguish arc at the fault point; the hybrid flexible grounding method is as follows: the neutral point is grounded through an arc suppression coil, and a dual-frequency reverse fault potential is injected into the neutral point by an external dual-frequency active arc suppression device.

2. A fault identification method based on transition resistor TVS, characterized in that: The arc extinguishing method according to claim 1 is used to extinguish a ground fault arc. The fault identification method includes: T1. A low-frequency power supply is injected into the neutral point of the generator, wherein the frequency of the low-frequency power supply is less than 50 Hz; T2. Obtain the voltage and current at the generator neutral point during normal operation (the first moment), from the time the fault occurs to the time the ground fault arc is extinguished (the second moment), and the third moment of stabilization after arc extinguishing. Use Fourier transform to extract the low-frequency components of the voltage and current, which are consistent with the frequency of the low-frequency power supply. T3. Calculate the ground impedance during normal operation by using the voltage and current low-frequency components of the neutral point at the first moment. , calculate the ground impedance during ground fault by using the voltage and current low-frequency components of the neutral point at the second moment , calculate the impedance to ground when arc extinction is complete and stable through the voltage and current low-frequency components of the neutral point at the third moment ,comprehensive and Calculate the ground transition resistance of the primary side of the generator stator winding when a ground fault occurs ,comprehensive and Calculate the ground transition resistance when the arc is extinguished and stable ; T4. Identify the nature of the fault using the following rules: in, is the lower limit margin coefficient; is the upper margin coefficient.

3. The fault identification method according to claim 2, wherein: Ground impedance The calculation formula is as follows: in, and are the low-frequency components of the voltage and current at the neutral point, is the middle CT ratio, is the voltage divider ratio.

4. The fault identification method according to claim 2, wherein: Ground transition resistance The calculation formula is as follows: in, is the middle CT ratio, is the voltage divider ratio.

5. The fault identification method according to claim 2, wherein: After determining the nature of the fault, if it is a transient ground fault and the arc is extinguished successfully, the external voltage source is directly removed to restore the system to normal operation. If it is a permanent ground fault, the neutral point voltage is kept equal to the fault electromotive force amplitude, the ground fault current is suppressed, and the protection is activated after the load is transferred, and the generator is tripped smoothly. Regardless of whether it is a transient ground fault or a permanent ground fault, the injection of external current will eventually stop.

6. A ground fault arc suppression system based on slot potential, characterized in that: include: at least one memory for storing a program; At least one processor is configured to enter the program stored in the memory. When the program stored in the memory is entered, the processor is configured to enter the fault arc extinguishing method according to claim 1.

7. A fault identification system based on transition resistor TVS, characterized in that: include: at least one memory for storing a program; At least one processor is used to enter the program stored in the memory, and when the program stored in the memory is entered, the processor is used to enter the fault identification method according to any one of claims 2 to 5.

Images