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

Abstract

The invention belongs to the technical field of safety protection of large generators, and particularly discloses a slot potential-based ground fault arc extinction and TVS fault identification method and system. The fundamental wave slot potential and the third harmonic slot potential of each slot conductor are calculated by obtaining the fundamental wave and third harmonic voltage of the neutral point and the generator end of the generator. And furthermore, the real fault position is determined through matching with the ground fault potential, so that fault positioning at any position in a full winding range is realized, the limitation of a traditional method is broken through, and the coverage range of fault positioning is remarkably expanded. According to the invention, through the voltage and current low-frequency components of the neutral point of the generator, the grounding transition resistance during a grounding fault and the grounding transition resistance during stabilization after arc extinction are respectively calculated, and the fault property is judged by comparing the transition resistances in different states, so that an instantaneous fault and a permanent fault can be accurately distinguished; simple and effective fault identification is provided, engineering realization is easy, and fault properties can be rapidly and accurately judged.

Description

Technical Field

[0001] This application belongs to the technical field of large generator safety protection, and more specifically, relates to a method and system for arc suppression of grounding faults and fault identification of TVS based on slot potential. Background Art

[0002] Single-phase grounding fault of the stator winding is one of the most common faults in large generators. When a single-phase grounding fault occurs in the stator winding of a generator, according to whether an external injection device is required, the existing arc suppression methods can be mainly divided into passive and active arc suppression methods. Among them, the passive method is mainly grounding through an arc suppression coil at the neutral point to compensate for the fault current. However, the arc suppression coil can only basically compensate for the single-frequency fault component and cannot compensate for the harmonic components in the fault current, and the residual current is still large after compensation. Practical operation experience shows that the existing generator neutral grounding methods cannot achieve reliable arc suppression in different fault scenarios. The active arc suppression method controls the voltage at the fault point to be lower than the arc reignition voltage through an external injection source, and theoretically avoids arc reignition. However, the active arc suppression method for generator stator grounding faults requires a large-capacity inverter power supply, which is large in volume and high in cost.

[0003] The existing compensation amount calculation method based on turn potential cannot achieve arc suppression at non-coil connection points, resulting in limited engineering applications of the existing methods.

[0004] Patent CN113777526A discloses a stator grounding fault location method and system based on the distribution of third harmonic potential, including: S1. Taking the third harmonic slot potential as a unit, calculating the third harmonic slot potential according to the third harmonic potential measured at the neutral point and the machine terminal, and calculating the third harmonic potential of the faulty part of the winding according to the winding connection sequence and the third harmonic slot potential; S2. Based on the third harmonic equivalent circuit of the generator, constructing a fault evaluation index in combination with the third harmonic potential; S3. Presetting multiple reference points in the faulty phase, calculating the fault evaluation index values of each reference point, and regarding the reference point with the smallest calculated value as the fault location to determine the slot number where the fault is located.

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

[0006] Aiming at the defects of the prior art, the purpose of this application is to provide a grounding fault arc suppression method based on slot potential and a fault identification method and system for TVS, aiming to solve the problems that the existing positioning technology cannot solve the dual-frequency fault potential and cannot realize the identification of fault nature.

[0007] The first aspect of this application relates to a grounding fault arc suppression method based on slot potential, and the arc suppression method includes: S1. For the neutral point and the machine terminal of the generator, respectively, obtain the fundamental voltage and the third harmonic voltage after normal operation and grounding fault in real time; S2. Calculate the fundamental slot potential amplitude of each stator slot conductor according to the fundamental voltage of the machine terminal and the neutral point during normal operation, and calculate the third harmonic slot potential amplitude of each stator slot conductor according to the third harmonic voltage of the machine terminal and the neutral point during normal operation; S3. Use the fundamental slot potential amplitude and the connection sequence of the stator slot conductors to construct a fundamental fault potential expression with the fault location as the independent variable , use the third harmonic slot potential amplitude and the connection sequence of the stator slot conductors to construct a third harmonic fault potential expression with the fault location as the independent variable , use the fundamental voltage and the third harmonic voltage of the generator neutral point after grounding fault to calculate the intermediate variables A and B; S4. Construct an 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. Use the hybrid flexible grounding method for the neutral point of the generator to eliminate the arc at the fault point; the hybrid flexible grounding method is: the neutral point is grounded through an arc suppression coil, and a dual-frequency reverse fault potential is injected into the neutral point through an external dual-frequency active arc suppression device.

[0008] In some embodiments, the intermediate variables A and B are specifically as follows:

[0009] Wherein, is the intermediate vector, and are respectively the fundamental voltage and the third harmonic voltage of the generator neutral point after grounding fault, is the third harmonic potential of the midpoint of the -th turn coil of the fault phase to the neutral point, is the third harmonic phase potential of the fault phase, represents the imaginary number, represents the angular frequency, represents the equivalent ground capacitance value of a single-turn coil of the fault phase, represents the per-phase equivalent capacitance to ground value at the generator terminal of the direct connection system, is the equivalent inductance of the winding, represents the capacitance of the generator stator winding to ground, is the total number of turns of the stator winding of the faulty phase.

[0010] The second aspect of the present application relates to a fault identification method based on a transient voltage suppressor (TVS) for a transition resistance, and the identification method includes: T1. Inject a low-frequency power supply at the neutral point of the generator, and the frequency of the low-frequency power supply is less than 50 Hz; 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 until the start of arc suppression for the ground fault, and the third moment of stability after arc suppression is completed, respectively, and use Fourier transform to extract the low-frequency components of the voltage and current, and the low-frequency components are consistent with the frequency of the low-frequency power supply; T3. Calculate the impedance to ground during normal operation through the low-frequency components of the voltage and current at the neutral point at the first moment , calculate the impedance to ground during the ground fault through the low-frequency components of the voltage and current at the neutral point at the second moment , calculate the impedance to ground at stability after arc suppression is completed through the low-frequency components of the voltage and current at the neutral point at the third moment , and comprehensively and calculate the grounding transition resistance of the primary side of the generator stator winding during the ground fault , and comprehensively and calculate the grounding transition resistance at stability after arc suppression is completed ; T4. Identify the nature of the fault through the following rules:

[0011] wherein, is the lower margin coefficient; is the upper margin coefficient.

[0012] In some embodiments, the arc suppression method described in the first aspect is used for arc suppression of the fault.

[0013] In some embodiments, the calculation formula for the impedance to ground is as follows:

[0014] wherein, and are the low-frequency components of the voltage and current at the neutral point respectively, is the intermediate CT transformation ratio, is the voltage divider ratio.

[0015] In some embodiments, the grounding transition resistance has the following calculation formula:

[0016] wherein, is the intermediate CT transformation ratio, is the voltage divider ratio.

[0017] In some embodiments, after the fault nature is determined, if it is an instantaneous grounding fault and the arc suppression is successful, the externally added voltage source is directly removed to restore the normal operation of the system; if it is a permanent grounding fault, the neutral point voltage is kept equal to the amplitude of the fault electromotive force to suppress the grounding fault current. After the load is transferred, the protection operates to smoothly trip the generator; whether it is an instantaneous grounding fault or a permanent grounding fault, the externally applied current injection is finally stopped.

[0018] The third aspect of the present application relates to an arc suppression system for grounding faults based on slot electromotive force, including: at least one memory for storing programs; at least one processor for accessing the programs stored in the memory. When the programs stored in the memory are accessed, the processor is used to execute the arc suppression method as described in the first aspect.

[0019] The fourth aspect of the present application relates to a fault identification system based on a transient voltage suppressor (TVS) for transition resistance, including: at least one memory for storing programs; at least one processor for accessing the programs stored in the memory. When the programs stored in the memory are accessed, the processor is used to execute the identification method as described in the second aspect.

[0020] Generally speaking, compared with the prior art through the above technical solutions conceived by the present application, the following beneficial effects are achieved: (1) This application proposes a grounding fault arc suppression method based on slot electromotive force. By obtaining the fundamental wave and third harmonic voltages at the neutral point and the machine terminal of the generator, the fundamental wave slot electromotive force and the third harmonic slot electromotive force of each slot conductor are calculated. Further, the true fault location is determined by matching with the grounding fault electromotive force, 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. Compared with CN113777526A, this application comprehensively considers the fundamental wave and third harmonic slot electromotive forces, constructs expressions for the fundamental wave fault electromotive force and the third harmonic fault electromotive force with the fault location as the independent variable, and combines the matching conditions of the fault electromotive force to construct an objective function. Only the objective function value at the true fault location is the smallest, and the farther away from the true fault location, the larger the objective function value. By solving the fault location when the objective function value is the smallest, 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 adaptability of the system in complex fault scenarios and improving the robustness of fault location; this method accurately determines the fault location and the fault electromotive force, providing an accurate compensation basis for arc suppression. By injecting a dual-frequency reverse fault electromotive force through a dual-frequency active arc suppression device, the fault current can be effectively suppressed, and reliable arc suppression within the entire winding range can be achieved, significantly improving the reliability and effectiveness of arc suppression. Especially, the arc suppression effect at non-coil connection points is significantly better than that of traditional methods. The hybrid flexible grounding method combines an arc suppression coil and a dual-frequency active device, which not only reduces the equipment cost and volume while ensuring the arc suppression effect, but also improves the arc suppression effect, enhancing the feasibility and economy of engineering applications.

[0021] (2) This application proposes a fault identification method based on a transient voltage suppressor (TVS) for the transition resistance. By using the low-frequency components of the voltage and current at the neutral point of the generator, the grounding transition resistance during the grounding fault and the stable grounding transition resistance after the arc suppression are calculated respectively. By comparing the magnitudes of the transition resistances in different states, the nature of the fault can be judged accurately, and transient faults and permanent faults can be distinguished, and corresponding treatment measures can be taken. For transient faults, after successful arc suppression, the external voltage source is directly removed to restore the normal operation of the system. For permanent faults, the neutral point voltage is maintained equal to the amplitude of the fault electromotive force to suppress the grounding fault current, and the machine is smoothly tripped after transferring the load. According to the nature of the fault, targeted treatment measures are taken, avoiding the risks brought by misjudgment and improving the safety and reliability of the system. This application provides simple and effective fault identification rules, which are easy to implement in engineering, improving the practicality of fault identification and the convenience of engineering applications, and can quickly and accurately judge the nature of the fault, providing strong support for system operation. Brief Description of the Drawings

[0022] Figure 1Flowchart of an arc suppression method for grounding faults based on slot potential provided by an embodiment of the present application.

[0023] Figure 2 Flowchart of a fault identification method based on transient voltage suppressor (TVS) of transition resistance provided by an embodiment of the present application.

[0024] Figure 3 Schematic diagram of the hybrid flexible arc suppression effect based on slot potential provided by an embodiment of the present application. (a), (b), (c), and (d) respectively correspond to the fault positions at 0.29375, 0.5, 0.79375, and the generator terminal.

[0025] Figure 4 Variation law diagram of the transition resistance in the 500-ohm constant resistance model corresponding to the instantaneous grounding fault provided by an embodiment of the present application.

[0026] Figure 5 Variation law diagram of the transition resistance in the 500-ohm constant resistance model corresponding to the permanent grounding fault provided by an embodiment of the present application. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] First, the technical terms involved in the embodiments of the present application are introduced.

[0029] Large generator: A generator with an inherent ground capacitance current generally reaching more than 20A.

[0030] TVS: Transient Voltage Suppression, transition resistance.

[0031] Next, the embodiments of the present application are described with reference to the accompanying drawings in the embodiments of the present application.

[0032] As Figure 1 shown, the present application discloses an arc suppression method for grounding faults based on slot potential. The arc suppression method includes: S1. For the neutral point and the generator terminal of the generator, respectively obtain the fundamental voltage and the third harmonic voltage in normal operation and after the grounding fault in real time.

[0033] The present application is not limited to the judgment basis for whether a single-phase grounding fault occurs. Generally, the phase with the lowest voltage is used as the fault phase.

[0034] S2. Calculate the fundamental slot potential amplitude of each stator slot conductor based on the fundamental voltages at the generator terminal and neutral point during normal operation, and calculate the third harmonic slot potential amplitude of each stator slot conductor based on the third harmonic voltages at the generator terminal and neutral point during normal operation.

[0035] In some embodiments, in step S2, the fundamental slot potential amplitude of the slot conductor is calculated as follows:

[0036] where and are the fundamental voltages at the generator terminal and neutral point during normal operation respectively, ∠ represents the phase angle symbol, ~ represent the fundamental potential phases of each slot conductor, and the reference 0 phase of the fundamental potential is set artificially, , is the total number of slot conductors in a branch of one phase of the stator winding The third harmonic slot potential amplitude of the slot conductor is calculated as follows:

[0037] where and are the third harmonic voltages at the generator terminal and neutral point during normal operation respectively, represents the third harmonic potential phase of each slot conductor.

[0038] S3. Use the fundamental slot potential amplitude and the connection sequence of the stator slot conductors to construct a fundamental fault potential expression with the fault location as the independent variable , use the third harmonic slot potential amplitude and the connection sequence of the stator slot conductors to construct a third harmonic fault potential expression with the fault location as the independent variable , and use the fundamental voltage and the third harmonic voltage at the generator neutral point after the ground fault to calculate the intermediate variables A and B.

[0039] In some embodiments, in step S3, the fundamental fault potential expression with the fault location as the independent variable is as follows:

[0040] where represents the fundamental fault potential of the faulty 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, It indicates that the fault occurs on the first slot conductor, and so on for other cases. is the fundamental slot electromotive force amplitude of the slot conductor, and ∠ represents the phase angle symbol. ~ represents the fundamental electromotive force phase of each slot conductor. The reference 0 phase of the fundamental electromotive force is set artificially. represents the fundamental electromotive force from the generator neutral point to the first slot conductor at the machine terminal. represents the front vector sum of the fundamental electromotive forces of the slot conductors. .

[0041] In some embodiments, in step S3, the expression of the third-harmonic fault electromotive force with the fault location as the independent variable is specifically as follows:

[0042] Among them, represents the third-harmonic fault electromotive force of the faulty 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 electromotive force amplitude of the slot conductor, and ∠ represents the phase angle symbol. represents the third-harmonic electromotive force phase of each slot conductor. The reference 0 phase of the third-harmonic electromotive force is set artificially. represents the third-harmonic electromotive force from the generator neutral point to the first slot conductor at the machine terminal. represents the front vector sum of the third-harmonic electromotive forces of the slot conductors. .

[0043] Using the fundamental voltage and the third-harmonic voltage at the generator neutral point after the ground fault, calculate the intermediate variables A and B, specifically as follows:

[0044] Among them, is the intermediate vector. and are respectively the fundamental voltage and the third-harmonic voltage at the generator neutral point after the ground fault. is the third-harmonic electromotive force from the midpoint of the th turn of the faulty phase coil to the neutral point. is the third-harmonic phase electromotive force of the faulty phase. represents the imaginary number. represents the angular frequency, equal to . is the power frequency of 50 Hz, represents the equivalent capacitance to ground value of a single-turn coil of the faulty phase, represents the per-phase equivalent capacitance to ground value at the generator terminal of the directly connected system, is the equivalent inductance of the winding, represents the capacitance of the generator stator winding to ground, is the total number of turns of the stator winding of the faulty phase.

[0045] It is calculated according to parameters such as the number of slots, number of turns, slot pitch electrical angle, number of pole pairs, and rated voltage of the generator stator winding , and the calculation formula is as follows: =The third harmonic electromotive force from the end of the th turn coil to the neutral point + 1 / 2 of the turn electromotive force of the th turn coil. is the third harmonic electromotive force of the winding from the generator terminal to the neutral point of the entire faulty phase, which is calculated according to parameters such as the number of slots, number of turns, slot pitch electrical angle, number of pole pairs, and rated voltage of the generator stator winding.

[0046] S4. Construct the objective function , solve for the fault location when the objective function is minimized, and then determine the fundamental fault electromotive force value and the third harmonic fault electromotive force value.

[0047] Assuming that the measured values are all accurate ideal values, only the fundamental and third harmonic electromotive forces of the winding corresponding to the true fault location satisfy the minimum objective function value, that is, only when the optimal objective function value of the true fault slot conductor is the smallest, its corresponding is the true fault location. And the optimal objective function values of other slot conductors are larger as the distance from the true fault location is farther. In this way, the dual-frequency fault electromotive force can be accurately solved.

[0048] S5. Use the hybrid flexible grounding method for the neutral point of the generator to extinguish the arc at the fault point; the hybrid flexible grounding method is: the neutral point is grounded through an arc suppression coil, and a dual-frequency reverse fault electromotive force is injected into the neutral point through an external dual-frequency active arc suppression device.

[0049] As Figure 2 shown, this application discloses a fault identification method based on a transient voltage suppressor (TVS) for a transition resistance, and the identification method includes: T1. Inject a low-frequency power supply at the neutral point of the generator, and the frequency of the low-frequency power supply is less than 50 Hz.

[0050] In this embodiment, the low-frequency power supply is a 20 Hz current source.

[0051] T2. Obtain the voltage and current of the generator neutral point at the first moment of normal operation, the second moment from the occurrence of the fault to the start of arc suppression for the ground fault, and the third moment of stability after arc suppression respectively, and use Fourier transform to extract the low-frequency components of the voltage and current, and the low-frequency components are consistent with the frequency of the low-frequency power supply.

[0052] If is the ground transition resistance converted to the secondary side, is the three-phase capacitance to ground of the generator converted to the secondary side, is the transformation ratio of the intermediate CT, is the ratio of the voltage divider, is the resistance of the secondary side of the grounding transformer, and are the internal resistance and internal electromotive force of the injection power supply respectively, and the low-frequency voltage and low-frequency current measured by the injection protection can be obtained, and the calculation formula is:

[0053] Then it can be obtained that: .

[0054] T3. Calculate the impedance to ground during normal operation through the low-frequency components of the voltage and current of the neutral point at the first moment, calculate the impedance to ground during the ground fault through the low-frequency components of the voltage and current of the neutral point at the second moment, calculate the impedance to ground during stability after arc suppression through the low-frequency components of the voltage and current of the neutral point at the third moment, and comprehensively and calculate the ground transition resistance of the primary side of the generator stator winding during the ground fault, and comprehensively and calculate the ground transition resistance during stability after arc suppression.

[0055] Measure and during normal operation respectively, and calculate to obtain , then measure and during the ground fault respectively, and calculate to obtain . Since during normal operation, during the ground fault, the secondary side transition resistance can be obtained, and then the primary side transition resistance .

[0056] In some embodiments, the calculation formula of the impedance to ground is as follows:

[0057] Among them, and are respectively the low-frequency components of the voltage and current at the neutral point. is the transformation ratio of the intermediate CT. is the ratio of the voltage divider.

[0058] In some embodiments, the grounding transition resistance has the following calculation formula:

[0059] Among them, is the transformation ratio of the intermediate CT. is the ratio of the voltage divider.

[0060] T4. Identify the fault nature through the following rules:

[0061] Among them, is the lower margin coefficient, and the recommended value range is: 30 < < 100;; is the upper margin coefficient, and the recommended value range is: 1.2 < < 2.

[0062] In some embodiments, after the fault nature is determined, if it is an instantaneous grounding fault and the arc suppression is successful, directly remove the externally added voltage source to make the system return to normal operation; if it is a permanent grounding fault, keep the neutral point voltage equal to the amplitude of the fault electromotive force, suppress the grounding fault current, and wait for the protection to act after the load is transferred to smoothly trip the generator; whether it is an instantaneous grounding fault or a permanent grounding fault, finally stop injecting the externally applied current.

[0063] This application can perform hybrid flexible arc suppression on the single-phase grounding fault of the generator stator and identify the fault nature, which is crucial for preventing equipment damage, avoiding accident power outages, ensuring power supply reliability, and protecting personal safety.

[0064] Next, the effectiveness of the proposed modeling method is verified through simulation.

[0065] Taking the engine model with one-phase two-branches and eight windings per branch as an example in this embodiment as the prototype, a quasi-distributed parameter model is established to carry out simulation analysis. The capacity of this generator is 30 kVA, the rated voltage is 10.5 kV, the rated current is 2.86 A. Each branch is composed of 8 coils connected in series, the number of pole pairs is 1, the total number of slots is 48, the corresponding slot pitch electrical angle is 7.5°, the stator winding capacitance to ground per phase: 0.397 μF, and the equivalent capacitance to ground of the equipment directly connected to the machine terminal per phase: 0.405 μF. Taking the first branch of phase A as an example for analysis.

[0066] To verify the arc suppression effect based on the slot potential analysis unit, single-phase ground faults with a transition resistance of 500 Ω are set at 0.5 at the connection of the phase A coil of the generator and at the machine terminal; at 0.29375 and 0.79375 at the non-coil connection at 0.2 s. The hybrid flexible arc suppression effect based on the slot potential analysis method is as Figure 3 shown. Figure 3 In, the generator adopts the hybrid flexible grounding method, and the arc suppression coil grounding method corresponds to the over-compensation situation with a compensation degree of 10%. The active arc suppression device is put into operation at 0.24 s. In the figure, (a), (b), (c), and (d) respectively correspond to the fault positions at 0.29375, 0.5, 0.79375, and the machine terminal. Among them, the fault positions at 0.29375 and 0.79375 are the non-coil connection fault positions, and 0.5 and the machine terminal are the coil connection fault positions. The horizontal axis represents time, with the unit of second, and the vertical axis represents the fault current, with the unit of A. In Figure 3 , it can be seen that when the fault occurs at the non-coil connection of the winding, the arc suppression effect based on the fault potential calculation method with the slot potential as the analysis unit is better, and accurate and reliable arc suppression can also be achieved at the coil connection.

[0067] In the simulation model, a 500-ohm constant resistance model is used to simulate the grounding fault resistance and verify the fault arc suppression successful identification method proposed in this application.

[0068] Assume that the starting time of the single-phase ground fault is the 0.2 s, the duration of the transient fault is 0.3 s, and the hybrid flexible grounding method is used to suppress the arc at the fault point at 0.4 s. A 500-ohm constant resistance model is used to simulate the grounding fault resistance, and the waveform of the transition resistance calculated according to the method of this application is as Figure 4 shown. In the constant resistance model, the measured transition resistance at the time of fault occurrence is about 500 ohms, and the amplitude of the measured transition resistance after arc suppression stabilization is greater than 15000 ohms, then it is judged that the nature of the fault is a transient fault, verifying the effectiveness of this method.

[0069] Assume that the starting time of the single-phase grounding fault is 0.2 s, the duration of the permanent fault is 1.3 s, and the hybrid flexible grounding method is used to extinguish the arc at the fault point at 0.4 s. A 500-ohm constant resistance model is used to simulate the grounding fault resistance, and the waveform of the transition resistance calculated according to the method of this application is as Figure 5 shown. The transition resistance measured in the constant resistance model is about 500 ohms at the time of fault occurrence, and the amplitude of the transition resistance measured after the arc extinguishing is stable is less than 600 ohms, then it is determined that the fault nature is a permanent fault, verifying the effectiveness of the method.

[0070] It can be understood that the detailed function implementation of each of the above units / modules can be referred to the introduction in the foregoing method embodiments, and will not be elaborated here.

[0071] It should be understood that the above device is used to execute the method in the above embodiments. For the corresponding program modules in the device, the implementation principle and technical effects are similar to those described in the above method. The working process of the device can refer to the corresponding process in the above method, and will not be elaborated here.

[0072] Based on the method in the above embodiments, an embodiment of the present application provides an electronic device / image signal generator / network device / transmitter / terminal / base station / industrial control computer. The electronic device / image signal generator / network device / transmitter / terminal / base station / industrial control computer may include: a processor, a communications interface, a memory, and a communication bus. Among them, the processor, the communications interface, and the memory complete mutual communication through the communication bus. The processor can call the logic instructions in the memory to execute the method in the above embodiments.

[0073] In addition, when the logic instructions in the above memory are implemented in the form of software functional units and sold or used as an independent product, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art or a 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 several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application.

[0074] Based on the method in the above embodiments, an embodiment of the present application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program runs on a processor, it causes the processor to execute the method in the above embodiments.

[0075] Based on the method in the above embodiments, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, it causes the processor to execute the method in the above embodiments.

[0076] It can be understood that the processor in the embodiment of the present application may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or 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.

[0077] The method steps in the embodiment of the present application may be implemented in a hardware manner or by a processor executing software instructions. The software instructions may be composed of corresponding software modules. The software modules may be stored in a random access memory (RAM), flash memory, read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, hard disks, removable hard disks, CD-ROMs, or any other form of storage medium well 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 may also be a component of the processor. The processor and the storage medium may be located in an ASIC.

[0078] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted through 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 in a wired manner (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or a wireless manner (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or a data center that includes one or more integrated available media. The available medium can be a magnetic medium (such as a floppy disk, a hard disk, a magnetic tape), an optical medium (such as a DVD), or a semiconductor medium (such as a solid state disk (SSD)), etc.

[0079] It can be understood that the various numerical numbers involved in the embodiments of the present application are only for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0080] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A ground fault arc extinguishing method based on slot potential, characterized in that: The arc extinguishing method includes: S1. Obtain the fundamental voltage and third harmonic voltage in real time during normal operation and after a ground fault at the neutral point and the machine end of the generator; S2. Calculate the fundamental slot potential amplitude of each stator slot conductor based on the fundamental voltage of the normal operating machine end 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 machine end 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; S4. Constructing the objective function , solve the fault location where 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: the neutral point is grounded through an arc extinguishing coil, and a dual-frequency reverse fault potential is injected into the neutral point by an external dual-frequency active arc extinguishing device.

2. The arc extinguishing method according to claim 1, characterized in that: The intermediate variables A and B are as follows: in, is the middle vector, and They 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-connected system at the machine end. is the winding equivalent inductance, It represents the capacitance of the generator stator winding to ground. is the total number of stator winding turns of the fault phase.

3. A fault identification method based on transition resistor TVS, characterized in that: The identification method includes: T1. A low-frequency power source is injected into the neutral point of the generator, wherein the frequency of the low-frequency power source is less than 50 Hz; T2. Obtain the voltage and current of the neutral point of the generator at the first moment of normal operation, the second moment after the fault occurs and before the ground fault arc extinguishing begins, and the third moment of stability after the arc extinguishing 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; T3. Calculate the impedance to ground during normal operation by using the voltage and current low-frequency components of the neutral point at the first moment. , calculate the impedance to ground 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 completed 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 factor.

4. The identification method according to claim 3, characterized in that: Fault arc extinguishing is performed using the arc extinguishing method as described in claim 1 or 2.

5. The identification method according to claim 3, characterized in that: Impedance to ground The calculation formula is as follows: in, and are the low-frequency components of the voltage and current at the neutral point, is the intermediate CT ratio, is the voltage divider ratio.

6. The identification method according to claim 3, characterized in that: Ground transition resistance The calculation formula is as follows: in, is the intermediate CT ratio, is the voltage divider ratio.

7. The identification method according to claim 3, characterized in that: After determining the nature of the fault, if it is a transient ground fault and the arc is extinguished successfully, directly remove the external voltage source to restore the system to normal operation; if it is a permanent ground fault, keep the neutral point voltage equal to the fault electromotive force amplitude, suppress the ground fault current, and wait for the load to be transferred before the protection is activated to smoothly cut off the machine; Whether it is a transient ground fault or a permanent ground fault, the injection of external current will eventually stop.

8. A ground fault arc extinguishing system based on slot potential, 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. When the program stored in the memory is entered, the processor is used to enter the arc extinguishing method as described in claim 1 or 2.

9. 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. When the program stored in the memory is entered, the processor is used to enter the identification method as described in any one of claims 3 to 7.

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