Stator winding ground fault arc extinguishing method and system based on ground transition resistance

Abstract

The present invention discloses a method and system for arc extinguishing of stator winding ground fault based on ground transition resistance, comprising the following steps: S1. Real-time acquisition of fundamental voltage of neutral point and machine end during normal operation and after ground fault; S2. Calculation of fault phase potential E A1 , and calculate the fault phase potential E A1 Neutral point to ground voltage U N1 Phase angle d S3. Construct an analytical equation for locating the fundamental-wave fault in the generator stator winding grounding, substituting the aforementioned measurements and calculations to complete the fundamental-wave fault location. S4. If multiple solutions are found for the fundamental-wave fault location, introduce a low-frequency injection calibration criterion to select the correct transition resistance value. S5. High-resistance grounding is used to extinguish the arc at the fault point. This invention significantly improves the accuracy and reliability of fault location, eliminates the possibility of misjudgment, and provides an accurate compensation basis for arc extinguishing.

Description

Technical Field

[0001] The present invention relates to the technical field of arc extinguishing due to a ground fault of a stator winding, and in particular to a method and system for arc extinguishing due to a ground fault of a stator winding based on a ground transition resistance. Background Art

[0002] Generators on offshore nuclear power platforms are integrated energy systems that utilize thermal energy generated by nuclear reactors to drive steam turbines, providing continuous power to the offshore platform and surrounding facilities. Offshore nuclear power platforms operate in harsh marine environments, subject to high corrosion and high winds and waves. Single-phase ground faults in the generator stator windings are frequent. Large ground fault currents generate arcs, which damage winding insulation, burn the core, and sinter the core laminations. Furthermore, continued arcing at the fault point can easily lead to destructive short-circuit failures, posing a serious threat to equipment safety. Furthermore, the compact interior of the platform, coupled with the nuclear reactor load, is extremely sensitive to arcing. To mitigate damage to the generator from ground fault arcs and prevent threats to platform safety, reliable ground fault arc extinguishing methods are urgently needed, along with the ability to identify the nature of the fault after extinguishing the arc, enabling effective troubleshooting measures.

[0003] When a single-phase grounding fault occurs in the stator winding of a generator, the existing fault arc extinguishing methods can be mainly divided into passive and active arc extinguishing methods, depending on whether an external injection device is required. Among them, the passive method mainly grounds the neutral point through an arc extinguishing coil to compensate for the fault current. However, the arc extinguishing coil can only basically compensate for the fault component of a single frequency, and cannot compensate for the harmonic component in the fault current, resulting in a large residual current after compensation. Actual operating experience shows that the existing generator neutral point grounding method cannot achieve reliable fault arc extinguishing under different fault scenarios. The active arc extinguishing method controls the fault point voltage to be lower than the arc reignition voltage through an external injection source, which in principle avoids arc reignition. However, the existing active arc extinguishing method for generator stator grounding faults is prone to the problem of multiple fault location solutions, and there is a risk of secondary arcing.

[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 third-harmonic relationships. While this method offers some accuracy in certain scenarios, it suffers from the problem of multiple solutions. Relying solely on the third-harmonic potential makes it difficult to achieve a unique solution, and improper operation can easily lead to secondary arcing. Furthermore, this patent's location method cannot be used to determine the potential of dual-frequency faults, significantly limiting its practical application in arc suppression technology. Furthermore, this patent's location technology cannot identify the nature of the fault, which can delay fault resolution and cause serious damage to the generator. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a stator winding ground fault arc extinguishing method and system based on ground transition resistance, so as to solve the problems of multiple solutions, easy secondary arcing and inability to identify the nature of the fault in existing positioning technology.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0008] The arc extinguishing method for stator winding ground fault based on ground transition resistance includes the following steps:

[0009] S1. Obtain the fundamental voltage at the generator's neutral point and generator terminals in real time during normal operation and after a ground fault.

[0010] S2. Based on the terminal voltage at the time of fault U A and neutral point to ground voltage U N1 , calculate the fault phase potential by difference E A1 , according to Fourier analysis, calculate the fault phase potential E A1 Neutral point to ground voltage U N1 Phase angle δ ;

[0011] S3. Based on the fundamental wave potential phase distribution characteristics, an analytical location equation for the generator stator winding grounding fundamental wave fault is constructed with the fault location as the independent variable. The above calculation variables are then incorporated to complete the fundamental wave fault location.

[0012] S4. If multiple solutions are found for the fundamental fault location, a low-frequency injection calibration criterion is introduced to select the only correct transition resistance value. The corresponding location result is then considered the true fault location.

[0013] S5. Use high-resistance grounding to extinguish arc at the fault point of the generator's neutral point; the high-resistance grounding method is: the neutral point is grounded through high resistance, and a dual-frequency current is injected into the neutral point through an external dual-frequency active arc extinguishing device, so that the neutral point maintains a dual-frequency reverse fault potential.

[0014] Preferably, the fundamental wave fault analytical location equation in step S3 is specifically:

[0015]

[0016] Where, α represents the fault turns ratio, which is the ratio of the number of turns between the neutral point and the fault point of the generator stator winding to the number of turns of the complete fault branch; C ∑ is the three-phase capacitance to ground including the stator winding and direct-connected system; R N The neutral point is connected to the high resistance R N High resistance grounding.

[0017] Preferably, the low-frequency injection amount verification criterion in step S4 selects a unique correct positioning solution, and the specific method includes the following steps:

[0018] T1. Inject 20Hz low-frequency power into the neutral point of the generator. The low-frequency power will not affect the normal operation of the generator;

[0019] T2. Obtain the voltage and current at the generator neutral point at the first moment of normal operation and the second moment after the fault occurs and before the start of ground fault arc extinguishing, respectively. 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.

[0020] 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. Z 1. Calculate the ground impedance during ground fault by using the voltage and current low-frequency components of the neutral point at the second moment Z 2. Comprehensive Z 1 and Z 2Calculate the ground transition resistance of the generator when a ground fault occurs R f1 ;

[0021] T4. Use low-frequency injection to measure the actual ground transition resistance. Compare this with the multiple transition resistance values calculated using multiple solutions. Select the correct transition resistance value, and the corresponding location result is considered the actual fault location.

[0022] Preferably, the calculation formula of the ground impedance Z in step T3 is as follows:

[0023]

[0024] in, U oc and I ocare the low-frequency components of the voltage and current at the neutral point respectively;

[0025] The ground transition resistance in step T3 The calculation formula is as follows:

[0026] .

[0027] Preferably, the calculation formula for calculating multiple transition resistances in the multi-solution case in step T4 is as follows:

[0028]

[0029] in, R f ( α ) represents the ground transition resistance obtained by calculation.

[0030] Preferably, the dual-frequency currents injected in step S5 are:

[0031]

[0032]

[0033] in, I in1 is the injected fundamental current; I in3 is the injected third harmonic current; Represents the fundamental voltage from the neutral point to the fault point; Represents the third harmonic voltage from neutral point to fault point; U N3 is the third harmonic voltage from the center point to the ground.

[0034] Preferably, the method further includes a fault identification method based on the transition resistance measurement value, and the fault identification method includes the following steps:

[0035] M1. According to the ground transition resistance measurement method, continuously measure the ground transition resistance value, obtain the voltage and current of the generator neutral point at the third moment after the arc extinction is completed and stabilized, and use Fourier transform to extract the low-frequency components of the voltage and current to calculate the ground impedance after the ground fault is stabilized. Z 3. Comprehensive Z 2 and Z 3. Calculate the ground transition resistance of the generator after a ground fault occurs R f2 ;

[0036] M2. Identify the nature of the fault using the following rules:

[0037]

[0038] in, R SET The threshold to set.

[0039] Preferably, in step M2, after determining the nature of the fault, if it is a permanent fault, the neutral point voltage is kept equal to the fault electromotive force amplitude and opposite in phase to suppress the ground fault current; at this time, if the generator does not have sufficient backup power, the arc extinguishing state is maintained and the generator continues to operate. When sufficient backup power is available, the load is transferred, the protection is activated, and the generator is tripped smoothly; if the generator has sufficient backup power, the protection is activated and the generator is tripped quickly;

[0040] If it is a transient fault, the system will continue to operate, and the injection of external current will eventually stop regardless of whether it is a transient ground fault or a permanent ground fault.

[0041] The arc extinguishing system for stator winding ground fault based on ground transition resistance is characterized in that: the arc extinguishing system executes the arc extinguishing method; the arc extinguishing system includes

[0042] at least one memory for storing an arc extinguishing program;

[0043] At least one processor is used to execute the arc extinguishing program stored in the memory. When the arc extinguishing program stored in the memory is entered, the processor is used to execute the arc extinguishing method.

[0044] Preferably, the memory is also used to store a fault identification program; the processor is used to execute the fault identification program stored in the memory, and when the fault identification program stored in the memory is entered, the processor is used to execute the fault identification method.

[0045] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0046] The present invention obtains the fundamental voltage phase distribution characteristics at the generator neutral point and the generator terminal to obtain an analytical location equation for the generator stator winding ground fault, which may contain multiple solutions. Furthermore, by combining it with a low-frequency injection amount verification criterion, a unique location solution is screened out, the true fault location is determined, and fault location is achieved at any position in the entire winding. This overcomes the limitations of traditional methods and significantly improves the accuracy of fault location. Compared with CN113777526A, the present invention comprehensively considers the fundamental wave and low-frequency injection amount, constructs a fundamental wave fault analytical location equation with the fault location as the independent variable, and a low-frequency injection amount verification criterion, screens out a unique location solution, significantly improves the accuracy and reliability of fault location, eliminates the possibility of misjudgment, and provides an accurate compensation basis for arc extinguishing. By injecting dual-frequency current through a dual-frequency active arc extinguishing device, the neutral point maintains a dual-frequency reverse fault potential, effectively suppressing the fault current, achieving reliable arc extinguishing throughout the entire winding range, and preventing secondary arcing. This significantly improves the reliability and effectiveness of arc extinguishing, and the arc extinguishing effect at non-coil connection points is significantly better than that of traditional methods. Furthermore, the present invention can adapt to various complex fault scenarios, including faults at coil connection points and non-coil connection points, thereby enhancing the adaptability of the system in complex fault scenarios and improving the robustness of fault location.

[0047] The present invention uses the low-frequency components of the voltage and current at the generator neutral point to calculate the grounding transition resistance during a ground fault and the grounding transition resistance when the grounding state stabilizes after arc extinction. By comparing the transition resistance in different states with a threshold value, the nature of the fault can be determined. This allows accurate distinction between transient and permanent faults, and the appropriate treatment measures to be taken. Targeted treatment measures are taken based on the nature of the fault, avoiding the risks of misjudgment and improving the safety and reliability of the system. Furthermore, the present invention provides simple and effective fault identification rules that are easy to implement in engineering, improving the practicality of fault identification and the convenience of engineering applications. It can quickly and accurately determine the nature of the fault, providing strong support for system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a flow chart of the present invention;

[0049] Figure 2 A flowchart for selecting a unique correct positioning solution based on the low-frequency injection amount verification criterion in step S4 of the present invention;

[0050] Figure 3 Flowchart of the fault identification method based on transition resistance measurement value of the present invention;

[0051] Figure 4 This is a schematic diagram of the positioning effect of the present invention, wherein: Figure 4 (a) The present invention is for α= Schematic diagram of the fault location effect at 0.125. Figure 4(b) The present invention is α= Schematic diagram of the fault location effect at 0.250. Figure 4 (c) The present invention is α= Schematic diagram of the fault location effect at 0.375. Figure 4 (d) The present invention is α= Schematic diagram of the fault location effect at 0.50;

[0052] Figure 5 Schematic diagram of arc extinguishing effect of the present invention, wherein: Figure 5 (a) The present invention is for α= Schematic diagram of arc extinguishing effect of fault arc extinguishing at 0.125, Figure 5 (b) The present invention is α= Schematic diagram of arc extinguishing effect of fault arc extinguishing at 0.250. Figure 5 (c) The present invention is α= Schematic diagram of arc extinguishing effect of fault arc extinguishing at 0.375, Figure 5 (d) The present invention is α= Schematic diagram of arc extinguishing effect of fault arc extinguishing at 0.50;

[0053] Figure 6 This is a diagram showing the change pattern of transition resistance in a 300Ω constant resistance model corresponding to a transient ground fault of the present invention;

[0054] Figure 7 This is a diagram showing the change regularity of the transition resistance in the 300Ω constant resistance model corresponding to the permanent ground fault of the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] A stator winding ground fault arc extinguishing method based on ground transition resistance, combined with Figure 1 As shown, the following steps are included:

[0057] S1. Obtain the fundamental voltage at the neutral point and generator terminal during normal operation and after a ground fault in real time.

[0058] The present invention is not limited to the basis for determining whether a single-phase grounding fault occurs, and generally the phase with the lowest voltage is used as the fault phase.

[0059] S2. Based on the terminal voltage at the time of the fault U A and neutral point to ground voltage U N1 , calculate the fault phase potential by difference E A1 , according to Fourier analysis, calculate the fault phase potentialE A1 Neutral point to ground voltage U N1 Phase angle δ .

[0060] S3. Based on the fundamental wave potential phase distribution characteristics, an analytical positioning equation for the generator stator winding grounding fundamental wave fault is constructed with the fault location as the independent variable. The above calculation variables are then substituted into the equation to complete the fundamental wave fault positioning.

[0061] Specifically, the fundamental wave fault analytical location equation is as follows:

[0062]

[0063] Where, α represents the fault turns ratio (i.e., the ratio of the number of turns between the neutral point and the fault point of the generator stator winding to the number of turns of the complete fault branch. The present invention uses the fault turns ratio to indicate the fault location); C ∑ is the three-phase capacitance to ground including the stator winding and direct-connected system; R N For high resistance, the neutral point is R N High resistance grounding. Using the fundamental zero sequence voltage after the fault and the fault phase electromotive force, α ∈[0,1] range to find f ( α ) is closest to 0, we can calculate α .

[0064] S4. If there are multiple solutions for fundamental wave fault location, a low-frequency injection calibration criterion is introduced to select the only correct transition resistance value. The corresponding location result can be regarded as the true fault location.

[0065] like Figure 2 As shown in the figure, the low-frequency injection amount verification criterion selects the only correct positioning solution. The specific method includes the following steps:

[0066] T1. A 20Hz low-frequency power supply is injected into the neutral point of the generator. The low-frequency power supply will not affect the normal operation of the generator.

[0067] T2. Obtain the voltage and current at the generator neutral point at the first moment of normal operation and the second moment after the fault occurs and before the start of ground fault arc extinction. Use Fourier transform to extract the low-frequency components of the voltage and current. The low-frequency components are consistent with the frequency of the low-frequency power supply.

[0068] 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. Z1. Calculate the ground impedance during ground fault by using the voltage and current low-frequency components of the neutral point at the second moment Z 2. Comprehensive Z 1 and Z 2Calculate the ground transition resistance of the generator when a ground fault occurs R f1 .

[0069] T4. Use low-frequency injection to measure the actual ground transition resistance value. Compare it with the multiple transition resistance values calculated in the multi-solution case, and select the correct transition resistance value. The corresponding positioning result can be regarded as the actual fault location.

[0070] Specifically, in step T3, the ground impedance Z is calculated as follows:

[0071]

[0072] in, U oc and I oc are the low-frequency components of the voltage and current at the neutral point, respectively.

[0073] Specifically, in step T3, the ground transition resistance The calculation formula is as follows:

[0074]

[0075] Specifically, in step T4, the calculation formula for calculating multiple transition resistances in the case of multiple solutions is as follows:

[0076]

[0077] in, R f ( α ) represents the ground transition resistance obtained by calculation.

[0078] S5. Use high-resistance grounding of the neutral point of the generator to extinguish arc at the fault point. The high-resistance grounding method is as follows: the neutral point is grounded through high resistance, and a dual-frequency current is injected into the neutral point through an external dual-frequency active arc extinguishing device to keep the neutral point at a dual-frequency reverse fault potential.

[0079] Specifically, the injected dual-frequency currents are:

[0080]

[0081]

[0082] in, I in1 is the injected fundamental current;I in3 is the injected third harmonic current; Represents the fundamental voltage from the neutral point to the fault point; Represents the third harmonic voltage from the neutral point to the fault point.

[0083] like Figure 3 As shown, the method also includes a fault identification method based on the transition resistance measurement value, and the fault identification method includes the following steps:

[0084] M1. Continuously measure the ground transition resistance value according to the ground transition resistance measurement method in step S4, obtain the voltage and current at the neutral point of the generator at the third moment after the arc extinguishing is completed and stabilized, and use Fourier transform to extract the low-frequency components of the voltage and current to calculate the ground impedance after the ground fault is stabilized. Z 3. Comprehensive Z 2 and Z 3. Calculate the ground transition resistance of the generator after a ground fault occurs R f2 ;

[0085] M2. Identify the nature of the fault using the following rules:

[0086]

[0087] in, R SET The threshold for setting is 8000~10000Ω.

[0088] Specifically, after determining the nature of the fault, if it is a permanent fault, the neutral point voltage should be kept equal in magnitude and opposite in phase to the fault electromotive force to suppress the ground fault current. If the generator does not have sufficient backup power, the arc is suppressed and operation continues. Once sufficient backup power is available, the load is transferred, the protection is activated, and the generator is tripped smoothly. If the generator has sufficient backup power, the protection is activated and the generator is tripped quickly.

[0089] If the fault is transient, the system continues to operate. Whether it is a transient ground fault or a permanent ground fault, the external current injection will eventually stop.

[0090] The present invention can flexibly extinguish arcs on single-phase grounding faults in generator stators and identify the nature of the faults, which is crucial for preventing equipment damage, avoiding accidental power outages, ensuring power supply reliability, and protecting personal safety.

[0091] The effectiveness of the above method is verified through simulation below.

[0092] The generator in this embodiment has two winding branches per phase, each consisting of eight coils connected in series. The rated voltage is 10.5 kV, the stator winding resistance per phase is 1.528 mΩ, the stator winding leakage inductance per phase is 2.84 mH, and the stator winding capacitance per phase is 0.397 μF. The number of pole pairs is 1, the total number of slots is 48, and the corresponding slot pitch angle is 7.5°. The neutral point grounding resistance is 2286 Ω, and the direct-connected system capacitance to ground per phase is 0.405 μF. This analysis takes the first branch of phase A as an example.

[0093] In order to verify the arc extinguishing effect based on the slot potential analysis unit, at the connection of the generator A phase coil at 0.2s α= 0.125, α= 0.250, α= 0.375, α= A single-phase ground fault with a transition resistance of 300Ω is set at 0.50. The positioning results based on the method of the present invention are as follows Figure 4 As shown, and the above different a The schematic diagrams of the fault location effect at the value are as follows: Figure 4 As shown in (a), (b), (c), and (d), the arc extinguishing results are as follows: Figure 5 As shown, and the above different α The arc extinguishing effect diagrams of the fault arc extinguishing at the value are as follows: Figure 5 As shown in (a), (b), (c), and (d). Figure 4 Middle, horizontal axis Indicates time in seconds, vertical axis α Indicates the fault location. It can be seen that the method of the present invention can achieve accurate positioning and eliminate the problem of multiple solutions. Figure 5 In the process, the generators are all grounded with high resistance, and the active arc suppression device is put into operation at 0.3s. Indicates time in seconds, vertical axis I f Indicates the fault current in A. U f Indicates the fault potential in kV. Figure 5 It can be seen that the arc extinguishing effect of the method of the present invention is very good, secondary arcing can be avoided, and accurate and reliable arc extinguishing can be achieved.

[0094] In the simulation model, a 300 ohm constant resistance model is used to simulate the ground fault resistance and verify the fault identification method proposed in this application.

[0095] 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 0.5s. A 300Ω constant resistance model is used to simulate the ground fault resistance. The transition resistance change waveform calculated according to the present method is as follows: Figure 6 The transition resistance measured in the constant resistance model is approximately 300Ω when the fault occurs. After arc extinction stabilizes, the transition resistance value measured is greater than the set threshold of 10,000Ω, indicating that the fault is transient, verifying the effectiveness of this method.

[0096] Assuming that the start time of a single-phase ground fault is 0.2s, a permanent fault is set, and at 0.4s, a hybrid flexible grounding method is used to extinguish the arc at the fault point. A 300Ω constant resistance model is used to simulate the ground fault resistance. The transition resistance change waveform calculated by the method according to the present invention is as follows: Figure 7 The transition resistance measured in the constant resistance model is approximately 300Ω when the fault occurs. After the arc is extinguished and stabilized, the transition resistance is less than 10,000Ω, indicating that the fault is a permanent fault, verifying the effectiveness of this method.

[0097] A stator winding ground fault arc extinguishing system based on ground transition resistance includes: a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus, and the processor can call the logic instructions in the memory to execute the above method. Specifically, the arc extinguishing system includes at least one memory for storing an arc extinguishing program; at least one processor for executing the arc extinguishing program stored in the memory, and when the arc extinguishing program stored in the memory is entered, the processor is used to execute the arc extinguishing method of the present invention. The memory is also used to store a fault identification program; the processor is used to execute the fault identification program stored in the memory, and when the fault identification program stored in the memory is entered, the processor is used to execute the fault identification method of the present invention.

[0098] In addition, the logical instructions in the aforementioned memory can be implemented in the form of a software functional unit and, when sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes a number of instructions for causing 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 of the present invention.

[0099] Based on the method of the present invention, the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method of the present invention.

[0100] Based on the method of the present invention, the present invention provides a computer program product. When the computer program product runs on a processor, the processor is enabled to execute the method of the present invention.

[0101] It is understood that the processor in the present invention 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.

[0102] The method steps of the present invention can be implemented via 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, a hard disk, a removable hard disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from 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.

[0103] The above embodiments can be implemented in whole or in part through 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. A computer program product comprises one or more computer instructions. When the computer program instructions are loaded and executed on a computer, they fully or partially generate the process or functions of the method according to the present invention. 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 a 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 that can be accessed by a computer, or a data storage device such as a server or data center that integrates one or more available media. Available media can include magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state drives (SSDs)).

Claims

1. A stator winding ground fault arc extinguishing method based on ground transition resistance, characterized by: The following steps are involved: S1. Obtain the fundamental voltage at the generator's neutral point and generator terminals in real time during normal operation and after a ground fault. S2. Based on the terminal voltage at the time of fault U A and neutral point to ground voltage U N1 , calculate the fault phase potential by difference E A1 , according to Fourier analysis, calculate the fault phase potential E A1 Neutral point to ground voltage U N1 Phase angle δ ; S3. Based on the fundamental wave potential phase distribution characteristics, an analytical location equation for the generator stator winding grounding fundamental wave fault is constructed with the fault location as the independent variable. The above calculation variables are then incorporated to complete the fundamental wave fault location. The fundamental wave fault analytical location equation in step S3 is specifically: Where, represents the fault turns ratio, which is the ratio of the number of turns between the neutral point and the fault point of the generator stator winding to the number of turns of the complete fault branch; is the three-phase capacitance to ground including the stator winding and direct-connected system; The neutral point is connected to the high resistance High resistance grounding; S4. If multiple solutions are found for the fundamental fault location, a low-frequency injection calibration criterion is introduced to select the only correct transition resistance value. The corresponding location result is then considered the true fault location. In step S4, the low-frequency injection amount verification criterion selects the only correct positioning solution, and the specific method includes the following steps: T1. Inject 20Hz low-frequency power into the neutral point of the generator. The low-frequency power will not affect the normal operation of the generator; T2. Obtain the voltage and current at the generator neutral point at the first moment of normal operation and the second moment after the fault occurs and before the start of ground fault arc extinguishing, respectively. 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. Z 1. Calculate the ground impedance during ground fault by using the voltage and current low-frequency components of the neutral point at the second moment Z 2. Comprehensive Z 1 and Z 2Calculate the ground transition resistance of the generator when a ground fault occurs ; T4. Use low-frequency injection to measure the actual ground transition resistance. Compare this with the multiple transition resistance values calculated using multiple solutions. Select the correct transition resistance value, and the corresponding location result is considered the actual fault location. S5. The neutral point of the generator is grounded with high resistance to extinguish the arc at the fault point; the high resistance grounding method is as follows: the neutral point is grounded with high resistance, and a dual-frequency current is injected into the neutral point by an external dual-frequency active arc suppression device, so that the neutral point maintains a dual-frequency reverse fault potential; The method further includes a fault identification method based on the transition resistance measurement value, the fault identification method comprising the following steps: M1. According to the ground transition resistance measurement method, continuously measure the ground transition resistance value, obtain the voltage and current of the generator neutral point at the third moment after the arc extinction is completed and stabilized, and use Fourier transform to extract the low-frequency components of the voltage and current to calculate the ground impedance after the ground fault is stabilized. Z 3. Comprehensive Z 2 and Z 3. Calculate the ground transition resistance of the generator after a ground fault occurs ; M2. Identify the nature of the fault using the following rules: in, The threshold to set.

2. The arc extinguishing method for stator winding ground fault based on ground transition resistance according to claim 1, characterized in that: The calculation formula of the ground impedance Z in step T3 is as follows: in, and are the low-frequency components of the voltage and current at the neutral point respectively; The ground transition resistance in step T3 The calculation formula is as follows: 。 3. The arc extinguishing method for stator winding ground fault based on ground transition resistance according to claim 1, characterized in that: The calculation formula for calculating multiple transition resistances in the case of multiple solutions in step T4 is as follows: in, Represents the calculated ground transition resistance.

4. The arc extinguishing method for stator winding ground fault based on ground transition resistance according to claim 1, characterized in that: The dual-frequency currents injected in step S5 are: in, is the injected fundamental current; is the injected third harmonic current; Represents the fundamental voltage from the neutral point to the fault point; Represents the third harmonic voltage from neutral point to fault point; is the third harmonic voltage from the center point to the ground.

5. The arc extinguishing method for stator winding ground fault based on ground transition resistance according to claim 1, characterized in that: In step M2, after determining the nature of the fault, if it is a permanent fault, the neutral point voltage is kept equal to the fault electromotive force in amplitude and opposite in phase to suppress the ground fault current; At this time, if the generator does not have sufficient backup power, it will maintain the arc extinguishing state and continue to operate. When sufficient backup power is available, the load will be transferred, the protection will be activated, and the generator will be shut down smoothly. If the generator has sufficient backup power, the protection will be activated and the generator will be shut down quickly. If it is a transient fault, the system will continue to operate, and the injection of external current will eventually stop regardless of whether it is a transient ground fault or a permanent ground fault.

6. The stator winding ground fault arc suppression system based on ground transition resistance is characterized by: The arc extinguishing system performs the arc extinguishing method according to any one of claims 1 to 5; the arc extinguishing system comprises at least one memory for storing an arc extinguishing program; At least one processor is used to execute the arc extinguishing program stored in the memory. When the arc extinguishing program stored in the memory is entered, the processor is used to execute the arc extinguishing method.

7. The stator winding ground fault arc extinguishing system based on ground transition resistance according to claim 6, characterized in that: The memory is also used to store a fault identification program; The processor is used to execute the fault identification program stored in the memory. When the fault identification program stored in the memory is entered, the processor is used to execute the fault identification method.

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