Generator stator single-phase grounding fault positioning method and processing terminal

Abstract

The present application relates to a generator stator single-phase ground fault positioning method and a processing terminal, the method comprising: obtaining characteristic parameters of a fault phase and fault voltage parameters when a single-phase ground fault occurs; wherein the characteristic parameters include ground capacitance at a normal operation time, neutral point ground impedance and stator winding potential distribution characteristic parameters, and the fault voltage parameters include neutral point zero sequence voltage and machine terminal voltage; obtaining a target function constructed based on a single-phase ground fault zero sequence equivalent circuit; based on a minimization algorithm, solving the target function according to the characteristic parameters and the fault voltage parameters to obtain a plurality of alternative fault points; and screening each of the alternative fault points to determine the specific position of the fault point. The present application realizes accurate positioning of a stator single-phase ground fault point and can also avoid deviation of positioning results caused by phase problems.

Description

Technical Field

[0001] This invention relates to the field of grounding fault detection technology, and in particular to a method and processing terminal for locating a single-phase grounding fault in a generator stator. Background Technology

[0002] As a core component of the power system, the safe and stable operation of generators directly affects the reliability and economy of power grid supply. With the expansion of power system scale and the continuous increase in generator unit capacity, the problem of locating single-phase ground faults in generator stator windings with high-resistance neutral grounding has received increasing attention. As a core component of the generator, single-phase ground faults in the stator windings can not only burn the iron core, causing repair difficulties and economic losses, but may also develop into phase-to-phase or turn-to-turn short circuits, threatening the safe operation of the unit. Traditional stator grounding protection is mostly based on the fundamental zero-sequence voltage and third harmonic voltage principles. However, in applications with high-resistance neutral grounding, the fault current is limited to within 10-15A to reduce the risk of iron core damage. This also results in weak ground fault characteristic signals, making traditional protection methods insufficiently sensitive and difficult to accurately identify the phase and location of high-resistance ground faults.

[0003] Existing fault location technologies face multiple challenges in high-resistance grounding environments. On one hand, accurate calculation of the transition resistance is crucial for fault location; however, the nonlinear relationship between the zero-sequence voltage phase characteristics and the transition resistance of large salient-pole or non-salient-pole generators is often overlooked, leading to location errors. For example, the phase shift of the winding potential of a non-salient-pole generator significantly affects the distribution characteristics of the zero-sequence voltage; neglecting this factor will drastically reduce location accuracy. Therefore, a highly accurate single-phase grounding fault location method is urgently needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for locating single-phase grounding faults in generator stator and a processing terminal.

[0005] The technical solution adopted by this invention to solve its technical problem is: constructing a method for locating a single-phase ground fault in a generator stator, comprising: The characteristic parameters of the faulted phase and the fault voltage parameters when a single-phase ground fault occurs are obtained; wherein, the characteristic parameters include the ground capacitance, neutral point grounding impedance and stator winding potential distribution characteristic parameters during normal operation, and the fault voltage parameters include the neutral point zero-sequence voltage and the terminal voltage; Obtain the objective function constructed based on the zero-sequence equivalent circuit of a single-phase ground fault; Based on the minimization algorithm, the objective function is solved according to the feature parameters and the fault voltage parameters to obtain several candidate fault points; Each of the candidate fault points is screened to determine the specific location of the fault point.

[0006] Preferably, the step of solving the objective function based on the minimization algorithm according to the feature parameters and the fault voltage parameters includes: Substitute the characteristic parameters and the fault voltage parameters into the objective function, and solve the problem with the aim of finding the minimum value of the objective function to obtain a solution set; The solutions that meet the set selection rules are extracted from the solution set to obtain several alternative fault points.

[0007] Preferably, extracting solutions that conform to the set selection rules from the solution set includes: Extract solutions from the solution set whose target value is less than a set threshold, and generate corresponding alternative fault points based on all extracted solutions for each solution; or The solutions in the solution set are arranged from smallest to largest based on the size of the target value to obtain a solution sequence; corresponding candidate fault points are generated according to the 1st to Hth solutions in the solution sequence; where H is a natural number greater than 1.

[0008] Preferably, the screening of each of the candidate fault points includes: Determine if the number of potential fault points is greater than one; When the number of candidate fault points is no more than 1, the specific location of the fault point is determined based on the candidate fault points. When the number of candidate fault points is greater than one, the candidate fault point with the highest fault probability is selected from the candidate fault points by the injection device screening method or the third harmonic screening method, and the specific location of the fault point is determined based on the selected candidate fault point.

[0009] Preferably, the candidate fault point with the highest failure probability is selected from each of the candidate fault points using an injection device screening method, including: The actual fault transition resistance of the faulty phase is measured using an injection device. Calculate the theoretical fault transition resistance corresponding to each of the candidate fault points; The first fault probability of each of the candidate fault points is calculated based on the actual fault transition resistance and the theoretical fault transition resistance, so as to determine the candidate fault point with the highest fault probability.

[0010] Preferably, the expression for the theoretical fault transition resistance is: , This represents the theoretical fault transition resistance corresponding to the k-th candidate fault point. This represents the fundamental longitudinal potential from the fault location to the neutral point. Represents the zero-sequence voltage at the neutral point. This represents the total impedance of the generator to ground; The expression for the first failure probability is: , Indicates the probability of the first failure. This represents the actual fault transition resistance.

[0011] Preferably, the candidate fault point with the highest fault probability is selected from among the candidate fault points using the third harmonic screening method, including: Obtain the pre-fault neutral point third harmonic voltage and the generator terminal third harmonic voltage before the single-phase ground fault occurs, and the post-fault neutral point third harmonic voltage after the single-phase ground fault occurs. The change in the neutral point third harmonic voltage is calculated based on the neutral point third harmonic voltage before the fault and the neutral point third harmonic voltage after the fault. Calculate the theoretical fault transition resistance corresponding to each of the candidate fault points; The third harmonic fault transition resistance of each of the candidate fault points is calculated based on the third harmonic voltage of the neutral point before the fault and the change in the third harmonic voltage of the neutral point. The second fault probability of each of the candidate fault points is calculated based on the theoretical fault transition resistance and the third harmonic fault transition resistance, so as to determine the candidate fault point with the highest fault probability.

[0012] Preferably, the expression for the theoretical fault transition resistance is: , This represents the theoretical fault transition resistance corresponding to the k-th candidate fault point. This represents the fundamental longitudinal potential from the fault location to the neutral point. Represents the zero-sequence voltage at the neutral point. This represents the total impedance of the generator to ground; The expression for the third harmonic fault transition resistance is: , This represents the transition resistance during third harmonic faults. This indicates the third harmonic voltage at the neutral point before the fault. This represents the change in the third harmonic voltage at the neutral point. Indicates the neutral point grounding impedance. Indicates the operating frequency of the generator. This represents the capacitance to ground during normal operation. This represents the third harmonic longitudinal potential from the fault location to the neutral point. This represents the phase difference between the k-th turn of the winding and the phase potential. This represents the third harmonic potential of each turn of the winding. This indicates the third harmonic voltage at the terminal. This represents the third harmonic voltage at the neutral point; The expression for the second failure probability is: , This represents the probability of the second failure.

[0013] Preferably, the objective function is expressed as: in, , , , , , Indicates the winding percentage position. Indicates the winding turn number. This represents the target value corresponding to the fault location x of the y-th turn of the winding. This represents the fundamental longitudinal potential from the fault location to the neutral point. This represents the phase difference between the k-th turn of the winding and the phase potential. This represents the potential of each turn of the winding. Indicates the terminal voltage. Represents the zero-sequence voltage at the neutral point. This represents the real part of the reciprocal of the zero-sequence voltage at the neutral point. This represents the imaginary part of the reciprocal of the zero-sequence voltage at the neutral point. This represents the total impedance of the generator to ground. Indicates the neutral point grounding impedance. Indicates the operating frequency of the generator. This represents the capacitance to ground during normal operation. This indicates taking the real part of the complex phase. This indicates taking the imaginary part of the complex phasor.

[0014] The present invention also constructs a processing terminal, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the generator stator single-phase ground fault location method described above.

[0015] The technical solution of this invention, by combining the zero-sequence equivalent circuit of stator grounding fault and the potential distribution characteristics of stator winding, achieves the location of stator single-phase grounding fault point. It not only provides accurate location but also avoids the problem of deviation in location results caused by phase issues. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a flowchart of the generator stator single-phase ground fault location method in some embodiments of the present invention; Figure 2 This is a circuit diagram of the zero-sequence equivalent circuit for a single-phase ground fault in some embodiments of the present invention; Figure 3 This is a circuit structure block diagram of the processing terminal in some embodiments of the present invention. Detailed Implementation

[0017] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0018] It should be noted that the flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0019] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0020] Figure 1 This is a flowchart illustrating a generator stator single-phase ground fault location method in some embodiments of the present invention. This method can accurately determine the location of a single-phase ground fault.

[0021] like Figure 1 As shown, the generator stator single-phase ground fault location method may include steps S10, S20, S30 and S40.

[0022] Step S10 includes: acquiring the characteristic parameters of the faulty phase and the fault voltage parameters when a single-phase ground fault occurs. The characteristic parameters include the ground capacitance, neutral point grounding impedance, and stator winding potential distribution characteristics during normal operation; the fault voltage parameters include the neutral point zero-sequence voltage and the terminal voltage.

[0023] The capacitance to ground during normal operation refers to the capacitance to ground of the generator during normal operation. It can be obtained by testing the generator on-site using existing technology, and will not be elaborated here.

[0024] The neutral point grounding impedance is determined based on the type of grounding device. For example: 1. When the grounding device is a resistor (i.e., the neutral point is grounded through a high-resistance circuit), the neutral point grounding impedance can be the resistance value; 2. When the grounding device is an arc suppression coil (i.e., the neutral point is grounded through an inductor circuit), the neutral point grounding impedance can be the inductive reactance of the arc suppression coil; 3. When the grounding device is a combined grounding device (i.e., grounded through a circuit consisting of a resistor and an arc suppression coil connected in parallel), the neutral point grounding impedance can be the impedance formed by the parallel connection of the resistor and the inductive reactance, i.e., R. N / / jωL,R N The value of the grounding resistance is represented by jωL, and the inductive reactance of the arc suppression coil is represented by jωL (since "i" usually represents current in electrical engineering, "j" is used here to represent the imaginary unit, ω represents the angular frequency, and L represents the inductance of the arc suppression coil). The neutral point grounding impedance can be obtained through existing technology, and will not be elaborated here.

[0025] The stator winding potential distribution characteristic parameters include the potential of each turn of the generator winding and the phase difference between each turn and the potential of that phase (i.e., the phase to which the winding corresponds). These stator winding potential distribution characteristic parameters can usually be obtained from the generator manufacturer, or they can be obtained through existing testing techniques.

[0026] The neutral point zero-sequence voltage can be obtained by testing a first voltage measuring device pre-set at the neutral point, while the terminal voltage can be obtained by testing a second voltage measuring device pre-set at the terminal. It should be noted that both the first and second voltage measuring devices can be existing voltage measuring devices (such as voltage transformers), as long as they can measure the corresponding voltage parameters (including fundamental voltage, third harmonic voltage, etc.), which will not be elaborated here.

[0027] Step S20 includes: obtaining the objective function constructed based on the zero-sequence equivalent circuit of a single-phase ground fault.

[0028] Figure 2 This is a circuit diagram of the zero-sequence equivalent circuit for a single-phase ground fault in some embodiments of the present invention. Accordingly, in some embodiments, the objective function can be: .

[0029] in, This indicates taking the real part of the complex phasor, for example Indicates taking The real part of the complex phase, Indicates taking The real part of the complex phase. This indicates taking the imaginary part of the complex phasor, for example... Pick The imaginary part of the complex phase.

[0030] This indicates the position of the winding percentage. This indicates the winding turn number. This represents the target value corresponding to the fault location x of the y-th turn of the winding. It is easy to understand that... Used to characterize the degree of grounding faults, the smaller the target value, the greater the probability of a grounding fault.

[0031] This represents the total impedance of the generator to ground. , Indicates the neutral point grounding impedance. This indicates the generator's operating frequency (usually 50Hz). This indicates the capacitance to ground during normal operation.

[0032] In this formula, when y=1, When y > 1, . This represents the fundamental longitudinal potential from the fault location to the neutral point. This represents the phase difference between the k-th turn of the winding and the phase potential. Representing the potential of each turn of the winding, the stator winding potential distribution characteristic parameters, which are easily understood, include... , ... and the potential of each turn of the winding. Furthermore, , This indicates the terminal voltage. This represents the zero-sequence voltage at the neutral point.

[0033] The real part of the reciprocal of the zero-sequence voltage at the neutral point is, i.e. . The imaginary part of the reciprocal of the zero-sequence voltage at the neutral point is... .

[0034] Step S30 includes: solving the objective function based on the minimization algorithm, according to the characteristic parameters and fault voltage parameters, to obtain several candidate fault points. In this step, the "minimization algorithm" refers to solving the objective function with the aim of calculating the minimum value of the objective function (i.e., the minimum objective value). Moreover, the minimum objective value may not be a unique solution. Therefore, there may be several candidate fault points, and each candidate fault point may include the objective value and the solution (the solution consists of the winding percentage position and the winding turn number).

[0035] Furthermore, the selected candidate fault points are not limited to solutions containing the minimum target value. When the difference between the minimum target value and the second, third, and fourth minimum target values ​​is small, the selected candidate fault points may also include solutions corresponding to the second to fourth minimum target values ​​and their corresponding target values. The minimum target value is the smallest target value (also called the first minimum target value), the second minimum target value is the target value that is only greater than the minimum target value, the third minimum target value is the target value that is only greater than the second minimum target value and the minimum target value, and so on. It is easy to understand that the more candidate fault points there are, the better the positioning accuracy will be.

[0036] Based on step S30, in some embodiments, the objective function can be solved by performing the following steps: substituting the characteristic parameters and fault voltage parameters into the objective function and solving it with the aim of calculating the minimum value of the objective function to obtain a solution set; extracting solutions that meet the set selection rules from the solution set to obtain several candidate fault points.

[0037] In this step, the solution set can include a subset of solutions for each turn winding at different fault locations x. Each solution subset can be: (x, y, ... ).

[0038] In the first embodiment, solutions conforming to a set selection rule can be extracted from the solution set by performing the following steps: extracting solutions whose target value is less than a set threshold from the solution set, and generating corresponding candidate fault points based on all extracted solutions. In this embodiment, the set threshold can be customized according to requirements; a larger threshold results in higher positioning accuracy but lower efficiency. Furthermore, candidate fault points can be represented as (x, y, ... ).

[0039] In the second embodiment, the following steps can be performed to extract solutions that conform to the set selection rules from the solution set: The solutions in the solution set are arranged from smallest to largest based on the size of the target value to obtain a solution sequence; corresponding candidate fault points are generated according to the 1st to Hth solutions in the solution sequence. Here, H is a natural number greater than 1. It is easy to understand that this embodiment can extract the H solutions with the smallest target values, and then generate candidate fault points for the solution subsets corresponding to these solutions (each solution subset corresponds to one candidate fault point).

[0040] To improve positioning efficiency, based on the second embodiment, the method may further include: calculating sequentially: , … , This represents the objective value corresponding to the H-th solution in the solution sequence. This represents the objective value corresponding to the (H-1)th solution in the solution sequence, ... This represents the objective value corresponding to the first solution in the solution sequence, where C1 represents the first absolute value, C2 represents the second absolute value, and so on. Indicates the first Absolute value; each time an absolute value is calculated, it is determined whether the absolute value is greater than the set absolute value threshold. If it is, the minuend used to calculate the absolute value and the solution whose sequence number is greater than the minuend are removed from the H solutions, and the solution subsets corresponding to the remaining solutions are used to generate candidate fault points.

[0041] For example, when When the value exceeds the set absolute value threshold, it indicates that there is a significant difference between the target value of the first solution and the third solution. This means that starting from the third solution, the probability of grounding failure in subsequent solutions begins to decrease significantly. Therefore, the third to the Hth solutions can be eliminated, which can reduce the amount of computation and improve the positioning efficiency.

[0042] Step S40 includes: screening each candidate fault point to determine the specific location of the fault point. The purpose of this step is to further screen the candidate fault points to identify the most likely candidate fault points for grounding faults, thereby accurately determining the specific location of the fault point.

[0043] In some embodiments, the following steps can be performed to screen each candidate fault point: determine whether the number of candidate fault points is greater than 1; when the number of candidate fault points is not greater than 1 (i.e., there is only a single candidate fault point), determine the specific location of the fault point based on the single candidate fault point; when the number of candidate fault points is greater than 1, select the candidate fault point with the highest fault probability from each candidate fault point using the injection device screening method or the third harmonic screening method, and determine the specific location of the fault point based on the selected candidate fault point with the highest fault probability.

[0044] In this embodiment, the actual fault transition resistance can be measured using an existing injection device, which can be a conventional generator stator ground fault protection injection device capable of measuring the transition resistance of a single-phase ground fault in the stator winding. Specific methods can be found in existing technologies and will not be elaborated here. Specifically, the faulty turn can be determined by the winding turn number from the candidate fault points with the highest fault probability; for example, when y equals 5, it indicates that the 5th winding is the faulty turn. Furthermore, the percentage position of the fault point can be determined based on the winding percentage position from the candidate fault points with the highest fault probability; for example, when x equals 50%, x points to the 50% position of the corresponding winding (i.e., the middle position of the faulty turn).

[0045] Furthermore, when the system is configured with an injection device for measurement, the injection device screening method is preferred. When no injection device is configured for measurement, the screening method can be performed by the third harmonic screening method, so that the present invention can take into account both sensitivity and selectivity and improve robustness.

[0046] In some embodiments, the step of selecting the candidate fault point with the highest fault probability from among the candidate fault points by the injection device screening method may include: measuring the actual fault transition resistance of the fault phase by the injection device; calculating the theoretical fault transition resistance corresponding to each candidate fault point; calculating the first fault probability of each candidate fault point based on the actual fault transition resistance and the theoretical fault transition resistance, so as to determine the candidate fault point with the highest fault probability (that is, the candidate fault point corresponding to the maximum first fault probability is the candidate fault point with the highest fault probability).

[0047] In some embodiments, the expression for the theoretical fault transition resistance can be: .in This represents the theoretical fault transition resistance corresponding to the kth alternative fault point.

[0048] In some embodiments, the expression for the first failure probability can be: . This represents the first failure probability. The higher the first failure probability, the greater the likelihood that the candidate failure point corresponding to this first failure probability is the actual failure point. This represents the actual fault transition resistance. It is easy to understand that this formula calculates the fault probability by performing a deviation analysis between the theoretical fault transition resistance and the actual fault transition resistance.

[0049] In some embodiments, the step of selecting the candidate fault point with the highest fault probability from among the candidate fault points using the third harmonic screening method may include: obtaining the pre-fault third harmonic voltage of the neutral point and the third harmonic voltage of the generator terminal before the single-phase ground fault, and the post-fault third harmonic voltage of the neutral point after the single-phase ground fault; calculating the change in the neutral point third harmonic voltage based on the pre-fault and post-fault neutral point third harmonic voltages; calculating the theoretical fault transition resistance corresponding to each candidate fault point; calculating the third harmonic fault transition resistance of each candidate fault point based on the pre-fault and post-fault third harmonic voltages; and calculating the second fault probability of each candidate fault point based on the theoretical fault transition resistance and the third harmonic fault transition resistance, so as to determine the candidate fault point with the highest fault probability (i.e., the candidate fault point corresponding to the maximum second fault probability is the candidate fault point with the highest fault probability).

[0050] In this embodiment, the pre-fault neutral point third harmonic voltage and the post-fault neutral point third harmonic voltage can be measured using the first voltage measuring device described above, while the terminal third harmonic voltage can be measured using the second voltage measuring device described above. The change in the neutral point third harmonic voltage can be obtained by subtracting the pre-fault neutral point third harmonic voltage from the post-fault neutral point third harmonic voltage. Furthermore, the calculation method for the theoretical fault transition resistance can be found above and will not be repeated here.

[0051] In some embodiments, the expression for the third harmonic fault transition resistance can be: .

[0052] It is easy to understand that when hour, = When y > 1, .in, This represents the transition resistance during third harmonic faults. This indicates the third harmonic voltage at the neutral point before the fault. This represents the change in the third harmonic voltage at the neutral point. This represents the capacitive reactance corresponding to the capacitance to ground, where i represents the imaginary unit. This represents the third harmonic longitudinal potential from the fault location to the neutral point. This represents the phase difference between the k-th turn of the winding and the phase potential. This represents the third harmonic potential of each turn of the winding. This indicates the third harmonic voltage at the terminal. This represents the third harmonic voltage at the neutral point.

[0053] In some embodiments, the expression for the second failure probability can be: , This represents the second failure probability. The higher the second failure probability, the greater the likelihood that the candidate failure point corresponding to this second failure probability will be the actual failure point.

[0054] In some embodiments, steps S01 and S02 may be included before step S10 is performed.

[0055] Step S01 includes: determining whether a grounding fault has occurred.

[0056] In some embodiments, it can be determined whether a generator has experienced a ground fault by using an existing ground fault detection device to determine whether a ground fault has occurred in the generator stator. Ground fault detection devices are commonly used and mature key equipment in modern power systems. They combine computer technology, signal processing technology, and automatic control technology, and are characterized by high precision, high reliability, and intelligence, enabling them to accurately determine whether a ground fault has occurred.

[0057] Step S02 includes: when a ground fault occurs, identifying the faulty phase and proceeding to step S10; when no ground fault occurs, returning to S01.

[0058] In some embodiments, the faulty phase can be determined by: acquiring the effective voltage values ​​of each phase line using a second voltage measuring device; analyzing the fundamental zero-sequence voltage at the terminal to identify the phase with the smallest amplitude as the faulty phase. For example, when UC≤UB and UC≤UA, the faulty phase can be identified as phase C, where UA, UB, and UC represent the effective voltage values ​​of phases A, B, and C, respectively.

[0059] In one specific embodiment, a fault model built using MATLAB / Simulink was used to verify the effectiveness of the invention. Specifically, a single-phase ground fault was designed to occur at multiple locations on different windings of phase C. The tested windings included the 2nd, 5th, and 7th turns of the winding. The transition resistance values ​​at the multiple locations were 0.01Ω, 100Ω, 1000Ω, and 5600Ω, respectively. The verification results are shown in Table 1.

[0060] As shown in Table 1, the final calculated fault location is highly accurate. It should be noted that for (100%, 2), since the fault point is located at the end of the second turn of the winding and also at the beginning of the third turn, the x-value of this group appears to have a large error on the surface. However, considering the value of y, the simulation test results of this group are still accurate.

[0061] The technical solution of this invention, by combining the zero-sequence equivalent circuit of stator grounding fault and the potential distribution characteristics of stator winding, achieves the location of stator single-phase grounding fault point. It not only provides accurate location but also avoids the problem of deviation in location results caused by phase issues.

[0062] The present invention also provides a processing terminal, such as Figure 3 As shown, the processing terminal includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the generator stator single-phase ground fault location method provided in this embodiment of the invention.

[0063] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0064] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0065] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0066] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for locating a single-phase ground fault in a generator stator, characterized in that, include: The characteristic parameters of the faulted phase and the fault voltage parameters when a single-phase ground fault occurs are obtained; wherein, the characteristic parameters include the ground capacitance, neutral point grounding impedance and stator winding potential distribution characteristic parameters during normal operation, and the fault voltage parameters include the neutral point zero-sequence voltage and the terminal voltage; Obtain the objective function constructed based on the zero-sequence equivalent circuit of a single-phase ground fault; Based on the minimization algorithm, the objective function is solved according to the feature parameters and the fault voltage parameters to obtain several candidate fault points; Each of the candidate fault points is screened to determine the specific location of the fault point.

2. The generator stator single-phase ground fault location method according to claim 1, characterized in that, The step of solving the objective function based on the minimization algorithm, according to the feature parameters and the fault voltage parameters, includes: Substitute the characteristic parameters and the fault voltage parameters into the objective function, and solve the problem with the aim of finding the minimum value of the objective function to obtain a solution set; The solutions that meet the set selection rules are extracted from the solution set to obtain several alternative fault points.

3. The generator stator single-phase ground fault location method according to claim 2, characterized in that, Extracting solutions that meet the set selection rules from the solution set includes: Extract solutions from the solution set whose target value is less than a set threshold, and generate corresponding alternative fault points based on all extracted solutions for each solution; or The solutions in the solution set are arranged from smallest to largest based on the size of the target value to obtain a solution sequence; corresponding candidate fault points are generated according to the 1st to Hth solutions in the solution sequence; where H is a natural number greater than 1.

4. The generator stator single-phase ground fault location method according to claim 1, characterized in that, The process of screening each of the candidate fault points includes: Determine if the number of potential fault points is greater than one; When the number of candidate fault points is no more than 1, the specific location of the fault point is determined based on the candidate fault points. When the number of candidate fault points is greater than one, the candidate fault point with the highest fault probability is selected from the candidate fault points by the injection device screening method or the third harmonic screening method, and the specific location of the fault point is determined based on the selected candidate fault point.

5. The generator stator single-phase ground fault location method according to claim 4, characterized in that, The candidate fault points with the highest failure probability are selected from each of the candidate fault points using an injection device screening method, including: The actual fault transition resistance of the faulty phase is measured using an injection device. Calculate the theoretical fault transition resistance corresponding to each of the candidate fault points; The first fault probability of each of the candidate fault points is calculated based on the actual fault transition resistance and the theoretical fault transition resistance, so as to determine the candidate fault point with the highest fault probability.

6. The generator stator single-phase ground fault location method according to claim 5, characterized in that, The expression for the theoretical fault transition resistance is: , This represents the theoretical fault transition resistance corresponding to the k-th candidate fault point. This represents the fundamental longitudinal potential from the fault location to the neutral point. Represents the zero-sequence voltage at the neutral point. This represents the total impedance of the generator to ground; The expression for the first failure probability is: , Indicates the probability of the first failure. This represents the actual fault transition resistance.

7. The generator stator single-phase ground fault location method according to claim 4, characterized in that, The third harmonic filtering method is used to select the candidate fault points with the highest failure probability from among the candidate fault points, including: Obtain the pre-fault neutral point third harmonic voltage and the generator terminal third harmonic voltage before the single-phase ground fault occurs, and the post-fault neutral point third harmonic voltage after the single-phase ground fault occurs. The change in the neutral point third harmonic voltage is calculated based on the neutral point third harmonic voltage before the fault and the neutral point third harmonic voltage after the fault. Calculate the theoretical fault transition resistance corresponding to each of the candidate fault points; The third harmonic fault transition resistance of each of the candidate fault points is calculated based on the third harmonic voltage of the neutral point before the fault and the change in the third harmonic voltage of the neutral point. The second fault probability of each of the candidate fault points is calculated based on the theoretical fault transition resistance and the third harmonic fault transition resistance, so as to determine the candidate fault point with the highest fault probability.

8. The generator stator single-phase ground fault location method according to claim 7, characterized in that, The expression for the theoretical fault transition resistance is: , This represents the theoretical fault transition resistance corresponding to the k-th candidate fault point. This represents the fundamental longitudinal potential from the fault location to the neutral point. Represents the zero-sequence voltage at the neutral point. This represents the total impedance of the generator to ground; The expression for the third harmonic fault transition resistance is: , This represents the transition resistance during third harmonic faults. This indicates the third harmonic voltage at the neutral point before the fault. This represents the change in the third harmonic voltage at the neutral point. Indicates the neutral point grounding impedance. Indicates the operating frequency of the generator. This represents the capacitance to ground during normal operation. This represents the third harmonic longitudinal potential from the fault location to the neutral point. This represents the phase difference between the k-th turn of the winding and the phase potential. This represents the third harmonic potential of each turn of the winding. This indicates the third harmonic voltage at the terminal. This represents the third harmonic voltage at the neutral point; The expression for the second failure probability is: , This represents the probability of the second failure.

9. The generator stator single-phase ground fault location method according to any one of claims 1 to 8, characterized in that, The objective function is expressed as: in, , , , , , Indicates the winding percentage position. Indicates the winding turn number. This represents the target value corresponding to the fault location x of the y-th turn of the winding. This represents the fundamental longitudinal potential from the fault location to the neutral point. This represents the phase difference between the k-th turn of the winding and the phase potential. This represents the potential of each turn of the winding. Indicates the terminal voltage. Represents the zero-sequence voltage at the neutral point. This represents the real part of the reciprocal of the zero-sequence voltage at the neutral point. This represents the imaginary part of the reciprocal of the zero-sequence voltage at the neutral point. This represents the total impedance of the generator to ground. Indicates the neutral point grounding impedance. Indicates the operating frequency of the generator. This represents the capacitance to ground during normal operation. This indicates taking the real part of the complex phase. This indicates taking the imaginary part of the complex phasor.

10. A processing terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the generator stator single-phase ground fault location method as described in any one of claims 1 to 9.

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