Pumped storage group stator winding grounding fault positioning and multi-solution screening method

Abstract

The invention discloses a ground fault positioning and multi-solution screening method for a stator winding of a pumped storage unit, and belongs to the field of relay protection. The method is combined with a special structure of a stator winding of a variable-speed pumped storage unit, and a function relationship between a fault winding potential and a fault position is established by taking a slot potential as an analysis unit. In a phasor plane, by drawing a three-phase ground voltage phasor and a neutral point voltage phasor, an included angle relation between a fault point voltage phasor and the neutral point voltage phasor and a phasor triangle relation are utilized to determine an alternative fault point. And then, an optimization model for fault positioning is established, and a homonuclear molecule optimization algorithm is adopted for solving, so that accurate positioning of a plurality of alternative fault points is realized. And finally, third harmonic voltage information is introduced as auxiliary information, and a unique solution is screened out from the plurality of alternative fault points. The method is high in reliability, small in positioning result error and suitable for the positioning requirement of the variable-speed pumped storage unit stator grounding fault.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection for pumped - storage units, and particularly relates to a method for locating stator winding grounding faults and screening multiple solutions in pumped - storage units. Background Technique

[0002] Stator grounding faults are the fault types with the highest probability in large - capacity units and are also precursors to winding short - circuit faults. When the grounding protection operates and the unit shuts down, the staff needs to check the internal and external insulation of the unit, locate the fault position and carry out repairs. The workload is large and the shutdown time is long. The fault repair procedure is related to the fault position. For terminal faults, repairs can be directly carried out, while for grounding faults inside the winding, repairs need to be carried out after the rotor is lifted. Therefore, if the accurate location of the grounding fault can be realized in advance, it can reduce the troubleshooting work and optimize the repair process, which is of great significance.

[0003] Existing methods assume that the potential of the faulty winding is in the same direction as the potential of the faulty phase, ignoring the differences in the potentials of each branch of each phase, making it impossible to locate the faulty branch; or ignoring the influence of short - pitched windings on the potential distribution, resulting in a large theoretical error when the fault position is not at the coil connection point, making the judgment result of the faulty branch unreliable and causing the problem of misjudgment of the faulty branch. Summary of the Invention

[0004] The present invention proposes a method for locating stator winding grounding faults and screening multiple solutions in pumped - storage units to solve the problems existing in the above - mentioned prior art. Its purpose is to sensitively, reliably and accurately realize the location of stator winding grounding faults and screening of multiple solutions in variable - speed pumped - storage units.

[0005] To achieve the above - mentioned purpose, the present invention provides a method for locating stator winding grounding faults and screening multiple solutions in pumped - storage units, including the following steps:

[0006] According to the stator winding structure of the variable - speed pumped - storage unit, construct a functional relationship between the potential of the faulty stator winding and the fault position with the slot potential as the analysis unit;

[0007] Draw the three - phase ground voltage phasors and the neutral - point voltage phasor in the phasor plane, calculate the included - angle relationship between the fault - point voltage phasor and the neutral - point voltage phasor in the phasor diagram, and draw the fault - point voltage phasor according to the included - angle relationship;

[0008] Determine a phasor triangle according to the three - phase ground voltage phasors and the neutral - point voltage phasor. The fault - point voltage phasor will divide the phasor triangle into a new phasor triangle determined by the neutral - point voltage phasor, the fault - point voltage phasor and the faulty - winding potential phasor. Draw the faulty - phase winding potential phasor according to the relationship of the new phasor triangle;

[0009] Take the intersection point of the fault point voltage phasor and the fault phase winding electromotive force phasor as the alternative fault point;

[0010] Establish a fault location optimization model based on the neutral point voltage phasor and the fault phase winding electromotive force phasor, and solve it through the homonuclear molecule optimization algorithm to obtain the accurate positions of multiple alternative fault points;

[0011] Introduce the third harmonic voltage information and combine the functional relationship between the stator fault winding electromotive force and the fault position to screen out the final fault point from multiple alternative fault points.

[0012] Preferably, the expression of the functional relationship between the stator fault winding electromotive force and the fault position is:

[0013]

[0014] In the formula, is the fault winding electromotive force, α is the fault position, is the slot electromotive force, is the terminal-to-ground voltage of the machine of the phase where this branch is located, is the fundamental frequency zero-sequence voltage measured at the neutral point. Denote the slot conductor electromotive force of the slot numbered x as β x = ±xθ, θ is the slot pitch electrical angle, 1 ≤ j ≤ 2i, and i is the number of turns of the coil.

[0015] Preferably, the calculation expression of the included angle relationship is:

[0016]

[0017] In the formula, R eq = R n + R k , R n is the primary value of the neutral point grounding resistance, R k is the resistance of the short-circuit impedance, Xk is the reactance component of the short-circuit impedance, X eq = 1 / (3ωC z + 3ωC g ), Cg and Cz are the single-phase winding-to-ground capacitance and the external equivalent-to-ground capacitance respectively.

[0018] Preferably, the expression of the new phasor triangle relationship is:

[0019]

[0020] In the formula, is the fundamental frequency zero-sequence voltage measured at the neutral point, is the fault winding electromotive force, is the fault point voltage phasor, R eq = R n + Rk , R n is the primary value of the neutral grounding resistance, R k is the resistance of the short-circuit impedance, Xk is the reactance component of the short-circuit impedance, X eq = 1 / (3ωC z + 3ωC g ), Cg and Cz are respectively the capacitance to ground of the single-phase winding and the external equivalent capacitance to ground, R f is the fault transition resistance.

[0021] Preferably, the expression of the fault location optimization model is:

[0022]

[0023] In the formula, is the fundamental frequency zero-sequence voltage measured at the neutral point, is the potential of the fault winding, ∠() is the calculation symbol for finding the phase, obj(α) is the optimal objective function, and the fault location α is the decision variable.

[0024] Preferably, the steps of solving through the homonuclear molecule optimization algorithm include the initialization stage, the exploration stage, the development stage, the iteration and reduction stage:

[0025] In the initialization stage, an initial population of the decision variable α is generated based on pseudo-random numbers;

[0026] In the exploration stage, the fitness evaluation of each decision variable α is calculated according to the specific distribution positions of the atoms and their electrons;

[0027] In the development stage, some atoms move towards the most important atoms to form homonuclear molecules, and different decision variables α are obtained to find the local optimum or optimize the local structure of the current solution;

[0028] In the iteration and reduction stage, the optimal decision variable is obtained by reducing the size of the electron cloud around the atomic nucleus in each iteration, and the accurate fault location is obtained.

[0029] Preferably, the final fault point is screened out by calculating the probability index, and the calculation expression of the probability index is:

[0030]

[0031] In the formula, P h is the probability index that the h-th alternative fault point is the actual fault location, α h ′ is the fault location of the h-th alternative fault point, R f ′ h is the calculated transition resistance of the h-th alternative fault point, d h is R f and R f ′h The difference, R f is the fault transition resistance, is the third harmonic voltage at the machine terminal, is the third harmonic voltage at the neutral point, is the third harmonic electromotive force of the faulty winding at the fault position of the h-th alternative fault point, X g = 1 / ωC g , X z = 1 / ωC z , C g and C z are respectively the capacitance of the single-phase winding to the ground and the external equivalent capacitance to the ground, X k is the reactance component of the short-circuit impedance, 1 ≤ j ≤ 2i, where i is the number of turns of the coil.

[0032] The present invention also provides a computer device, including a memory, a processor, and a computer program stored on the memory, and the processor executes the computer program to implement the steps of the method.

[0033] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method are implemented.

[0034] The present invention also provides a computer program product, including a computer program, and when the computer program is executed by a processor, the steps of the method are implemented.

[0035] Compared with the prior art, the present invention has the following advantages and technical effects:

[0036] The present invention discloses a method for locating and screening multiple solutions of stator winding ground faults of a pumped-storage unit. This method combines the special structure of the stator winding of a variable-speed pumped-storage unit, takes the slot electromotive force as the analysis unit, and establishes a functional relationship between the electromotive force of the faulty winding and the fault position. In the phasor plane, by drawing the three-phase voltage phasors to the ground and the neutral point voltage phasor, using the included angle relationship between the fault point voltage phasor and the neutral point voltage phasor, as well as the phasor triangle relationship, alternative fault points are determined. Then, an optimization model for fault location is established and solved using the co-nuclear molecule optimization algorithm to achieve precise location of multiple alternative fault points. Finally, the third harmonic voltage information is introduced as auxiliary information to screen out the unique solution from multiple alternative fault points. This method has strong reliability, small error in the positioning result, and is applicable to the positioning requirements of stator ground faults of variable-speed pumped-storage units.

[0037] The present invention proposes an idea for stator winding grounding fault location based on the intersection of phasor trajectories and an optimal fault location model. The potential distribution characteristics of the stator windings of a variable-speed pumped storage unit are analyzed and summarized. Aiming at the problem of simplified errors in the existing winding potential calculation methods, an accurate calculation method for winding potential with slot potential as the analysis unit is introduced. By introducing the measurement information of the third harmonic voltage to achieve multi-solution screening, the proposed location method can not only determine the fault branch but also accurately locate the specific fault location, providing guidance for fault maintenance. This method has no simplified errors, can provide a basis for accurately identifying the fault branch of the grounding fault, and its comprehensive location performance is better than that of the existing location methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0039] Figure 1 is the flowchart of the method according to the embodiment of the present invention;

[0040] Figure 2 is the fundamental frequency zero-sequence equivalent circuit of the stator grounding fault according to the embodiment of the present invention;

[0041] Figure 3 is the potential distribution of each branch of the stator winding of the variable-speed pumped storage unit and its details according to the embodiment of the present invention;

[0042] Figure 4 is the actual distribution of the potential of branch A of the stator winding according to the embodiment of the present invention 1 of the present invention;

[0043] Figure 5 is the solution result under the fault condition of Case1 according to the embodiment of the present invention, where Fig. (a) is the fundamental frequency vector diagram of Case1 and Fig. (b) is the judgment result diagram of the alternative fault points of Case1;

[0044] Figure 6 is the solution result under the fault condition of Case2 according to the embodiment of the present invention, where Fig. (a) is the fundamental frequency vector diagram of Case2 and Fig. (b) is the judgment result diagram of the alternative fault points of Case2;

[0045] Figure 7 is the solution result under the fault condition of Case3 according to the embodiment of the present invention, where Fig. (a) is the fundamental frequency vector diagram of Case3 and Fig. (b) is the judgment result diagram of the alternative fault points of Case3;

[0046] Figure 8The solution results under the Case 4 fault condition of the embodiment of the present invention, where Figure (a) is the fundamental frequency vector diagram of Case 4, and Figure (b) is the judgment result diagram of the alternative fault points of Case 4. Detailed implementation manners

[0047] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The following will describe this application in detail with reference to the drawings and in combination with the embodiments.

[0048] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0049] Embodiment 1

[0050] As Figure 1 shown, this embodiment provides a method for locating and multi-solution screening of stator winding grounding faults of a pumped-storage unit, including the following steps:

[0051] According to the stator winding structure of the variable-speed pumped-storage unit, establish a functional relationship between the potential of the faulty winding of the stator and the fault location with the slot potential as the analysis unit;

[0052] Draw the three-phase ground voltage phasors and the neutral point voltage phasor in the phasor plane, calculate the included angle relationship between the fault point voltage phasor and the neutral point voltage phasor in the phasor diagram, and draw the fault point voltage phasor according to the included angle relationship;

[0053] Determine a phasor triangle according to the three-phase ground voltage phasors and the neutral point voltage phasor. The fault point voltage phasor will divide the phasor triangle into a new phasor triangle determined by the neutral point voltage phasor, the fault point voltage phasor, and the potential phasor of the faulty winding. Draw the potential phasor of the faulty phase winding according to the relationship of the new phasor triangle;

[0054] Take the intersection point of the fault point voltage phasor and the potential phasor of the faulty phase winding as the alternative fault point;

[0055] Establish a fault location optimization model according to the neutral point voltage phasor and the potential phasor of the faulty phase winding, and solve it through the homonuclear molecule optimization algorithm to obtain the accurate positions of multiple alternative fault points;

[0056] Introduce the third-harmonic voltage information and combine it with the functional relationship between the potential of the faulty stator winding and the fault location to screen out the final fault point from multiple alternative fault points.

[0057] Specifically, it includes the following steps:

[0058] S1. Combine with the special structure of the stator winding of the variable-speed pumped storage unit to obtain the functional relationship between the electromotive force of the faulty winding with the slot electromotive force as the analysis unit and the fault location;

[0059] Specifically, step S1 includes:

[0060] S11. Represent the connection sequence of the stator winding of the variable-speed pumped storage unit as (x 1 U, x 2 L), (x 3 U, x 4 L), …, (x 2i-1 U, x 2i L), where x 1 ~x 2i represents the slot number, U represents the upper-layer conductor in the slot, L represents the lower-layer conductor in the slot, and (x 2i-1 U, x 2i L) forms one turn of the coil, and i is the number of coil turns.

[0061] S12. The functional relationship between the electromotive force of the faulty winding and the fault location obtained is:

[0062]

[0063] Among them, is the electromotive force of the faulty-phase winding, α is the fault location, is the slot electromotive force, is the voltage of the machine terminal to ground of the phase where this branch is located, is the fundamental-frequency zero-sequence voltage measured at the neutral point, and can be directly measured, and the stator slot electromotive force and is identified online according to the measured values Denote the electromotive force of the slot conductor numbered x as β x = ±xθ, where θ is the slot pitch electrical angle, and “±” is determined according to the operating condition of the pumped storage unit, 1 ≤ j ≤ 2i.

[0064] S2. In the phasor plane, draw the three-phase voltages to ground phasors and the neutral point voltage phasor. First, determine a phasor triangle relationship based on the three-phase voltages to ground phasors and the neutral point voltage phasor. Then, draw the fault point voltage phasor according to the included angle relationship between the fault point voltage phasor and the neutral point voltage phasor in the phasor diagram. The fault point voltage phasor will divide the above phasor triangle into a new phasor triangle determined by the neutral point voltage phasor, the fault point voltage phasor, and the faulty winding electromotive force phasor. Thus, the faulty-phase winding electromotive force phasor can be determined, and the intersection point of the fault point voltage phasor and the faulty-phase winding electromotive force phasor is taken as the alternative fault point;

[0065] Specifically, step S2 includes:

[0066] S21. The parameters in the fundamental frequency zero-sequence equivalent circuit of the stator ground fault are expressed as: R f is the fault transition resistance, R k and X k are the resistance and reactance components of the short-circuit impedance respectively, R n is the primary value of the neutral grounding resistance, R eq = R n + R k . C g and C z are the capacitance of the single-phase winding to the ground and the external equivalent capacitance to the ground respectively, X eq = 1 / (3ωC z + 3ωC g ), X g = 1 / ωC g , Xz = 1 / ωCz.

[0067] S22. The included angle between the voltage phasor at the fault point and the voltage phasor at the neutral point in the phasor diagram is:

[0068]

[0069] where is the voltage vector at the fault point, is and 's included angle.

[0070] S23. The new phasor triangle relationship existing among the voltage phasor at the neutral point, the voltage phasor at the fault point, and the fault winding electromotive force is:

[0071]

[0072] In the drawn phasor diagram, and 's included angle is and form a new phasor triangle. The voltage phasor at the fault point and the fault phase winding electromotive force have as many intersection points as there are alternative fault points. The position of each alternative fault point and the calculated fault transition resistance are respectively denoted as α' and R f '.

[0073] S3. Establish an optimization model for fault location and solve it using the homonuclear molecule optimization algorithm to achieve precise location of multiple alternative fault points;

[0074] Specifically, step S3 includes:

[0075] The fault location optimization model is as follows:

[0076]

[0077] Among them, ∠() is the calculation symbol for obtaining the phase, obj(α) is the optimal objective function, and the fault location α is the decision variable.

[0078] The proposed homonuclear molecule optimization algorithm includes four steps: the initialization stage, the exploration stage, the development stage, and the iteration and reduction stage. 1) In the initialization stage, the initial population of the decision variable α is generated based on pseudo-random numbers. 2) In the exploration stage, the fitness evaluation of each decision variable α is calculated according to the specific distribution positions of the atoms and their electrons. 3) In the development stage, some atoms move towards the most important atoms to form homonuclear molecules, so as to find the local optimum for different decision variables α or optimize the local structure of the current solution. 4) In the iteration and reduction stage, by shrinking the size of the electron cloud around the atomic nucleus in each iteration, the convergence is accelerated and a more accurate solution to the problem is found, obtaining the optimal decision variable and realizing accurate fault location.

[0079] S4. Introduce the third harmonic voltage information as auxiliary information to screen out the unique solution from multiple alternative fault points.

[0080] Specifically, step S4 includes:

[0081] The functional relationship between the third harmonic electromotive force of the faulty winding and the fault location is:

[0082]

[0083] Among them, is the third harmonic electromotive force of the faulty winding, and are the third harmonic voltages at the machine terminal and the neutral point respectively, and both can be directly measured. is the third harmonic slot electromotive force, 1 ≤ j ≤ 2i,

[0084] The difference between the actual fault transition resistance and the calculated fault transition resistance of the h-th alternative fault point is:

[0085]

[0086] Among them, α h ′ is the fault location of the h-th alternative fault point, R f ′ h is the calculated transition resistance of the h-th alternative fault point, d h is for R f and R f ′ h The difference between them. Ideally, for the actual fault point, dh is equal to 0.

[0087] S43. The probability index of the hth candidate fault point being the actual fault location is:

[0088]

[0089] Among them, P h is the probability index of the hth candidate fault point being the actual fault location. The sum of the probability indexes of all candidate fault points is 1. The larger the probability index, the greater the possibility that it is the actual fault point.

[0090] The effectiveness of the proposed protection and positioning method is verified through simulation below.

[0091] Taking a 300MW actual variable-speed pumped storage unit as an example, the number of stator slots is 252, the number of pole pairs is 7, the slot pitch electrical angle is 10°, the pole pitch is 18, the pitch is 15 (short-pitch winding), the number of parallel branches per phase of the stator is 4, and the number of series turns per branch is 21. Since the slot pitch electrical angle is 10°, 6 turns of coil can form a 60-degree phase belt, and each branch has 21 turns of coil. Its winding potential is composed of three sections of 60-degree phase belts (a total of 18 turns of coils) and one section of irregular phase belt (a total of 3 turns of coils, using jumper connection, the phase belt is about 40 degrees). The fundamental frequency zero-sequence equivalent circuit after a single-phase grounding fault occurs in a large variable-speed pumped storage unit is as follows: Figure 2 According to the actual three-phase winding connection sequence of the unit, the potential distribution of each branch of the stator winding is drawn using the turn potential phasor as a unit (i.e., the envelope method). Figure 3 As shown on the left, the details of the potential distribution of each branch winding of phase A are as follows Figure 3 Shown on the right.

[0092] The stator windings of large variable speed pumped storage units are mostly short-distance windings, and the induced potentials of the two slot conductors that make up each turn of the coil have phase differences. If this phase difference is taken into account, Figure 3 Based on this, we further refine the stator winding A using slot potential phasor as the unit. 1 The actual potential distribution of the branch, such as Figure 4 As shown, only A 1 Taking the branch as an example, other branches have similar characteristics.

[0093] Taking the A phase connection fault as an example, in order to verify the performance of the proposed positioning method under different fault conditions, four grounding faults are set, namely: Case 1: The fault is located at A 1 On the 9th slot conductor on the branch side from the neutral point, the winding length from the fault point to the neutral point accounts for A 1 The ratio of the total length of the branch winding is 0.2, that is, α = 0.2; Case 2: The fault is located at A 2On the 17th slot conductor of the branch from the neutral point side, the winding length from the fault point to the neutral point accounts for A 1 The proportion of the total length of the branch winding is 0.4, that is, α = 0.4; Case 3: The fault is located at A 3 On the 26th slot conductor of the branch from the neutral point side, the winding length from the fault point to the neutral point accounts for A 3 The proportion of the total length of the branch winding is 0.6, that is, α = 0.6; Case 4: The fault is located at A 4 On the 34th slot conductor of the branch from the neutral point side, the winding length from the fault point to the neutral point accounts for A 4 The proportion of the total length of the branch winding is 0.8, that is, α = 0.8.

[0094] Set the fault transition resistance to 100 Ω. After the fault, based on the measured values of the three-phase fundamental frequency ground voltages at the machine terminal and the neutral point fundamental frequency ground voltage, and the winding connection sequence, draw the fundamental frequency phasor diagrams omitting the potential distributions of the non-fault phase windings and the judgment result diagrams of each alternative fault point in the four cases of Case 1 to Case 4 after the fault, as Figures 5 to 8 shown, where Figure (a) is the fundamental frequency phasor diagram and Figure (b) is the judgment diagram of the alternative fault points.

[0095] Since the fault location α is the decision variable of the optimization model, the fault location results corresponding to each alternative fault point and the calculated values of the corresponding fault transition resistance can be obtained through solution. On this basis, introduce the measurement information of the third harmonic voltage as auxiliary information to screen the alternative fault points. The fault location and multi-solution screening results under different fault conditions are shown in Table 1.

[0096] Table 1

[0097]

[0098] The number of alternative fault points under different fault conditions is different, and the actual fault point is among multiple alternative fault points, and there is no missed selection. In addition, the location results and the calculated values of the transition resistance corresponding to the actual fault point are more accurate than those of other alternative fault points. The third harmonic screening method can correctly screen out the actual fault point, and the probability index corresponding to the actual fault point is much larger than that of other alternative fault points, verifying the effectiveness and sensitivity of the proposed screening method. Under different fault locations, the proposed location method can accurately locate the fault slot conductor, and the location error does not exceed 25% of the length of a single slot conductor, with high location accuracy. Using this method, the slot number of the fault slot conductor can be accurately reported to the maintenance department, which is of great significance for accelerating fault maintenance.

[0099] Combined with the winding method and parameter characteristics of a variable-speed pumped storage unit, the present invention proposes a method for locating and screening multiple solutions of stator winding ground faults in a pumped storage unit. According to the phasor relationship of each parameter in the zero-sequence equivalent circuit, a ground fault location idea based on the intersection of phasor trajectories and an optimization model for fault location are proposed. Furthermore, a homonuclear molecule optimization algorithm is introduced to solve this location model. On this basis, the reasons for multiple solutions of the location results are explained in combination with the characteristics of winding potential distribution. By introducing the measurement information of the third harmonic voltage, multiple solutions are screened, and the location result is screened to the only true solution on the fault branch. Through simulation analysis, the effectiveness of the proposed location method is verified, and the proposed location method has high location accuracy under different fault conditions.

[0100] This embodiment also proposes a computer device, including a memory, a processor, and a computer program stored on the memory, and the processor executes the computer program to implement the steps of the method.

[0101] This embodiment also proposes a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method are implemented.

[0102] This embodiment also proposes a computer program product, including a computer program, and when the computer program is executed by a processor, the steps of the method are implemented.

[0103] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for locating and screening grounding faults of stator windings of pumped storage units, characterized in that: The following steps are involved: According to the stator winding structure of variable speed pumped storage unit, the functional relationship between stator fault winding potential and fault position is constructed with slot potential as the analysis unit. Draw the three-phase-to-ground voltage phasors and the neutral point voltage phasor in the phasor plane, calculate the angle relationship between the fault point voltage phasor and the neutral point voltage phasor in the phasor diagram, and draw the fault point voltage phasor according to the angle relationship; A phasor triangle is determined according to the three-phase-to-ground voltage phasors and the neutral point voltage phasor, the fault point voltage phasor divides the phasor triangle into a new phasor triangle determined by the neutral point voltage phasor, the fault point voltage phasor and the fault winding potential phasor, and the fault phase winding potential phasor is drawn according to the relationship of the new phasor triangle; The intersection point of the voltage phasor at the fault point and the potential phasor of the fault phase winding is taken as the candidate fault point; A fault location optimization model is established based on the neutral point voltage phasor and the fault phase winding potential phasor, and the precise locations of multiple candidate fault points are obtained by solving it through the same core molecular optimization algorithm. The third harmonic voltage information is introduced and combined with the functional relationship between the stator fault winding potential and the fault location, and the final fault point is screened out from multiple candidate fault points.

2. The method according to claim 1, characterized in that The functional relationship between the stator fault winding potential and the fault position is expressed as: In the formula, is the fault winding potential, α is the fault location, is the cell potential, is the voltage from the machine end to the ground of the phase where the fault branch is located, is the fundamental frequency zero-sequence voltage measured at the neutral point, and the potential of the slot conductor numbered x is recorded as β x =±xθ, θ is the electrical angle of the slot pitch, 1≤j≤2i, i is the number of coil turns.

3. The method according to claim 1, characterized in that The calculation expression of the angle relationship is: In the formula, R eq =R n +R k , R n is the primary value of the neutral point grounding resistance, R k is the resistance of the short-circuit impedance, Xk is the reactance component of the short-circuit impedance, and X eq =1 / (3ωC z +3ωC g ), Cg and Cz are the single-phase winding capacitance to ground and the external equivalent capacitance to ground respectively.

4. The method according to claim 1, characterized in that The new phasor triangle relationship expression is: In the formula, is the fundamental frequency zero-sequence voltage measured at the neutral point, is the fault winding potential, is the voltage phasor at the fault point, R eq =R n +R k , R n is the primary value of the neutral point grounding resistance, R k is the resistance of the short-circuit impedance, Xk is the reactance component of the short-circuit impedance, and X eq =1 / (3ωC z +3ωC g ), Cg and Cz are the single-phase winding capacitance to ground and the external equivalent capacitance to ground respectively, R f is the fault transition resistance.

5. The method according to claim 1, characterized in that The fault location optimization model expression is: In the formula, is the fundamental frequency zero-sequence voltage measured at the neutral point, is the fault winding potential, ∠() is the calculation symbol for phase, obj(α) is the optimal objective function, and the fault position α is the decision variable.

6. The method according to claim 1, characterized in that The steps of solving the problem by the homonuclear molecular optimization algorithm include initialization phase, exploration phase, development phase, iteration and reduction phase: The initialization phase generates the initial population of decision variables α based on pseudo-random numbers; The exploration phase calculates the fitness evaluation of each decision variable α based on the specific distribution positions of atoms and their electrons; In the development phase, some atoms move toward the most important atoms to form homonuclear molecules, and different decision variables α are obtained to find the local optimum or optimize the local structure of the current solution; The iteration and reduction stage obtains the optimal decision variables and the precise fault location by reducing the size of the electron cloud around the nucleus in each iteration.

7. The method according to claim 1, characterized in that The final fault point is screened out by calculating the probability index. The calculation expression of the probability index is: Where P h is the probability index that the hth candidate fault point is the actual fault location, α h ′ is the fault location of the hth candidate fault point, R f ' h is the calculated transition resistance of the hth candidate fault point, d h For R f With R f ' h The difference, R f is the fault transition resistance, is the third harmonic voltage at the machine end, is the third harmonic voltage at the neutral point, is the third harmonic potential of the fault winding at the hth candidate fault location, X g =1 / ωC g , X z =1 / ωC z , C g and C z They are the single-phase winding capacitance to ground and the external equivalent capacitance to ground, X k is the reactance component of the short-circuit impedance, 1≤j≤2i, i is the number of coil turns.

8. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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