Generator grounding fault phase selection method and system, storage medium and processing terminal

Abstract

The application relates to a generator ground fault phase selection method and system, a storage medium and a processing terminal, and the method comprises the following steps: obtaining a transition resistance measured by an injected stator ground protection device; obtaining generator operation data, a lagging phase potential angle and a leading phase potential angle; wherein the generator operation data comprises three-phase ground capacitance, a neutral point ground impedance, an A-phase electromotive force and neutral point zero sequence voltage data before and after a fault; calculating a phase difference between a fault electromotive force and the A-phase electromotive force according to the transition resistance and the generator operation data; determining a phase selection criterion range according to the lagging phase potential angle and the leading phase potential angle, and determining a fault phase according to the phase difference and the phase selection criterion range. The application solves the defect that a traditional phase selection method based on a zero sequence voltage fault component is prone to misselecting a phase when a fault position is close to a neutral point and is affected by unbalanced voltage, ensures that the phase can be stably and accurately selected in a complex operation environment, and improves phase selection accuracy.

Description

Technical Field

[0001] This invention relates to the field of phase selection technology for grounding faults, and in particular to a method and system for selecting phases for generator grounding faults, a storage medium, and a processing terminal. Background Technology

[0002] As a core piece of equipment in a power system, the safe and stable operation of generators directly affects the reliability of the entire power supply. Ground faults are one of the most common types of generator faults, and accurate and rapid fault identification is crucial for timely fault isolation and repair measures and for minimizing fault losses.

[0003] Most existing generator ground fault phase selection methods are derived from distribution network phase selection methods. Among them, phase selection elements based on phase voltage magnitude suffer from low sensitivity when handling high-resistance ground faults. Furthermore, due to factors such as the generator neutral grounding method, stator winding capacitance to ground, and grounding resistance, the phase with the lowest voltage is not necessarily the faulty phase, easily leading to misselection. Phase selection methods based on zero-sequence voltage fault components offer significantly improved impedance resistance compared to low-voltage methods, achieving good phase selection results when the generator's three phases are well-balanced and the fault location is far from the neutral point. However, their phase selection criteria ignore the neutral point unbalanced voltage before the fault. When the fault location is close to the neutral point, the combined phasor of the zero-sequence voltage fault component and the neutral point unbalanced voltage becomes dominant, causing a contradiction between the phase relationship and the phase selection criteria, thus leading to misselection and failing to meet the phase selection requirements of large generators in complex fault scenarios. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a generator grounding fault phase selection method and system, storage medium and processing terminal.

[0005] The technical solution adopted by this invention to solve its technical problem is: constructing a generator grounding fault phase selection method, comprising: Obtain the transition resistance measured by the injection-type stator grounding protection device; Acquire generator operating data, lagging phase potential angle, and leading phase potential angle; wherein, the generator operating data includes three-phase grounding capacitance, neutral point grounding impedance, A-phase electromotive force, and neutral point zero-sequence voltage data before and after the fault; The phase difference is calculated based on the transition resistance and the generator operating data; The phase selection criterion range is determined based on the lagging phase potential angle and the leading phase potential angle, and the faulty phase is determined based on the phase difference and the phase selection criterion range.

[0006] Preferably, determining the phase selection criterion range based on the lagging phase potential angle and the leading phase potential angle includes: The phase selection criterion range for phase A is defined as: [A1- A2+ ]; The phase selection criterion range for phase B is defined as: [B1- B2+ ]; The selection criterion range for phase C is defined as: [C1- C2+ ]; Where A1 represents the lower limit of phase selection for phase A, A2 represents the upper limit of phase selection for phase A, the phase difference between A1 and B1 and the phase difference between C1 and A1 are both 120°, and the phase difference between A2 and B2 and the phase difference between C2 and A2 are both 120°. This indicates the angle of the hysteresis phase potential. This indicates the angle of the leading phase potential; The step of determining the faulty phase based on the phase difference and the phase selection criterion range includes: Determine whether the phase difference is within [A1- A2+ If the faulty phase is determined to be phase A; Determine whether the phase difference is within [B1- B2+ If the faulty phase is determined to be phase B; Determine whether the phase difference is within [C1- C2+ If the faulty phase is determined to be phase C.

[0007] Preferably, the setting range of A1 is -20° to -10°, and the setting range of A2 is 10° to 20°.

[0008] Preferably, A1 is -15° and A2 is 15°.

[0009] Preferably, the step of calculating the phase difference based on the transition resistance and the generator operating data includes: The neutral point zero-sequence voltage before the fault and the change in neutral point zero-sequence voltage before and after the fault are determined based on the neutral point zero-sequence voltage data before and after the fault. The fault point potential is calculated based on the pre-fault neutral point zero-sequence voltage, the change in neutral point zero-sequence voltage, the three-phase grounding capacitance, the neutral point grounding impedance, and the transition resistance. The phase of the injected signal is calculated based on the fault point potential and the phase A electromotive force.

[0010] Preferably, the expression for the fault point potential is: ; Indicates the potential at the fault point. This represents the change in zero-sequence voltage at the neutral point. Indicates the transition resistance. Indicates the neutral point grounding impedance. Represents the imaginary unit. Indicates three-phase grounding capacitance. This indicates the zero-sequence voltage at the neutral point before the fault.

[0011] Preferably, the expression for the phase difference is: ; Indicates phase, Indicates the potential at the fault point. This represents the electromotive force of phase A.

[0012] In addition, the present invention also constructs a computer storage medium storing a computer program, which, when executed by a processor, implements the generator grounding fault phase selection method described above.

[0013] Furthermore, 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 grounding fault phase selection method described above.

[0014] Furthermore, this invention also constructs a generator grounding fault phase selection system, comprising: An injection-type stator grounding protection device is used to measure transition resistance; and The processing terminal described above.

[0015] The technical solution of this invention solves the defect of traditional phase selection methods based on zero-sequence voltage fault components, which are prone to incorrect phase selection when the fault location is close to the neutral point due to the influence of unbalanced voltage. It can ensure stable and accurate phase selection even in complex operating environments, significantly improving the accuracy of phase selection. Moreover, this invention does not require a large amount of additional hardware equipment, and has the advantages of low implementation cost and ease of implementation. 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 grounding fault phase selection method in some embodiments of the present invention; Figure 2 This is a schematic diagram of the generator grounding fault phase selection system 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 of a generator grounding fault phase selection method in some embodiments of the present invention. This generator grounding fault phase selection method selects the fault phase based on the correlation characteristics between phase, lagging phase potential angle, and leading phase potential angle, which can significantly improve the accuracy and anti-interference capability of generator grounding fault phase selection in complex scenarios such as high-resistance grounding and near-neutral point grounding.

[0021] like Figure 1 As shown, the generator ground fault phase selection method may include steps S20, S30, and S40.

[0022] Step S10 includes: obtaining the transition resistance measured by the injection-type stator grounding protection device.

[0023] It should be noted that in current power systems, large generators with high rated capacity are typically equipped with injection-type stator grounding protection devices. These devices can continuously inject a sinusoidal signal of a specific frequency (up to 20Hz) into the secondary side of a neutral-point grounded transformer around the clock, reducing the impact of fault type and grounding resistance magnitude, and providing reliable data support for subsequent phase selection. In this invention, the injection-type stator grounding protection device is primarily used to measure the transition resistance.

[0024] Step S20 includes: acquiring generator operating data, lagging phase potential angle, and leading phase potential angle.

[0025] Generator operating data can include three-phase grounding capacitance, neutral point grounding impedance, phase A electromotive force (EMF), and neutral point zero-sequence voltage data before and after a fault. The three-phase grounding capacitance, phase A EMF, and neutral point zero-sequence voltage data before and after a fault can all be measured using existing equipment or technology. For example, a voltage transformer (PT) can be used to monitor the neutral point zero-sequence voltage in real time to obtain the neutral point zero-sequence voltage data before and after a fault. It should be noted that "phase A" in phase A EMF does not specifically refer to a fixed phase line of the generator system; any phase line can be used.

[0026] The lagging phase potential angle refers to the angle at which the generator windings form a lagging phase potential, while the leading phase potential angle refers to the angle at which the generator windings form a leading phase potential. The values ​​of these angles are determined by the connection sequence of the generator's stator windings. Different types of generators have different stator winding connection methods, resulting in variations in their corresponding lagging and leading phase potential angles. Initial values ​​can usually be obtained from the generator's factory technical parameters, or they can be measured using existing technology. To ensure accuracy, if the maximum absolute value of the acquired lagging and leading phase potential angles exceeds 30°, the generator is considered to be in abnormal condition and requires shutdown and maintenance. The lagging and leading phase potential angles will then be remeasured after maintenance.

[0027] Step S30 includes: calculating the phase difference between the fault electromotive force and the A-phase electromotive force based on the transition resistance and generator operating data.

[0028] In some embodiments, the phase difference can be calculated by performing steps S301 to S303.

[0029] Step S301 includes: determining the neutral point zero-sequence voltage before the fault and the change in neutral point zero-sequence voltage before and after the fault based on the neutral point zero-sequence voltage data before and after the fault.

[0030] In this step, it can be determined whether a ground fault has occurred and the timing of the ground fault using existing technology or equipment. Then, in the neutral point zero-sequence voltage data before and after the fault, the average voltage measured within a first set time period before the ground fault is set as the neutral point zero-sequence voltage before the fault. Next, in the neutral point zero-sequence voltage data before and after the fault, the average voltage measured within a second set time period after the ground fault is set as the neutral point zero-sequence voltage after the fault. Finally, the difference between the neutral point zero-sequence voltage after the fault and the neutral point zero-sequence voltage before the fault is calculated to obtain the change in neutral point zero-sequence voltage before and after the fault. The first and second set times can be customized according to actual needs and are not limited here.

[0031] Step S301 includes: calculating the fault point potential based on the neutral point zero-sequence voltage before the fault, the change in neutral point zero-sequence voltage, the three-phase grounding capacitance, the neutral point grounding impedance, and the transition resistance.

[0032] In some embodiments, the expression for the fault point potential can be: . Indicates the potential at the fault point. This represents the change in zero-sequence voltage at the neutral point. Indicates the transition resistance. Indicates the neutral point grounding impedance. Represents the imaginary unit. Indicates three-phase grounding capacitance. This indicates the zero-sequence voltage at the neutral point before the fault.

[0033] In this embodiment, an injection signal can be input through an injection-type stator grounding protection device to provide stable electrical quantity support for the detection and analysis of grounding faults. Furthermore, under grounding fault scenarios, the relationship between the change in neutral point zero-sequence voltage and other electrical quantities can be analyzed, resulting in the expression for the change in neutral point zero-sequence voltage as follows: It is easy to understand that by deriving and transforming the expression for the change in the neutral point zero-sequence voltage in the above equation, the expression for the fault point potential can be obtained.

[0034] Step S303 includes: calculating the phase of the injected signal based on the fault point potential and the A-phase electromotive force.

[0035] In some embodiments, the phase difference can be expressed as: .in, Indicates phase, Indicates the potential at the fault point. This represents the electromotive force of phase A.

[0036] It should be noted that this embodiment uses the ratio of the fault point potential to the electromotive force of phase A to perform inverse trigonometric function calculation, rather than the ratio to the phase voltage of phase A. This design can improve the accuracy of phase selection when a metallic ground fault occurs in phase A, because the calculation relies on the phase relationship of the potential signal rather than the phase voltage. Therefore, it will not be affected by abnormal interference or noise of the phase voltage due to a large drop in the phase voltage of phase A.

[0037] Step S40 includes: determining the phase selection criterion range based on the lagging phase potential angle and the leading phase potential angle, and determining the faulty phase based on the phase difference and the phase selection criterion range.

[0038] In some embodiments, based on step S40, the step of determining the phase selection criterion range according to the lagging phase potential angle and the leading phase potential angle may include: determining the phase selection criterion range of phase A as: [A1- A2+ The phase selection criterion range for phase B is defined as: [B1- B2+ The selection criterion range for phase C is defined as: [C1- C2+ Where A1 represents the lower limit of phase selection for phase A, A2 represents the upper limit of phase selection for phase A, the phase difference between A1 and B1 and between C1 and A1 can both be 120°, and the phase difference between A2 and B2 and between C2 and A2 can both be 120°. This indicates the angle of the hysteresis phase potential. This indicates the angle of the leading phase potential.

[0039] Accordingly, the faulty phase can be determined by performing the following steps S401 to S403.

[0040] Step S401 includes: determining whether the phase difference is within [A1- A2+ If the faulty phase is determined to be phase A, then proceed to step S402.

[0041] Step S402 includes: determining whether the phase difference is within [B1- B2+ If the faulty phase is determined to be phase B, then proceed to step S403. Step S403 includes: determining whether the phase difference is within [C1- C2+ If the faulty phase is determined to be phase C.

[0042] In this embodiment, the above steps can be performed sequentially, and the process can end after the faulty phase is determined. Since the phase is affected by factors such as the environment and generator parasitic electrical parameters (including parasitic capacitance and inductance), distortion may occur during the phase transmission of the injected signal. A1, A2, B1, B2, C1, and C2 are phase selection boundaries, which can set a suitable fluctuation range for the criteria in steps S401 to S403, improving the fault tolerance of the phase selection criteria, optimizing the accuracy of the criteria, and thus improving the precision of the phase selection result.

[0043] In some embodiments, the setting range of A1 can be -20° to -10°, and the setting range of A2 can be 10° to 20°. Through extensive simulations and actual measurements, A1 is preferably -15° and A2 is preferably 15°. Under these design values, phase selection can be achieved very accurately. Correspondingly, when A1 is -15°, B1 is -135° and C1 is 105°; when A2 is 15°, B2 is -105° and C2 is 135°.

[0044] In some embodiments, a fault model can be constructed using MATLAB / Simulink software to verify the effectiveness of the invention. The process of simulation verification using the fault model may include: setting the three-phase grounding capacitance (e.g., 1 microfarad, 0.9 microfarads, etc.), neutral point grounding impedance (e.g., 4000 ohms, 5000 ohms, etc.), and fundamental frequency (typically 50Hz); setting the sampling time of the fundamental voltage (which can be 1 / 1200 seconds) and the fault time (which can be 0.2 seconds to 0.5 seconds); then, simulating grounding faults occurring on each phase line at different locations (e.g., at 1 / 3, 1 / 2, and 2 / 3 of the distance from the neutral point), and then using the above method to determine the faulty phase. It is easily understood that during the verification process, the appropriateness of the values ​​of A1, A2, B1, B2, C1, and C2 can be verified, and A1, A2, B1, B2, C1, and C2 can be adjusted based on the experimental data to ensure the accuracy of phase selection.

[0045] To understand the description of the location, let's take the 1 / 2 position as an example. The 1 / 2 position refers to the midpoint between the end of the faulty phase connected to the neutral point and the end furthest from the neutral point.

[0046] The technical solution of this invention utilizes the stable injection signal provided by the injection-type stator grounding protection device, which can significantly improve the phase selection sensitivity and accuracy in high-resistance grounding fault scenarios. Furthermore, by introducing a method for determining the fault phase based on phase, lagging phase potential angle, and leading phase potential angle, it solves the problem of traditional phase selection methods based on zero-sequence voltage fault components being prone to misselection due to unbalanced voltage when the fault location is close to the neutral point. This ensures stable and accurate phase selection even in complex actual operating environments, significantly improving phase selection accuracy. Moreover, the optimization of this invention mainly relies on existing equipment for signal input and data acquisition, without requiring a large amount of additional hardware, thus offering advantages such as low implementation cost and ease of implementation.

[0047] The present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, implements the generator grounding fault phase selection method provided in the embodiments of the present invention.

[0048] The present invention also provides 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 grounding fault phase selection method provided in the embodiments of the present invention.

[0049] like Figure 2 As shown, the present invention also provides a generator grounding fault phase selection system, including: an injection-type stator grounding protection device for measuring transition resistance and a processing terminal provided in the embodiments of the present invention.

[0050] In some embodiments, the generator ground fault phase selection system may further include measuring devices for measuring generator operating data. These measuring devices may include existing ground capacitance measuring devices, ground impedance measuring devices, electromotive force measuring devices, and zero-sequence voltage measuring devices.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 selecting the phase in a generator grounding fault, characterized in that, include: Obtain the transition resistance measured by the injection-type stator grounding protection device; Acquire generator operating data, lagging phase potential angle, and leading phase potential angle; wherein, the generator operating data includes three-phase grounding capacitance, neutral point grounding impedance, A-phase electromotive force, and neutral point zero-sequence voltage data before and after the fault; The phase difference between the fault electromotive force and the A-phase electromotive force is calculated based on the transition resistance and the generator operating data; The phase selection criterion range is determined based on the lagging phase potential angle and the leading phase potential angle, and the faulty phase is determined based on the phase difference and the phase selection criterion range.

2. The generator grounding fault phase selection method according to claim 1, characterized in that, The determination of the phase selection criterion range based on the lagging phase potential angle and the leading phase potential angle includes: The phase selection criterion range for phase A is defined as: [A1- A2+ ]; The phase selection criterion range for phase B is defined as: [B1- B2+ ]; The selection criterion range for phase C is defined as: [C1- C2+ ]; Where A1 represents the lower limit of phase selection for phase A, A2 represents the upper limit of phase selection for phase A, the phase difference between A1 and B1 and the phase difference between C1 and A1 are both 120°, and the phase difference between A2 and B2 and the phase difference between C2 and A2 are both 120°. This indicates the angle of the hysteresis phase potential. This indicates the angle of the leading phase potential; The step of determining the faulty phase based on the phase difference and the phase selection criterion range includes: Determine whether the phase difference is within [A1- A2+ If the faulty phase is determined to be phase A; Determine whether the phase difference is within [B1- B2+ If the faulty phase is determined to be phase B; Determine whether the phase difference is within [C1- C2+ If the faulty phase is determined to be phase C.

3. The generator grounding fault phase selection method according to claim 2, characterized in that, The setting range of A1 is -20° to -10°, and the setting range of A2 is 10° to 20°.

4. The generator grounding fault phase selection method according to claim 3, characterized in that, A1 is -15°, and A2 is 15°.

5. The generator grounding fault phase selection method according to claim 1, characterized in that, The step of calculating the phase difference based on the transition resistance and the generator operating data includes: The neutral point zero-sequence voltage before the fault and the change in neutral point zero-sequence voltage before and after the fault are determined based on the neutral point zero-sequence voltage data before and after the fault. The fault point potential is calculated based on the pre-fault neutral point zero-sequence voltage, the change in neutral point zero-sequence voltage, the three-phase grounding capacitance, the neutral point grounding impedance, and the transition resistance. The phase difference is calculated based on the fault point potential and the phase A electromotive force.

6. The generator grounding fault phase selection method according to claim 5, characterized in that, The expression for the fault point potential is: ; Indicates the potential at the fault point. This represents the change in zero-sequence voltage at the neutral point. Indicates the transition resistance. Indicates the neutral point grounding impedance. Represents the imaginary unit. Indicates three-phase grounding capacitance. This indicates the zero-sequence voltage at the neutral point before the fault.

7. The generator grounding fault phase selection method according to claim 5, characterized in that, The expression for the phase difference is: ； Indicates phase, Indicates the potential at the fault point. This represents the electromotive force of phase A.

8. A computer storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the generator grounding fault phase selection method according to any one of claims 1 to 7.

9. 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 grounding fault phase selection method as described in any one of claims 1 to 7.

10. A generator grounding fault phase selection system, characterized in that, include: Injection-type stator grounding protection device, used to measure transition resistance; as well as The processing terminal as described in claim 9.

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