A method for detecting single-phase ground fault of generator stator winding based on third harmonic voltage fault transient component

Abstract

The application discloses a kind of generator stator winding single-phase ground fault detection methods based on third harmonic voltage fault transient component, comprising the following steps: first, the zero-sequence voltage of generator neutral point and machine end side before and after fault is collected, and the fault transient component of machine end and neutral point is obtained;Second, using empirical wavelet decomposition (EWT) to extract fundamental zero-sequence voltage fault component and third harmonic zero-sequence voltage fault component;Then, based on neutral point and machine end side third harmonic voltage addition modulus to obtain action amount, subtraction modulus to obtain brake amount;Finally, using and calculating the spectral energy of action signal and brake signal in a cycle, obtain brake coefficient, construct detection criterion.The application is based on the characteristics of machine end and neutral point zero-sequence fundamental and third harmonic voltage fault transient component, and the brake coefficient is adaptively adjusted using the ratio of spectral energy, which improves the sensitivity of detection criterion.

Description

Technical Field

[0001] This invention relates to a method for detecting single-phase grounding faults in generator stator windings, belonging to the field of power system relay protection detection technology. Background Technology

[0002] Single-phase grounding faults in the stator windings are among the most common electrical faults in generators. Most generators use grounding via an arc suppression coil or a high-resistance grounding method for the neutral point. While a single-phase grounding fault in the stator windings does not generate a large fault current, it can often trigger phase-to-phase or turn-to-turn faults. Furthermore, after a single-phase grounding fault, the voltage of the non-faulty phases increases, and there is a risk of arc overvoltage, which is detrimental to the safe operation of the generator. Simultaneously, the fault current may burn out the iron core, and in more severe cases, may cause permanent and irreparable damage to the stator core.

[0003] Therefore, in-depth research on single-phase grounding fault detection technology for generator stator windings is particularly important. Immediate protection action upon fault occurrence minimizes the arc burning time and energy at the fault point, fundamentally preventing core burnout, effectively suppressing overvoltage, preventing the fault from escalating into a phase-to-phase fault, and maintaining the stable operation of the entire power system. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for detecting single-phase ground faults in generator stator windings based on the transient component of third harmonic faults. By utilizing spectral energy to calculate the braking coefficient, an adaptive detection criterion is constructed, overcoming the problems of traditional detection methods based on third harmonic ratio values ​​and improving the sensitivity and accuracy of detection.

[0005] A method for detecting single-phase ground faults in generator stator windings based on the transient component of third harmonic faults includes the following steps:

[0006] Step 1: Collect the neutral point zero-sequence voltage before and after the generator stator winding fault. Zero-sequence voltage at the terminal ;

[0007] Step 2: Subtract the pre-fault cycle data from the post-fault cycle data to obtain the neutral point fault transient component. Transient components of machine-side faults ;

[0008] Step 3: Based on Empirical Wavelet Transform (EWT), extract the fundamental voltage from the transient component of the neutral point zero-sequence voltage fault. and third harmonic voltage and based on neutral point zero-sequence voltage Extract the fundamental zero-sequence voltage at the neutral point before the fault. ;

[0009] Step 4: Extract the fundamental voltage from the transient component of the zero-sequence voltage fault at the machine terminal based on Empirical Wavelet Transform (EWT). and third harmonic voltage ;

[0010] Step 5: Calculate the action quantity based on the extracted fundamental zero-sequence voltage and third harmonic voltage components. and braking amount ;

[0011] Step 6: Let U g It is equal to 10% of the amplitude of the fundamental zero-sequence voltage at the neutral point before the fault, based on the obtained fundamental zero-sequence voltage fault transient component. , Calculate the braking signal ;

[0012] Step 7: Based on the obtained fundamental zero-sequence voltage fault transient component , Calculate action signals ;

[0013] Step 8: Based on the obtained braking signal and action signals Calculate the spectral energy of the braking signal within one cycle after the fault. and the spectral energy of the action signal ;

[0014] Step 9: Spectral energy obtained in Step 8 and Calculate the braking coefficient ;

[0015] Step 10: Comparison and The effective value within one cycle after the fault, if it satisfies (The subscript rms indicates the effective value), then it is considered that a single-phase ground fault has occurred in the generator stator winding. If it does not meet the condition, return to step 1.

[0016] Preferably, the data acquisition in step 1 includes acquiring the zero-sequence voltages at the neutral point and the terminal side before and after the fault.

[0017] Preferably, in step 2, the fault transient component is calculated by subtracting the zero-sequence voltage cycle data before the fault from the zero-sequence voltage cycle data after the fault. Utilizing the fault transient component allows for accurate capture of fault components and highlights the transient characteristics of the fault.

[0018] Preferably, the empirical wavelet transform in step 3 uses the db4 wavelet to extract the fundamental component from the transient component of the neutral point zero-sequence voltage fault. and third harmonic components The fundamental zero-sequence voltage in the neutral point zero-sequence voltage component The use of db4 wavelet can effectively analyze local abrupt changes in non-stationary signals, capture the transient characteristics, abrupt change points and local details of the signal, and reduce oscillations near signal discontinuities, thus making the waveform smoother.

[0019] Preferably, the empirical wavelet transform in step 4 uses the db4 wavelet to extract the fundamental component from the transient component of the zero-sequence voltage fault at the machine terminal. and third harmonic components The use of db4 wavelet can effectively analyze local abrupt changes in non-stationary signals, capture the transient characteristics, abrupt change points and local details of the signal, and reduce oscillations near signal discontinuities, thus making the waveform smoother.

[0020] Preferably, the specific process of step 5 includes:

[0021] Step 5.1: Based on the third harmonic components extracted in Steps 3 and 4 Calculate the action quantity of the fault criterion. ;

[0022] Step 5.2: Based on the third harmonic components extracted in Steps 3 and 4 Calculate the braking amount for fault diagnosis. .

[0023] Preferably, the specific process of step 6 includes:

[0024] Step 6.1: This is a floating threshold value that takes into account the influence of the fundamental zero-sequence voltage under normal conditions. In order to avoid the non-zero output of the fundamental increment under normal conditions, it is based on the neutral point fundamental zero-sequence voltage component extracted in step 3. ,make ( (The amplitude of the fundamental zero-sequence voltage at the neutral point before the fault);

[0025] Step 6.2: Based on the fundamental voltage fault transient component extracted in Step 2 It contains both the fundamental zero-sequence voltage and the third harmonic voltage, and can be used to calculate the braking signal that reflects the combined effect of the fundamental and third harmonic fault components. .

[0026] Preferably, in step 7, the fault transient component, which includes both the fundamental zero-sequence voltage and the third harmonic voltage, is utilized. It can calculate the action signal that reflects the combined effect of the fundamental and third harmonic fault components. .

[0027] Preferably, step 8 includes the following specific steps:

[0028] Step 8.1: Based on the braking signal obtained in Step 6 Calculate the spectral energy value within the corresponding period according to the following formula. :

[0029] ;

[0030] In the formula, N is the number of data points collected in one cycle; The sampling interval is... (f s (sampling rate); It is the sum of the squares of the braking signals within one cycle;

[0031] Step 8.2: Based on the action signal obtained in Step 7 Calculate the spectral energy value within the corresponding period according to the following formula. :

[0032]

[0033] In the formula, N is the number of data points collected in one cycle; The sampling interval is... (f s (sampling rate); It is the sum of squares of the action signals within one cycle.

[0034] Preferably, in step 9, the braking coefficient The ratio is obtained by taking the spectral energy obtained in step 8. This achieves adaptivity and combines the fundamental wave and the third harmonic, simplifying the criterion.

[0035] Preferably, the specific process of step 10 includes:

[0036] Step 10.1: Based on the calculations in Step 5 The braking coefficient obtained in step 9 ,calculate ;

[0037] Step 10.2: Calculate according to the following formulas respectively and Valid values ​​within one cycle after the fault:

[0038] ;

[0039] In the formula, N is the number of sampling points in one period; x(k) is the signal whose effective value needs to be obtained; Let x(k) be the sum of squares of the signal over one period after the fault.

[0040] If satisfied If the condition is not met, it is determined that a single-phase ground fault has occurred in the generator stator winding. If not, return to step 1 to collect and measure again.

[0041] Preferably, the detection criterion adaptively adjusts the braking coefficient in the detection criterion by using the relative relationship between the spectral energy of the fundamental and third harmonic fault transient components at the generator terminals and neutral point, effectively improving the accuracy of detection and the sensitivity of protection.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. This invention utilizes the transient component of the fault and adaptively adjusts the braking coefficient by combining the ratio of the spectral energy of the action signal and the braking signal. This significantly improves the detection capability for high-resistance grounding and faults near the neutral point, ensuring reliable operation without false tripping when operating conditions change and sensitive operation during faults. It also overcomes the problems of low sensitivity of traditional fundamental zero-sequence voltage protection, the existence of protection dead zone near the neutral point, and the significant influence of operating conditions on traditional third harmonic voltage protection.

[0044] 2. This invention combines the fundamental zero-sequence voltage and the fault transient component of the third harmonic voltage into a single criterion, which simplifies the criterion structure and improves the detection speed.

[0045] 3. The present invention calculates the braking coefficient λ based on the ratio of spectral energy, which allows noise to cancel each other out during calculation. This overcomes the problem that traditional criteria based on instantaneous value comparison are easily affected by noise. The criterion proposed in this invention has strong robustness. Attached Figure Description

[0046] Figure 1 This is a flowchart of the fault detection process of the present invention;

[0047] Figure 2 This is a schematic diagram of a generator stator single-phase ground fault applied in this invention.

[0048] Figure 3 This is a simulation schematic diagram of the generator stator winding used in this invention;

[0049] Figure 4 The transient component diagram of the third harmonic fault when the first branch of phase A of the generator stator winding is faulted.

[0050] Figure 5 This is the spectral energy diagram of the first branch fault in phase A of the generator stator winding.

[0051] Figure 6 The waveforms of the action and braking quantities when the first branch of phase A of the generator stator winding is faulty are shown. Detailed Implementation

[0052] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0053] This invention provides a method for detecting single-phase ground faults in generator stator windings based on the transient component of third harmonic faults, such as... Figure 1 As shown, it includes the following steps:

[0054] Step 1: Collect the neutral point zero-sequence voltage before and after the generator stator winding fault. Zero-sequence voltage at the terminal ;

[0055] Step 2: Subtract the pre-fault cycle data from the post-fault cycle data to obtain the neutral point fault transient component. Transient components of machine-side faults ;

[0056] Step 3: Based on Empirical Wavelet Transform (EWT), extract the fundamental voltage from the transient component of the neutral point zero-sequence voltage fault. and third harmonic voltage and based on neutral point zero-sequence voltage Extract the fundamental zero-sequence voltage at the neutral point before the fault. ;

[0057] Step 4: Extract the fundamental voltage from the transient component of the zero-sequence voltage fault at the machine terminal based on Empirical Wavelet Transform (EWT). and third harmonic voltage ;

[0058] Step 5: Calculate the action quantity based on the extracted fundamental zero-sequence voltage and third harmonic voltage components. and braking amount ;

[0059] Step 6: Let U g It is equal to 10% of the amplitude of the fundamental zero-sequence voltage at the neutral point before the fault, based on the obtained fundamental zero-sequence voltage fault transient component. , Calculate the braking signal ;

[0060] Step 7: Based on the obtained fundamental zero-sequence voltage fault transient component , Calculate action signals ;

[0061] Step 8: Based on the obtained braking signal and action signals Calculate the spectral energy of the braking signal within one cycle after the fault. and the spectral energy of the action signal ;

[0062] Step 9: Spectral energy obtained in Step 8 and Calculate the braking coefficient ;

[0063] Step 10: Comparison and The effective value within one cycle after the fault, if it satisfies (The subscript rms indicates the effective value), then it is considered that a single-phase ground fault has occurred in the generator stator winding. If it does not meet the condition, return to step 1.

[0064] As shown above, this generator stator winding single-phase ground fault detection method acquires the zero-sequence voltage of the neutral point and generator terminals through data acquisition; it uses EWT to extract the fundamental zero-sequence and third harmonic voltage components, effectively capturing the transient characteristics of the signal and making the signal smooth and clear; subsequently, based on the extracted fundamental and third harmonic components, it accurately calculates the braking amount, the action amount, and the braking coefficient; finally, it calculates and compares the effective values ​​of the braking amount and the action amount to accurately determine the occurrence of the winding fault. This method significantly improves the accuracy and reliability of fault detection, reduces the false positive and false negative rates, and provides an effective protection means for complex generator systems.

[0065] In this invention, step 1 specifically involves: collecting zero-sequence voltage signals from the generator stator winding terminals and neutral point before and after a fault.

[0066] As can be seen from the above, by collecting zero-sequence voltage data from the stator winding terminals and neutral point... Furthermore, by collecting data starting before the fault occurs, it helps to obtain comprehensive and systematic generator operating status information, ensuring the integrity and timeliness of the data, and providing a reliable data foundation for subsequent accurate detection of single-phase grounding faults in the stator winding.

[0067] In this invention, step 2 specifically involves subtracting the zero-sequence voltage from the zero-sequence voltage of the period preceding the fault from the zero-sequence voltage acquired in the period following the fault, to obtain the fault transient components at the machine terminal and the neutral point, respectively. .

[0068] As can be seen from the above, the fault transient component of the collected voltage data amplifies the slight changes caused by the fault. In essence, it is also a process of denoising and enhancement, which enhances the identification of fault characteristics and can clearly analyze the characteristics of the fault itself, providing a reliable and crucial basis for subsequent accurate judgment of whether there is a fault.

[0069] In this invention, steps 3 and 4 specifically include: extracting the fundamental zero-sequence voltage transient component from the fault transient component based on empirical wavelet transform (EWT). The fundamental zero-sequence voltage in the neutral point zero-sequence voltage and the transient component of the third harmonic voltage .

[0070] As can be seen from the above, empirical wavelet transform can effectively and adaptively extract transient components from signals, effectively analyze local abrupt changes in non-stationary signals, capture transient features, abrupt change points and local details of signals, and reduce oscillations near signal discontinuities, making the waveform smoother. This improves the accuracy and reliability of fault feature extraction and provides a solid data foundation for accurate judgment of single-phase grounding faults.

[0071] In this invention, step 5 specifically includes the following process:

[0072] Step 5.1: Based on the third harmonic components extracted in Steps 3 and 4 Calculate the action quantity of the fault criterion. ;

[0073] Step 5.2: Based on the third harmonic components extracted in Steps 3 and 4 Calculate the braking amount for fault diagnosis. .

[0074] As shown above, based on the different characteristics of the third harmonic under normal operating conditions and fault conditions, this study uses the fault transient component of the third harmonic as the detection criterion, which greatly improves the detection sensitivity of faults near the neutral point and has a strong adaptive capability.

[0075] In this invention, step 6 specifically includes the following process:

[0076] Step 6.1: This is a floating threshold value that takes into account the influence of the fundamental zero-sequence voltage under normal conditions. In order to avoid the non-zero output of the fundamental increment under normal conditions, it is based on the neutral point fundamental zero-sequence voltage component extracted in step 3. ,make ( (The amplitude of the fundamental zero-sequence voltage at the neutral point before the fault);

[0077] Step 6.2: Based on the transient components of the neutral point and terminal zero-sequence voltage fault obtained in Step 2. Calculate the braking signal .

[0078] As can be seen from the above, by setting a floating threshold voltage value, the influence of normal unbalanced voltage can be eliminated, preventing maloperation of the protection under normal operating conditions; and by utilizing the fault transient components containing the fundamental zero-sequence component and the third harmonic component. Solving for the braking signal simplifies the criteria, improves the sensitivity of detection and the reliability of protection, and provides a strong guarantee for the safe and stable operation of the generator.

[0079] In this invention, step 7 specifically includes the zero-sequence voltage fault transient component obtained in step 2. Calculate action signals .

[0080] As can be seen from the above, the fault transient component is used when calculating the action signal. It can reflect the combined effect of fundamental zero-sequence and third harmonic fault components, enhance the reliability and robustness of the criterion, and simplify protection configuration and logic.

[0081] In this invention, step 8 specifically includes the following process:

[0082] Step 8.1: Based on the braking signal obtained in Step 6 The spectral energy value within one period after the fault is calculated according to the following formula. :

[0083] ;

[0084] In the formula, N is the number of data points collected in one cycle; The sampling interval is... (f s The sampling rate is taken here. ); It is the sum of the squares of the braking signals within one cycle;

[0085] Step 8.2: Based on the action signal obtained in Step 7 The spectral energy value within one period after the fault is calculated according to the following formula. :

[0086]

[0087] In the formula, N is the number of data points collected in one cycle; The sampling interval is... (f s The sampling rate is taken here. ); It is the sum of squares of the action signals within one cycle.

[0088] As can be seen from the above, the spectral energy of the braking signal and the action signal within one cycle is introduced when constructing the criterion, which enables the criterion to be adaptively adjusted, improving sensitivity and reliability; in addition, the switch from instantaneous value to energy value can better reflect the intensity and duration of fault transients.

[0089] In this invention, step 9 specifically involves calculating the braking coefficient of the criterion based on the spectral energy of the braking signal and the action signal obtained in step 8. .

[0090] As can be seen from the above, the braking coefficient It overcomes the problem of protection malfunction that may be caused by the traditional fixed braking coefficient, and realizes adaptive adjustment according to changes in the operating environment, which simplifies the setting and configuration of protection and enhances the robustness and reliability of protection.

[0091] In this invention, step 10 specifically includes the following process:

[0092] Step 10.1: Based on the calculations in Step 5 The braking coefficient obtained in step 9 ,calculate ;

[0093] Step 10.2: Calculate according to the following formulas respectively and Valid values ​​within one cycle after the fault:

[0094] ;

[0095] In the formula, N is the number of sampling points in one period; x(k) is the signal whose effective value needs to be obtained; Let x(k) be the sum of squares of the signal over one period after the fault;

[0096] If satisfied If the condition is met, it is determined that a single-phase ground fault has occurred in the generator stator winding. If not, return to step 1 to re-acquire and measure.

[0097] As can be seen from the above, the introduction of fault transient components and spectral energy to construct detection criteria not only highlights fault characteristics but also adaptively adjusts the braking coefficient, exhibiting high sensitivity and reliability. Furthermore, by comparing the magnitudes of the effective values ​​within one cycle after the fault, the effective values ​​directly reflect the average energy level of the signal within one cycle, demonstrating good stability and noise immunity. This method is simple to implement and can accurately and quickly detect the occurrence of faults.

[0098] The following provides a further explanation of the principles behind the above steps:

[0099] 1. Fault transient components

[0100] This invention abandons the traditional approach of using steady-state components and instead uses transient components to construct the criterion. The fault transient component refers to the component obtained by subtracting the steady-state operating component before the fault from the electrical component after the fault, which only contains the abrupt change. It can more sensitively capture the sudden change in electromagnetic energy caused by the ground fault, and its magnitude directly reflects the severity of the fault, showing obvious fault characteristics.

[0101] 2. Phase difference of the third harmonic component

[0102] This study uses the third harmonics at the neutral point and the machine terminal, which exhibit significant phase differences in their transient components under normal operating conditions and fault conditions. Under normal conditions, the phase difference between the third harmonics at the neutral point and the machine terminal is between 90° and 180°. During a fault, the phases of the third harmonics at the neutral point and the machine terminal are approximately the same, with a phase difference of approximately 0°. Therefore, this pattern can be used to propose preliminary detection criteria. During normal operation, because the phase difference between the transient components of the third harmonics at the neutral point and the machine terminal is greater than 90°, the magnitude of the difference between the two harmonics will be greater than the magnitude of the sum of the two harmonics. After a fault occurs, the phase difference between the transient components of the third harmonics at the neutral point and the machine terminal is approximately 0°, therefore the magnitude of the difference between the two harmonics is less than the magnitude of the sum of the two harmonics. Based on this, preliminary detection criteria can be proposed. ,in These are constant coefficients.

[0103] 3. Adaptive braking coefficient based on spectral energy

[0104] Spectral energy is defined as the total energy integral over a specific time interval for a continuous signal. Its spectral energy within the time window [0,T] is For a discrete sampling system, the spectral energy is In the formula, N is the number of sampling points, and Δt is the sampling interval. Therefore, spectral energy essentially transforms the instantaneous amplitude information of a signal into a global feature quantity characterizing its overall intensity through square integration or summation operations. The braking coefficient λ is constructed using the ratio of spectral energies to achieve dynamically adjusted criterion coefficients, thus forming an adaptive criterion. This improves the sensitivity and reliability of the criterion, and also has strong anti-interference and robustness.

[0105] Example: When the generator stator experiences such as Figure 2 When a single-phase ground fault is shown, a setup is constructed as follows: Figure 3 The simulation model of the generator stator winding shown is illustrated in Table 1. The specific parameters of the generator stator winding are shown in Table 1.

[0106] Table 1. Generator stator winding parameters

[0107]

[0108] When a single-phase ground fault occurs in the first branch of phase A, the simulation sampling rate is 20kHz, the power frequency period is 0.02s, the fault resistance is 0.07Ω, and the fault location is 1 / 7 of the distance from the neutral point. At this time, the following can be obtained: Figure 4 The waveform diagram of the transient component of the third harmonic fault at the machine terminal and neutral point shown in the diagram correctly reflects the phase difference law of the third harmonic. Figure 5 The image shows the spectral energy waveforms of the braking signal and the action signal; from Figure 6 The waveforms of the action and braking quantities shown indicate that the action quantity is much greater than the braking quantity during a fault, thus the fault can be detected accurately and reliably.

[0109] In addition, to verify the feasibility and effectiveness of the technology, various fault scenarios were set up for verification, including different fault locations, fault resistances, and different neutral grounding methods.

[0110] Table 2 below shows the simulation results when the neutral point is connected to ground through a resistor and an inductor in parallel.

[0111] Table 2 Simulation results when the neutral point is connected to ground in parallel via a resistor and an inductor.

[0112]

[0113] As shown in Table 2, after using the transient component of the third harmonic voltage fault and introducing spectral energy as the adaptive criterion coefficient, regardless of the fault resistance value, it can always be observed that the effective value of the action quantity is always greater than the effective value of the braking quantity within one cycle after the fault occurs, which satisfies the adaptive fault criterion and can accurately detect the occurrence of single-phase ground fault.

[0114] Table 3 below shows the simulation results when the neutral point is grounded through a resistor.

[0115] Table 3 Simulation results when the neutral point is grounded via a resistor.

[0116]

[0117] Analysis of the simulation results shown in Table 3 shows that when the generator neutral point is grounded through a high resistance, the adaptive fault detection criteria proposed in this study can operate correctly and reliably.

[0118] Through the above methods, the present invention provides a generator stator winding single-phase ground fault detection method based on the transient component of the third harmonic fault. This method can adaptively adjust the braking coefficient according to changes in the operating environment, improve the sensitivity and reliability of the detection criteria, and accurately and quickly detect generator stator winding ground faults.

[0119] A generator stator winding single-phase ground fault detection system based on the transient component of third harmonic faults, utilizing the aforementioned generator stator winding single-phase ground fault detection method based on the transient component of third harmonic faults, includes:

[0120] The data acquisition module is used to collect the neutral point zero-sequence voltage and the generator terminal zero-sequence voltage before and after a fault in the generator stator winding.

[0121] The fault transient component calculation module is connected to the data acquisition module. It is used to obtain the neutral point fault transient component and the terminal fault transient component by subtracting the zero-sequence voltage in the previous cycle from the zero-sequence voltage in the cycle after the fault.

[0122] The harmonic component extraction module is connected to the fault transient component calculation module. It uses empirical wavelet transform (EWT) to extract the fundamental voltage and third harmonic voltage in the transient component of neutral point zero-sequence voltage fault, as well as the fundamental voltage and third harmonic voltage in the transient component of terminal zero-sequence voltage fault.

[0123] The fault criterion calculation module is connected to the harmonic component extraction module and is used to calculate the action quantity and braking quantity based on the extracted fundamental zero-sequence voltage and third harmonic voltage components, respectively.

[0124] The braking signal and action signal calculation module is connected to the fault criterion calculation module and is used to calculate the braking signal and action signal.

[0125] The spectral energy calculation module is connected to the braking signal and action signal calculation module and is used to calculate the spectral energy of the braking signal and the spectral energy of the action signal within one cycle after the fault.

[0126] The braking coefficient calculation module is connected to the spectral energy calculation module and is used to calculate the braking coefficient based on the spectral energy.

[0127] The fault diagnosis module is connected to the braking coefficient calculation module. It is used to compare the effective value of the action signal with the effective value of the braking signal. If the effective value of the action signal is greater than the effective value of the braking signal, it is determined that a single-phase ground fault has occurred in the generator stator winding.

[0128] This application provides an electronic device applicable to the above-described generator stator winding single-phase ground fault detection method based on the transient component of third harmonic faults, including:

[0129] Memory is used to protect computer programs and data;

[0130] A processor is used to run system programs.

[0131] This application provides a computer storage medium applicable to the above-mentioned generator stator winding single-phase ground fault detection system based on the transient component of third harmonic fault, and performs hierarchical confidentiality management of the above system and data in accordance with confidentiality management requirements.

[0132] Those skilled in the art will understand that embodiments of this application can be provided as a system or a computer program product. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0133] This application is described with reference to flowchart illustrations and / or block diagrams of devices (systems) and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0134] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0135] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0136] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0137] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0138] Computer-readable media include both permanent and non-permanent, removable and non-removable media, which can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0139] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0140] The embodiments of the present invention are given for the purposes of illustration and description. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for detecting single-phase ground faults in generator stator windings based on the transient component of third harmonic voltage faults, characterized in that, Includes the following steps: Step 1: Collect the neutral point zero-sequence voltage before and after the generator stator winding fault. Zero-sequence voltage at the terminal ; Step 2: Subtract the zero-sequence voltage of the previous cycle from the zero-sequence voltage of the cycle following the fault to obtain the transient component of the neutral point fault. Transient components of machine-side faults ; Step 3: Extract the fundamental voltage from the transient component of the neutral point zero-sequence voltage fault based on Empirical Wavelet Transform (EWT). and third harmonic voltage and based on neutral point zero-sequence voltage Extract the fundamental zero-sequence voltage at the neutral point before the fault. ; Step 4: Extract the fundamental voltage from the transient component of the zero-sequence voltage fault at the machine terminal based on Empirical Wavelet Transform (EWT). and third harmonic voltage ; Step 5: Calculate the action quantity based on the extracted fundamental zero-sequence voltage and third harmonic voltage components. and braking amount ; Step 6: Let U g Equal to the fundamental zero-sequence voltage of the neutral point before the fault 10% of the amplitude, based on the obtained zero-sequence voltage fault transient component. , Calculate the braking signal ; Step 7: Based on the obtained zero-sequence voltage fault transient component , Calculate action signals ; Step 8: Based on the obtained braking signal and action signals Calculate the spectral energy of the braking signal within one cycle after the fault. and the spectral energy of the action signal ; Step 9: Based on the obtained spectral energy and Calculate the braking coefficient ; Step 10: Comparison and The magnitude of the effective value within one cycle after the fault, if it satisfies If the condition is met, it is considered that a single-phase ground fault has occurred in the generator stator winding. If not, return to step 1.

2. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: The specific process of step 2 includes: Step 2.1: Based on the neutral point zero-sequence voltage collected in Step 1 before and after the fault The neutral point zero-sequence voltage fault transient component is obtained by subtracting the zero-sequence voltage of the previous cycle from the zero-sequence voltage of the cycle following the fault. ,Right now Where k is a point within a cycle after the fault; This is the zero-sequence voltage corresponding to the k-th point after the fault; Sampling rate; T is the system period; Step 2.2: Based on the zero-sequence voltages at the machine terminals before and after the fault collected in Step 1 Similarly, in step 2.1, by subtracting the zero-sequence voltage of the previous cycle from the zero-sequence voltage of the cycle following the fault, the transient component of the zero-sequence voltage at the generator terminal can be obtained. .

3. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: In step 3, in order to effectively analyze the fault signal, the empirical wavelet transform uses the db4 wavelet to extract the transient component of the neutral point zero-sequence voltage fault. The fundamental component and third harmonic components Extract the neutral point zero-sequence voltage component The fundamental voltage component .

4. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: In step 4, in order to effectively analyze the fault signal, the empirical wavelet transform uses the db4 wavelet to extract the transient component of the zero-sequence voltage fault at the machine terminal. The fundamental component and third harmonic components .

5. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: The specific process of step 5 includes: Step 5.1: Based on the third harmonic components extracted in Steps 3 and 4 Calculate the action quantity of the fault criterion. ; Step 5.2: Based on the third harmonic components extracted in Steps 3 and 4 Calculate the braking amount for fault diagnosis. .

6. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: The specific process of step 6 includes: Step 6.1: It is a floating threshold value that takes into account the influence of the fundamental zero-sequence voltage under normal conditions. In order to avoid the non-zero output of the fundamental increment under normal conditions, it is based on the extracted neutral point fundamental zero-sequence voltage component. ,make ;in, The magnitude of the fundamental zero-sequence voltage at the neutral point before the fault; Step 6.2: Based on the fundamental voltage fault transient component extracted in Step 2 It contains both the fundamental zero-sequence voltage and the third harmonic voltage, and can be used to calculate the braking signal that reflects the combined effect of the fundamental and third harmonic fault components. .

7. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: In step 7, the fundamental voltage fault transient component extracted in step 2 is used as the basis. It contains both the fundamental zero-sequence voltage and the third harmonic voltage, and the operating signal reflecting the combined effect of the fundamental and third harmonic fault components can be calculated. .

8. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: The specific process of step 8 includes: Step 8.1: Based on the braking signal obtained in Step 6 The spectral energy value within one period after the fault is calculated according to the following formula. : ； In the formula, N is the number of data points collected in one cycle; The sampling interval is... (f s (sampling rate); It is the sum of the squares of the braking signals within one cycle; Step 8.2: Based on the action signal obtained in Step 7 The spectral energy value within one period after the fault is calculated according to the following formula. : In the formula, N is the number of data points collected in one cycle; The sampling interval is... ; where f s Sampling rate; It is the sum of squares of the action signals within one cycle.

9. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: In step 9, the braking coefficient can be obtained by calculating their ratio based on the spectral energy obtained in step 8. Action signals for spectral energy utilization and braking signal It includes both the fundamental wave component and the third harmonic fault transient component, so as to achieve the fusion of the fundamental wave and the third harmonic and simplify the judgment criteria.

10. The generator stator winding single-phase ground fault detection method based on the transient component of third harmonic voltage fault as described in claim 1, characterized in that: The specific process of step 10 includes: Step 10.1: Based on the calculations in Step 5 The braking coefficient calculated in step 9 ,calculate ; Step 10.2: Calculate according to the following formulas respectively and Valid values ​​within one cycle after the fault: ； In the formula, N is the number of sampling points in one period; x(k) is the signal whose effective value needs to be obtained; Let x(k) be the sum of squares of the signal over one period after the fault; If satisfied If the condition is met, it is determined that a single-phase ground fault has occurred in the generator stator winding. If not, return to step 1 to re-acquire and measure.

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