Online Diagnosis Method for Inter-turn Short Circuit Faults in Hydro Generator Rotors Based on Air Gap Magnetic Field Phasor Decomposition

Abstract

This invention discloses an online diagnostic method for inter-turn short-circuit faults in a hydro-generator rotor based on air gap magnetic field phasor decomposition. The steps include: 1) real-time acquisition of the air gap magnetic field monitored by the magnetic field sensor and the A-phase current, B-phase current, and C-phase current monitored by the current sensor using a synchronous data acquisition card; 2) calculation of the magnitude of the stator component and the rotor component of the air gap magnetic field at time t; 3) processing the magnitude of the stator component and the rotor component of the air gap magnetic field at time t to calculate the criterion FI1(t) for the existence of the inter-turn short circuit; 4) determining the existence of the short circuit based on the criterion FI1(t). 1max > Check if TH is true. If it is true, then determine that there is a rotor inter-turn short circuit in the hydro-generator; 5) Find t F Rotor position angle θ at time t F The method determines the magnetic pole where the inter-turn short circuit fault occurs based on the rotor position angle. This method is not affected by the uneven length of the generator air gap and can reliably diagnose the rotor inter-turn short circuit fault under any air gap length distribution.

Description

Technical Field

[0001] This invention relates to the field of fault detection for hydro-generators, specifically to an online diagnostic method for inter-turn short-circuit faults in hydro-generator rotors based on air gap magnetic field phasor decomposition. Background Technology

[0002] Rotor winding inter-turn short circuit is a common electrical fault in generators. A minor short circuit may not seriously affect generator operation, but if the fault continues to develop, it can cause adverse effects such as increased excitation current, reduced reactive power output, and intensified rotor vibration. Localized overheating at the short circuit point can also cause the fault to evolve into a rotor ground fault, damaging the rotor core and potentially causing rotor shaft magnetization, posing a significant threat to the safe operation of the unit. In the 1990s, three out of four 300MW generators at a thermal power plant in my country ultimately suffered shaft magnetization due to rotor inter-turn short circuits and other reasons; two of these generators also burned out their retaining rings. In 2005, an inter-turn short circuit fault in the rotor of generator No. 6 at the Fengtan Hydropower Station triggered the activation of the main protection system.

[0003] Centrifugal force during rotor rotation causes mutual compression and displacement deformation between windings, thermal deformation of the excitation winding, and localized overheating due to poor ventilation. These are important causes of inter-turn short circuits in generator rotor windings. Faults caused by these factors usually only become apparent when the generator is operating under actual conditions. Therefore, online monitoring and protection against inter-turn short circuit faults in rotor windings are particularly necessary.

[0004] Currently, traditional methods for detecting inter-turn short-circuit faults in generator rotors mainly include: the open transformer method, the air-gap coil detection method, the excitation current method, and the electromotive force comparison method. While the first method is relatively sensitive, it is an offline detection method, only possible after the generator is stopped and the rotor removed. Furthermore, it is affected by factors such as the material of the rotor slot wedges, and cannot detect dynamic inter-turn short circuits generated during rotation. The basic principle of the air-gap coil detection method is to collect the rotor leakage magnetic field in the air gap of the operating synchronous generator, analyze the magnetic field waveform, diagnose whether there is an inter-turn short-circuit fault in the rotor windings, and accurately display the location of the faulty slot. However, air-gap coil detection can only be performed under no-load and three-phase short-circuit conditions. Under load conditions, the detection effect is not significant due to armature reaction. The first two methods of inter-turn short-circuit fault detection have limitations, as they can only be performed after the unit is disconnected from the grid.

[0005] In order to improve the safety and reliability of large hydro-generator operation, it is necessary to study methods that can accurately detect rotor turn-to-turn short-circuit faults. Summary of the Invention

[0006] The purpose of this invention is to provide an online diagnostic method for inter-turn short-circuit faults in the rotor of a hydro-generator based on air gap magnetic field phasor decomposition, comprising the following steps:

[0007] 1) Install a magnetic field sensor on the air gap side surface of the stator teeth of the hydro generator to monitor the air gap magnetic field, and install current sensors at the output terminals of the three-phase windings respectively.

[0008] Define the magnetic pole numbering: Select any N pole as magnetic pole number 1, and then number each magnetic pole sequentially in a counterclockwise direction; magnetic pole number 1 is subjected to a positive excitation current, and the direction of the generated magnetic flux is positive radial;

[0009] Define the rotor position by selecting any +A phase winding and setting the rotor position to 0 when the axis of magnetic pole 1 coincides with the axis of the winding; the +A phase winding is energized with positive current and generates magnetic flux in the positive radial direction.

[0010] 2) Use a synchronous data acquisition card to acquire [t] n -(p+1)·T,t n Within the time period, the air gap magnetic field monitored by the magnetic field sensor, the A-phase current, B-phase current, C-phase current, and rotor position monitored by the current sensor; t n It is the time corresponding to the most recent data in the synchronous data acquisition card up to the current moment; T is the time period, p is the pole number; let k = 0;

[0011] 3) Process the data acquired by the synchronous data acquisition card to obtain the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor Rotor position angle θ Ω (t), where t = t n -(p+0.5-0.1k)·T;

[0012] 4) Calculate the magnitude of the stator component of the air gap magnetic field at time t. and rotor component magnitude

[0013] 5) Let k = k + 1, then check if k = 10p is true. If not, repeat steps 3) to 4). If yes, terminate the loop and proceed to step 6).

[0014] 6) For [t] n -(p+0.5)·T]≤t<[t n The magnitude of the stator component of the air gap magnetic field within the time range of -0.5T] and rotor component magnitude The process is performed to calculate the criterion FI1(t) for the existence of rotor inter-turn short circuits;

[0015] 7) Find the maximum value of the rotor inter-turn short-circuit existence criterion FI1(t), and denote it as the short-circuit existence criterion FI. 1max The time corresponding to the maximum value is denoted as t. F .

[0016] 8) Criterion for determining the existence of a short circuit (FI) 1max >Whether TH is true or false. If it is true, it is determined that there is a short circuit between rotor turns of the hydro generator and proceeds to step 9). If it is false, proceeds to step 11. TH is the fault existence judgment threshold.

[0017] 9) Find t F Rotor position angle θ at time t F (t F ), and determine the magnetic pole where the inter-turn short circuit fault occurs based on the rotor position angle;

[0018] 10) Calculate the short-circuit turns estimate N used to assess the severity of the fault. F ;

[0019] 11) The current mechanical cycle diagnosis is complete. Let t0 = t0 + p·T, and return to step 2).

[0020] Furthermore, the magnetic field sensor includes a Hall sensor and a magnetic field detection coil.

[0021] Furthermore, the air gap magnetic field includes a radial component of the air gap magnetic field.

[0022] Furthermore, step 3) involves processing the data acquired by the synchronous data acquisition card, including:

[0023] 3.1) Acquire the air gap magnetic field, A-phase current, B-phase current, and C-phase current data collected by the synchronous data acquisition card during the time period from t-0.5T to t+0.5T. Calculate the fundamental phasor of each data point using Fast Fourier Transform, and record them as the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor

[0024] 3.2) Obtain the rotor position angle at time t, denoted as θ. Ω (t).

[0025] Furthermore, the magnitude of the stator component of the air gap magnetic field at time t and rotor component magnitude They are shown below:

[0026]

[0027]

[0028] In the formula, The fundamental phasor of the air gap magnetic field The phase;

[0029] Among them, the phase of the stator component of the air gap magnetic field at time t Air gap magnetic field rotor component phase As shown below:

[0030]

[0031]

[0032] In the formula, θ A θ is the tangential angle between the centerline of the +A phase winding closest to the magnetic field sensor and the magnetic field sensor. Ω (t) represents the rotor position at time t.

[0033] Furthermore, in step 6), the step of calculating the rotor inter-turn short-circuit existence criterion FI1(t) includes:

[0034] 6.1) In [t n -(p+0.5)·T]≤t<[t n Within the time range of -0.5T, the stator component of the air gap magnetic field Rotor components Low-pass filtering is performed to obtain the filtered air gap magnetic field stator component B. slf (t), rotor component B rlf (t); p is the number of generator pole pairs;

[0035] 6.2) Calculate the normalized value B of the stator component of the air gap magnetic field. s1 (t), Rotor component normalized value B r1 (t), that is:

[0036]

[0037]

[0038] In the formula, τ is the time variable;

[0039] 6.3) Calculate the rotor inter-turn short-circuit existence criterion FI1(t), i.e.:

[0040] FI1(t)=|B s1 (t)-B r1 (t)| (7)

[0041] In the formula, B s1 (t), B r1(t) represents the normalized values ​​of the stator component and rotor component of the air gap magnetic field.

[0042] Furthermore, the stator component of the air gap magnetic field... Rotor components The steps for low-pass filtering include: removing the stator component of the air gap magnetic field. Rotor components The portion of frequencies higher than 1.2f; where f is the synchronous electrical frequency.

[0043] Furthermore, the fault existence determination threshold TH < 1 / N s N s This represents the number of turns in the rotor winding per pole.

[0044] Furthermore, the steps for determining the magnetic pole where the inter-turn short-circuit fault occurred based on the rotor position angle include:

[0045] 9.1) Calculate the estimated value L of the faulty magnetic pole number. F0 ,Right now:

[0046]

[0047] In the formula, θ F For t F The rotor position angle at that moment;

[0048] 9.2) Estimated value L for the faulty magnetic pole number F0 Rounding to the nearest integer, we get L. F L F This refers to the magnetic pole number where the inter-turn short circuit fault occurred.

[0049] Furthermore, the estimated number of short-circuit turns N F Positively correlated with the severity of short-circuit faults;

[0050] Short-circuit turns estimate N F As shown below:

[0051] N F =(2+α)FI 1max ·N s (9)

[0052] In the formula, α is the correction coefficient; N s This represents the number of turns in the rotor winding per pole.

[0053] The technical effect of this invention is beyond doubt. This method achieves effective diagnosis of inter-turn short circuits in hydro-generators based on the phasor decomposition of the air gap magnetic field. By analyzing and comparing the relative magnitude changes of the stator and rotor components of the air gap magnetic field, the inter-turn short circuits of the rotor can be diagnosed. This method can effectively eliminate the interference caused by the change in the total air gap magnetic field due to the change in air gap length, and is more adaptable to the actual situation of uneven air gaps in hydro-generators.

[0054] This method can monitor the generator for rotor inter-turn short-circuit faults in real time and effectively. It features high sensitivity; a short circuit in even one turn of the winding of any rotor pole is sufficient for effective diagnosis. This method is unaffected by uneven air gap length and can reliably diagnose rotor inter-turn short-circuit faults under any air gap length distribution. Attached Figure Description

[0055] Figure 1 A schematic diagram of the method for decomposing stator and rotor components of a magnetic field;

[0056] Figure 2 A schematic diagram of the magnetic field change caused by a short circuit between rotor turns and the magnetic field detection coil;

[0057] Figure 3 The difference lies in the impact of uneven air gap length and short circuits between rotor turns on the stator and rotor components of the magnetic field. Figure 3 (a) indicates uneven air gap length; Figure 3 (b) is a rotor turn-to-turn short circuit;

[0058] Figure 4 (a)-(d) represent the corresponding values ​​of B under the conditions of normal operation, 1-turn short circuit, 2-turn short circuit, and 4-turn short circuit when the air gap is uniform. s1 and B r1 ;

[0059] Figure 5 FI1 represents the normal condition and the short circuit condition with different numbers of turns when the air gap is uniform.

[0060] Figure 6 (a)-(b) represent the B values ​​corresponding to normal operation and 1-turn short circuit under conditions of uneven air gap. s1 and B r1 ;

[0061] Figure 7 FI1 represents the normal condition and the condition with a 1-turn short circuit when the air gap is uneven. Detailed Implementation

[0062] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0063] Example 1:

[0064] See Figures 1 to 7 An online diagnostic method for inter-turn short-circuit faults in the rotor of a hydro-generator based on air gap magnetic field phasor decomposition includes the following steps:

[0065] 1) Install a magnetic field sensor on the air gap side surface of the stator teeth of the hydro generator to monitor the air gap magnetic field, and install current sensors at the output terminals of the three-phase windings respectively.

[0066] Define the magnetic pole numbering: Select any N pole as magnetic pole number 1, and then number each magnetic pole sequentially in a counterclockwise direction; magnetic pole number 1 is subjected to a positive excitation current, and the direction of the generated magnetic flux is positive radial;

[0067] Define the rotor position by selecting any +A phase winding and setting the rotor position to 0 when the axis of magnetic pole 1 coincides with the axis of the winding; the +A phase winding is energized with positive current and generates magnetic flux in the positive radial direction.

[0068] 2) Use a synchronous data acquisition card to acquire [t] n -(p+1)·T,t n Within the time period, the air gap magnetic field monitored by the magnetic field sensor, the A-phase current, B-phase current, C-phase current, and rotor position monitored by the current sensor; t n It is the time corresponding to the most recent data in the synchronous data acquisition card up to the current moment; T is the time period, p is the pole number; let k = 0;

[0069] 3) Process the data acquired by the synchronous data acquisition card to obtain the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor Rotor position angle θ Ω (t), where t = t n -(p+0.5-0.1k)·T;

[0070] 4) Calculate the magnitude of the stator component of the air gap magnetic field at time t. and rotor component magnitude

[0071] 5) Let k = k + 1, then check if k = 10p is true (i.e., k = 10p - 1 is the value of the last loop). If not, repeat steps 3) to 4). If yes, terminate the loop and proceed to step 6).

[0072] 6) For [t] n -(p+0.5)·T]≤t<[t n The magnitude of the stator component of the air gap magnetic field within the time range of -0.5T] and rotor component magnitude The process is performed to calculate the criterion FI1(t) for the existence of rotor inter-turn short circuits;

[0073] 7) Find the maximum value of the rotor inter-turn short-circuit existence criterion FI1(t), and denote it as the short-circuit existence criterion FI. 1max The time corresponding to the maximum value is denoted as t. F .

[0074] 8) Criterion for determining the existence of a short circuit (FI) 1max >Whether TH is true or false. If it is true, it is determined that there is a short circuit between rotor turns of the hydro generator and proceeds to step 9). If it is false, proceeds to step 11. TH is the fault existence judgment threshold.

[0075] 9) Find t F Rotor position angle θ at time t F (t F ), and determine the magnetic pole where the inter-turn short circuit fault occurs based on the rotor position angle;

[0076] 10) Calculate the short-circuit turns estimate N used to assess the severity of the fault. F ;

[0077] 11) The current mechanical cycle diagnosis is complete. Let t0 = t0 + p·T, and return to step 2).

[0078] The magnetic field sensor includes a Hall sensor and a magnetic field detection coil.

[0079] The air gap magnetic field includes the radial component of the air gap magnetic field.

[0080] Step 3) involves processing the data acquired by the synchronous data acquisition card, including:

[0081] 3.1) Acquire the air gap magnetic field, A-phase current, B-phase current, and C-phase current data collected by the synchronous data acquisition card during the time period from t-0.5T to t+0.5T. Calculate the fundamental phasor of each data point using Fast Fourier Transform, and record them as the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor

[0082]

[0083] 3.2) Obtain the rotor position angle at time t, denoted as θ. Ω (t).

[0084] The magnitude of the stator component of the air gap magnetic field at time t and rotor component magnitude They are shown below:

[0085]

[0086]

[0087] In the formula, The fundamental phasor of the air gap magnetic field The phase;

[0088] Among them, the phase of the stator component of the air gap magnetic field at time t Air gap magnetic field rotor component phase As shown below:

[0089]

[0090]

[0091] In the formula, θ A θ is the tangential angle between the centerline of the +A phase winding closest to the magnetic field sensor and the magnetic field sensor. Ω (t) represents the rotor position at time t.

[0092] Step 6) involves calculating the rotor inter-turn short-circuit existence criterion FI1(t), which includes:

[0093] 6.1) In [t n -(p+0.5)·T]≤t<[t n Within the time range of -0.5T, the stator component of the air gap magnetic field Rotor components Low-pass filtering is performed to obtain the filtered air gap magnetic field stator component B. slf (t), rotor component B rlf (t); p is the number of generator pole pairs;

[0094] 6.2) Calculate the normalized value B of the stator component of the air gap magnetic field. s1 (t), Rotor component normalized value B r1 (t), that is:

[0095]

[0096]

[0097] In the formula, τ is the time variable;

[0098] 6.3) Calculate the rotor inter-turn short-circuit existence criterion FI1(t), i.e.:

[0099] FI1(t)=|B s1 (t)-B r1 (t)| (7)

[0100] In the formula, B s1 (t), B r1(t) represents the normalized values ​​of the stator component and rotor component of the air gap magnetic field.

[0101] Stator component of air gap magnetic field Rotor components The steps for low-pass filtering include: removing the stator component of the air gap magnetic field. Rotor components The portion of frequencies higher than 1.2f; where f is the synchronous electrical frequency.

[0102] Fault existence determination threshold TH < 1 / N s N s This represents the number of turns in the rotor winding per pole.

[0103] The steps for determining the magnetic pole where an inter-turn short circuit fault occurs based on the rotor position angle include:

[0104] 9.1) Calculate the estimated value L of the faulty magnetic pole number. F0 ,Right now:

[0105]

[0106] In the formula, θ F For t F The rotor position angle at that moment;

[0107] 9.2) Estimated value L for the faulty magnetic pole number F0 Rounding to the nearest integer, we get L. F L F This refers to the magnetic pole number where the inter-turn short circuit fault occurred.

[0108] Short-circuit turns estimate N F Positively correlated with the severity of short-circuit faults;

[0109] Short-circuit turns estimate N F As shown below:

[0110] N F =(2+α)FI 1max ·N s (9)

[0111] In the formula, α is the correction coefficient; N s This represents the number of turns in the rotor winding per pole.

[0112] Example 2:

[0113] See Figures 1 to 7 An online diagnostic method for inter-turn short-circuit faults in the rotor of a hydro-generator based on air gap magnetic field phasor decomposition includes the following:

[0114] When an inter-turn short circuit occurs in the generator rotor, the effective ampere-turns of the excitation at the corresponding magnetic pole of the faulted winding decrease, which in turn leads to a decrease in the rotor magnetic field near the fault. Figure 2 As shown in the figure. Based on this phenomenon, diagnosis can be made according to the spatial distribution of the motor's magnetic field.

[0115] Based on the above fundamental principles, this method measures the motor's magnetic field by installing a small detection coil on the stator teeth. Since the rotor inter-turn short circuit follows the rotor's rotation, a single sensor can completely measure the entire rotor circumference. Figure 2 As shown.

[0116] The air gap lengths of the rotor at different magnetic poles of a hydro-generator are not exactly the same. Therefore, even if there is no inter-turn short circuit in the motor, the magnitude of the magnetic field corresponding to the position of the sensor at different magnetic poles will be different. This is a key issue in diagnosing rotor inter-turn short circuits. To address this, this paper proposes a diagnostic method based on magnetic field phasor decomposition. This method analyzes the stator and rotor components of the magnetic field at the sensor location based on real-time rotor position and phase current data. Furthermore, based on the stator and rotor component phases, the measured magnetic field stator and rotor components are separated, such as... Figure 1 As shown.

[0117] After separating the stator and rotor components of the magnetic field, short circuits between rotor turns can be effectively identified even when the air gap length is uneven. This is because although both uneven air gap length and short circuits between rotor turns cause changes in the magnetic field, they are significantly different: air gap changes alter the loop reluctance, resulting in similar changes in the stator and rotor components of the magnetic field; short circuits between rotor turns only reduce the rotor component of the magnetic field, while the stator component remains largely unaffected. Figure 3 As shown. The relative relationship between the stator and rotor components of the magnetic field can be used to effectively diagnose rotor inter-turn short circuits; therefore, the fault can be accurately located by using the magnetic pole number at the sensor when an inter-turn short circuit fault is detected.

[0118] The specific steps include:

[0119] 1. Preliminary preparations (not as a claim)

[0120] a) Select any N pole as pole number 1, and number the rotor poles sequentially in the opposite direction of the generator rotor rotation. If the generator has 2p poles, then the poles are numbered 1, 2, 3...2p sequentially.

[0121] b) When the rotor position is 0°, a magnetic field sensor (Hall sensor or detection coil) is installed on the air gap side surface of the stator tooth opposite the No. 1 magnetic pole to measure the change of the air gap magnetic field (only the radial component is measured) over time.

[0122] c) Install a current sensor at each of the three-phase stator winding output terminals of the generator to measure the change of three-phase current over time.

[0123] d) Output the measured air gap magnetic field, A-phase current, B-phase current, C-phase current and rotor position to the synchronous data acquisition card. The sampling frequency of the acquisition card should be an integer multiple of the generator synchronous frequency f and not less than 1000 Sa / s.

[0124] e) Based on the generator winding structure, determine the position of the central axis of the +A phase winding closest to the magnetic field sensor, and denote the tangential angle between the central axis of +A and the magnetic field sensor as θ. A (Mechanical angle with the rotor rotation direction as positive).

[0125] 2. Diagnostic process

[0126] 1) Obtain (t) n -(p+1)T,t n The data collected by the acquisition card within the time range, where t n It is the time corresponding to the most recent data in the data acquisition card up to the current day.

[0127] 2) Let the calculation time t = t n -(p+0.5)T.

[0128] 3) Acquire the signal from t-0.5T to t+0.5T using the acquisition card, and obtain the fundamental phasors of the air gap magnetic field and each phase current at time t through Fast Fourier Transform.

[0129] 4) Record the rotor position θ at time t. Ω (t).

[0130] 5) Calculate the phase of the stator component of the air gap magnetic field at time t.

[0131]

[0132] 6) Calculate the rotor component phase of the air gap magnetic field at time t.

[0133]

[0134] 7) Record The phase is Calculate the magnitude of the stator component of the air gap magnetic field at time t. and rotor component magnitude

[0135]

[0136]

[0137] 8) Let the calculation time t = t + 0.1T, and repeat steps 3) to 7) until t = t n The loop terminates at -0.5T and proceeds to step 9).

[0138] 9) In [t n -(p+0.5)T]<t≤[t n Within the time range of -0.5T, for Perform a low-pass filter to remove frequencies higher than 1.2f, where f is the synchronous electrical frequency; the filtered results are denoted as B, B, and C respectively. slf (t), B rlf (t).

[0139] 10) Calculate the normalized values ​​of the stator and rotor components of the air gap magnetic field:

[0140]

[0141]

[0142] 11) Calculate the criterion FI1(t) for the existence of rotor inter-turn short circuit:

[0143] FI1(t)=|B s1 (t)-B r1 (t)|

[0144] 12) Find the maximum value of FI1(t), which is FI 1max The time when the maximum value occurs is denoted as t. F .

[0145] 13) Diagnose whether the motor has an inter-turn short circuit: If FI 1max If the value is greater than TH, it is determined that there is a rotor inter-turn short circuit in the motor, and step 14) is executed; otherwise, it is determined that there is no rotor inter-turn short circuit in the motor, and step 16) is executed. TH is the fault existence judgment threshold, which can generally be taken as 0.01, or it can be calibrated according to the time situation. TH should be greater than the FI that may occur during normal operation of the generator. 1max And less than 1 / N s , where N s It is the number of turns of the rotor winding per pole.

[0146] 14) Find t F The rotor position angle corresponding to the given moment is denoted as θ. F Calculate the estimated value L of the faulty magnetic pole number. F0 :

[0147]

[0148] 15) For LF0 Rounding to the nearest integer gives L F L F This refers to the magnetic pole number where the inter-turn short circuit fault occurred.

[0149] 16) Calculate the estimated number of short-circuit turns N. F N F It is the diagnostic result of the fault severity; the larger the value, the more severe the short circuit fault.

[0150] N F =(2+α)FI 1max ·N s

[0151] Here, α is a correction factor, typically ranging from 0.5 to 0.7, or it can be determined through simulation or experimentation based on FI. 1max The relationship between the actual number of short-circuit turns and the calibration.

[0152] 17) The current mechanical cycle diagnosis is complete. After waiting for one mechanical cycle (p·T), proceed with step 1).

[0153] Example 3:

[0154] The simulation experiment of the online diagnosis method for inter-turn short-circuit faults in hydro-generator rotors based on air gap magnetic field phasor decomposition includes the following:

[0155] Taking a 56-pole hydro-generator as an example, its air gap is uniform (the air gap length corresponding to each magnetic pole is the same). Under rated operating conditions, the B value corresponds to the normal operation of the motor and the inter-turn short circuit at pole 1. s1 B r1 Figure 4 FI1 Figure 5 As shown (TH = 0.01).

[0156] Considering the uneven air gap of the generator (the air gap length corresponding to each magnetic pole is slightly different), under rated operating conditions, the B corresponding to normal operation of the motor and the inter-turn short circuit of pole 1 is... s1 B r1 Figure 4 FI1 Figure 5 As shown (TH = 0.01).

[0157] from Figure 4 , Figure 6 It can be seen that when the motor is normal, B s1 and B r1 They basically overlap, and under the condition of uniform air gap, B s1 and B r1 Approximately equal to 1, it basically does not change with time. However, the air gap length corresponding to different magnetic poles in an actual hydro-generator will vary to some extent. Considering the non-uniformity of the air gap, B... s1 and Br1 The magnitude of the magnetic field will also change accordingly. This is because the different air gap lengths when different magnetic poles sweep across the sensor cause variations in the magnitude of the magnetic field. However, B s1 and B r1 The variation pattern is consistent and will not affect the diagnosis. When there is a rotor turn-to-turn short circuit in one of the motor's magnetic poles, B... s1 and B r1 They still overlap, indicating that most of the magnetic poles are normal, but around 0.05s, B... s1 and B r1 The significant difference indicates an inter-turn short circuit fault at the magnetic poles swept across the sensor; this pattern holds true for both uniform and non-uniform air gaps, demonstrating that the diagnostic method is unaffected by air gap length non-uniformity; from Figure 4 It can be seen that the more short-circuit turns there are, the more B... s1 and B r1 The greater the difference, the more effectively the diagnostic method can reflect the degree of short-circuit fault.

[0158] from Figure 5 , Figure 7 It can be seen that, under both uniform and non-uniform air gap conditions, FI1 remains below 0.003 when the motor is normal, far less than the threshold (0.01). When the motor has a rotor inter-turn short circuit, FI1 suddenly increases around 0.05s, rapidly exceeding the threshold. For the least severe single-turn short circuit, the maximum FI1 value is approximately 0.018, significantly greater than the threshold (0.01). This indicates that the method of this invention can effectively diagnose inter-turn short circuits in the turbine generator rotor and is unaffected by air gap non-uniformity. On the other hand, the magnetic pole that sweeps across the sensor at 0.05s is precisely the 56th magnetic pole where the fault is set, indicating that this method can effectively locate the faulty magnetic pole.

[0159] Figures 4-7 The simulation results show the fault presence diagnosis for all states, and the fault pole number (L). F0 L F ), Fault severity (r) F The diagnostic results are shown in Table 1 (TH = 0.01). Figures 4-7 The simulation results show the fault presence diagnosis for all states, and the fault pole number (L). F0 L F ), Fault severity (r) F The diagnostic results are shown in Table 1 (TH = 0.01). Figures 4-7 The simulation results show the fault presence diagnosis for all states, and the fault pole number (L). F0 L F ), number of short-circuit turns (N) F The diagnostic results are shown in Table 1 (TH = 0.01, α = 0.6).

[0160] Table 1. Results of rotor inter-turn short circuit diagnosis under various conditions

[0161]

[0162] As shown in Table 1, under both uniform and non-uniform air gap conditions, the diagnostic results for normal motor operation indicate no rotor inter-turn short circuit fault; however, when an inter-turn short circuit occurs, the diagnostic results consistently indicate the presence of a rotor inter-turn short circuit. The short circuit fault is located on the 56th magnetic pole, and the estimated fault pole number L obtained from the diagnostic results is... F0 L F0 L F0 All values ​​are close to 56. After rounding, the fault pole number diagnosis result is 56, consistent with the settings. When the number of short-circuit turns is 1, 2, and 4, the corresponding number of short-circuit turns N is... F The values ​​were 0.97 (1.03 when the air gap is uneven), 1.89, and 3.72, respectively. The diagnostic results were close to the number of short-circuited turns, with a maximum error of only 0.28 turns. These results indicate that the diagnostic method of this invention can effectively diagnose rotor inter-turn short circuits. It can effectively detect faults when the number of short-circuited turns is only 1, demonstrating high sensitivity and accurate location of the faulty magnetic pole. It effectively reflects the severity of the fault, and the non-uniform air gap that may exist in hydro-generators does not affect the effectiveness of this method.

[0163] Example 4:

[0164] An online diagnostic method for inter-turn short-circuit faults in hydro-generator rotors based on air gap magnetic field phasor decomposition includes the following steps:

[0165] 1) Install a magnetic field sensor on the air gap side surface of the stator teeth of the hydro generator to monitor the air gap magnetic field, and install current sensors at the output terminals of the three-phase windings respectively.

[0166] Define the magnetic pole numbering: Select any N pole as magnetic pole number 1, and then number each magnetic pole sequentially in a counterclockwise direction; magnetic pole number 1 is subjected to a positive excitation current, and the direction of the generated magnetic flux is positive radial;

[0167] Define the rotor position by selecting any +A phase winding and setting the rotor position to 0 when the axis of magnetic pole 1 coincides with the axis of the winding; the +A phase winding is energized with positive current and generates magnetic flux in the positive radial direction.

[0168] 2) Use a synchronous data acquisition card to acquire [t] n -(p+1)·T,t n Within the time period, the air gap magnetic field monitored by the magnetic field sensor, the A-phase current, B-phase current, C-phase current, and rotor position monitored by the current sensor; t nIt is the time corresponding to the most recent data in the synchronous data acquisition card up to the current moment; T is the time period, p is the pole number; let k = 0;

[0169] 3) Process the data acquired by the synchronous data acquisition card to obtain the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor Rotor position angle θ Ω (t), where time t = t n -(p+0.5-0.1k)·T;

[0170] 4) Calculate the magnitude of the stator component of the air gap magnetic field at time t. and rotor component magnitude

[0171] 5) Let k = k + 1, then check if k = 10p is true. If not, repeat steps 3) to 4). If yes, terminate the loop and proceed to step 6).

[0172] 6) For [t] n -(p+0.5)·T]≤t<[t n The magnitude of the stator component of the air gap magnetic field within the time range of -0.5T] and rotor component magnitude The process is performed to calculate the criterion FI1(t) for the existence of rotor inter-turn short circuits;

[0173] 7) Find the maximum value of the rotor inter-turn short-circuit existence criterion FI1(t), and denote it as the short-circuit existence criterion FI. 1max The time corresponding to the maximum value is denoted as t. F .

[0174] 8) Criterion for determining the existence of a short circuit (FI) 1max >Whether TH is true or false. If it is true, it is determined that there is a short circuit between rotor turns of the hydro generator and proceeds to step 9). If it is false, proceeds to step 11. TH is the fault existence judgment threshold.

[0175] 9) Find t F Rotor position angle θ at time t F (t F ), and determine the magnetic pole where the inter-turn short circuit fault occurs based on the rotor position angle;

[0176] 10) Calculate the short-circuit turns estimate N used to assess the severity of the fault. F ;

[0177] 11) The current mechanical cycle diagnosis is complete. Let t0 = t0 + p·T, and return to step 2).

[0178] Example 5:

[0179] The online diagnostic method for inter-turn short circuit faults of hydro-generator rotors based on air gap magnetic field phasor decomposition is described in Example 4. The magnetic field sensor includes a Hall sensor and a magnetic field detection coil.

[0180] Example 6:

[0181] The online diagnostic method for inter-turn short circuit faults of hydro-generator rotors based on air gap magnetic field phasor decomposition is described in Example 4. The air gap magnetic field includes the radial component of the air gap magnetic field.

[0182] Example 7:

[0183] The online diagnosis method for inter-turn short-circuit faults in hydro-generator rotors based on air gap magnetic field phasor decomposition is described in Example 4. Step 3), which involves processing the data acquired by the synchronous data acquisition card, includes:

[0184] 1) Acquire the air gap magnetic field, A-phase current, B-phase current, and C-phase current data collected by the synchronous data acquisition card during the time period from t-0.5T to t+0.5T. Calculate the fundamental phasor of each data point using Fast Fourier Transform, and record them as the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor

[0185] 2) Obtain the rotor position angle at time t, denoted as θ. Ω (t).

[0186] Example 8:

[0187] An online diagnostic method for inter-turn short-circuit faults in the rotor of a hydro-generator based on air gap magnetic field phasor decomposition is described in Example 4. The main content is given in Example 4, where the magnitude of the stator component of the air gap magnetic field at time t is... and rotor component magnitude They are shown below:

[0188]

[0189]

[0190] In the formula, The fundamental phasor of the air gap magnetic field The phase;

[0191] Among them, the phase of the stator component of the air gap magnetic field at time t Air gap magnetic field rotor component phase As shown below:

[0192]

[0193]

[0194] In the formula, θ A θ is the tangential angle between the centerline of the +A phase winding closest to the magnetic field sensor and the magnetic field sensor. Ω (t) represents the rotor position at time t.

[0195] Example 9:

[0196] The online diagnostic method for inter-turn short-circuit faults in hydro-generator rotors based on air gap magnetic field phasor decomposition is described in Example 4. Step 6), which involves calculating the rotor inter-turn short-circuit existence criterion FI1(t), includes the following steps:

[0197] 1) In [t n -(p+0.5)·T]≤t<[t n Within the time range of -0.5T, the stator component of the air gap magnetic field Rotor components Low-pass filtering is performed to obtain the filtered air gap magnetic field stator component B. slf (t), rotor component B rlf (t); p is the number of generator pole pairs;

[0198] 2) Calculate the normalized value B of the stator component of the air gap magnetic field. s1 (t), Rotor component normalized value B r1 (t), that is:

[0199]

[0200]

[0201] In the formula, τ is the time variable;

[0202] 3) Calculate the criterion FI1(t) for the existence of rotor inter-turn short circuit, i.e.:

[0203] FI1(t)=|B s1 (t)-B r1 (t)| (3)

[0204] In the formula, B s1 (t), B r1 (t) represents the normalized values ​​of the stator component and rotor component of the air gap magnetic field.

[0205] Example 10:

[0206] The online diagnosis method for inter-turn short-circuit faults in the rotor of a hydro-generator based on air gap magnetic field phasor decomposition is described in Example 4. The main content includes the analysis of the stator components of the air gap magnetic field. Rotor components The steps for low-pass filtering include: removing the stator component of the air gap magnetic field. Rotor components The portion of frequencies higher than 1.2f; where f is the synchronous electrical frequency.

[0207] Example 11:

[0208] An online diagnostic method for inter-turn short-circuit faults in the rotor of a hydro-generator based on air gap magnetic field phasor decomposition is described in Example 4. The fault existence threshold TH < 1 / N is used. s N s This represents the number of turns in the rotor winding per pole.

[0209] Example 12:

[0210] The online diagnosis method for inter-turn short-circuit faults in hydro-generator rotors based on air gap magnetic field phasor decomposition is described in Example 4. The step of determining the magnetic pole where the inter-turn short-circuit fault occurs based on the rotor position angle includes:

[0211] 1) Calculate the estimated value L of the faulty magnetic pole number. F0 ,Right now:

[0212]

[0213] In the formula, θ F For t F The rotor position angle at that moment;

[0214] 2) Estimated value L for the faulty magnetic pole number F0 Rounding to the nearest integer, we get L. F L F This refers to the magnetic pole number where the inter-turn short circuit fault occurred.

[0215] Example 13:

[0216] An online diagnostic method for inter-turn short-circuit faults in the rotor of a hydro-generator based on air gap magnetic field phasor decomposition is described in Example 4. The estimated number of short-circuit turns N is... F Positively correlated with the severity of short-circuit faults;

[0217] Short-circuit turns estimate N F As shown below:

[0218] N F =(2+α)FI 1max ·N s (1)

[0219] In the formula, α is the correction coefficient; N s This represents the number of turns in the rotor winding per pole.

Claims

1. A method for on-line diagnosis of inter-turn short circuit fault of a hydro-generator rotor based on air-gap magnetic field phasor decomposition, characterized in that, Includes the following steps: Step 1) Install a magnetic field sensor on the air gap side surface of the stator teeth of the hydro generator to monitor the air gap magnetic field, and install current sensors at the output terminals of the three-phase windings respectively. Define the magnetic pole numbering: Select any N pole as magnetic pole number 1, and then number each magnetic pole sequentially in a counterclockwise direction; magnetic pole number 1 is subjected to a positive excitation current, and the direction of the generated magnetic flux is positive radial; Define the rotor position by selecting any phase A winding and setting the rotor position to 0 when the axis of magnetic pole 1 coincides with the axis of the winding; the phase A winding is energized with positive current, and the magnetic flux generated is in the positive radial direction. Step 2) Acquire data using a synchronous data acquisition card. During the time period, the air gap magnetic field monitored by the magnetic field sensor, the A-phase current, B-phase current, C-phase current, and rotor position monitored by the current sensor; It is the time corresponding to the most recent data in the synchronized data acquisition card up to the current moment; T is the time period, p is the number of generator pole pairs; let k=0; Step 3) Process the data acquired by the synchronous data acquisition card to obtain the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor Rotor position angle , among which time ; Step 4) Calculate the magnitude of the stator component of the air gap magnetic field at time t. And rotor component magnitude ; Step 5) Let Then judge If the condition is not met, repeat steps 3) to 4). If the condition is met, terminate the loop and proceed to step 6). Step 6) Magnitude of the stator component of the air gap magnetic field within the time range And rotor component magnitude The process is performed to calculate the criterion for the existence of rotor inter-turn short circuits. ; Step 7) Find the criterion for the existence of rotor inter-turn short circuits. The maximum value is denoted as the short-circuit existence criterion. The time corresponding to the maximum value is denoted as ; Step 8) Determine the short circuit existence criterion If the condition is true, it is determined that there is a rotor inter-turn short circuit in the hydro generator and proceeds to step 9); if the condition is false, proceed to step 11); TH is the fault existence judgment threshold. Step 9) Search Rotor position angle at time 10:00 And determine the magnetic pole where the inter-turn short circuit fault occurs based on the rotor position angle; Step 10) Calculate the short-circuit turns estimate used to assess the severity of the fault. ; Step 11) The current mechanical cycle diagnosis is complete. (Return to step 2) The magnitude of the stator component of the air gap magnetic field at time t And rotor component magnitude They are shown below: （1） （2） In the formula, The fundamental phasor of the air gap magnetic field The phase; Among them, the phase of the stator component of the air gap magnetic field at time t Air gap magnetic field rotor component phase As shown below: （3） （4） In the formula, The tangential angle between the centerline of the A-phase winding closest to the magnetic field sensor and the magnetic field sensor. The rotor position angle; In step 6), the criterion for the existence of rotor inter-turn short circuits is calculated. The steps include: Step 6.1) In Within the time range, the stator component of the air gap magnetic field Rotor components Low-pass filtering is performed to obtain the filtered stator component of the air gap magnetic field. Rotor components p represents the number of pole pairs of the generator; Step 6.2) Calculate the normalized values ​​of the stator components of the air gap magnetic field. Rotor component normalized value ,Right now: （5） （6） In the formula, It is a time variable; Step 6.3) Calculate the criterion for the existence of rotor inter-turn short circuits. ,Right now: （7） In the formula, , These are the normalized values ​​of the stator component and the rotor component of the air gap magnetic field.

2. The online diagnosis method for inter-turn short-circuit faults of a hydro-generator rotor based on air gap magnetic field phasor decomposition according to claim 1, characterized in that: The magnetic field sensor includes a Hall sensor and a magnetic field detection coil.

3. The online diagnosis method for inter-turn short-circuit faults of a hydro-generator rotor based on air gap magnetic field phasor decomposition according to claim 1, characterized in that: The air gap magnetic field includes the radial component of the air gap magnetic field.

4. The online diagnosis method for inter-turn short-circuit faults in a hydro-generator rotor based on air gap magnetic field phasor decomposition according to claim 1, characterized in that, Step 3) involves processing the data acquired by the synchronous data acquisition card, including: Step 1) Obtain arrive The air gap magnetic field, A-phase current, B-phase current, and C-phase current data collected by the synchronous data acquisition card within a time period are used to calculate the fundamental phasor of each data point using Fast Fourier Transform, and are respectively denoted as the fundamental phasor of the air gap magnetic field at time t. A-phase current fundamental phasor B-phase current fundamental phasor C-phase current fundamental phasor ; Step 2) Obtain the rotor position angle at time t, denoted as .

5. The online diagnosis method for inter-turn short-circuit faults in a hydro-generator rotor based on air gap magnetic field phasor decomposition according to claim 1, characterized in that, Stator component of air gap magnetic field Rotor components The steps for low-pass filtering include: removing the stator component of the air gap magnetic field. Rotor components The portion of frequencies higher than 1.2f; where f is the synchronous electrical frequency.

6. The online diagnosis method for inter-turn short-circuit faults in a hydro-generator rotor based on air gap magnetic field phasor decomposition according to claim 1, characterized in that, Fault existence determination threshold value TH < 1 / N s ; N s is the number of turns of the rotor winding for each pole.

7. The online diagnosis method for inter-turn short-circuit faults in a hydro-generator rotor based on air gap magnetic field phasor decomposition according to claim 1, characterized in that, The steps for determining the magnetic pole where an inter-turn short circuit fault occurs based on the rotor position angle include: Step 1) Calculate the estimated value of the faulty magnetic pole number. ,Right now: （8） In the formula, for The rotor position angle at that moment; Step 2) Estimating the faulty magnetic pole number Rounding to the nearest integer, we get... , This refers to the magnetic pole number where the inter-turn short circuit fault occurred.

8. The online diagnosis method for inter-turn short-circuit faults in a hydro-generator rotor based on air gap magnetic field phasor decomposition according to claim 1, characterized in that, Short-circuit turns estimate Positively correlated with the severity of short-circuit faults; Short-circuit turns estimate As shown below: （9） In the formula, N is the correction factor; s This represents the number of turns in the rotor winding per pole.

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