A diagnostic method and system for the problem of positive correlation between rotor vibration and excitation current

Abstract

The present invention discloses a method and system for diagnosing the problem of positive correlation between rotor vibration and excitation current. When there is an obvious positive correlation between rotor vibration and excitation current, rotor inter-turn short circuit detection should be analyzed and carried out. The existing methods have certain limitations in application. The present invention combines the historical operation data of the unit, adopts the test diagnosis of active and reactive output adjustment, and adopts the load increase method of increasing active power by setting reactive power to judge whether the increase in rotor vibration is correlated with the increase in active power under the premise that reactive power remains unchanged. The present invention solves the problem that there is no effective and clear diagnostic means for thermal faults of damping windings in the existing rotor guard rings, deformation of the top turns of the rotor coils, and expansion obstruction faults, and that maintenance is easily delayed or over-maintained. It improves the diagnostic accuracy and efficiency of the problem of positive correlation between rotor vibration and excitation current, and solves the limitation of the current standard that focuses only on inter-turn short circuit faults for positive correlation problems.

Description

Technical Field

[0001] The present invention belongs to the technical field of generator diagnosis, and in particular to a method and system for diagnosing the problem of positive correlation between rotor vibration and excitation current. Background Art

[0002] At present, China's electric power industry standard DL / T 1525 "Guidelines for Diagnosis of Rotor Inter-turn Short Circuit Faults of Non-salient Pole Synchronous Generators" and other standards point out that when there is an obvious positive correlation between rotor vibration and excitation current, rotor inter-turn short circuit detection should be analyzed and carried out. The above method has certain limitations in application. The main reason is that the positive correlation characteristics between rotor vibration and excitation current have diverse causes. Some of these reasons are difficult to detect under power outage test conditions, resulting in unreasonable rotor maintenance strategy formulation on site, which may lead to problems of fault expansion or excessive maintenance. This phenomenon is particularly prone to occur in units that frequently operate in flexible operation conditions.

[0003] Under the dual-carbon climate, frequent starts and stops and deep peak-shaving have become common operating conditions for large-capacity units. Problems such as rotor top-turn deformation and coil expansion obstruction have become increasingly prominent. These problems all result in a positive correlation between rotor vibration and excitation current and are difficult to detect through power outage testing. Rotor top-turn deformation, if not promptly addressed, will further exacerbate the deformation and ultimately lead to a serious inter-coil short-circuit fault. The treatment of coil expansion obstruction differs from that of inter-turn short-circuit faults. Failure to accurately determine the cause will result in excessive maintenance costs and time, and may even prevent the fault from being effectively resolved. Furthermore, under conventional load-raising operation, the unit's active power, reactive power, and rotor excitation current all increase, making it difficult to effectively distinguish the relationship between rotor vibration and other factors, such as electrical, thermal, and coil deformation. Summary of the Invention

[0004] In view of this, the present invention provides a method and system for diagnosing the problem of positive correlation between rotor vibration and excitation current. The method adopts test diagnosis of active and reactive output adjustment, and diagnoses deformation of the rotor top turn coil, obstructed coil expansion and rare burning faults of the damping winding of the hidden pole generator through analysis and comparison of the unit status in different test sections, so as to improve the accuracy and efficiency of diagnosing the problem of positive correlation between rotor vibration and excitation current.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions.

[0006] In a first aspect, the present invention provides a method for diagnosing the problem of positive correlation between rotor vibration and excitation current, comprising the steps of:

[0007] 1) For units that did not experience an increase in rotor vibration with increasing excitation current before grid connection, select the starting time point when the rotor vibration increased with increasing excitation current, adjust the unit's active power and excitation current to the unit state at this time point, and record the unit's reactive power and rotor vibration at this time as Q0 and z0 respectively;

[0008] 2) Keep the reactive power of the unit unchanged and increase the active power P' of the unit to the rated active power. This process is S1. The rotor vibration of the unit at this time is z1, and the first vibration difference z is calculated. s1 =z1-z0;

[0009] 3) Keep the active power P' of the unit at the rated active power and increase the reactive power from Q0 to the rated reactive power. This process is S2. The rotor vibration of the unit at this time is z2, and the second vibration difference z is calculated. s2 =z2-z1;

[0010] 4) Keep the active power P' of the unit at the rated active power and reduce the reactive power from the rated reactive power to Q0. This process is S3. The rotor vibration of the unit at this time is z3, and calculate the third vibration difference z s3 =z2-z3;

[0011] 5) Analyze the historical operation data of the unit, taking the time point when the positive correlation between rotor vibration and excitation current first appears as the starting point and the time point when the unit was last shut down as the end point, determine the historical data analysis period L, and record the maximum rotor vibration value z within L. Lmax ;

[0012] 6) Calculate (z1 / z Lmax ) and compared with the first preset value, when (z1 / z Lmax )>first preset value, the first process quantity A1=1, otherwise the first process quantity A1=0;

[0013] 7) Calculate (z2 / z Lmax ) and [z s1 / (z s2 +z s1 )] and compared with the first preset value respectively, when (z2 / z Lmax )>first preset value and [z s1 / (z s2 +z s1 )]>first preset value, the second process quantity A2=1, otherwise the second process quantity A2=0;

[0014] 8) Calculate the correlation between the rotor vibration and the active power during the S1 process of step 2), record it as X3, calculate the correlation between the rotor vibration and the excitation current during the S2 process of step 3), record it as X4, and compare X3 and X4. When X3>X4, the third process quantity A3=1, otherwise the third process quantity A3=0;

[0015] 9) When [(A1+A2)·A3]>0, maintenance should be carried out to check for thermal faults in the guard ring and the damping winding inside the guard ring.

[0016] Furthermore, the diagnostic method further comprises the steps of:

[0017] 10) Compare z s1 、z s2 and z s2 、z s3 , when z s2 >z s1 And z s2 >z s3 When , the first intermediate quantity B1 = 1, otherwise the first intermediate quantity B1 = 0;

[0018] 11) Calculate [(z s2 -z s3 ) / z s2 ] and compared with the first preset value, when [(z s2 -z s3 ) / z s2 ]>first preset value, the second intermediate value B2=1, otherwise the second intermediate value B2=0;

[0019] 12) Calculate the correlation between the rotor vibration and the excitation current during S3 in step 4) and record it as X5. Compare X1, X2 with X4, X5. When X1>X2 and X4>X5 and [(z s2 -z s3 ) / z s2 ]>the second preset value, the third intermediate value B3=1, otherwise the third intermediate value B3=0;

[0020] 13) If the rotor is diagnosed with a dynamic inter-turn short circuit fault by any of the determination methods other than the positive correlation, the fourth intermediate quantity B4=1; otherwise, the fourth intermediate quantity B4=0;

[0021] 14) When [B1·(B2+B3)·B4]>0, an inspection should be carried out to check for deformation of the top turn of the rotor coil; when [B1·(B2+B3)]>0 and B4=0, the rotor coil is blocked from expanding;

[0022] The step 5) further includes: calculating the correlation between the rotor vibration and the excitation current during the time period in which the active power in L is constant and the reactive power increases, recorded as X1, and calculating the correlation between the rotor vibration and the excitation current during the time period in which the active power in L is constant and the reactive power decreases, recorded as X2.

[0023] Furthermore, in the step 1), when recording the reactive power and rotor vibration of the unit as Q0 and z0 respectively, if the vibration values ​​at the bearings on both sides of the rotor are inconsistent, the data on the side with the larger value is used for analysis.

[0024] Furthermore, the first preset value is 0.65-0.75, and most preferably 0.7.

[0025] Furthermore, the second preset value is 0.55-0.65, and most preferably is 0.6.

[0026] Furthermore, the diagnostic method further comprises:

[0027] For the units that have experienced the increase of rotor vibration with the increase of excitation current during the boost process before grid connection, select the starting time point when the rotor vibration increases with the increase of excitation current before grid connection, and record the rotor vibration at this time as z1; after grid connection, select the time point when the excitation current is maximum during this operation, and record the rotor vibration at this time as z2; reduce the reactive power to near zero, and record the rotor vibration at this time as z3, and let the first vibration difference z s1 =0, calculate the second vibration difference z s2 and the third vibration difference z s3 ;

[0028] Then perform step 10), step 11), step 13) and step 14);

[0029] For a unit in which rotor vibration increases with the increase of excitation current during the boost process before grid connection, the third intermediate quantity B3=0.

[0030] In a second aspect, the present invention provides a diagnostic system for the problem of positive correlation between rotor vibration and excitation current, comprising:

[0031] Selection and adjustment unit: For units that did not experience an increase in rotor vibration with the increase of excitation current before grid connection, select the starting time point when the rotor vibration increased with the increase of excitation current, adjust the unit's active power and excitation current to the unit state at this time point, and record the unit's reactive power and rotor vibration at this time as Q0 and z0 respectively;

[0032] The first vibration difference calculation unit: keep the reactive power of the unit unchanged, increase the active power P' of the unit to the rated active power, this process is S1, record the rotor vibration of the unit at this time as z1, and calculate the first vibration difference z s1=z1-z0;

[0033] The second vibration difference calculation unit: keep the active power P' of the unit unchanged at the rated active power, increase the reactive power from Q0 to the rated reactive power, this process is S2, record the rotor vibration of the unit at this time as z2, and calculate the second vibration difference z s2 =z2-z1;

[0034] The third vibration difference calculation unit: keep the active power P' of the unit at the rated active power unchanged, and reduce the reactive power from the rated reactive power to Q0. This process is S3. The rotor vibration of the unit at this time is z3, and calculate the third vibration difference z s3 =z2-z3;

[0035] Correlation calculation unit: Analyze the historical operation data of the unit, take the time point when the positive correlation between rotor vibration and excitation current first appears as the starting point, and the time point when the unit is most recently shut down as the end point, determine the historical data analysis period L, and record the maximum rotor vibration value z within L. Lmax ;

[0036] The first process quantity calculation unit: calculate (z1 / z Lmax ) and compared with the first preset value, when (z1 / z Lmax )>first preset value, the first process quantity A1=1, otherwise the first process quantity A1=0;

[0037] The second process quantity calculation unit: calculate (z2 / z Lmax ) and [z s1 / (z s2 +z s1 )] and compared with the first preset value respectively, when (z2 / z Lmax )>first preset value and [z s1 / (z s2 +z s1 )]>first preset value, the second process quantity A2=1, otherwise the second process quantity A2=0;

[0038] A third process quantity calculation unit: calculates the correlation between the rotor vibration and the active power during the S1 process of step 2), which is recorded as X3, and calculates the correlation between the rotor vibration and the excitation current during the S2 process of step 3), which is recorded as X4, and compares X3 and X4. When X3>X4, the third process quantity A3=1, otherwise the third process quantity A3=0;

[0039] First fault judgment unit: When [(A1+A2)·A3]>0, maintenance should be carried out to check the thermal fault of the guard ring and the damping winding inside the guard ring.

[0040] The beneficial effects of the present invention are as follows: Compared with traditional technologies, the present invention solves the problem that there is a lack of effective and clear diagnostic means for thermal faults of the damping winding in the existing rotor guard ring, deformation of the top turns of the rotor coil, and expansion obstruction faults, which are prone to untimely or excessive maintenance. It improves the diagnostic accuracy and efficiency of the positive correlation problem between rotor vibration and excitation current, and solves the limitation of the current standard that focuses on inter-turn short-circuit faults for the positive correlation problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The following is a brief introduction to the drawings required for describing the embodiments of the present invention.

[0042] Figure 1 A flow chart of a method for diagnosing the positive correlation between rotor vibration and excitation current according to the present invention;

[0043] Figure 2 Another flow chart of the method for diagnosing the problem of positive correlation between rotor vibration and excitation current according to the present invention;

[0044] Figure 3 This is a structural diagram of a diagnostic system for the problem of positive correlation between rotor vibration and excitation current according to the present invention;

[0045] Figure 4 This is an on-site disassembly diagram of diagnosing a burnout fault of a rotor damping winding of a large non-salient-pole synchronous generator in Application Example 1 of the present invention;

[0046] Figure 5 This is an on-site disassembly diagram of diagnosing a deformation fault of a top turn of a rotor coil of a large non-salient pole synchronous generator in Application Example 2 of the present invention. DETAILED DESCRIPTION

[0047] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0048] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0049] Example 1

[0050] This embodiment provides a method for diagnosing the problem of positive correlation between rotor vibration and excitation current. Figure 1 As shown, the steps are as follows:

[0051] a) For units that did not experience an increase in rotor vibration with increasing excitation current before grid connection, select the starting time point of the most recent increase in rotor vibration with increasing excitation current, adjust the unit's active power and excitation current to the unit state at this time point, and record the unit's reactive power and rotor vibration at this time as Q0 and z0, respectively. When the vibration values ​​at the bearings on both sides of the rotor are inconsistent, use the data from the side with the larger value for analysis.

[0052] b) Keep the reactive power of the unit unchanged and increase the active power P' of the unit to the rated active power. This process is S1. The rotor vibration of the unit at this time is z1, and the first vibration difference z is calculated. s1 =z1-z0.

[0053] When the generator is operated in normal mode, the load is increased, the active power increases and the excitation current is automatically adjusted, and the reactive power of the unit also increases at the same time. At this time, it is impossible to visually observe the correlation between the increase in active power and the increase in excitation current and the increase in rotor vibration. The load increase method of increasing active power by keeping the reactive power constant can determine whether the increase in rotor vibration is correlated with the increase in active power under the premise that the reactive power remains unchanged.

[0054] c) Keep the active power P' of the unit at the rated active power and increase the reactive power from Q0 to the rated reactive power. This process is S2. The rotor vibration of the unit at this time is z2, and the second vibration difference z is calculated. s2 =z2-z1.

[0055] d) Keep the active power P' of the unit at the rated active power and reduce the reactive power from the rated reactive power to Q0. This process is S3. The rotor vibration of the unit at this time is z3, and calculate the third vibration difference z s3 =z2-z3.

[0056] e) Analyze the historical operation data of the unit, taking the time point when the positive correlation between rotor vibration and excitation current first appeared as the starting point and the time point when the unit was last shut down as the end point, determine the historical data analysis period L, and record the maximum rotor vibration value z within L. Lmax .

[0057] f) Calculate (z1 / z Lmax ) and compared with the first preset value, that is, when (z1 / z Lmax )>0.7, the first process quantity A1=1, otherwise the first process quantity A1=0.

[0058] g) Calculate (z2 / z Lmax ) and [z s1 / (z s2 +z s1 )] and compared with the first preset value respectively, that is, when (z2 / z Lmax)>0.7 and [z s1 / (z s2 +z s1 )]>0.7, the second process quantity A2=1, otherwise the second process quantity A2=0.

[0059] h) Calculate the correlation between the rotor vibration and the active power during the S1 process of step b), record it as X3, calculate the correlation between the rotor vibration and the excitation current during the S2 process of step c), record it as X4, and compare X3 and X4. When X3>X4, the third process quantity A3=1; otherwise, the third process quantity A3=0.

[0060] i) When [(A1+A2)·A3]>0, maintenance should be carried out to check for thermal faults in the guard ring and the damping winding inside the guard ring.

[0061] When [(A1+A2)·A3]>0, it indicates that the increase in rotor vibration mainly occurs during the S1 process. The main reason for the increase in rotor vibration is the simultaneous increase in active power and the increase in cooling medium temperature. There is a local cooling problem in the rotor body, which leads to increased vibration. During the S2 process, the increase in excitation current leads to an increase in rotor coil temperature, resulting in a low increase in rotor vibration. This indicates that the equipment defect is most likely located in the rotor guard ring and the damping winding inside the guard ring rather than the rotor coil. In the normal operation mode of the unit, it is difficult to clearly draw the above conclusion when the active power and excitation current change simultaneously. However, the present invention can intuitively draw the above conclusion from the operating data by increasing the active power with equal reactive power and increasing the reactive power with equal active power.

[0062] Example 2

[0063] This embodiment provides a method for diagnosing the problem of positive correlation between rotor vibration and excitation current. Figure 2 As shown, the steps are as follows:

[0064] a) For units that did not experience an increase in rotor vibration with increasing excitation current before grid connection, select the starting time point of the most recent increase in rotor vibration with increasing excitation current, adjust the unit's active power and excitation current to the unit state at this time point, and record the unit's reactive power and rotor vibration at this time as Q0 and z0, respectively. When the vibration values ​​at the bearings on both sides of the rotor are inconsistent, use the data from the side with the larger value for analysis.

[0065] b) Keep the reactive power of the unit unchanged and increase the active power P' of the unit to the rated active power. This process is S1. The rotor vibration of the unit at this time is z1, and the first vibration difference z is calculated. s1 =z1-z0.

[0066] When the generator is operated in normal mode, the load is increased, the active power increases and the excitation current is automatically adjusted, and the reactive power of the unit also increases at the same time. At this time, it is impossible to visually observe the correlation between the increase in active power and the increase in excitation current and the increase in rotor vibration. The load increase method of increasing active power by keeping the reactive power constant can determine whether the increase in rotor vibration is correlated with the increase in active power under the premise that the reactive power remains unchanged.

[0067] c) Keep the active power P' of the unit at the rated active power and increase the reactive power from Q0 to the rated reactive power. This process is S2. The rotor vibration of the unit at this time is z2, and the second vibration difference z is calculated. s2 =z2-z1.

[0068] d) Keep the active power P' of the unit at the rated active power and reduce the reactive power from the rated reactive power to Q0. This process is S3. The rotor vibration of the unit at this time is z3, and calculate the third vibration difference z s3 =z2-z3.

[0069] e) Analyze the historical operation data of the unit, taking the time point when the positive correlation between rotor vibration and excitation current first appeared as the starting point and the time point when the unit was last shut down as the end point, determine the historical data analysis period L, and record the maximum rotor vibration value z within L. Lmax , calculate the correlation between the rotor vibration and the excitation current during the time period in L when the active power remains unchanged and the reactive power increases, recorded as X1, and calculate the correlation between the rotor vibration and the excitation current during the time period in L when the active power remains unchanged and the reactive power decreases, recorded as X2.

[0070] f) Calculate (z1 / z Lmax ) and compared with the first preset value, that is, when (z1 / z Lmax )>0.7, the first process quantity A1=1, otherwise the first process quantity A1=0.

[0071] g) Calculate (z2 / z Lmax ) and [z s1 / (z s2 +z s1 )] and compared with the first preset value respectively, that is, when (z2 / z Lmax )>0.7 and [z s1 / (z s2 +z s1 )]>0.7, the second process quantity A2=1, otherwise the second process quantity A2=0.

[0072] h) Calculate the correlation between the rotor vibration and the active power during the S1 process of step b), record it as X3, calculate the correlation between the rotor vibration and the excitation current during the S2 process of step c), record it as X4, and compare X3 and X4. When X3>X4, the third process quantity A3=1; otherwise, the third process quantity A3=0.

[0073] i) When [(A1+A2)·A3]>0, maintenance should be carried out to check for thermal faults in the guard ring and the damping winding inside the guard ring.

[0074] When [(A1+A2)·A3]>0, it indicates that the increase in rotor vibration mainly occurs during the S1 process. The main reason for the increase in rotor vibration is the simultaneous increase in active power and the increase in cooling medium temperature. There is a local cooling problem in the rotor body, which leads to increased vibration. During the S2 process, the increase in excitation current leads to an increase in rotor coil temperature, resulting in a low increase in rotor vibration. This indicates that the equipment defect is most likely located in the rotor guard ring and the damping winding inside the guard ring rather than the rotor coil. In the normal operation mode of the unit, it is difficult to clearly draw the above conclusion when the active power and excitation current change simultaneously. However, the present invention can intuitively draw the above conclusion from the operating data by increasing the active power with equal reactive power and increasing the reactive power with equal active power.

[0075] j) Compare z s1 、z s2 and z s2 、z s3 , when z s2 >z s1 And z s2 >z s3 When , the first intermediate quantity B1=1, otherwise the first intermediate quantity B1=0.

[0076] k)Calculate [(z s2 -z s3 ) / z s2 ] and compared with the first preset value, that is, when [(z s2 -z s3 ) / z s2 ]>0.7, the second intermediate quantity B2=1, otherwise the second intermediate quantity B2=0.

[0077] l) Calculate the correlation between the rotor vibration and the excitation current during S3 in step d) and record it as X5, and compare X1, X2 with X4, X5. When X1>X2 and X4>X5 and [(z s2 -z s3 ) / z s2 ]>0.6, the third intermediate quantity B3=1, otherwise the third intermediate quantity B3=0.

[0078] m) Referring to the standard DL / T 1525 "Guidelines for Diagnosis of Rotor Interturn Short Circuit Faults of Non-salient Pole Synchronous Generators", if there are other determination methods other than positive correlation to diagnose the presence of a dynamic interturn short circuit fault in the rotor, then the fourth intermediate quantity B4=1; otherwise, the fourth intermediate quantity B4=0.

[0079] n) When [B1·(B2+B3)·B4]>0, maintenance should be carried out to check for deformation of the top turn of the rotor coil; when [B1·(B2+B3)]>0 and B4=0, the rotor coil is obstructed from expanding.

[0080] When [B1·(B2+B3)]>0, it indicates that the abnormal growth stage of rotor vibration mainly occurs during the S2 process. At the same time, under the conditions of constant active power and equal reactive power variation, the increase in rotor vibration is significantly greater than the decrease in rotor vibration. The rotor coil has a top turn deformation or coil expansion obstruction fault. The increase in excitation current will exacerbate the coil deformation and the degree of non-uniform expansion, causing increased rotor vibration. Because factors such as coil deformation are affected by centrifugal force, gravity, and thermal stress during operation and are difficult to completely and immediately recover with a decrease in excitation current, the vibration reduction caused by a decrease in excitation current will be significantly smaller than the vibration increase caused by an equivalent increase in excitation current. When B4=1, the unit air gap composite magnetic flux has been distorted, and the rotor coil has a top turn deformation fault. When B4=0, the unit air gap composite magnetic flux is not distorted, the rotor coil expansion is obstructed, and its unevenness has not yet caused insulation damage. Under reactive power variation conditions such as inter-turn short circuit faults, the increase and decrease in rotor vibration will be significantly closer.

[0081] In addition, for the units whose rotor vibration increases with the increase of excitation current during the boost process before grid connection, the starting time point of the increase of rotor vibration with the increase of excitation current before grid connection is selected, and the rotor vibration at this time is recorded as z1; after grid connection, the time point of the maximum excitation current during this operation is selected, and the rotor vibration at this time is recorded as z2; the reactive power is reduced to near zero, and the rotor vibration at this time is recorded as z3. Let the first vibration difference z s1 =0, calculate the second vibration difference z s2 and the third vibration difference z s3 , z s2 =z2-z1,z s3 = z2 - z3. Then, steps j), k), m), and n) are performed, i.e., the S1 process in step b), the S2 process in step c), the S3 process in step d), and steps e) to i) are omitted; the third intermediate quantity B3 = 0.

[0082] Example 3

[0083] This embodiment provides a diagnostic system for the problem of positive correlation between rotor vibration and excitation current. Figure 3As shown, it consists of a selection and adjustment unit, a first vibration difference calculation unit, a second vibration difference calculation unit, a third vibration difference calculation unit, a correlation calculation unit, a first process quantity calculation unit, a second process quantity calculation unit, a third process quantity calculation unit, a first fault judgment unit, a first intermediate quantity calculation unit, a second intermediate quantity calculation unit, a third intermediate quantity calculation unit, a fourth intermediate quantity calculation unit, a second fault judgment unit and a time point selection unit.

[0084] The selection and adjustment unit: for a unit that did not experience an increase in rotor vibration with an increase in excitation current before grid connection, select the starting time point when the most recent rotor vibration increased with an increase in excitation current, adjust the unit's active power and excitation current to the unit state at this time point, and record the unit's reactive power and rotor vibration at this time as Q0 and z0, respectively.

[0085] The first vibration difference calculation unit: keep the reactive power of the unit unchanged, increase the active power P' of the unit to the rated active power, this process is S1, record the rotor vibration of the unit at this time as z1, and calculate the first vibration difference z s1 =z1-z0.

[0086] The second vibration difference calculation unit: keep the active power P' of the unit unchanged at the rated active power, increase the reactive power from Q0 to the rated reactive power, this process is S2, record the rotor vibration of the unit at this time as z2, and calculate the second vibration difference z s2 =z2-z1.

[0087] The third vibration difference calculation unit: keep the active power P' of the unit at the rated active power unchanged, and reduce the reactive power from the rated reactive power to Q0. This process is S3. The rotor vibration of the unit at this time is z3, and calculate the third vibration difference z s3 =z2-z3.

[0088] Correlation calculation unit: Analyze the historical operation data of the unit, take the time point when the positive correlation between rotor vibration and excitation current first appears as the starting point, and the time point when the unit is most recently shut down as the end point, determine the historical data analysis period L, and record the maximum rotor vibration value z within L. Lmax , calculate the correlation between the rotor vibration and the excitation current during the time period in L when the active power remains unchanged and the reactive power increases, recorded as X1, and calculate the correlation between the rotor vibration and the excitation current during the time period in L when the active power remains unchanged and the reactive power decreases, recorded as X2.

[0089] The first process quantity calculation unit: calculate (z1 / z Lmax ) and compared with the first preset value, when (z1 / z Lmax )>first preset value, the first process quantity A1=1, otherwise the first process quantity A1=0.

[0090] The second process quantity calculation unit: calculate (z2 / z Lmax ) and [z s1 / (z s2 +z s1 )] and compared with the first preset value respectively, when (z2 / z Lmax )>first preset value and [z s1 / (z s2 +z s1 )]>first preset value, the second process quantity A2=1, otherwise the second process quantity A2=0.

[0091] The third process quantity calculation unit: calculates the correlation between the rotor vibration and the active power during the S1 process of step 2), recorded as X3, calculates the correlation between the rotor vibration and the excitation current during the S2 process of step 3), recorded as X4, and compares X3 and X4. When X3>X4, the third process quantity A3=1, otherwise the third process quantity A3=0.

[0092] First fault judgment unit: When [(A1+A2)·A3]>0, maintenance should be carried out to check the thermal fault of the guard ring and the damping winding inside the guard ring.

[0093] The first intermediate quantity calculation unit: comparison z s1 、z s2 and z s2 、z s3 , when z s2 >z s1 And z s2 >z s3 When , the first intermediate quantity B1=1, otherwise the first intermediate quantity B1=0.

[0094] The second intermediate quantity calculation unit: calculates [(z s2 -z s3 ) / z s2 ] and compared with the first preset value, when [(z s2 -z s3 ) / z s2 ]>first preset value, the second intermediate quantity B2=1, otherwise the second intermediate quantity B2=0.

[0095] The third intermediate quantity calculation unit: calculates the correlation between the rotor vibration and the excitation current in the S3 process of step 4), and records it as X5, and compares X1, X2 with X4, X5. When X1>X2 and X4>X5 and [(z s2 -z s3 ) / z s2 ]>the second preset value, the third intermediate quantity B3=1, otherwise the third intermediate quantity B3=0.

[0096] Fourth intermediate quantity calculation unit: if there are other determination methods except positive correlation to diagnose that the rotor has a dynamic inter-turn short circuit fault, then the fourth intermediate quantity B4=1; otherwise, the fourth intermediate quantity B4=0.

[0097] Second fault judgment unit: When [B1·(B2+B3)·B4]>0, maintenance should be carried out to check for deformation of the top turn of the rotor coil; when [B1·(B2+B3)]>0 and B4=0, the rotor coil is obstructed from expanding.

[0098] In the first adjustment unit, when recording the reactive power and rotor vibration of the unit as Q0 and z0 respectively, if the vibration values ​​at the bearings on both sides of the rotor are inconsistent, the data on the side with the larger value is used for analysis.

[0099] The first preset value is 0.65-0.75, preferably 0.7; the second preset value is 0.55-0.65, preferably 0.6.

[0100] The time point selection unit: for a unit that has experienced a rise in rotor vibration with the increase of excitation current during the boost process before grid connection, select the starting time point when the rotor vibration of the unit rises with the increase of excitation current before grid connection, and record the rotor vibration at this time as z1; after grid connection, select the time point when the excitation current is maximum during this operation, and record the rotor vibration at this time as z2; reduce the reactive power to near zero, and record the rotor vibration at this time as z3, and set the first vibration difference z s1 =0, calculate the second vibration difference z s2 and the third vibration difference z s3 ; Then execute the first intermediate quantity calculation unit, the second intermediate quantity calculation unit, the fourth intermediate quantity calculation unit and the second fault judgment unit; the third intermediate quantity B3=0.

[0101] Application Example 1

[0102] The method described in Example 1 of the present invention is used for the following application.

[0103] On August 17, 2022, after a 148.5MVA generator was connected to the grid, the shaft vibration gradually increased. This phenomenon occurred for the first time in many years. As the unit load increased, the rotor vibration and excitation current increased at the same time. The active power and excitation current at the starting time point when the rotor vibration and excitation current increased simultaneously were P' and i'. When the load was added to 97MW (reactive power was 18MVar), the X-direction shaft vibration data of the No. 4 tile on the excitation side of the generator reached a maximum of 4.4mils (1mil=25μm), and the Y-direction shaft vibration data of the No. 4 tile was 2.39mils. The X-direction shaft vibration data of the No. 3 tile on the turbine side of the generator was 3.26mils, and the Y-direction data of the No. 3 tile was 2.1mil. The vibration values ​​of the No. 4 tile in the X and Y directions were higher than the vibration data of the No. 3 tile in the X and Y directions, respectively.

[0104] On August 20, 2022, the generator was started. Before being connected to the grid, there was no increase in rotor vibration with the increase of excitation current. The active power and excitation current of the generator were adjusted to P' and i' respectively. During this period, the rotor vibration did not increase significantly. The reactive power and rotor vibration at this time were recorded as Q0 and z0 respectively.

[0105] During S1, the reactive power Q0 was kept constant, and the rotor vibration continued to climb as the load was increased. After the load reached the full load state, the axial vibration data of the No. 4 bearing on the excitation side in the X direction was 3 mils, and the axial vibration data of the No. 4 bearing on the Y direction was 1.8 mils. The vibration values ​​of the No. 4 bearing in the X and Y directions were higher than the vibration data of the No. 3 bearing in the X and Y directions, respectively. During S2, the active power was kept constant and the reactive power was increased to the rated value. The axial vibration data of the No. 4 bearing on the rotor excitation side in the X direction increased to 3.15 mils, and the axial vibration data in the Y direction increased to 1.9 mils, with no significant increase in vibration.

[0106] Vibration diagnosis was carried out using the X-direction data of the No. 4 tile and the historical operation data of the unit was analyzed. Lmax =4.4mils, z1=3mils, z2=3.15mils, (z2 / z Lmax )=0.72>0.7,z s2 =z2-z1=0.15mils, z s1 =z1-z0>2mils, [z s1 / (z s2 +z s1 )]>0.7, so A2=1.

[0107] During S1, there is a significant correlation between rotor vibration and active power. When reactive power remains unchanged and active power increases, rotor vibration significantly increases. During S2, when excitation current increases, the absolute value and relative proportion of rotor vibration increase are significantly smaller. The correlation between rotor vibration and excitation current is low. Therefore, X3>X4, A3=1.

[0108] [(A1+A2)·A3]>0, during maintenance, check the thermal fault of the guard ring and the damping winding inside the guard ring, and find that the damping winding inside the guard ring has serious burning fault, such as Figure 4 Using the data of the Y direction of the No. 4 tile for vibration diagnosis, we can also obtain [(A1+A2)·A3]>0.

[0109] The rotor damping system directly determines the rotor's ability to withstand negative-sequence currents under unbalanced load conditions. Damping winding burnout can cause serious consequences such as localized rotor cracking or even melting under unbalanced load conditions. Failures in the damping winding within the retaining ring of a non-salient-pole synchronous generator are difficult to detect and lack appropriate testing methods because routine maintenance, including Class A maintenance, involves extracting the rotor from the stator bore without removing the rotor retaining ring. However, the method presented in this invention allows for timely detection of equipment defects, preventing further escalation of the fault.

[0110] Application Example 2

[0111] The method described in Example 2 of the present invention is used for the following application.

[0112] On July 18, 2020, the steam turbine generator was started. At 8:37, the grid-connected operation began. After the magnetic field switch was closed, the generator excitation current was 920A, and the rotor shaft vibration increased significantly: the 6X shaft vibration increased from 51μm to 98μm, the 6Y shaft vibration increased from 26μm to 52μm, the 5X shaft vibration increased from 7μm to 68μm, and the 5Y shaft vibration increased from 10μm to 50μm. The vibration values ​​of the No. 6 tile in the X and Y directions are higher than the vibration data of the No. 5 tile in the X and Y directions, respectively. Vibration diagnosis was carried out based on the data in the X direction of the No. 6 tile. Before the unit was connected to the grid, the rotor vibration increased with the increase of the excitation current during the boost process. s1 =0, z1=51μm.

[0113] At 8:38, the generator was connected to the grid and the 6X axis vibration continued to rise, reaching a maximum of 136μm. (At 9:24, the active power was 61MW, the reactive power was 57MVar, and the excitation current was 1250A.) The 6Y axis vibration continued to rise by 65μm, and the 5X axis vibration rose to 80μm. The 5Y axis vibration reached a maximum of 56μm and then fell back to 42μm. z2 = 136μm, z s2 =z2-z1=85μm.

[0114] The operator adjusted the reactive power. When the reactive power was reduced to below 10MVar and close to zero reactive power, the 6X axis vibration dropped to about 122μm, the 6Y axis vibration dropped to 56μm, the 5X axis vibration dropped to 71μm, and the 5Y axis vibration dropped to 36μm. s3 =z2-z3=14μm.

[0115] z s2 >z s1 And z s2 >z s3 , B1=1;

[0116] [(z s2 -z s3 ) / z s2]=0.84>0.7, B2=1;

[0117] The reference standard rotor air gap detection coil waveform shows that the rotor has a dynamic inter-turn short circuit fault. All static tests are normal, indicating that the rotor has no inter-turn short circuit fault, B4 = 1;

[0118] [B1·(B2+B3)·B4]>0, the rotor coil top turn deformation fault was checked and it was found that coils 4 to 8 had obvious top turn deformation, such as Figure 5 Using the data of the Y direction of the No. 6 tile to conduct vibration diagnosis, we can also obtain [B1·(B2+B3)·B4]>0.

[0119] There is a lack of sensitive testing methods for detecting rotor top turn deformation faults. During routine maintenance, including Class A maintenance, the rotor is pulled out of the stator bore, but the rotor guard ring is not removed, making it difficult to detect the fault in a timely manner. Generators with rotor top turn deformation faults show no abnormalities in the power outage test state. Even if the rotor shows a dynamic inter-turn short circuit fault during operation, it is easy to misjudge the rotor as having a non-metallic inter-turn short circuit and not requiring maintenance. Disassembly and maintenance are performed only after static test results show insulation degradation. At this time, the top turn deformation fault will further expand, forming a serious rotor inter-coil short circuit fault. The application of the method of the present invention timely discovers the equipment defect and prevents further expansion of the fault.

[0120] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A method for diagnosing the problem of positive correlation between rotor vibration and excitation current, characterized in that: Including steps: 1) For units that did not experience an increase in rotor vibration with increasing excitation current before grid connection, select the starting time point when the rotor vibration increased with increasing excitation current, adjust the unit's active power and excitation current to the unit state at this time point, and record the unit's reactive power and rotor vibration at this time as Q0 and z0 respectively; 2) Keep the reactive power of the unit unchanged and increase the active power P' of the unit to the rated active power. This process is S1. The rotor vibration of the unit at this time is z1, and the first vibration difference z is calculated. s1 =z1-z0; 3) Keep the active power P' of the unit at the rated active power and increase the reactive power from Q0 to the rated reactive power. This process is S2. The rotor vibration of the unit at this time is z2, and the second vibration difference z is calculated. s2 =z2-z1; 4) Keep the active power P' of the unit at the rated active power and reduce the reactive power from the rated reactive power to Q0. This process is S3. The rotor vibration of the unit at this time is z3, and calculate the third vibration difference z s3 =z2-z3; 5) Analyze the historical operation data of the unit, taking the time point when the positive correlation between rotor vibration and excitation current first appears as the starting point and the time point when the unit was last shut down as the end point, determine the historical data analysis period L, and record the maximum rotor vibration value z within L. Lmax ; 6) Calculate (z1 / z Lmax ) and compared with the first preset value, when (z1 / z Lmax )>first preset value, the first process quantity A1=1, otherwise the first process quantity A1=0; 7) Calculate (z2 / z Lmax ) and [z s1 / (z s2 +z s1 )] and compared with the first preset value respectively, when (z2 / z Lmax )>first preset value and [z s1 / (z s2 +z s1 )]>first preset value, the second process quantity A2=1, otherwise the second process quantity A2=0; 8) Calculate the correlation between the rotor vibration and the active power during the S1 process of step 2), record it as X3, calculate the correlation between the rotor vibration and the excitation current during the S2 process of step 3), record it as X4, and compare X3 and X4. When X3>X4, the third process quantity A3=1, otherwise the third process quantity A3=0; 9) When [(A1+A2)·A3]>0, maintenance should be carried out to check for thermal faults in the guard ring and the damping winding inside the guard ring.

2. The method for diagnosing the positive correlation problem between rotor vibration and excitation current according to claim 1, characterized in that: Also includes the steps: 10) Compare z s1 、z s2 and z s2 、z s3 , when z s2 >z s1 And z s2 >z s3 When , the first intermediate quantity B1 = 1, otherwise the first intermediate quantity B1 = 0; 11) Calculate [(z s2 -z s3 ) / z s2 ] and compared with the first preset value, when [(z s2 -z s3 ) / z s2 ]>first preset value, the second intermediate value B2=1, otherwise the second intermediate value B2=0; 12) Calculate the correlation between the rotor vibration and the excitation current during S3 in step 4) and record it as X5. Compare X1, X2 with X4, X5. When X1>X2 and X4>X5 and [(z s2 -z s3 ) / z s2 ]>the second preset value, the third intermediate value B3=1, otherwise the third intermediate value B3=0; 13) If the rotor is diagnosed with a dynamic inter-turn short circuit fault by any of the determination methods other than the positive correlation, the fourth intermediate quantity B4=1; otherwise, the fourth intermediate quantity B4=0; 14) When [B1·(B2+B3)·B4]>0, an inspection should be carried out to check for deformation of the top turn of the rotor coil; when [B1·(B2+B3)]>0 and B4=0, the rotor coil is blocked from expanding; The step 5) further includes: calculating the correlation between the rotor vibration and the excitation current during the time period in which the active power in L is constant and the reactive power increases, recorded as X1, and calculating the correlation between the rotor vibration and the excitation current during the time period in which the active power in L is constant and the reactive power decreases, recorded as X2.

3. The method for diagnosing the positive correlation problem between rotor vibration and excitation current according to claim 2, characterized in that: In step 1), when recording the reactive power and rotor vibration of the unit as Q0 and z0 respectively, if the vibration values ​​at the bearings on both sides of the rotor are inconsistent, the data on the side with the larger value is used for analysis.

4. The method for diagnosing the positive correlation problem between rotor vibration and excitation current according to claim 2, characterized in that: The first preset value is 0.65-0.75; the second preset value is 0.55-0.

65.

5. The method for diagnosing the positive correlation problem between rotor vibration and excitation current according to any one of claims 2 to 4, characterized in that: Also includes: For the units that have experienced the increase of rotor vibration with the increase of excitation current during the boost process before grid connection, select the starting time point when the rotor vibration increases with the increase of excitation current before grid connection, and record the rotor vibration at this time as z1. After grid connection, select the time point when the excitation current is maximum during this operation, and record the rotor vibration at this time as z2. Reduce the reactive power to near zero, and record the rotor vibration at this time as z3. Let the first vibration difference z s1 =0, calculate the second vibration difference z s2 and the third vibration difference z s3 ; Then perform step 10), step 11), step 13) and step 14); For a unit in which rotor vibration increases with the increase of excitation current during the boost process before grid connection, the third intermediate quantity B3=0.

6. A diagnostic system for the problem of positive correlation between rotor vibration and excitation current, characterized in that: include: Selection and adjustment unit: For units that did not experience an increase in rotor vibration with the increase of excitation current before grid connection, select the starting time point when the rotor vibration increased with the increase of excitation current, adjust the unit's active power and excitation current to the unit state at this time point, and record the unit's reactive power and rotor vibration at this time as Q0 and z0 respectively; The first vibration difference calculation unit: keep the reactive power of the unit unchanged, increase the active power P' of the unit to the rated active power, this process is S1, record the rotor vibration of the unit at this time as z1, and calculate the first vibration difference z s1 =z1-z0; The second vibration difference calculation unit: keep the active power P' of the unit unchanged at the rated active power, increase the reactive power from Q0 to the rated reactive power, this process is S2, record the rotor vibration of the unit at this time as z2, and calculate the second vibration difference z s2 =z2-z1; The third vibration difference calculation unit: keep the active power P' of the unit at the rated active power unchanged, and reduce the reactive power from the rated reactive power to Q0. This process is S3. The rotor vibration of the unit at this time is z3, and calculate the third vibration difference z s3 =z2-z3; Correlation calculation unit: Analyze the historical operation data of the unit, take the time point when the positive correlation between rotor vibration and excitation current first appears as the starting point, and the time point when the unit is most recently shut down as the end point, determine the historical data analysis period L, and record the maximum rotor vibration value z within L. Lmax ; The first process quantity calculation unit: calculate (z1 / z Lmax ) and compared with the first preset value, when (z1 / z Lmax )>first preset value, the first process quantity A1=1, otherwise the first process quantity A1=0; The second process quantity calculation unit: calculate (z2 / z Lmax ) and [z s1 / (z s2 +z s1 )] and compared with the first preset value respectively, when (z2 / z Lmax )>first preset value and [z s1 / (z s2 +z s1 )]>first preset value, the second process quantity A2=1, otherwise the second process quantity A2=0; A third process quantity calculation unit: calculates the correlation between the rotor vibration and the active power during the S1 process of step 2), which is recorded as X3, and calculates the correlation between the rotor vibration and the excitation current during the S2 process of step 3), which is recorded as X4, and compares X3 and X4. When X3>X4, the third process quantity A3=1, otherwise the third process quantity A3=0; First fault judgment unit: When [(A1+A2)·A3]>0, maintenance should be carried out to check the thermal fault of the guard ring and the damping winding inside the guard ring.

7. The diagnostic system for the positive correlation problem between rotor vibration and excitation current according to claim 6, characterized in that: Also includes: The first intermediate quantity calculation unit: comparison z s1 、z s2 and z s2 、z s3 , when z s2 >z s1 And z s2 >z s3 When , the first intermediate quantity B1 = 1, otherwise the first intermediate quantity B1 = 0; The second intermediate quantity calculation unit: calculates [(z s2 -z s3 ) / z s2 ] and compared with the first preset value, when [(z s2 -z s3 ) / z s2 ]>first preset value, the second intermediate value B2=1, otherwise the second intermediate value B2=0; The third intermediate quantity calculation unit: calculates the correlation between the rotor vibration and the excitation current in the S3 process of step 4), and records it as X5, and compares X1, X2 with X4, X5. When X1>X2 and X4>X5 and [(z s2 -z s3 ) / z s2 ]>the second preset value, the third intermediate value B3=1, otherwise the third intermediate value B3=0; Fourth intermediate quantity calculation unit: if the determination method other than positive correlation is used to diagnose the presence of a dynamic inter-turn short circuit fault in the rotor, the fourth intermediate quantity B4=1; otherwise, the fourth intermediate quantity B4=0; Second fault judgment unit: When [B1·(B2+B3)·B4]>0, maintenance should be carried out to check for deformation of the top turn of the rotor coil; when [B1·(B2+B3)]>0 and B4=0, the rotor coil has expansion obstruction; The correlation calculation unit is also used to calculate the correlation between the rotor vibration and the excitation current during the time period in which the active power remains unchanged and the reactive power increases within L, which is recorded as X1; and calculate the correlation between the rotor vibration and the excitation current during the time period in which the active power remains unchanged and the reactive power decreases within L, which is recorded as X2.

8. The diagnostic system for the positive correlation problem between rotor vibration and excitation current according to claim 7, characterized in that: In the selection and adjustment unit, when recording the reactive power and rotor vibration of the unit as Q0 and z0 respectively, if the vibration values ​​at the bearings on both sides of the rotor are inconsistent, the data on the side with the larger value is used for analysis.

9. The diagnostic system for the positive correlation problem between rotor vibration and excitation current according to claim 7, characterized in that: The first preset value is 0.65-0.75; the second preset value is 0.55-0.

65.

10. The diagnostic system for the positive correlation problem between rotor vibration and excitation current according to any one of claims 7 to 9, characterized in that: Also includes: Time point selection unit: For the units that have experienced the increase of rotor vibration with the increase of excitation current during the boost process before grid connection, select the starting time point when the rotor vibration increases with the increase of excitation current before grid connection, and record the rotor vibration at this time as z1. After grid connection, select the time point when the excitation current is maximum during this operation, and record the rotor vibration at this time as z2. Reduce the reactive power to near zero, and record the rotor vibration at this time as z3. Let the first vibration difference z s1 =0, calculate the second vibration difference z s2 and the third vibration difference z s3 ; Then, the first intermediate quantity calculation unit, the second intermediate quantity calculation unit, the fourth intermediate quantity calculation unit and the second fault judgment unit are executed; For a unit in which rotor vibration increases with the increase of excitation current during the boost process before grid connection, the third intermediate quantity B3=0.

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