Prejudgment method for cold and hot cycle life of stator bar

Abstract

The invention discloses a stator bar cold and hot cycle life pre-judgment method, and belongs to the field of power generation equipment health assessment. According to a stator bar cold and hot cycle test, through performance test data such as dielectric loss and partial discharge tests, life end point cycle index pre-judgment logic is established, and the stator bar cold and hot cycle index and the remaining service life are obtained. The method has the advantages of being scientific in principle, clear in process, efficient in calculation and convenient to use, can quickly pre-judge the cold and hot cycle life end point of the sub-bar according to a small amount of cold and hot cycle experimental data, is particularly suitable for health assessment of the stator bar of a generator motor of a pumped storage power station which is frequently started and stopped, and has a good application prospect. And an effective technical means is provided for the evaluation direction of the cold and hot cycle life.

Description

Technical Field

[0001] The present invention relates to the field of health assessment of power generation equipment, and in particular to a method for predicting the cold and hot cycle life of a stator wire bar of a power generation equipment. Background Art

[0002] As a key equipment in the new power system, the main component of power generation equipment, the stator bars, are subjected to large currents and strong magnetic fields during operation. Especially for the generator motors of pumped-storage power stations, due to frequent changes in operating conditions and a large number of unit starts and shutdowns, the stator bars are frequently subjected to hot and cold cycle stresses during operation, which can easily cause internal damage to the main insulation and affect the insulation life.

[0003] The stator wire bar hot and cold cycle test is one of the most important tests to examine the hot and cold cycle capability of the stator wire bar. The hot and cold cycle test usually undergoes more than hundreds of hot and cold alternations, and the standard is 500 times. Due to the complex structure of the heating and cooling equipment and the cumbersome disassembly and assembly of the stator wire bar, the stator wire bar is generally only disassembled for performance testing at a limited cycle, such as 0 cycles, 50 cycles, 100 cycles, 250 cycles and 500 cycles. The amount of data obtained in this way is very limited, and it becomes extremely difficult to estimate the hot and cold cycle life of the stator wire bar.

[0004] It is urgent to deeply mine data information, establish the relationship between performance test data and failure life, and provide a solution for predicting the hot and cold cycle life of stator wire bars. Summary of the invention

[0005] The purpose of the present invention is to provide a method for predicting the cold and hot cycle life of a stator bar. The technical solution of the present invention comprises the following steps:

[0006] S1. Determine the number of stator bars N for the hot and cold cycle test and the lower limit of the hot and cold cycle temperature T 0 , Temperature upper limit T 1 , heating rate K 1 , cooling rate K 2 , total hot and cold cycle X, number of performance test trials C, cycle x corresponding to each performance test 1 、x 2 , …, x C ;

[0007] S2. In each performance test, each stator bar is subjected to dielectric loss and partial discharge tests to obtain 0.2 times the rated voltage U N Lower dielectric loss factor δ xn 、0.6U N and 0.2U N The dielectric loss factor increment γ of the difference between the dielectric loss factors of xn ,1.0U N The lower partial discharge pxn , where x represents the cycle period and n represents the stator bar number;

[0008] S3. Determine the limits of each performance test data: Dielectric loss factor limit δ z , dielectric loss factor increment limit γ z and partial discharge limit p z ;

[0009] S4. Obtain the average value of the test results of N stator bars in each performance test, that is, the average value of the dielectric loss factor after the xth hot and cold cycle δ x , dielectric loss factor incremental average value γ x , average partial discharge value p x For the initial state of the stator bar, the average value of the initial dielectric loss factor is δ 0 , initial dielectric loss factor incremental average value γ 0 , average partial discharge value p 0 ;

[0010] S5. According to the performance test limit and the average value of the performance test after each hot and cold cycle, the failure degree s of the stator bar hot and cold cycle after the xth hot and cold cycle is obtained. x , expressed as:

[0011]

[0012] s x <1 indicates that the stator bars are in qualified condition after the hot and cold cycle. x ≥1 indicates that the stator bar is in a failure state after the hot and cold cycle. x = 1 is the end of the life of the stator bar after the hot and cold cycle. For the initial state of the stator bar, there is an initial failure degree s 0 for:

[0013]

[0014] S6. Establish the stator bar hot and cold cycle period x and failure degree s x Relationship:

[0015] s=s 0 +Ax B

[0016] In the formula, A and B are fitting constants, both of which are positive numbers greater than 0. The failure degree s obtained by C performance tests is x1 、s x2 ,…,s xC , use the least squares method to fit the above relationship s and get the A and B values;

[0017] S7, get the number of stator bar hot and cold cycle failures X z and failure life L z for:

[0018]

[0019] The beneficial effects of the present invention are:

[0020] The present invention proposes a method for predicting the cold and hot cycle life of a stator bar. Through this innovative method, the following technical effects can be achieved:

[0021] 1. Establish the relationship between the performance data and failure life of the stator wire bar after hot and cold cycles. By analyzing the test data of the stator wire bar hot and cold cycle performance test, a failure data model is established. The relationship between the number of hot and cold cycles and the failure degree can be fitted through a small amount of test data, and the hot and cold cycle life information can be mined;

[0022] 2. Pre-determine the actual application life of stator wire bars. For stator wire bars with frequent hot and cold cycles, especially for generator motors in pumped storage power stations, frequent hot and cold cycles have a particularly significant impact on the life of stator wire bars. This method can be used to inspect and predict the hot and cold cycle life of stator wire bars in advance, effectively ensuring the safety of stator wire bar application;

[0023] 3. Online evaluation of the hot and cold cycle life of stator wire bars. There has been no effective method to evaluate the impact of hot and cold cycle conditions on the life of stator wire bars during unit operation. This method provides an effective idea for the life evaluation of hot and cold cycles. By analyzing the online monitoring conditions, stator wire bar temperature and other data in real time, an online evaluation system for the life loss of stator wire bar hot and cold cycles can be established, which has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a flow chart of the method for predicting the hot and cold cycle life of stator wire bars. DETAILED DESCRIPTION

[0025] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present application.

[0026] A method for predicting the cold and hot cycle life of a stator bar, wherein a specific implementation method 1 comprises the following steps:

[0027] S1, such as Figure 1 As shown in the figure, determine the number of stator bars N for the hot and cold cycle test and determine the lower limit of the hot and cold cycle temperature T 0 , Temperature upper limit T 1 , heating rate K 1 , cooling rate K 2, total hot and cold cycle X, number of performance test trials C, cycle x corresponding to each performance test 1 、x 2 , …, x C ;

[0028] S2, such as Figure 1 As shown, in each performance test, each stator bar is subjected to dielectric loss and partial discharge tests to obtain 0.2 times the rated voltage U N Lower dielectric loss factor δ xn 、0.6U N and 0.2U N The dielectric loss factor increment γ of the difference between the dielectric loss factors of xn ,1.0U N The lower partial discharge p xn , where x represents the cycle period and n represents the stator bar number;

[0029] S3, such as Figure 1 As shown in the figure, the limits of each performance test data are determined as follows: Dielectric loss factor limit δ z , dielectric loss factor increment limit γ z and partial discharge limit p z ;

[0030] S4, such as Figure 1 As shown in the figure, the average value of the test results of N stator bars in each performance test is obtained, that is, the average value of the dielectric loss factor after the xth hot and cold cycle δ x , dielectric loss factor incremental average value γ x , average partial discharge value p x For the initial state of the stator bar, the average value of the initial dielectric loss factor is δ 0 , initial dielectric loss factor incremental average value γ 0 , average partial discharge value p 0 ;

[0031] S5, such as Figure 1 As shown in the figure, according to the performance test limit and the average value of the performance test after each hot and cold cycle, the failure degree s of the stator bar hot and cold cycle after the xth hot and cold cycle is obtained. x , expressed as:

[0032]

[0033] s x <1 indicates that the stator bars are in qualified condition after the hot and cold cycle. x ≥1 indicates that the stator bar is in a failure state after the hot and cold cycle. x= 1 is the end of the life of the stator bar after the hot and cold cycle. For the initial state of the stator bar, there is an initial failure degree s 0 for:

[0034]

[0035] S6, such as Figure 1 As shown, the stator bar hot and cold cycle period x and failure degree s are established x Relationship:

[0036] s=s 0 +Ax B

[0037] In the formula, A and B are fitting constants, both of which are positive numbers greater than 0. The failure degree s obtained by C performance tests is x1 、s x2 ,…,s xC , use the least squares method to fit the above relationship s and get the A and B values;

[0038] S7, such as Figure 1 As shown, the number of stator bar hot and cold cycle failures X is obtained. z and failure life L z for:

[0039]

[0040] In this embodiment, a method for predicting the hot and cold cycle life of stator wire rods is sequentially constructed, including determining experimental parameters, processing test results, determining failure degree, determining the number of failures and failure life, etc. By constructing a failure degree model that comprehensively considers performance test results and hot and cold cycle periods, a comprehensive evaluation of the number of hot and cold cycle failures and failure life is achieved.

[0041] Finally, the protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope and spirit of the present invention. If these changes and modifications fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes and modifications.

Claims

1. A method for predicting the hot and cold cycle life of a stator bar, the characteristics of which include Follow these steps: S1. Determine the number of stator bars N for the hot and cold cycle test, determine the lower limit T0 of the hot and cold cycle temperature, the upper limit T1 of the temperature, the heating rate K1, the cooling rate K2, the total hot and cold cycle period X, the number of performance test trials C, and the cycle period x1, x2, ..., x corresponding to each performance test trial C ; S2. In each performance test, each stator bar is subjected to dielectric loss and partial discharge tests to obtain 0.2 times the rated voltage U N Lower dielectric loss factor δ xn 、0.6U N and 0.2U N The dielectric loss factor increment γ of the difference between the dielectric loss factors of xn ,1.0U N The lower partial discharge p xn , where: x represents the cycle period, n represents the stator bar number; S3. Determine the limits of each performance test data: Dielectric loss factor limit δ z , dielectric loss factor increment limit γ z and partial discharge limit p z ; S4. Obtain the average value of the test results of N stator bars in each performance test, that is, the average value of the dielectric loss factor after the xth hot and cold cycle δ x , dielectric loss factor incremental average value γ x , average partial discharge value p x , for the initial state of the stator bar, there are the average value of the initial dielectric loss factor δ0, the average value of the initial dielectric loss factor increment γ0, and the average value of the partial discharge amount p0; S5. According to the performance test limit and the average value of the performance test after each hot and cold cycle, the failure degree s of the stator bar hot and cold cycle after the xth hot and cold cycle is obtained. x , expressed as: s x <1 indicates that the stator bars are in qualified condition after the hot and cold cycle. x ≥1 indicates that the stator bar is in a failure state after the hot and cold cycle. x =1 is the end of the life of the stator bar after the hot and cold cycle. For the initial state of the stator bar, the initial failure degree s0 is: S6. Establish the stator bar hot and cold cycle period x and failure degree s x Relationship: s=s0+Ax B In the formula, A and B are fitting constants, both of which are positive numbers greater than 0. The failure degree s obtained by C performance tests is x1 、s x2 ,…,s xC , use the least squares method to fit the above relationship s and get the A and B values; S7, get the number of stator bar hot and cold cycle failures X z and failure life L z for:

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