KR20010086815A - Method for inspecting windings of generator stator - Google Patents

Abstract

PURPOSE: A method for inspecting a stator coil of a generator is provided to improve an operation and a reliability of a generator by eliminating a coil resonance generated in driving the generator and minimizing a phenomenon of a coil leakage. CONSTITUTION: A detecting sensor(12) is attached to the end of a stator coil(10). An impact hammer(14) has a built-in power measure sensor. The detecting sensor(12) is connected to an amplifier(16) and amplifies a detecting value detected from the detecting sensor(12), to thereby secure the reliability. The impact hammer(14) is connected to an FFT(fast Fourier transform) analyzer(18) and analyzes the power detected from the power measure sensor had the built-in impact hammer(14). The FFT analyzer(18) is connected to the amplifier(16) and analyzes the detecting value detected from the detecting sensor(12) and the power detecting sensor. The FFT analyzer(18) is connected to a computer(20), measures a response of a frequency by using the result analyzed by the FFT analyzer(18), and displays the result to process same.

Description

Generator stator winding inspection method {METHOD FOR INSPECTING WINDINGS OF GENERATOR STATOR}

The present invention relates to a method for inspecting a generator stator winding, and more particularly, to a method for inspecting a stator winding that can accurately evaluate mechanical health by inspecting a state of a generator stator end portion. In addition, the present invention relates to a generator stator winding complementary method that can examine the stator winding of the generator to improve the operation reliability and increase the lifetime of the generator according to the result.

Power plants are equipped with generators for generating electricity. These generators can be classified into air-cooled and water-cooled according to the cooling method, and also divided into direct current generator, synchronous generator, and induction generator according to the operation method. Such generators are of course equipped with stators and rotors. During operation of the generator, an electromagnetic force is always maintained between the stator and the rotor, and an excitation force of, for example, 120 Hz is generated by the electromagnetic force. The stator of the generator, on the other hand, has a stator core 1 in the center and a stator bar 2 on the wedge 3, as its end is schematically shown in FIG. 1. Is fixed by. The stator bar 2 is also provided with a number of winding rings 4, support rings 5, winding ring support 6, etc. for supporting the windings.

However, according to such a configuration, the stator winding is a double winding and is supported by the core and the terminal winding support device, and the core is restrained by a wedge or the like so that the supporting state is very good, but in the case of the terminal portion, the stator winding is relatively As a result, there is a problem that the restraint state is lowered. Accordingly, each of the windings of the winding terminal part is exposed to vibration fatigue due to an electromagnetic force, and in particular, when the intrinsic characteristics of the windings are close to 120 Hz, a serious risk may occur due to resonance.

In addition, when a water-cooled generator is used for a long time, leakage or fatigue cracking occurs in the winding terminal part due to corrosion and vibration of the stator winding. In addition, the generator may be suddenly stopped due to abrasion caused by the vibration of the winding terminal part.

Therefore, the electricity supplier should investigate the inherent characteristics of the circumferential and tangential directions for each winding to evaluate the mechanical health of them from time to time to prevent any risks that may arise.

However, the conventional method for evaluating the health of generator stator windings is Tan. Mainly electrical methods such as PI test, high voltage test, etc., only electrical tests are performed as part of the life assessment of generator stators in power plants. Accordingly, the mechanical integrity evaluation of the stator of the generator is not made. In addition, there is a problem in that the risk as described above is not prevented in advance due to the lack of inspection of the stator.

Thus, the present invention has been invented to solve the above-described problems, an object of the present invention to provide a generator stator winding inspection method that can accurately and easily inspect the mechanical integrity of the stator windings during generator operation.

Another object of the present invention is to provide a method for stabilizing a generator stator winding which can increase the operational reliability and increase the service life of a generator according to a test result of the mechanical integrity of the stator winding.

According to the present invention, it is possible to improve the reliability of the power plant equipment by minimizing the damage caused by the vibration of the generator stator by evaluating, analyzing, and managing the integrity of the generator stator using a diagnostic technique developed in terms of mechanical aspects.

1 is a partial side cross-sectional view showing a portion of a winding of a typical generator stator.

Figure 2a and 2b is a process chart showing the linearity test step of the generator stator windings, respectively, according to the present invention.

3A and 3B are graphs showing the results of the linearity test step in FIGS. 2A and 2B.

Figure 4 is a block diagram showing an apparatus for testing the frequency response of the generator stator windings according to the present invention.

5A and 5B are graphs comparing before and after supplementing a generator stator winding in accordance with the present invention.

Figure 6 is a photograph showing a state in which the generator stator is complemented in accordance with the present invention.

Figure 7 is a schematic diagram showing an embodiment of the mode test results for generator stator inspection according to the present invention.

♠ Explanation of symbols on the main parts of the drawing ♠

10: stator winding 12: detection sensor

14: Impact Hammer 16: Amplifier

18: FFT Analyzer 20: Computer

These objectives are to measure the frequency response in response to each other at different points in the generator stator winding inspection method to determine whether the stator field can be interpreted and to compare the constraints and linearity of the stator winding terminations. Determining; A frequency response test step for measuring the natural frequencies and magnitudes of the stator windings and the phase-connected windings, and determining the possibility of resonance by electromagnetic force during generator operation; And a mode test step for determining whether the resonance mode of the winding terminal portion matches the number of poles of the generator in order to analyze the behavior characteristic of the natural frequency of the stator terminal portion due to the electromagnetic force during the generator operation. It can be achieved by the stator winding inspection method.

Hereinafter, the generator stator winding inspection method according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, the linearity of the windings must first be evaluated to examine the generator stator windings. That is, the linearity of the generator stator field is examined to determine whether the stator field can be analyzed by mode test. As an example of such a linearity evaluation method, as shown in FIG. 2A, the frequency response is measured at the winding terminal portion at 6 o'clock after applying an impact to the winding terminal portion at the 12 o'clock position of the winding 10 of the stator. On the contrary, after the impact is applied to the 3 o'clock terminal of the stator winding 10, the response of the 12 o'clock winding terminal is measured, and the respective measured values are compared with each other to compare the measured values with each other. Determine if linearity is present. In addition, as shown in Fig. 2b, the 3 o'clock and 9 o'clock directions are applied in the same manner, that is, at the winding end of the 3 o'clock direction after the impact is applied to the winding end of the 9 o'clock direction of the winding 10 of the stator. The frequency response is measured, and vice versa, the impact is applied to the three o'clock terminal of the stator winding 10, and then the response of the stator winding at the nine o'clock is measured and the respective measured values are compared with each other. The overall constraint state and linearity of the terminal unit are determined. In this way, the frequency response is measured, and the impact, ie, the excitation force versus response, applied to each end of the winding is measured, and linearity is analyzed and evaluated by comparing these frequencies and magnitudes with each other.

For reference, the test results of the linearity tested in the same manner as in FIG. 2A among the linearity tests inspected in the manner described above are graphically shown in FIGS. 3A and 3B. Here, FIG. 3A shows the result of the frequency response in the 9 o'clock direction with respect to the excitation force in the 3 o'clock direction, and FIG. 3B shows the result of the frequency response in the 3 o'clock direction with respect to the excitation force in the 9 o'clock direction. The results shown in FIGS. 3A and 3B show that the frequencies measured in opposite directions and their magnitudes coincide with each other, indicating that there is no abnormality in the linearity of the stator winding terminal portion.

Next, the frequency response of the stator windings is tested. That is, the natural frequency and magnitude of each stator winding and phase connection winding are measured, and the state or soundness of each winding is evaluated by identifying the resonance caused by the electromagnetic force during generator operation. The test system for testing such a frequency response, as shown in FIG. 4, has a detection sensor 12 attachable to the distal end of the stator winding 10 and an impact hammer 14 with a built-in force measuring sensor. do. In addition, the amplifier 16 is connected to the detection sensor 12 to amplify the detection value detected from the detection sensor to ensure reliability, the impact hammer 14 is connected to the FFT analyzer 18 is connected to the impact It analyzes the force detected by the force sensor built into the hammer. Of course, the FFT analyzer 18 is connected to the amplifier 16 to analyze the detection value detected from the detection sensor 12 as well as the force detection sensor, the FFT analyzer 18 is also connected to the computer 20 The results analyzed by the FFT analyzer 18 may be used to measure the frequency response as well as display or process the results.

On the other hand, it is possible to diagnose whether the stator windings can be resonated using the measured data to evaluate the mechanical integrity of the device, and also diagnose the defects and looseness of the winding support devices. For example, according to the method of diagnosing whether the stator winding is possible to resonate, the acquired data is analyzed to determine whether the natural frequency of each winding coincides with 120 Hz, which is the excitation frequency caused by the electromagnetic force, thereby resonating the winding during generator operation. You can determine whether or not. In addition, the change in vibration characteristics of the structure due to the material of the structure or the damage of the support device may appear as a change in the stiffness and damping characteristics, so that the defects and loosening of the winding support devices can be diagnosed. Indeed, if a change in stiffness and attenuation occurs in the generator stator winding termination, the change can be detected through a frequency response test. Changes in stiffness and attenuation change the frequency shift and peak magnitude and bandwidth in the transfer function. In other words, it is possible to easily detect changes in stiffness and attenuation by comparing the vibration characteristics of the end of the winding in a good state with the response of the end of the current winding, which can be used as a reference. It can be diagnosed.

Then, the mode test is performed on the generator stator terminal to analyze the behavior characteristics of the natural frequency of the stator terminal by the electromagnetic force during generator operation. Such a mode test can be performed by determining whether the resonant mode of the winding end portion matches the number of poles of the generator. For example, in the case of thermal power plants, the number of poles is 2, so whether the secondary mode matches 120 Hz, and in the case of nuclear power plants, the number of poles is 4, so the analysis can be performed by analyzing whether the 4th mode matches 120 Hz. have.

In detail with respect to such a mode test step by step, first attach a sensor to a reference point, which is a set point of the stator winding terminal, and then connect the cable to the sensor. Then, after measuring the circumferential length of the end portion of the winding by equal intervals to select the measuring point and then using the impact hammer in turn to receive the frequency response signal. Finally, the mode test is performed by evaluating and evaluating the mode shape using the mode analysis program. An example of such a mode test result is shown in FIG.

On the other hand, by using the result shown through the method of the stator winding inspection method of the generator as described above, it is possible to interrupt the abnormality of the stator winding in advance or to repair or supplement the winding detected as abnormal. For example, after diagnosing whether the stator winding is possible to resonate as shown in the graph of FIG. 5A, if a resultant natural frequency coincides with or approximates 120 Hz, which is an excitation frequency caused by the electromagnetic force, it may cause resonance in the stator winding. Of course, it can be determined that the winding support devices are defective or loosened. On the basis of these results, or before the manufacture or installation of the stator windings, complementing or compensating by enclosing or wrapping the stator windings as shown in FIG. 6, the frequency shift and magnitude are reduced as shown in the graph shown in FIG. 5B. It can be seen that.

As a result, according to the method of the generator stator winding inspection according to the present invention, it is possible to accurately determine whether or not the mechanical integrity of the stator winding to compensate for the defective winding, thereby eliminating the possibility of winding resonance that can occur during generator operation. There is an effect to be improved.

In addition, by reducing the vibration of the stator winding to minimize the leakage of the winding due to vibration fatigue cracking has the advantage of improving the generator operation reliability and improve the life.

In addition, the stator windings can be preventively maintained, thus reducing the costs associated with the maintenance of the windings.In addition, the stator windings and generators can be supplemented by design changes or windings by judging the possibility of resonance due to the electromagnetic force of the stator windings during initial production of the generator. There is an advantage to improve the overall reliability of the.

Claims (4)

In the generator stator winding inspection method, Determining the restraint state and linearity of the stator winding terminations by measuring the frequency responses responsive to each other at different points to determine whether or not the stator field can be interpreted; A frequency response test step for measuring the natural frequencies and magnitudes of the stator windings and the phase-connected windings, and for determining the possibility of resonance by the electromagnetic force and the fault progression of the generator during operation; And Generator stator comprising a mode test step for determining whether the resonant mode of the winding terminal is consistent with the number of poles of the generator in order to analyze the behavior of the natural frequency of the stator terminal by the electromagnetic force during generator operation Winding inspection method. The method of claim 1, wherein the linearity determining step comprises: applying an excitation force to each of the mutually opposing points of the terminal portion of the stator winding; measuring a frequency response toward the mutually opposing point by applying the excitation force; Generator stator winding inspection method comprising the step of comparing the respective measured values with each other. The method of claim 1, wherein the step of testing the frequency response of the stator winding comprises applying an excitation force to an end of the stator winding with an impact hammer having a built-in force measuring sensor, and analyzing the force detected by the force measuring sensor with an FFT analyzer; Attaching a detection sensor to the distal end of the stator winding, detecting a frequency, amplifying with an amplifier, analyzing the FFT analyzer, comparing the detected values detected by the respective sensors, and comparing the analysis value and the comparison value with each other. Generator stator winding inspection method comprising the step of processing with a computer. The method of claim 1, wherein the mode test attaches a sensor to a reference point, which is a point set in the stator winding terminal part, connects a cable to the sensor, and selects a measurement point by dividing the circumference of the terminal part of the winding at equal intervals. And receiving the frequency response signal by excitation in turn using an impact hammer, and obtaining and analyzing a mode shape by using a mode analysis program. method of inspection.