Steam Turbine Generator Shaft Voltage Measurement Method and Device

Abstract

This invention provides a method and apparatus for measuring the shaft voltage of a steam turbine generator. The generator's main shaft has an excitation end and a steam end, the steam end including a grounding carbon brush. The measurement method includes: controlling the generator to operate under preset conditions; directly grounding the grounding carbon brush to obtain a first shaft voltage value at both ends of the generator's main shaft; short-circuiting the grounding carbon brush to obtain a second shaft voltage value at both ends of the generator's main shaft; obtaining a third shaft voltage value at the excitation end of the generator's main shaft relative to ground; and determining the state of the generator's shaft voltage based on the first, second, and third shaft voltage values. The steam turbine generator shaft voltage measurement method of this invention can meet the requirements of both rated no-load operation measurement and measurement under generator load operation, ensuring the actual structural layout of the equipment, guaranteeing safety, and avoiding adverse human-caused situations. It also allows for analysis and judgment based on the test data to obtain accurate conclusions.

Description

Technical Field

[0001] This invention belongs to the field of generator technology, specifically relating to a method and device for measuring the shaft voltage of a steam turbine generator. Background Technology

[0002] During the design, manufacturing, installation, and operation of large steam turbine generators, a voltage of a certain amplitude may be generated between the two ends of the generator shaft or between the shaft and the bearing bush due to various reasons. This voltage is called shaft voltage. Since the main shaft of a steam turbine generator is generally grounded at the steam end, the voltage between the excitation end of the main shaft and ground is the shaft voltage. Shaft voltage is a common electrical phenomenon during generator operation, especially serious in large and high-speed generators. Under normal circumstances, the shaft voltage is low, and the lubricating oil film between the generator shaft and the bearing provides good insulation. If, for some reason, the shaft voltage rises to a certain value, or if there are defects on the bearing surface, the quality or flow of the lubricating oil is substandard, or abnormal vibration of the generator occurs, the oil film may break down. In the case of poor bearing insulation to ground, the shaft voltage forms a circuit through the journal, oil film, bearing, base, and the bottom layer of the foundation, which may generate a large current in the circuit, forming a shaft current discharge circuit that causes great harm. Therefore, it is essential to measure and check the shaft voltage of the generator during operation, which is of great significance for determining whether the bearing insulation is good and whether the grounding brush is reliably grounded during unit maintenance.

[0003] To address the aforementioned problems, it is necessary to propose a reasonably designed and effective method and device for measuring the shaft voltage of a steam turbine generator. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a method and device for measuring the shaft voltage of a steam turbine generator.

[0005] This invention provides a method for measuring the shaft voltage of a steam turbine generator. The generator's main shaft has an excitation end and a steam end. The excitation end is equipped with an excitation end bearing, which is enclosed in a bearing housing. The steam end includes a grounding carbon brush. The measurement method includes:

[0006] Control the generator to operate under preset conditions;

[0007] The grounding carbon brush is directly grounded to obtain the first shaft voltage value at both ends of the generator shaft.

[0008] Short-circuit the grounding carbon brush to obtain the second shaft voltage value at both ends of the generator shaft.

[0009] Obtain the third shaft voltage value of the excitation end of the generator main shaft relative to ground;

[0010] The state of the generator shaft voltage is determined based on the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value.

[0011] Optionally, determining the state of the generator shaft voltage based on the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value includes:

[0012] The state of the generator shaft voltage is determined based on the relationship between the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value.

[0013] Optionally, determining the state of the generator shaft voltage based on the magnitude relationship between the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value includes:

[0014] If the first shaft voltage value is much greater than the second shaft voltage value, and / or the third shaft voltage value is much less than the first shaft voltage value and the second shaft voltage value, respectively, then the generator shaft voltage is determined to be abnormal.

[0015] Optionally, the method further includes:

[0016] An alarm is output once the abnormality of the generator shaft voltage is determined.

[0017] Optionally, determining the state of the generator shaft voltage based on the magnitude relationship between the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value includes:

[0018] If the first shaft voltage value is approximately equal to the second shaft voltage value, the second shaft voltage value is approximately equal to the third shaft voltage value, and the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value are all less than a preset voltage threshold, then the generator shaft voltage is determined to be normal.

[0019] Optionally, short-circuiting the grounding carbon brush includes:

[0020] A shorting wire is provided, with its two ends connected in parallel across the two ends of the grounding carbon brush.

[0021] Optionally, controlling the generator to operate under preset conditions includes:

[0022] The generator is controlled to operate under no-load or under load at rated voltage and rated speed.

[0023] Another aspect of the present invention provides a turbine generator shaft voltage measuring device, which uses the shaft voltage measuring method described above to measure the shaft voltage of the turbine generator, the device comprising:

[0024] The first shaft voltage measuring device is used to obtain the first shaft voltage value at both ends of the generator shaft when the grounding carbon brush is directly grounded.

[0025] The second axis voltage measuring device is used to obtain the second axis voltage value at both ends of the main shaft when the grounding carbon brush is short-circuited.

[0026] The third-axis voltage measuring device is used to obtain the third-axis voltage value of the excitation end of the generator shaft to ground;

[0027] The control module is used to determine the state of the generator's shaft voltage based on the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value.

[0028] Optionally, the control module is further configured to determine the state of the generator shaft voltage based on the magnitude relationship between the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value.

[0029] Optionally, an alarm module is also included, which is electrically connected to the control module and is used to output an alarm when the generator shaft voltage is abnormal.

[0030] This invention provides a method and apparatus for measuring the shaft voltage of a steam turbine generator. The generator's main shaft has an excitation end and a steam end, with the steam end including a grounding carbon brush. The measurement method includes: controlling the generator to operate under preset conditions; directly grounding the grounding carbon brush to obtain a first shaft voltage value at both ends of the generator's main shaft; short-circuiting the grounding carbon brush to obtain a second shaft voltage value at both ends of the generator's main shaft; obtaining a third shaft voltage value at the excitation end of the generator's main shaft relative to ground; and determining the state of the generator's shaft voltage based on the first, second, and third shaft voltage values. The method for measuring the shaft voltage of a steam turbine generator according to this invention can meet the requirements of both rated no-load operation measurement and measurement under load operation, ensuring the actual structural layout of the equipment, guaranteeing safety, and avoiding adverse human-caused situations. It also allows for analysis and judgment based on the test data to obtain accurate conclusions. This measurement method has been widely used in the shaft voltage measurement of high-temperature gas-cooled reactor steam turbine generators. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the turbine generator and some measuring devices in a turbine generator shaft voltage measurement method according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic flowchart of a turbine generator shaft voltage measurement method according to another embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of a turbine generator shaft voltage measuring device according to another embodiment of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the steam turbine generator 100 includes a generator body 110 and a main shaft. The main shaft has an excitation end 121 and a steam end 122. An excitation end bearing 130 is provided at the end of the main shaft facing the generator body 110. The excitation end bearing 130 is connected to a bearing housing 135 via a first insulating gasket 131, a metal gasket 132, and a second insulating gasket 133 connected in sequence. The excitation end bearing 130 is provided with an insulation measurement lead-out point 134, which is connected to the metal gasket 132. A steam end bearing 140 is provided at the end of the main shaft facing the generator body 110. Both the excitation end bearing 130 and the steam end bearing 140 are fully enclosed within a bearing housing. The steam end 122 of the main shaft includes a grounding carbon brush 150.

[0036] like Figure 2 As shown, one aspect of the present invention provides a method S100 for measuring the shaft voltage of a steam turbine generator, the method S100 comprising:

[0037] S110. Control the generator to operate under preset conditions.

[0038] Specifically, firstly, the generator is controlled to operate under no-load or under load at rated voltage and rated speed.

[0039] Secondly, ensure that the generator grounding carbon brush 150 is reliably grounded throughout the measurement process. In other words, the grounding carbon brush 150 must remain grounded throughout the generator shaft voltage measurement process and must not be allowed to lift off.

[0040] The turbine generator shaft voltage measurement method of the present invention can realize the measurement of shaft voltage of generator under load. However, the national standard stipulates that the shaft voltage test conditions are that the generator is at rated speed and under no-load conditions. The preset conditions of the present invention expand the generator shaft voltage test conditions stipulated by the national standard.

[0041] S120. Directly ground the grounding carbon brush to obtain the first shaft voltage value at both ends of the generator shaft.

[0042] Specifically, such as Figure 1As shown, the grounding carbon brush 150 is directly grounded, and the two ends of the first shaft voltage measuring device 210 are connected to the excitation end 121 and the steam end 122 of the main shaft, respectively, to obtain the first shaft voltage U11 at both ends of the generator main shaft. That is, the first shaft voltage U11 on both sides of the generator main shaft is measured under the condition that the grounding carbon brush 150 is grounded during generator operation.

[0043] In this embodiment, the first axis voltage measuring device 210 is a high internal resistance AC voltmeter, but other devices can also be used. This embodiment does not make specific limitations.

[0044] S130. Short-circuit the grounding carbon brush to obtain the second shaft voltage value at both ends of the generator shaft.

[0045] Specifically, such as Figure 1 As shown, a shorting wire 160 is set, with its two ends connected in parallel across the grounding carbon brush 150 to short-circuit the grounding carbon brush 150. The first end of the second shaft voltage measuring device 220 is connected to the excitation end 121 of the main shaft, and the second end of the second shaft voltage measuring device 220 is connected to both the grounding carbon brush 150 and the grounding end to obtain the second shaft voltage value U12 across the generator main shaft when the grounding carbon brush 150 is short-circuited. In other words, the first shaft voltage U12 across the generator main shaft is measured under the condition that the grounding carbon brush 150 is reliably grounded during generator operation.

[0046] In this embodiment, the second voltage measuring device 220 is a high internal resistance AC voltmeter, but other devices can also be used. This embodiment does not make specific limitations.

[0047] S140. Obtain the third shaft voltage value of the excitation end of the generator shaft relative to ground.

[0048] Specifically, such as Figure 1 As shown, the first end of the third-axis voltage measuring device 230 is connected to the excitation end of the main shaft, and the second end of the third-axis voltage measuring device 230 is connected to the excitation end bearing 130 and the grounding end respectively to obtain the third-axis voltage value U13 of the excitation end 121 of the generator main shaft relative to ground.

[0049] In this embodiment, the third-axis voltage measuring device 230 is a high internal resistance AC voltmeter, but other devices can also be used. This embodiment does not make specific limitations.

[0050] S150. Determine the state of the generator shaft voltage based on the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value.

[0051] For example, the state of the generator shaft voltage is determined based on the magnitude relationship between the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value.

[0052] Specifically, under the condition that the generator grounding carbon brush is well grounded, if the first shaft voltage value U11 is much greater than the second shaft voltage value U12, it indicates that the generator grounding carbon brush 150 may have poor contact with the main shaft due to rotor oil contamination, carbon brush wear, or other reasons. The large first shaft voltage value U11 may cause the steam-side main shaft to discharge to the bearing, resulting in instantaneous oil film breakdown, bearing damage, and increased vibration of the main shaft and bearing during operation. In this case, the grounding condition of the grounding carbon brush should be checked and addressed.

[0053] If the third shaft voltage value U13 is much smaller than the first shaft voltage value U11 and the second shaft voltage value U12, it may indicate that there is a discharge circuit in the generator excitation end bearing, poor oil quality, or poor insulation.

[0054] In other words, assuming the generator's grounding carbon brush is properly grounded, if the first shaft voltage value U11 is significantly greater than the second shaft voltage value U12, and / or the third shaft voltage value U13 is significantly less than both the first and second shaft voltage values ​​U11 and U12, respectively, then the generator shaft voltage is considered abnormal. Any one of these conditions is sufficient to determine if the generator shaft voltage is abnormal.

[0055] In this embodiment, as Figure 3 As shown, a control module 240 is used to determine the state of the generator shaft voltage based on the first shaft voltage value U11, the second shaft voltage value U12, and the third shaft voltage value U13. The input terminals of the control module 240 are electrically connected to the first shaft voltage measuring device 210, the second shaft voltage measuring device 220, and the third shaft voltage measuring device 230, respectively. The first shaft voltage value U11, the second shaft voltage value U12, and the third shaft voltage value U13 obtained by the first shaft voltage measuring device 210, the second shaft voltage measuring device 220, and the third shaft voltage measuring device 230 are all input to the control module 240. The control module 240 determines the state of the generator shaft voltage based on the relationship between these values. The control module 240 can be a CPU, a PLC, or an MCU; this embodiment does not impose a specific limitation.

[0056] More specifically, such as Figure 3 As shown, after confirming an abnormal generator shaft voltage, the alarm module 250 outputs an alarm. The alarm module 250 is electrically connected to the control module 240. The alarm module 250 can consist of a relay and a buzzer, or a relay and an indicator light. When the control module 240 sends a signal indicating an abnormal shaft voltage, the normally open contact of the relay in the alarm module 250 closes, causing the buzzer to sound or the indicator light to illuminate. At this time, the grounding status of the carbon brushes should be immediately checked and addressed to ensure generator safety and prevent dangerous situations.

[0057] For example, determining the state of the generator shaft voltage based on the magnitude relationship between the first shaft voltage value, the second shaft voltage value, and the third shaft voltage value includes:

[0058] If the first shaft voltage value U11 is approximately equal to the second shaft voltage value U12, the second shaft voltage value U12 is approximately equal to the third shaft voltage value U13, and the first shaft voltage value U11, the second shaft voltage value U12, and the third shaft voltage value U13 are all less than a preset voltage threshold, then the generator shaft voltage is determined to be normal. In this embodiment, the preset voltage threshold ranges from 9V to 11V, and preferably, the preset voltage threshold is 10V.

[0059] In other words, under the condition that the generator grounding carbon brush is well grounded, if U11≈U12≈U13, and U11<10V, U12<10V, U13<10V, it means that the generator grounding carbon brush is well grounded during operation and the generator shaft voltage is normal.

[0060] It should be noted that the turbine generator shaft voltage measurement method of the present invention is applicable to the shaft voltage measurement of turbine generators under no-load and load operation, and is specifically designed for generator structures in which the insulation measurement lead point of the excitation end bearing on the fully enclosed excitation end shaft is connected to the metal gasket between the two insulating gaskets of the excitation end bearing to ground.

[0061] The method for measuring the shaft voltage of a steam turbine generator according to the present invention can meet the requirements of both rated no-load operation measurement and measurement under load operation. It ensures the actual structural layout of the equipment, guarantees safety, and avoids adverse human-caused situations. The test data obtained by this method can be analyzed and judged to obtain accurate conclusions. The measurement method of the present invention has been widely used in the shaft voltage measurement of high-temperature gas-cooled reactor steam turbine generators.

[0062] like Figure 3 As shown, another aspect of the present invention provides a turbine generator shaft voltage measuring device 200, which uses the shaft voltage measuring method S100 described above to measure the shaft voltage of the turbine generator. The specific measurement steps of the shaft voltage measuring method S100 have been described in detail above and will not be repeated here. The shaft voltage measuring device 200 includes a first shaft voltage measuring instrument 210, a second shaft voltage measuring instrument 220, a third shaft voltage measuring instrument 230, and a control module 240.

[0063] The two ends of the first shaft voltage measuring device 210 are connected to the excitation end 121 and the steam end 122 of the main shaft, respectively, to obtain the first shaft voltage value U11 at both ends of the generator main shaft when the grounding carbon brush 150 is directly grounded.

[0064] The first end of the second shaft voltage measuring device 220 is connected to the excitation end 121 of the main shaft, and the second end of the second shaft voltage measuring device 220 is connected to the grounding carbon brush 150 and the grounding end respectively to obtain the second shaft voltage value U12 at both ends of the generator main shaft when the grounding carbon brush 150 is short-circuited.

[0065] The first end of the third-axis voltage measuring device 230 is connected to the excitation end of the main shaft, and the second end of the third-axis voltage measuring device 230 is connected to the excitation end bearing 130 and the grounding end respectively to obtain the third-axis voltage value U13 of the excitation end 121 of the generator main shaft relative to ground.

[0066] In this embodiment, the first-axis voltage measuring device 210, the second-axis voltage measuring device 220, and the third-axis voltage measuring device 230 are all high-internal-resistance AC voltmeters. Other devices may also be used, and this embodiment does not impose any specific limitations.

[0067] The control module 240 is used to determine the state of the motor's shaft voltage based on the first shaft voltage value U11, the second shaft voltage value U12, and the third shaft voltage value U13.

[0068] The input terminals of the control module 240 are electrically connected to the first shaft voltage measuring device 210, the second shaft voltage measuring device 220, and the third shaft voltage measuring device 230, respectively. The first shaft voltage value U11, the second shaft voltage value U12, and the third shaft voltage value U13 obtained by the first shaft voltage measuring device 210, the second shaft voltage measuring device 220, and the third shaft voltage measuring device 230, respectively, are all input to the control module 240. The control module 240 determines the state of the generator shaft voltage based on the relationship between them. The control module 240 can be a CPU, PLC, or MCU; this embodiment does not impose a specific limitation.

[0069] For example, the shaft voltage measuring device 200 also includes an alarm module 250, which is electrically connected to the control module 240 and is used to output an alarm when the generator shaft voltage is abnormal. The alarm module 250 can consist of a relay and a buzzer, or a relay and an indicator light. When the control module 240 sends a signal indicating an abnormal shaft voltage, the normally open contact of the relay in the alarm module 250 closes, causing the buzzer to sound or the indicator light to illuminate. At this time, the grounding status of the grounding carbon brush should be checked and addressed immediately to ensure the safety of the generator and prevent dangerous situations.

[0070] The turbine generator shaft voltage measuring device of the present invention can meet the requirements of measuring the generator under rated no-load operation as well as under load operation. It ensures the actual structural layout of the equipment, guarantees safety, and avoids adverse situations caused by human error. It can analyze and judge based on the test data of the device and draw accurate conclusions.

[0071] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method of measuring shaft voltage of a turbogenerator, a large shaft of the generator having a field end and a steam end, the field end being provided with a field end bearing, the field end bearing being enclosed in a bearing housing, the steam end including a ground carbon brush, characterized in that, The application relates to a shaft voltage measurement method suitable for a turbine generator in no-load and load operation, and the method comprises the following steps: controlling the generator to operate under preset conditions; directly grounding the grounding carbon brush to obtain a first shaft voltage value at both ends of a large shaft of the generator; wherein the grounding carbon brush is reliably grounded during the measurement; short-circuiting the grounding carbon brush to obtain a second shaft voltage value at both ends of the large shaft of the generator; obtaining a third shaft voltage value of an excitation end of the large shaft of the generator relative to the ground; determining the state of the shaft voltage of the generator according to the size relationship among the first shaft voltage value, the second shaft voltage value and the third shaft voltage value; wherein if the first shaft voltage value is much larger than the second shaft voltage value, and / or the third shaft voltage value is much smaller than the first shaft voltage value and the second shaft voltage value respectively, then it is determined that the shaft voltage of the generator is abnormal; if the first shaft voltage value is approximately equal to the second shaft voltage value, the second shaft voltage value is approximately equal to the third shaft voltage value, and the first shaft voltage value, the second shaft voltage value and the third shaft voltage value are all smaller than a preset voltage threshold, then it is determined that the shaft voltage of the generator is normal.

2. The method of claim 1, wherein, The method further comprises: outputting an alarm after it is determined that the shaft voltage of the generator is abnormal.

3. The method of claim 1, wherein, The short-circuiting of the grounding carbon brush comprises: setting a short-circuiting wire, and the two ends of the short-circuiting wire are arranged in parallel at both ends of the grounding carbon brush.

4. The method according to any one of claims 1 to 3, characterized in that, The controlling of the generator to operate under preset conditions comprises: controlling the generator to operate in no-load under rated voltage and rated speed or controlling the generator to operate in load.

5. A turbine generator shaft voltage measuring device characterized by comprising: The device for measuring the shaft voltage of the turbine generator by using the shaft voltage measurement method in any one of claims 1 to 4 comprises: a first shaft voltage measurer for obtaining the first shaft voltage value at both ends of the large shaft of the generator when the grounding carbon brush is directly grounded; a second shaft voltage measurer for obtaining the second shaft voltage value at both ends of the large shaft when the grounding carbon brush is short-circuited; a third shaft voltage measurer for obtaining the third shaft voltage value of the excitation end of the large shaft of the generator relative to the ground; a control module for determining the state of the shaft voltage of the generator according to the first shaft voltage value, the second shaft voltage value and the third shaft voltage value.

6. The apparatus of claim 5, wherein, The control module is further used for determining the state of the shaft voltage of the generator according to the size relationship among the first shaft voltage value, the second shaft voltage value and the third shaft voltage value.

7. The apparatus of claim 5, wherein, The device further comprises an alarm module, which is electrically connected with the control module and is used for outputting an alarm when the shaft voltage of the generator is abnormal.

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