A method and device for monitoring the insulation of generator set bearings

Abstract

This invention provides a method and apparatus for monitoring the insulation of generator set bearings. The generator set includes at least one generator, and each generator includes a generator bearing, an inner insulating layer surrounding the outer surface of the generator bearing, an intermediate conductive layer surrounding the outer surface of the inner insulating layer, and an outer insulating layer surrounding the outer surface of the intermediate conductive layer. The method for monitoring the insulation of the generator set bearings includes: acquiring the ground insulation resistance value of the intermediate conductive layer of each generator in the generator set; and determining whether a failure layer exists in the inner and outer insulating layers of the generator based on a comparison between the ground insulation resistance value and a preset insulation resistance alarm threshold. In this invention, by directly monitoring the ground insulation resistance value of the intermediate conductive layer of the generator, real-time monitoring of the generator bearing insulation level is achieved, ensuring the safe production of power companies.

Description

Technical Field

[0001] This invention relates to the field of generator bearing condition monitoring and fault diagnosis, specifically to a method and device for monitoring the insulation of generator set bearings. Background Technology

[0002] Bearings are critical components of the generator support system, used to support the high-speed rotation of the rotor. During generator operation, due to fluid erosion, friction, and factors such as asymmetry and magnetic leakage in the circuit, a voltage of several volts or even tens of volts is generated on the rotor shaft; this voltage is called shaft voltage. Because of the presence of shaft voltage, when the insulation of the shaft support bearing fails, the shaft voltage will form a circuit through the support bearing, generating a large short-circuit current. This can easily cause the shaft and bearing bushes to burn and overheat, leading to loss of lubrication and even shaft seizure. Therefore, to ensure the safe operation of the unit, international standards stipulate that the insulation resistance of thermal power units, measured with a 1000V insulation resistance tester, should be greater than 1 MΩ.

[0003] To ensure that the insulation of generator bearings is at a reasonable level, power plants generally measure the insulation of generator bearings periodically or after maintenance using an insulation megohmmeter, but there is a lack of online monitoring methods. Patent "CN201710113075.4" discloses a method for predicting the insulation level by monitoring shaft current and shaft voltage in combination, but this method is an indirect judgment and belongs to the post-judgment. It still cannot obtain the real-time value of bearing insulation online, and there are no relevant standards for the selection of alarm threshold. It is actually a shaft current detection device. Summary of the Invention

[0004] This invention provides a method and apparatus for monitoring the insulation of generator bearings, thereby addressing the technical problem of the lack of existing online monitoring methods for generator bearing insulation.

[0005] This invention provides a method for monitoring the insulation of a generator set bearing, wherein the generator set includes at least one generator, the generator includes a generator bearing, an inner insulating layer surrounding the outer surface of the generator bearing, an intermediate conductive layer surrounding the outer surface of the inner insulating layer, and an outer insulating layer surrounding the outer surface of the intermediate conductive layer, the method comprising:

[0006] Obtain the ground insulation resistance value of the intermediate conductive layer of each generator in the generator set;

[0007] Based on the comparison between the ground insulation resistance value and the preset insulation resistance alarm threshold, it is determined whether there is a failure layer in the inner insulation layer and the outer insulation layer of the generator.

[0008] In some embodiments of the present invention, if the insulation resistance to ground is less than the insulation resistance alarm threshold, it is determined that there is a failure layer in the inner insulation layer and the outer insulation layer of the generator corresponding to the insulation resistance to ground.

[0009] In some embodiments of the present invention, the method further includes:

[0010] Obtain the voltage value of the intermediate conductive layer of each generator in the generator set;

[0011] Based on the comparison results of the voltage value with a preset first voltage threshold and the comparison results of the voltage value with a preset second voltage threshold, it is determined whether the outer insulation layer and the inner insulation layer of the generator are the failure layers, wherein the second voltage threshold is less than the first voltage threshold.

[0012] In some embodiments of the present invention, the step of determining whether the outer insulation layer and the inner insulation layer of the generator are the failed layers based on the comparison result of the voltage value with a preset first voltage threshold and the comparison result of the voltage value with a preset second voltage threshold includes:

[0013] When the voltage value is greater than the first voltage threshold, the inner insulation layer of the generator corresponding to the voltage value is determined to be the failed layer.

[0014] If the voltage value is less than the preset second voltage threshold, the outer insulation layer of the generator corresponding to the voltage value is determined to be the failure layer.

[0015] In some embodiments of the present invention, the method further includes:

[0016] Obtain the shaft current of each generator in the generator set;

[0017] When the shaft current is greater than the preset shaft current alarm threshold and the voltage value of the intermediate conductive layer is less than the second voltage threshold, it is determined that the outer insulation layer and the inner insulation layer of the generator corresponding to the shaft current are both the failed layers.

[0018] In some embodiments of the present invention, the method further includes:

[0019] If the insulation resistance to ground is greater than or equal to the preset insulation resistance alarm threshold, then the insulation resistance of the generator bearing of the generator corresponding to the insulation resistance to ground is determined to be normal.

[0020] The present invention also provides a generator set bearing insulation monitoring device for monitoring multiple generators within a generator set. The generators include generator bearings, an inner insulating layer surrounding the outer surface of the generator bearing, an intermediate conductive layer surrounding the outer surface of the inner insulating layer, and an outer insulating layer surrounding the outer surface of the intermediate conductive layer. The generator set bearing insulation monitoring device includes:

[0021] The detection module is used to obtain the ground insulation resistance value of the intermediate conductive layer of each generator in the generator set; and

[0022] The processing module is used to determine whether there is a failed layer in the inner insulation layer and the outer insulation layer based on the comparison result between the insulation resistance value to ground and the preset insulation resistance alarm threshold.

[0023] In some embodiments of the present invention, a selection module is further included for electrically connecting the detection module and the intermediate conductive layer. The selection module includes multiple selection branches. The intermediate conductive layers of the multiple generators in the generator set are electrically connected to the detection module through the multiple selection branches. The multiple selection branches are used to control the connection and disconnection between the detection module and the intermediate conductive layers of the multiple generators so that the detection module sequentially detects the insulation resistance to ground of the multiple generators.

[0024] In some embodiments of the present invention, the detection module is used to obtain the voltage value of the intermediate conductive layer of each generator in the generator set, and the processing module is used to determine whether the outer insulating layer and the inner insulating layer of the generator are the failure layers based on the comparison result of the voltage value with a preset first voltage threshold and the comparison result of the voltage value with a preset second voltage threshold, wherein the second voltage threshold is less than the first voltage threshold.

[0025] In some embodiments of the present invention, the processing module is used to obtain the shaft current of each generator in the generator set. When the shaft current is greater than a preset shaft current alarm threshold and the voltage value of the intermediate conductive layer is less than the second voltage threshold, it is determined that the outer insulating layer and the inner insulating layer of the generator corresponding to the shaft current are both the failure layers.

[0026] The generator bearing insulation monitoring method provided in this embodiment of the invention directly monitors the ground insulation resistance of the intermediate conductive layer of the generator, rather than predicting the insulation level of the generator bearing by monitoring shaft current and shaft voltage as in the prior art. This achieves real-time monitoring of the generator bearing insulation level, providing a strong basis for power plants to analyze insulation degradation trends and carry out preventive maintenance, thus ensuring the safe production of power companies. At the same time, by performing real-time online monitoring of generator sets including multiple generators, the monitoring efficiency of multiple generators is improved, which is also beneficial to the safe production of power companies. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating the generator set bearing insulation monitoring method provided by the present invention;

[0029] Figure 2 This is another schematic diagram of the generator set bearing insulation monitoring method provided by the present invention;

[0030] Figure 3 This is another schematic diagram of the generator set bearing insulation monitoring method provided by the present invention;

[0031] Figure 4 This is another schematic diagram of the generator set bearing insulation monitoring method provided by the present invention;

[0032] Figure 5 This is a schematic diagram of the structure of the generator set bearing insulation monitoring device provided by the present invention;

[0033] Figure 6 This is another structural schematic diagram of the generator set bearing insulation monitoring device provided by the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0035] To address the technical problem of the lack of existing online monitoring methods for generator bearing insulation, this invention provides a method for monitoring the bearing insulation of a generator set. The generator set includes at least one generator, and the generator includes a generator bearing, an inner insulating layer surrounding the outer surface of the generator bearing, an intermediate conductive layer surrounding the outer surface of the inner insulating layer, and an outer insulating layer surrounding the outer surface of the intermediate conductive layer, as shown below. Figure 1 As shown, the generator set bearing insulation monitoring method includes:

[0036] Step S1: Obtain the ground insulation resistance value of the intermediate conductive layer of each generator in the generator set;

[0037] Step S2: Based on the comparison result between the ground insulation resistance value and the preset insulation resistance alarm threshold, determine whether there is a failure layer in the inner insulation layer and the outer insulation layer of the generator.

[0038] In this embodiment, the insulation resistance to ground of the intermediate conductive layer of the generator is directly monitored, rather than predicting the insulation level of the generator bearing by monitoring the shaft current and shaft voltage as in the prior art. This enables real-time monitoring of the insulation level of the generator bearing, thus providing a strong basis for power plants to analyze insulation degradation trends and carry out preventive maintenance, and ensuring the safe production of power companies.

[0039] Meanwhile, in this embodiment, by performing real-time online monitoring of the generator set including multiple generators, the monitoring efficiency of multiple generators is improved, which is also beneficial to the safe production of power companies.

[0040] Understandably, in this embodiment, comparing the ground insulation resistance value with the preset insulation resistance alarm threshold can only determine the insulation level of the generator bearing, that is, whether there is a failure layer in the outer insulation layer and the inner insulation layer or whether there is no failure layer in the outer insulation layer and the inner insulation layer. However, when it is determined that there is a failure layer in the outer insulation layer and the inner insulation layer, it is not possible to further determine whether the outer insulation layer is the failure layer, or the inner insulation layer is the failure layer, or both the inner insulation layer and the outer insulation layer are failure layers.

[0041] Specifically, in this embodiment, if the insulation resistance to ground is less than the insulation resistance alarm threshold, it is determined that there is a failure layer in the inner insulation layer and the outer insulation layer of the generator corresponding to the insulation resistance to ground.

[0042] Understandably, if the insulation resistance to ground is greater than or equal to the insulation resistance alarm threshold, then the insulation resistance of the generator bearing of the generator corresponding to the insulation resistance to ground is determined to be normal.

[0043] In this embodiment, the magnitude of the insulation resistance to ground represents the insulation level of the generator bearing. The larger the insulation resistance to ground, the higher the insulation level of the generator bearing; conversely, the smaller the insulation resistance to ground, the worse the insulation level of the generator bearing. The insulation resistance alarm threshold is typically set to 1MΩ.

[0044] Furthermore, such as Figure 2 As shown, the generator set bearing insulation monitoring method further includes:

[0045] Step S3: Obtain the voltage value of the intermediate conductive layer of each generator in the generator set;

[0046] Step S4: Based on the comparison result of the voltage value with a preset first voltage threshold and the comparison result of the voltage value with a preset second voltage threshold, determine whether the outer insulation layer and the inner insulation layer of the generator are the failure layers, wherein the second voltage threshold is less than the first voltage threshold.

[0047] In this embodiment, when the ground insulation resistance is detected to be less than the preset insulation resistance alarm threshold, that is, when there is a failed layer in the inner and outer insulation layers of the generator, the voltage value of the intermediate conductive layer of the generator is obtained, and based on the comparison result of the voltage value with the first voltage threshold and the comparison result of the voltage value with the second voltage threshold, it can be determined whether the outer and inner insulation layers of the generator are the failed layers. This further determines whether the insulation failure of the generator bearing is caused by the inner insulation layer being the failed layer or by the outer insulation layer being the failed layer, thereby further locating the position of the failed layer, which is beneficial for subsequent maintenance and upkeep of the generator.

[0048] Step S4, which determines whether the outer and inner insulation layers of the generator are the failed layers based on a comparison between the voltage value and a preset first voltage threshold, and a comparison between the voltage value and a preset second voltage threshold, includes:

[0049] When the voltage value is greater than the first voltage threshold, the inner insulation layer of the generator corresponding to the voltage value is determined to be the failed layer.

[0050] If the voltage value is less than the second voltage threshold, the outer insulation layer of the generator corresponding to the voltage value is determined to be the failed layer.

[0051] The first voltage threshold is set with correction based on the shaft voltage of the generator, and the second voltage threshold is set with correction based on the zero voltage of the generator.

[0052] Furthermore, such as Figure 3 As shown, the generator set bearing insulation monitoring method further includes:

[0053] Step S5: Obtain the shaft current of each generator in the generator set;

[0054] Step S6: When the shaft current is greater than the preset shaft current alarm threshold and the voltage value of the intermediate conductive layer is less than the second voltage threshold, it is determined that the outer insulation layer and the inner insulation layer of the generator corresponding to the shaft current are both the failed layers.

[0055] In this embodiment, the shaft current of the generator is no longer monitored separately; the shaft current of the generator is the data already measured by the external shaft current monitoring device.

[0056] Please continue to refer to this. Figure 4 ,exist Figure 4 In the middle, RS R is the ground insulation resistance value of the intermediate conductive layer of the generator. L V is the preset insulation resistance alarm threshold. S V is the voltage value. H V is the preset first voltage threshold. L For the preset second voltage threshold, I Z I is the shaft current of the generator. max The preset shaft current alarm threshold is where, when R s <R L And V s >V H When R is in a state of failure, the inner insulation layer of the generator can be determined to be the failed layer. s <R L And V s< V L When Iz > Imax and R s <R L and V s< V L If this is the case, it can be determined that both the outer insulation layer and the inner insulation layer of the generator are the failed layers.

[0057] Furthermore, the present invention also provides a generator set bearing insulation monitoring device for monitoring multiple generators within a generator set. Each generator includes a generator bearing, an inner insulating layer surrounding the outer surface of the generator bearing, an intermediate conductive layer surrounding the outer surface of the inner insulating layer, and an outer insulating layer surrounding the outer surface of the intermediate conductive layer. The generator set bearing insulation monitoring device includes a detection module 100 and a processing module 200. The detection module 100 is used to acquire the ground insulation resistance value of the intermediate conductive layer of each generator within the generator set. The processing module 200 is used to determine whether a failure layer exists in the inner insulating layer and the outer insulating layer based on a comparison result between the ground insulation resistance value and a preset insulation resistance alarm threshold.

[0058] Optionally, such as Figure 5 As shown, the generator bearing insulation monitoring device further includes a selection module 300 electrically connected between the detection module 100 and the intermediate conductive layer. The selection module 300 includes multiple selection branches. The intermediate conductive layers of multiple generators in the generator set are electrically connected to the detection module 100 through the multiple selection branches. The multiple selection branches are used to control the connection and disconnection between the detection module 100 and the intermediate conductive layers of multiple generators so that the detection module sequentially detects the ground insulation resistance value of multiple generators.

[0059] It is understood that the intermediate conductive layer of the generator is formed by splicing two or more arc-shaped conductive layers into a ring-shaped intermediate conductive layer. Therefore, the intermediate conductive layer of a single generator requires multiple selection branches for control, wherein the number of selection branches is consistent with the number of splicing structures of the ring-shaped intermediate conductive layer.

[0060] In this embodiment, a control unit is further provided within the selection module 300 to control the opening and closing of multiple selection branches. By controlling the opening and closing of these multiple selection branches, the insulation performance of the generator bearings of multiple generators within the generator set is monitored in an orderly manner, thereby determining whether a failure layer exists in the inner and outer insulation layers.

[0061] Optionally, in some embodiments, the detection module 100 is used to obtain the voltage value of the intermediate conductive layer of each generator in the generator set, and the processing module 200 is used to determine whether the outer insulating layer and the inner insulating layer of the generator are the failed layers based on the comparison result of the voltage value with a preset first voltage threshold and the comparison result of the voltage value with a preset second voltage threshold, wherein the second voltage threshold is less than the first voltage threshold.

[0062] In this embodiment, the detection module 100 is used to acquire the voltage value of the intermediate conductive layer of each generator in the generator set. The processing module 200 determines whether the outer insulating layer and the inner insulating layer of the generator are the failed layers based on the comparison result of the voltage value with a preset first voltage threshold and the comparison result of the voltage value with a preset second voltage threshold. Specifically, when the voltage value is greater than the first voltage threshold, the outer insulating layer of the generator corresponding to the voltage value is determined to be the failed layer; and when the voltage value is less than the second voltage threshold, the inner insulating layer of the generator corresponding to the voltage value is determined to be the failed layer.

[0063] Optionally, in some embodiments, the processing module 200 is used to obtain the shaft current of each generator in the generator set. When the shaft current is greater than a preset shaft current alarm threshold and the voltage value of the intermediate conductive layer is less than the second voltage threshold, it is determined that the outer insulation layer and the inner insulation layer of the generator corresponding to the shaft current are both the failed layers.

[0064] It should be noted that, in this embodiment, the shaft current of each generator in the generator set obtained by the processing module 200 is the data already measured by the external shaft current monitoring device.

[0065] Specifically, such as Figure 6 As shown, in this embodiment, the selection branch in the selection module 300 can be configured as a circuit formed by a fuse, a current-limiting resistor, and a selection switch connected in series. The fuse and the current-limiting resistor can provide overcurrent and overvoltage protection. The detection module 100 can be composed of a sampling circuit, a signal amplification circuit, a data converter, and a microcontroller unit (MCU). The processing module 200 can be configured with a large-capacity disk industrial computer, a database, and a gateway device. The large-capacity disk industrial computer facilitates the storage of historical data and enables the analysis of the insulation degradation trend of the generator. The database and gateway device lay the foundation for the realization of digital resistance and facilitate the connection with the unit's intelligent diagnostic platform.

[0066] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for monitoring the insulation of generator set bearings, characterized in that, The generator set includes at least one generator, the generator including a generator bearing, an inner insulating layer surrounding the outer side of the generator bearing, an intermediate conductive layer surrounding the outer side of the inner insulating layer, and an outer insulating layer surrounding the outer side of the intermediate conductive layer. The method includes: Obtain the ground insulation resistance value of the intermediate conductive layer of each generator in the generator set; Based on the comparison result between the ground insulation resistance value and the preset insulation resistance alarm threshold, it is determined whether there is a failure layer in the inner insulation layer and the outer insulation layer of the generator; The method further includes: Obtain the voltage value of the intermediate conductive layer of each generator in the generator set; Based on the comparison results of the voltage value with a preset first voltage threshold and the comparison results of the voltage value with a preset second voltage threshold, it is determined whether the outer insulation layer and the inner insulation layer of the generator are the failed layers, wherein the second voltage threshold is less than the first voltage threshold: When the voltage value is greater than the first voltage threshold, the inner insulation layer of the generator corresponding to the voltage value is determined to be the failed layer. If the voltage value is less than the second voltage threshold, the outer insulation layer of the generator corresponding to the voltage value is determined to be the failed layer.

2. The generator set bearing insulation monitoring method according to claim 1, characterized in that, If the insulation resistance to ground is less than the insulation resistance alarm threshold, it is determined that there is a failure layer in the inner insulation layer and the outer insulation layer of the generator corresponding to the insulation resistance to ground.

3. The generator set bearing insulation monitoring method according to claim 1, characterized in that, The method further includes: Obtain the shaft current of each generator in the generator set; When the shaft current is greater than the preset shaft current alarm threshold and the voltage value of the intermediate conductive layer is less than the second voltage threshold, it is determined that the outer insulation layer and the inner insulation layer of the generator corresponding to the shaft current are both the failed layers.

4. The generator set bearing insulation monitoring method according to claim 1, characterized in that, The method further includes: If the insulation resistance to ground is greater than or equal to the insulation resistance alarm threshold, then the insulation resistance of the generator bearing of the generator corresponding to the insulation resistance to ground is determined to be normal.

5. A generator set bearing insulation monitoring device for monitoring multiple generators within a generator set, wherein each generator includes a generator bearing, an inner insulating layer surrounding the outer surface of the generator bearing, an intermediate conductive layer surrounding the outer surface of the inner insulating layer, and an outer insulating layer surrounding the outer surface of the intermediate conductive layer, characterized in that... The generator set bearing insulation monitoring device includes: The detection module is used to obtain the ground insulation resistance value of the intermediate conductive layer of each generator in the generator set; and The processing module is used to determine whether there is a failed layer in the inner insulation layer and the outer insulation layer based on the comparison result between the insulation resistance value to ground and the preset insulation resistance alarm threshold.

6. The generator set bearing insulation monitoring device according to claim 5, characterized in that, It also includes a selection module for electrically connecting the detection module and the intermediate conductive layer. The selection module includes multiple selection branches. The intermediate conductive layers of the multiple generators in the generator set are electrically connected to the detection module through the multiple selection branches. The multiple selection branches are used to control the on / off connection between the detection module and the intermediate conductive layers of the multiple generators so that the detection module can sequentially detect the insulation resistance to ground of the multiple generators.

7. The generator set bearing insulation monitoring device according to claim 5, characterized in that, The detection module is used to acquire the voltage value of the intermediate conductive layer of each generator in the generator set. The processing module is used to determine whether the outer insulation layer and the inner insulation layer of the generator are the failure layers based on the comparison result of the voltage value with a preset first voltage threshold and the comparison result of the voltage value with a preset second voltage threshold, wherein the second voltage threshold is less than the first voltage threshold.

8. The generator set bearing insulation monitoring device according to claim 7, characterized in that, The processing module is used to obtain the shaft current of each generator in the generator set. When the shaft current is greater than a preset shaft current alarm threshold and the voltage value of the intermediate conductive layer is less than the second voltage threshold, it is determined that the outer insulation layer and the inner insulation layer of the generator corresponding to the shaft current are both the failure layers.

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