A method for detecting corona discharge in stator bars

Abstract

This invention discloses a method for detecting corona discharge on stator bars. The method includes: placing the stator bar to be tested on top of a support and reflection unit; performing acoustic imaging detection using an acoustic imaging detection unit; and analyzing and judging sound sources at different frequencies separately, under the premise that the acoustic images at different frequencies do not overlap, to confirm the graphic characteristics of each sound source in the acoustic imaging image. The sound sources for further analysis of discharge formation include: point sound sources located outside the support and reflection unit insulator; point sound sources located within the support and reflection unit insulator; and strip sound sources with one end located within the support and reflection unit insulator. This invention can effectively detect discharge on the back of the stator bar and provides a method for judging and locating different discharge positions on the front and back of the bar, improving the detection efficiency and accuracy of corona tests.

Description

Technical Field

[0001] This invention belongs to the field of motor testing technology, and in particular to a method for detecting corona discharge of stator bars. Background Technology

[0002] Accurate detection of corona discharge in stator bars is crucial for ensuring the safe and stable operation of the generating unit. Currently, the corona discharge detection standards for stator bars use two methods: visual inspection in a darkroom and ultraviolet imaging. These methods, based on visual and optical principles, can only detect the discharge on the stator bars facing the operator. To accurately detect the presence of corona discharge and its initiation voltage on the back of the stator bars, additional personnel and instruments are required.

[0003] Meanwhile, the detection of corona discharge in the stator end windings of large generator sets also suffers from the same problems. Existing darkroom visual inspection and ultraviolet imaging methods can only effectively detect the corona discharge on the front of the upper layer bars of the stator end windings. Due to factors such as obstruction, it is difficult to effectively detect the corona discharge on the back of the upper layer bars and the lower layer bars. Summary of the Invention

[0004] In view of this, the present invention provides a method for detecting corona discharge of stator bars, which is based on acoustic imaging. The test device forms a reflection source of the back corona discharge acoustic signal while supporting the stator bars, and locates the back discharge source. At the same time, since acoustic detection is easily affected by factors such as the test environment, a method for confirming the detection results is proposed to avoid interference from factors such as the test environment and ensure the accuracy of the discharge signal detection.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method and apparatus for detecting corona discharge of stator bars, comprising the following steps:

[0006] Step 1) The sub-bar to be measured is placed on the upper part of the support and reflection unit, which includes multiple height-adjustable insulators; the acoustic imaging detection unit is used to perform acoustic imaging detection. Under the premise that the acoustic images of different frequencies do not overlap, the sound sources of different frequencies are analyzed and judged separately to confirm the graphic characteristics of each sound source in the acoustic imaging image.

[0007] Step 2): For a strip-shaped sound source with one end located at the insulator of the support and reflection unit, it is initially determined that the discharge point is located on the back of the stator bar. The discharge point is the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit. The discharge signal verification process is carried out: the strip-shaped sound source is located between the first insulator of the support and reflection unit and the adjacent second insulator, where the first insulator is the end of the strip-shaped sound source, the length of the stator bar through which the strip-shaped sound source passes is L1, and the length of the stator bar between the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit and the second insulator is L2. When L2≥L1, proceed to the next step of judgment.

[0008] Step 3) Lower the first insulator so that it has no contact with the stator bar and there is a clear gap. When the acoustic imaging of the strip sound source changes, the endpoint of the acoustic imaging of the strip sound source located at the non-support and reflective unit insulator remains unchanged, while the endpoint of the acoustic imaging of the strip sound source originally located at the first insulator changes to the second insulator. It is determined that the discharge point is located on the back of the stator bar. The specific location of the discharge point is the endpoint of the strip sound source located at the non-support and reflective unit insulator.

[0009] Step 4): When there are multiple point sound sources at the same frequency, all the insulators of the support and reflection unit are raised to the same height at the same time. If the position of the point sound source acoustic image on the stator bar changes, it is judged to be an interference signal.

[0010] Step 5): After the initial elimination of interference signals in Step 4), for point-like sound sources located at the insulator of the support and reflection unit, it is preliminarily determined that the discharge point is located on the front or back of the stator bar where the point-like sound source is located. The discharge signal verification process is carried out: lower the insulator at the location of the point-like sound source until it has no contact with the stator bar and there is a clear gap.

[0011] Step 6): After the initial elimination of interference signals in Step 4), for point-like sound sources located at the insulator of the non-support and reflection unit, the discharge point is directly determined to be the front side of the stator bar where the point-like sound source is located.

[0012] Furthermore, in step 1), the number of insulators in the support and reflection unit is redundantly configured. Because the number of insulators is redundantly configured, the decrease in height of any one insulator will not affect the support and reflection unit's support for the stator bars.

[0013] Furthermore, in step 1), the distance between each insulator in the support and reflection unit is equal.

[0014] Furthermore, the upper surface of the insulator is smooth, without sharp corners or burrs, and all edges are chamfered, which can prevent the insulator surface from discharging and forming interference signals during the detection process, thus affecting the detection results.

[0015] Furthermore, in the discharge signal verification process of step 5), if the acoustic image of the point sound source disappears, it is determined to be an interference signal.

[0016] Furthermore, in the discharge signal verification process of step 5), if the characteristics of the point-like sound source do not change, it is determined that the discharge point is located on the front side of the stator bar where the point-like sound source is located.

[0017] Furthermore, in the discharge signal verification process of step 5), if the point sound source becomes a strip sound source, and one end of the strip sound source acoustic image is the location of the previous point sound source, and the other end is located in the insulator closest to this point sound source, then it is determined that the discharge point is located on the back of the stator bar where the point sound source is located.

[0018] Further, in step 1), a pressurizing unit is used to pressurize the stator bar under test, and the imaging frequency range of the acoustic imaging detection unit is adjusted to the typical frequency range of stator bar corona discharge.

[0019] Furthermore, in step 1), the pressurization process is the same as required by the corona test standard.

[0020] Furthermore, in step 1), adjusting the dynamic range of the imaging display and gradually narrowing the imaging frequency range can help confirm the specific shape characteristics of the sound source.

[0021] Compared with traditional technologies, this invention can effectively detect discharge on the back of stator bars and provides methods for judging and locating different discharge positions on the front and back of the bars. It also provides a method for identifying interference signals, which can save manpower and instrument investment in detection. It can be applied to the corona detection of stator cable windings and can be further extended to the corona detection of the stator end windings of the entire generator, making up for the current problem of difficulty in effectively detecting corona discharge on the back of the upper bars and the lower bars. Attached Figure Description

[0022] The accompanying drawings used in the description of specific embodiments of the present invention will be briefly introduced below.

[0023] Figure 1 This is a schematic diagram of the stator bar corona discharge detection device of the present invention during detection;

[0024] Figure 2 This is a flowchart of the stator bar corona discharge detection method of the present invention;

[0025] Figure 3 This is a schematic diagram of the propagation of acoustic signals from the front discharge of the stator bar in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the propagation of acoustic signals from the discharge on the back side of the stator bar in an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0028] This invention provides a method for detecting stator bar corona discharge, which employs a stator bar corona discharge detection device. The device comprises three parts: a pressurization unit, a support and reflection unit, and an acoustic imaging detection unit. Figure 1 As shown.

[0029] The stator bar corona discharge detection method is as follows: Figure 2 As shown, the steps are as follows:

[0030] Step 1): Pressurize the stator bar under test using the pressurization unit, and adjust the imaging frequency range of the acoustic imaging detection unit to the typical frequency range of stator bar corona discharge. By adjusting the dynamic range of the imaging display and gradually narrowing the imaging frequency range, it is helpful to confirm the specific shape characteristics of the sound source. Place the stator bar under test on the upper part of the support and reflection unit, and use the acoustic imaging detection unit to perform acoustic imaging detection. Under the premise that the acoustic images of different frequencies do not overlap, analyze and judge the sound sources of different frequencies separately to confirm the graphic characteristics of each sound source in the acoustic imaging image.

[0031] The following three types of sound sources can be further analyzed as sound sources formed by discharge: point sound source located at the insulator of the non-supporting and reflecting unit, point sound source located at the insulator of the supporting and reflecting unit, and strip sound source with one end located at the insulator of the supporting and reflecting unit.

[0032] The support and reflection unit consists of multiple height-adjustable insulators, each with an individually adjustable height. The number of insulators in the support and reflection unit is redundantly configured, with equal spacing between each insulator. A decrease in the height of any one insulator will not affect the support and reflection unit's support effect on the stator bars. The upper surface of the insulators is smooth, without sharp corners or burrs, and all edges are chamfered, which largely prevents surface discharge during testing, thus avoiding interference signals that could affect the test results. The pressurization process described above is the same as the corona test standard requirements, and the acoustic imaging is formed by superimposing a visible light image and a sound field distribution cloud map.

[0033] Step 2): For a strip-shaped sound source with one end located at the insulator of the support and reflection unit, it is initially determined that the discharge point is located on the back of the stator bar. The discharge point is the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit. The discharge signal verification process is carried out: the strip-shaped sound source is located between the first insulator of the support and reflection unit and the adjacent second insulator, where the first insulator is the end of the strip-shaped sound source, the length of the stator bar through which the strip-shaped sound source passes is L1, and the length of the stator bar between the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit and the second insulator is L2. When L2≥L1, proceed to the next step of judgment.

[0034] When the discharge location is on the back of the stator bar, the sound signal generated by the discharge propagates along the solid, that is, the surface of the stator bar. The sound signal reaches the surface of the insulator of the nearest support and reflection unit and is detected by the acoustic imaging detection unit.

[0035] Step 3) Lower the first insulator so that it has no contact with the stator bar and there is a clear gap. When the acoustic imaging of the strip sound source changes, the endpoint of the acoustic imaging of the strip sound source located at the non-support and reflective unit insulator remains unchanged, while the endpoint of the acoustic imaging of the strip sound source originally located at the first insulator changes to the second insulator. It is determined that the discharge point is located on the back of the stator bar. The specific location of the discharge point is the endpoint of the strip sound source located at the non-support and reflective unit insulator.

[0036] Lowering the first insulator changes the shortest distance the acoustic signal generated by the discharge travels along the solid surface, since the distance between the insulators in each support and reflection unit is equal. The acoustic signal then travels along the back surface of the stator bar to the second insulator 2, and is detected by the acoustic imaging detection unit.

[0037] Step 4): When multiple point sound sources exist at the same frequency, all insulators of the support and reflection unit are raised to the same height at the same time. If the position of the point sound source acoustic image on the stator bar changes, it is determined to be an interference signal.

[0038] Step 5): After the initial elimination of interference signals in Step 4), for point-like sound sources located at the insulator of the support and reflection unit, it is preliminarily determined that the discharge point is located on the front or back of the stator bar where the point-like sound source is located. The discharge signal verification process is carried out: lower the insulator at the location of the point-like sound source until it has no contact with the stator bar and there is a clear gap.

[0039] If the acoustic image of a point sound source disappears, it is determined to be an interference signal.

[0040] If the characteristics of the point-source noise do not change, then the discharge point is determined to be located on the front side of the stator bar where the point-source noise is located.

[0041] If a point-like sound source transforms into a strip-like sound source, and one end of the acoustic image of the strip-like sound source is the location of the previous point-like sound source, while the other end is located on the insulator closest to this point-like sound source, then it is determined that the discharge point is located on the back side of the stator bar where the point-like sound source is located.

[0042] Step 6): After the initial elimination of interference signals in Step 4), for point-like sound sources located at the insulator of the non-support and reflection unit, the discharge point is directly determined to be the front side of the stator bar where the point-like sound source is located.

[0043] Example 1

[0044] This embodiment provides a method for detecting corona discharge in stator bars, the steps of which are as follows:

[0045] 1. Place the stator bar to be measured on the upper part of the support and reflection unit, pressurize the stator bar to be measured through the pressurization unit, adjust the imaging frequency range of the acoustic imaging detection unit to the typical frequency range of stator bar corona discharge, adjust the imaging display dynamic range and gradually reduce the imaging frequency range. Under the premise that the acoustic images of different frequencies do not overlap, analyze and judge the sound sources of different frequencies separately, and confirm the graphic characteristics of each sound source in the acoustic imaging image.

[0046] 2. A point-like sound source was found located at the insulator of the non-supporting and reflecting unit, and there was only one point-like sound source with the same frequency characteristics. It was determined that the discharge point was on the front of the stator bar where the point-like sound source was located. Figure 3 As shown.

[0047] Example 2

[0048] This embodiment provides a method for detecting corona discharge in stator bars, the steps of which are as follows:

[0049] 1. Place the stator bar to be measured on the upper part of the support and reflection unit, pressurize the stator bar to be measured through the pressurization unit, adjust the imaging frequency range of the acoustic imaging detection unit to the typical frequency range of stator bar corona discharge, adjust the imaging display dynamic range and gradually reduce the imaging frequency range. Under the premise that the acoustic images of different frequencies do not overlap, analyze and judge the sound sources of different frequencies separately, and confirm the graphic characteristics of each sound source in the acoustic imaging image.

[0050] 2. Multiple point-like sound sources with the same frequency characteristics were found, namely the first point-like sound source and the second point-like sound source. When all the insulators of the supporting and reflecting units were raised to the same height at the same time, if the position of the acoustic image of the second point-like sound source on the stator bar changed, it was determined that the second point-like sound source was an interference signal.

[0051] 3. If the first point source is located at the insulator of the non-supporting and reflecting unit, the discharge point is determined to be the front of the stator bar where the point source is located.

[0052] Example 3

[0053] This embodiment provides a method for detecting corona discharge in stator bars, the steps of which are as follows:

[0054] 1. Place the stator bar to be measured on the upper part of the support and reflection unit, pressurize the stator bar to be measured through the pressurization unit, adjust the imaging frequency range of the acoustic imaging detection unit to the typical frequency range of stator bar corona discharge, adjust the imaging display dynamic range and gradually reduce the imaging frequency range. Under the premise that the acoustic images of different frequencies do not overlap, analyze and judge the sound sources of different frequencies separately, and confirm the graphic characteristics of each sound source in the acoustic imaging image.

[0055] 2. If a point-like sound source is found at the insulator of the support and reflection unit, and there is only one point-like sound source with the same frequency characteristics, it is initially determined that the discharge point is located on the front or back of the stator bar where the point-like sound source is located. The discharge signal verification process is carried out: lower the insulator at the location of the point-like sound source until it has no contact with the stator bar and there is a clear gap.

[0056] 3. If the acoustic image of the point source disappears, the signal is judged to be an interference signal; if the characteristics of the point source do not change, the discharge point is judged to be located in front of the stator bar where the acoustic image of the point source is located.

[0057] Example 4

[0058] This embodiment provides a method for detecting corona discharge in stator bars, the steps of which are as follows:

[0059] 1. Place the stator bar to be measured on the upper part of the support and reflection unit, pressurize the stator bar to be measured through the pressurization unit, adjust the imaging frequency range of the acoustic imaging detection unit to the typical frequency range of stator bar corona discharge, adjust the imaging display dynamic range and gradually reduce the imaging frequency range. Under the premise that the acoustic images of different frequencies do not overlap, analyze and judge the sound sources of different frequencies separately, and confirm the graphic characteristics of each sound source in the acoustic imaging image.

[0060] 2. When a point-like sound source is found at the insulator of the support and reflection unit, and there is only one point-like sound source with the same frequency characteristics; it is preliminarily determined that the discharge point is located on the front or back of the stator bar where the point-like sound source is located, and the discharge signal verification process is carried out: lower the insulator at the location of the point-like sound source until it has no contact with the stator bar and there is a clear gap.

[0061] 3. If a point-like sound source becomes a strip-like sound source, and one end of the acoustic image of the strip-like sound source is the location of the previous point-like sound source, and the other end is located on the insulator closest to this point-like sound source, then it is determined that the discharge point is located on the back side of the stator bar where the point-like sound source is located.

[0062] Example 5

[0063] This embodiment provides a method for detecting corona discharge in stator bars, the steps of which are as follows:

[0064] 1. Place the stator bar to be measured on the upper part of the support and reflection unit, pressurize the stator bar to be measured through the pressurization unit, adjust the imaging frequency range of the acoustic imaging detection unit to the typical frequency range of stator bar corona discharge, adjust the imaging display dynamic range and gradually reduce the imaging frequency range. Under the premise that the acoustic images of different frequencies do not overlap, analyze and judge the sound sources of different frequencies separately, and confirm the graphic characteristics of each sound source in the acoustic imaging image.

[0065] 2. A strip-shaped sound source with one end located at the insulator of the support and reflection unit was found. It was initially determined that the discharge point was located on the back of the stator bar. The discharge point was the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit. The discharge signal verification process was carried out: the strip-shaped sound source was located between the first insulator of the support and reflection unit and the adjacent second insulator, where the first insulator was the end of the strip-shaped sound source. The length of the stator bar through which the strip-shaped sound source passed was L1. The length of the stator bar between the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit and the second insulator was L2. When L2≥L1, the next step of judgment was carried out.

[0066] 3. Lower the first insulator so that it has no contact with the stator bars and there is a significant gap. When the acoustic imaging of the strip-shaped sound source changes, the endpoint of the acoustic imaging of the strip-shaped sound source located at the insulator of the non-support and reflective unit remains unchanged, while the endpoint of the acoustic imaging of the strip-shaped sound source originally located at the first insulator changes to the second insulator. It can be determined that the discharge point is located on the back of the stator bars. The specific location of the discharge point is the endpoint of the strip-shaped sound source located at the non-support and reflective unit. Figure 4 As shown.

[0067] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention.

Claims

1. A method for detecting corona discharge in stator bars, characterized in that, include: Step 1) The sub-bar to be measured is placed on the upper part of the support and reflection unit, which includes multiple height-adjustable insulators; Acoustic imaging detection unit is used for acoustic imaging detection. Under the premise that the acoustic images of different frequencies do not overlap, the sound sources of different frequencies are analyzed and judged separately to confirm the graphic characteristics of each sound source in the acoustic imaging image. Step 2): For a strip-shaped sound source with one end located at the insulator of the support and reflection unit, it is initially determined that the discharge point is located on the back of the stator bar. The discharge point is the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit. The discharge signal verification process is carried out: the strip-shaped sound source is located between the first insulator of the support and reflection unit and the adjacent second insulator, where the first insulator is the end of the strip-shaped sound source, the length of the stator bar through which the strip-shaped sound source passes is L1, and the length of the stator bar between the end of the strip-shaped sound source located at the insulator of the non-support and reflection unit and the second insulator is L2. When L2≥L1, proceed to the next step of judgment. Step 3) Lower the first insulator so that it has no contact with the stator bar and there is a clear gap. When the acoustic imaging of the strip sound source changes, the endpoint of the acoustic imaging of the strip sound source located at the non-support and reflective unit insulator remains unchanged, while the endpoint of the acoustic imaging of the strip sound source originally located at the first insulator changes to the second insulator. It is determined that the discharge point is located on the back of the stator bar. The specific location of the discharge point is the endpoint of the strip sound source located at the non-support and reflective unit insulator. Step 4): When there are multiple point sound sources at the same frequency, all the insulators of the support and reflection unit are raised to the same height at the same time. If the position of the point sound source acoustic image on the stator bar changes, it is judged to be an interference signal. Step 5): After the initial elimination of interference signals in Step 4), for point-like sound sources located at the insulator of the support and reflection unit, it is preliminarily determined that the discharge point is located on the front or back of the stator bar where the point-like sound source is located. The discharge signal verification process is carried out: lower the insulator at the location of the point-like sound source until it has no contact with the stator bar and there is a clear gap. Step 6): After the initial elimination of interference signals in Step 4), for point-like sound sources located at the insulator of the non-support and reflection unit, the discharge point is directly determined to be the front side of the stator bar where the point-like sound source is located.

2. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In step 1), the number of insulators in the support and reflection unit satisfies the redundancy configuration.

3. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In step 1), the distance between each insulator in the support and reflection unit is equal.

4. The method for detecting stator bar corona discharge according to claim 1, characterized in that, The upper surface of the insulator is smooth, without sharp corners or burrs, and all edges are chamfered.

5. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In the discharge signal verification process of step 5), if the acoustic image of the point sound source disappears, it is determined to be an interference signal.

6. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In the discharge signal verification process of step 5), if the characteristics of the point sound source do not change, it is determined that the discharge point is located on the front side of the stator bar where the point sound source is located.

7. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In the discharge signal verification process of step 5), if the point sound source becomes a strip sound source, and one end of the strip sound source acoustic image is the location of the previous point sound source, and the other end is located in the insulator closest to this point sound source, then it is determined that the discharge point is located on the back of the stator bar where the point sound source is located.

8. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In step 1), the pressure unit is used to apply pressure to the stator bar under test, and the imaging frequency range of the acoustic imaging detection unit is adjusted to the typical frequency range of stator bar corona discharge.

9. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In step 1), the pressurization process is the same as the standard requirements for corona testing.

10. The method for detecting stator bar corona discharge according to claim 1, characterized in that, In step 1), adjusting the dynamic range of the imaging display and gradually narrowing the imaging frequency range can help confirm the specific shape characteristics of the sound source.

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