A partial discharge detection array and method for a hydro-generator stator bar

Abstract

This invention discloses a partial discharge detection array and method for stator bars of a hydro-generator, relating to the field of online insulation monitoring technology for large rotating electrical machines. The array includes a stator frame housing, multiple monitoring UHF antennas, and at least one interference reference UHF antenna. The outer surface of the stator frame housing is divided into a key monitoring area at the bar end, a key monitoring area in the bar slot, an interference-free zone, and a reference arrangement area. Multiple monitoring UHF antennas are arranged in the key monitoring areas at the bar end, the key monitoring area in the bar slot, and the corresponding areas of the bar lead-out connection channels. The reference UHF antenna is arranged in the reference arrangement area and faces a strong interference source. The antennas are sequentially connected to a synchronous acquisition unit, an interference suppression and identification module, a positioning analysis unit, and a monitoring terminal. This invention improves the stability of online identification and positioning of partial discharge in the stator bars of a hydro-generator through synchronous acquisition, reference channel comparison, interference template identification, and zoned positioning.

Description

Technical Field

[0001] This invention relates to the field of insulation condition monitoring technology for large hydro-generators, and in particular to a partial discharge detection array and method for stator bars of hydro-generators. Background Technology

[0002] Hydroelectric generators operate in environments characterized by high humidity, oil mist, vibration, and strong electromagnetic interference. Partial discharge is prone to occur at the upper and lower ends of the stator bars, the insulation of the slots, and the bar lead-out connections. Continued partial discharge can lead to insulation aging, creepage carbonization, inter-turn short circuits, and even unplanned shutdowns. Therefore, long-term, stable, and locatable online monitoring is necessary.

[0003] Ultra-high frequency (UHF) detection methods offer advantages such as fast response speed, relatively strong noise resistance, and ease of integration with positioning algorithms, making them suitable for monitoring the insulation condition of large rotating electrical machines. Related research indicates that partial discharge pulses from stator bars, after propagating outwards through end air gaps, slot channels, ventilation openings, and lead-out structures, can still be received by a broadband UHF antenna outside the machine. This provides a foundation for conducting bar-level online detection on the outer surface of the stator frame.

[0004] However, during the operation of a hydro-generator in the field, there are usually multiple sources of interference, including the excitation device and its leads, busbars, high-current cables, cooling fans, power supply units, and grounding circuits. These interferences are continuous, sudden, and directional, and can easily be superimposed on weak pulses of partial discharge from the stator bars, leading to false alarms, missed alarms, or stator bar positioning drift.

[0005] Existing solutions focus more on the structure of a single UHF sensor, the front-end acquisition circuit, or general anti-interference measures for the whole machine. However, they lack systematic layout schemes for the stator bar detection objects, such as "which locations are suitable for arranging monitoring antennas at the ends and slots of the stator bars, which locations should be designated as no-layout zones, which locations are suitable for arranging interference reference antennas, and how to form an array geometric relationship between different layers and circumferential angles that is conducive to bar partitioning and discrimination."

[0006] If only a few UHF antennas are randomly installed on the outer surface of the base, even if some pulses can be collected, the signal-to-noise ratio will be reduced due to proximity to strong interference sources, coplanar arrays, insufficient circumferential coverage, or unreasonable orientation. It is difficult to achieve stable on-site interference identification and reliable stator bar partition positioning. Therefore, there is an urgent need for an outer surface antenna array arrangement structure and method that focuses more on the detection of targets by stator bars. Summary of the Invention

[0007] The purpose of this invention is to provide a partial discharge detection array and method for stator bars of a hydro-generator, in order to solve the problems of existing external surface mounting schemes when monitoring stator bars, such as unclear area division, unclear array geometric constraints, insufficient interference reference, and unclear positioning analysis techniques.

[0008] This application discloses a partial discharge detection array for stator bars of a hydro generator, including a stator frame housing, multiple monitoring UHF antennas and at least one interference reference UHF antenna. The outer surface of the stator frame housing is divided into a bar end key monitoring area, a bar slot key monitoring area, an interference prohibition area and a reference arrangement area. Multiple monitoring UHF antennas are arranged in the bar end key monitoring area, the bar slot key monitoring area and the corresponding area of ​​the bar lead-out connection channel. The reference UHF antenna is arranged in the reference arrangement area and faces the strong interference source. The monitoring UHF antenna and the interference reference UHF antenna are sequentially connected to a synchronous acquisition unit, an interference suppression and identification module, a positioning analysis unit, and a monitoring terminal.

[0009] Preferably, the key monitoring area at the end of the stator bar is located on the projection area of ​​the upper end, lower end, stator bar lead-out connection area, or neutral point side stator bar connection area on the base housing, and extends 0.5D-2D to both sides along the axial direction, where D is the maximum external dimension of a single monitoring UHF antenna. The key monitoring area for the grooved section of the wire rod is located on the projection area of ​​the groove ventilation opening, the core ventilation window, the air gap above the groove wedge, or the leakage sensitive location of the groove in the middle section of the core onto the machine base shell, and extends 0.5D-2D to both sides along the axial direction; Preferably, the interference ban zone is a region that is less than 2D-5D away from a strong interference source or has an angle of less than 30 degrees between the direction directly opposite the strong interference source and the main sensitive direction of the monitoring UHF antenna. The reference arrangement area is located near the source of strong interference, but avoids the location of the end air gap, slot opening and the direct line-of-sight path of the lead-out connection channel of the wire rod.

[0010] Preferably, the plurality of monitoring UHF antennas are respectively disposed on the upper end bar monitoring layer and the lower end bar monitoring layer, and the upper end bar monitoring layer and the lower end bar monitoring layer are both axially arranged strips extending circumferentially on the outer surface of the stator frame housing. The axial distance between the upper end bar monitoring layer and the outer projection center line of the upper end face of the stator core or the upper end winding is not greater than D, and the axial distance between the lower end bar monitoring layer and the outer projection center line of the lower end face of the stator core or the lower end winding is not greater than D. The monitoring UHF antenna is located in the overlapping area of ​​the corresponding monitoring layer and the key monitoring area at the end of the bar or the key monitoring area in the groove of the bar.

[0011] Preferably, the circumferential angle between any two adjacent monitoring UHF antennas 6 is set to 30 degrees to 120 degrees; The axial spacing between the upper and lower bar monitoring layers is set to 2D-10D, and the upper and lower bar monitoring layers are offset by 10-60 degrees in the circumferential direction.

[0012] Preferably, the monitoring UHF antenna and the interference reference UHF antenna are fixed to the outer surface of the stator housing via an insulating mounting base; Both the monitoring UHF antenna and the interference reference UHF antenna include antenna elements, which are disposed inside a radome. The monitoring UHF antenna and the interference reference UHF antenna are provided with a metal shielding shell on the circumferential or opposite side of the strong interference source; a vibration damping sealing gasket is provided between the insulating mounting base and the wire lead-out position of the double-layer shielded transmission cable. A vibration-damping sealing gasket is provided between the contact surface of the insulating mounting base and the stator frame housing.

[0013] Preferably, the monitoring UHF antenna and the interference reference UHF antenna are connected to the synchronous acquisition unit via a double-shielded transmission cable; The double-shielded transmission cable is laid along a path away from strong interference sources and avoids being laid parallel to high-current cables for long distances.

[0014] Preferably, a pre-conditioning unit is provided at the antenna lead-out end of the monitoring UHF antenna and the interference reference UHF antenna, and the distance between the pre-conditioning unit and the corresponding antenna lead-out end is no greater than 1D; The pre-conditioning unit includes at least one of a limiting protection circuit, a bandpass filter circuit, and a low-noise amplifier circuit.

[0015] This application also discloses a method for detecting partial discharge of stator bars in a hydro-generator, based on the aforementioned partial discharge detection array for stator bars in a hydro-generator, comprising the following steps: S1. Establish axial-circumferential installation coordinates with the generator shaft direction and the frame circumference direction, and conduct surveys on the installation area of ​​the stator frame outer surface, the sensitive area of ​​partial discharge signal leakage of stator bars, and the distribution of strong interference sources on site. S2. Divide the key monitoring area at the end of the antenna bar, the key monitoring area in the slot of the antenna bar, the interference prohibition area, and the reference arrangement area, and determine the installation coordinates, layer, and orientation of each antenna; S3. Complete the fixing of the insulating mounting base, antenna installation, laying of double-shielded transmission cables, and single-point grounding connection. S4. Perform clock synchronization, cable delay calibration, amplitude and phase consistency calibration, and establish reference interference templates for each channel; S5. Collect pulse signals from each channel and use the synchronization response relationship between the interference reference UHF antenna and the monitoring UHF antenna to suppress on-site operational interference; S6. Perform arrival time difference localization and zonal mapping analysis on the screened candidate pulses, and output the suspected discharge stator bar region and early warning results.

[0016] Preferably, S5 includes: when the interference reference UHF antenna receives a pulse with the same shape before or simultaneously with multiple monitoring UHF antennas, and the normalized cross-correlation coefficient is not less than 0.6, and the pulse repeatedly appears in the direction corresponding to the strong interference source, it is determined to be on-site operational interference; When multiple monitoring UHF antennas exhibit a stable spatial time of arrival, the normalized cross-correlation coefficient between the interference reference UHF antenna channel and the monitoring UHF antenna channel is less than 0.6, and the earliest arriving channel or the channel with the largest amplitude is located in the key monitoring area at the end of the stator bar or the key monitoring area in the slot of the stator bar, it is determined as a candidate signal for partial discharge of the stator bar, and the suspected discharge bar partition is determined by combining the stator bar area corresponding to each monitoring UHF antenna.

[0017] The beneficial effects of this invention are: (1) The present invention changes the external surface array arrangement from a general arrangement facing the whole machine to a partitioned arrangement facing the key areas of the stator bar, so that the array design directly serves the bar-level partial discharge detection.

[0018] (2) By setting up an interference reference UHF antenna, a synchronous reference can be established for on-site operational interference such as excitation device, busbar, fan and cable, thereby improving the interference elimination capability.

[0019] (3) By layering, circumferentially interlacing and multi-area coverage, the discharge monitoring needs of the stator bar ends, slots and lead-out connection positions can be taken into account at the same time, and the geometric conditions of zoned positioning can be improved; fourth, by insulating installation, double-layer shielded transmission and single-point grounding, the reliability and stability of long-term online monitoring can be improved. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall layout of a UHF antenna array for partial discharge detection of stator bars in a hydro-generator, according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the circumferential-axial expansion and partitioning arrangement for the stator bar detection of a hydro-generator according to an embodiment of the present invention.

[0022] Figure 3 This is a schematic cross-sectional view of the installation structure of a single UHF antenna at a corresponding position on the stator bar, according to an embodiment of the present invention.

[0023] Figure 4This is a schematic diagram of the signal acquisition, interference suppression, and stator bar partitioning and positioning analysis process according to an embodiment of the present invention.

[0024] The attached figures are labeled as follows: 1-Stator base housing; 2-Upper bar monitoring layer; 3-Lower bar monitoring layer; 4-Bar lead-out connection area; 5-Neutral point side bar connection area; 6-Monitoring UHF antenna; 7-Interference reference UHF antenna; 8-Strong interference source; 9-Insulated mounting base; 10-Double-layer shielded transmission cable; 11-Synchronous acquisition unit; 12-Positioning analysis unit; 13-Interference suppression and identification module; 14-Key monitoring area at the end of the bar; 15-Key monitoring area in the bar slot; 16-Reference arrangement area; 17-Radar shield; 18-Metal shielding shell; 19-Vibration damping sealing gasket; 20-Antenna unit; 21-Single-point grounding terminal; 22-Pre-conditioning unit; 23-Monitoring terminal. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments.

[0026] One embodiment of this application discloses a partial discharge detection array for the stator bars of a hydro-generator, the structure and arrangement of which are as follows: Figures 1 to 4 As shown.

[0027] In a specific embodiment, for the surface of the stator frame housing 1 of a vertical or horizontal shaft hydro-generator, the axial-circumferential installation coordinates are first established with the generator shaft direction as the z-axis, the circumferential direction of the housing as the θ-axis, and the center line of the stator lead-out connection area 4 or the maintenance door centerline as the circumferential zero-degree reference. During the field survey, the projected coordinates of the outer side of the upper end of the stator stator, the outer side of the lower end, the outer side of the slot ventilation opening, the outer side of the stator lead-out connection area 4, and the outer side of the neutral point side stator connection area 5 are recorded. At the same time, the spatial coordinates of the excitation device and its leads, busbars, cooling fans, high-current cables, and grounding busbars, and other interference sources, are also recorded.

[0028] Based on the survey results, the outer surface of the stator frame housing 1 is divided into four key monitoring areas on the stator bar ends (14), key monitoring areas on the stator bar slots (15), interference prohibition zones, and reference arrangement zones (16), according to the partial discharge leakage path and operational interference distribution of the stator bars. The key monitoring area on the stator bar ends (14) is the projected area on the frame housing of the outer side of the upper end, lower end, stator bar lead-out connection area, or neutral point side stator bar connection area, extending 0.5D-2D axially to both sides, where D is the maximum external dimension of a single monitoring UHF antenna. The key monitoring area on the stator bar slots (15) is the projected area on the frame housing of the slot ventilation opening, core ventilation window, air gap above the slot wedge, or leakage-sensitive location in the middle section of the core slot, extending 0.5D-2D axially to both sides. The interference exclusion zone is a region less than 2D-5D away from the strong interference source 8, or where the angle between the strong interference source 8 and the main sensitive direction of the monitoring UHF antenna 6 is less than 30 degrees. The monitoring UHF antenna 6 is not placed in the interference exclusion zone. The reference arrangement area 16 is located near the strong interference source 8, but avoiding the end air gap, slot opening, and direct line-of-sight path of the lead-out connection channel of the wire bar, and is used to install the interference reference UHF antenna 7.

[0029] Furthermore, multiple monitoring UHF antennas 6 and at least one interference reference UHF antenna 7 are installed on the outer surface of the stator frame housing 1 of the hydro-generator. The multiple monitoring UHF antennas 6 consist of 4-8 UHF antennas, which are respectively arranged on the outer surface of the stator frame housing 1 in the key monitoring area 14 at the end of the bar, the key monitoring area 15 in the bar slot, and the area corresponding to the bar lead-out connection channel.

[0030] Multiple monitoring UHF antennas 6 are respectively installed in the upper bar monitoring layer 2 and the lower bar monitoring layer 3, with at least two monitoring UHF antennas 6 installed in each monitoring layer. Both the upper bar monitoring layer 2 and the lower bar monitoring layer 3 are axially arranged strips extending circumferentially on the outer surface of the stator housing 1. The upper bar monitoring layer 2 and the lower bar monitoring layer 3 are axial layer constraints, while the bar end key monitoring area 14, the bar slot key monitoring area 15, and the reference arrangement area 16 are functional area constraints on the outer surface of the stator housing 1. The monitoring UHF antennas 6 are installed in the overlapping area of ​​the corresponding monitoring layer and the bar end key monitoring area 14 or the bar slot key monitoring area 15. The interference reference UHF antenna 7 is installed in the reference arrangement area 16 and is not used as a primary positioning channel.

[0031] In one specific embodiment, six UHF monitoring antennas 6 are preferably configured, with three located in the upper stator bar monitoring layer 2 and three located in the lower stator bar monitoring layer 3. The axial distance between the upper stator bar monitoring layer 2 and the projection center line of the upper end face or the outer side of the upper end winding of the stator core is no greater than D, and the axial distance between the lower stator bar monitoring layer 3 and the projection center line of the lower end face or the outer side of the lower end winding of the stator core is no greater than D. The specific axial height is determined by the projection center line obtained from on-site survey. Two of the monitoring UHF antennas in the upper stator bar monitoring layer 2 are respectively aligned with the outer side of the upper end of the stator bar and the outer side of the bar lead-out connection area 4, and the other monitoring UHF antenna is aligned with the outer side of the slot leakage sensitive area. Two of the monitoring UHF antennas in the lower stator bar monitoring layer 3 are respectively aligned with the outer side of the lower end of the stator bar and the outer side of the neutral point side bar connection area 5, and the other monitoring UHF antenna is aligned with the corresponding slot leakage sensitive position in the middle section of the core.

[0032] Furthermore, the multiple monitoring UHF antennas 6 preferably form a non-planar spatial array. The circumferential angle between any two adjacent monitoring UHF antennas 6 is set to 30-120 degrees. The axial spacing between the upper rod monitoring layer 2 and the lower rod monitoring layer 3 is set to 2D-10D, and the two layers are staggered circumferentially by 10-60 degrees to avoid overlapping coverage in the same radial plane. The angle between the main sensing direction of each monitoring UHF antenna 6 and the normal direction of the corresponding end air gap, slot channel, rod lead-out connection channel, or neutral point connection channel is no greater than 30 degrees.

[0033] One or two interference reference UHF antennas 7 are installed at a distance of 2D-10D from the strong interference source 8. For example, they are installed at a distance of 2D-10D from the excitation lead, busbar corner, cooling fan casing, or high-current cable support, with their main sensitive direction facing the strong interference source 8. The interference reference UHF antennas 7 should avoid direct line-of-sight paths to the end air gap, slot opening, and lead-out channel of the wire rod. They do not serve a primary positioning function but are used to form a reference channel for field operational interference.

[0034] In one specific embodiment, to improve field adaptability, the monitoring UHF antenna 6 and the interference reference UHF antenna 7 can be broadband circularly polarized or quasi-circularly polarized antennas, preferably operating in the 300MHz-3000MHz frequency band, with an input impedance of 50 ohms and a voltage standing wave ratio of no more than 2.

[0035] In engineering applications, the array proposed in this embodiment is not limited to the arrangement of six monitoring UHF antennas 6 plus one interference reference UHF antenna 7. As long as the principles of at least two axial layers, circumferentially dispersed arrangement, separation of key monitoring areas and interference-free areas, effective characterization of on-site operational interference by the reference arrangement area, and coverage of the target stator bar end or slot leakage area are met, it falls within the protection scope of this application.

[0036] like Figure 3 As shown, the monitoring UHF antenna 6 and the interference reference UHF antenna 7 are fixed to the outer surface of the stator housing 1 by an insulating mounting base 9 with a low dielectric constant. The mounting base 9 can be made of insulating materials such as polytetrafluoroethylene, polyetheretherketone, glass fiber reinforced epoxy resin board, or ceramic fiber reinforced resin. The radome 17 can be made of wave-transmitting materials such as fiberglass, polycarbonate, or polytetrafluoroethylene. Both the monitoring UHF antenna 6 and the interference reference UHF antenna 7 include antenna elements 20. The antenna element 20 is a radiation receiving component used to receive UHF partial discharge signals. The radome 17, the metal shielding shell 18, and the insulating mounting base 9 are the protective, shielding, and fixing structures for the antenna element 20. The antenna element 20 is located inside the radome 17. The metal shielding shell 18 is provided on the side of the antenna circumferentially or away from the strong interference source 8. A vibration-damping sealing gasket 19 is provided between the insulating mounting base 9 and the wire exit position of the double-shielded transmission cable 10. In embodiments where improved sealing of the base contact surface is required, a vibration damping gasket 19 may also be provided between the contact surface of the insulating mounting base 9 and the stator base housing 1. The vibration damping gasket 19 may be made of silicone rubber, fluororubber, or EPDM rubber to adapt to vibration, moisture, and oil mist environments.

[0037] The transmission path uses a double-shielded transmission cable 10, preferably laid along a path away from strong interference sources 8, and avoids long-distance parallel laying with high-current cables. When crossing is unavoidable, the crossing angle between the double-shielded transmission cable 10 and the high-current cable is set to 60-90 degrees. The double-shielded transmission cable 10 is grounded at a single point only on the synchronous acquisition unit 11 side to reduce the influence of mechanical vibration, moisture, oil mist, and common-mode current on the detection results; the grounding end is a single-point grounding terminal 21. If necessary, a pre-conditioning unit 22 is set at the antenna lead-out end, and the distance between the pre-conditioning unit 22 and the corresponding antenna lead-out end is no greater than 1D. The pre-conditioning unit 22 includes at least one of a limiting protection circuit, a 300MHz-3000MHz bandpass filter circuit, and a low-noise amplification circuit, used for limiting protection, 300MHz-3000MHz bandpass filtering, or low-noise amplification.

[0038] Each antenna is connected to the pre-conditioning unit 22 and the synchronous acquisition unit 11 via a double-shielded transmission cable 10. The output of the synchronous acquisition unit 11 is connected in sequence to the interference suppression and identification module 13, the positioning analysis unit 12 and the monitoring terminal 23.

[0039] The synchronous acquisition unit 11 includes a unified clock source, a synchronous trigger circuit, a multi-channel analog-to-digital converter circuit, and a channel buffer circuit. Each monitoring UHF antenna channel and the interference reference UHF antenna channel share the same clock source. The synchronous acquisition unit 11 performs unified time-stamp acquisition on all monitoring UHF antennas 6 and interference reference UHF antennas 7, with a sampling rate of no less than 2 GS / s and an inter-channel time-stamp error of no more than 2 ns. After installation, the cable delay, amplitude gain, and phase response of each channel are calibrated using the same calibration pulse, and a reference interference template is established during normal generator operation or periods without significant partial discharge.

[0040] The interference suppression and identification module 13 performs bandpass filtering, envelope extraction threshold triggering, normalized cross-correlation calculation, time-of-arrival (TOA) calculation, and cross-channel amplitude ratio calculation on the synchronously acquired signal. The threshold is the mean background noise plus 4-8 times the standard deviation. Subsequently, within a preset time window, the normalized cross-correlation coefficient, TOA, and amplitude ratio between the interference reference UHF antenna 7 and each monitoring UHF antenna 6 are calculated. When the interference reference UHF antenna 7 receives a pulse with a waveform correlation coefficient of not less than 0.6 before or simultaneously with multiple monitoring UHF antennas 6, and this pulse repeatedly appears in the direction corresponding to the strong interference source 8, it is marked as on-site operational interference. When multiple monitoring UHF antennas 6 exhibit a stable spatial TOA, and the correlation coefficient with the interference reference UHF antenna 7 is less than 0.6, it is retained as a candidate signal for stator bar partial discharge and sent to the positioning analysis unit 12.

[0041] The positioning analysis unit 12 outputs information on suspected discharge stator bar areas and trends based on the installation coordinates of each monitoring UHF antenna 6 and the mapping relationship between the stator bar areas, using either time-of-arrival (TOA) positioning or zone-weighted scoring. The positioning analysis unit 12 stores the installation coordinates, main sensitive direction, and corresponding stator bar area mapping table for each monitoring UHF antenna 6, and performs zone-weighted scoring based on the earliest arrival channel, the channel with the largest amplitude, the cross-layer amplitude attenuation relationship, and the time-of-arrival. When the number of effective channels is no less than four, the positioning analysis unit 12 uses least-squares TOA positioning to calculate the suspected discharge location and maps the calculation results to the upper end, slot, lower end, lead-out connection area, or neutral point connection area. The monitoring terminal 23 outputs information on suspected discharge stator bar areas, trends, and early warning information.

[0042] Another embodiment of this application discloses a method for detecting partial discharge in the stator bars of a hydro-generator. This method is based on the aforementioned partial discharge detection array for the stator bars of a hydro-generator and includes the following steps: S1. Establish axial-circumferential installation coordinates with the generator shaft direction and the frame circumference direction, and conduct surveys on the installation area on the outer surface of the stator frame housing 1, the sensitive area for partial discharge signal leakage of stator bars, and the distribution of strong interference sources on site.

[0043] S2. Divide the key monitoring area at the end of the bar into 14, the key monitoring area in the bar slot into 15, the interference prohibition area, and the reference arrangement area into 16, and determine the installation coordinates, layer, and orientation of each antenna.

[0044] S3. Complete the fixing of the insulating mounting base 9, antenna installation, laying of double-shielded transmission cable 10, and single-point grounding connection.

[0045] S4. Perform clock synchronization, cable delay calibration, amplitude and phase consistency calibration, and establish reference interference templates for each channel.

[0046] S5. Collect pulse signals from each channel and use the synchronous response relationship between the interference reference UHF antenna 7 and the monitoring UHF antenna 6 to suppress on-site operational interference.

[0047] Specifically, when the interference reference UHF antenna 7 receives pulses of the same shape before or simultaneously with multiple monitoring UHF antennas 6, and the normalized cross-correlation coefficient is not less than 0.6, and the pulse repeatedly appears in the direction corresponding to the strong interference source, it is determined to be on-site operational interference. When multiple monitoring UHF antennas 6 exhibit a stable spatial arrival time difference, the normalized cross-correlation coefficient between the interference reference UHF antenna 7 channel and the monitoring UHF antenna 6 channel is less than 0.6, and the earliest arriving channel or the channel with the largest amplitude is located in the key monitoring area 14 at the end of the stator bar or the key monitoring area 15 in the stator bar slot, it is determined as a candidate signal for partial discharge of the stator bar, and the suspected discharge bar partition is determined by combining the stator bar area corresponding to each monitoring UHF antenna 6.

[0048] S6. Perform arrival time difference localization and zonal mapping analysis on the screened candidate pulses, and output the suspected discharge stator bar region and early warning results.

[0049] The core of the solution proposed in this application is not the shape of a single sensor, but the array arrangement logic of the outer surface facing the partial discharge detection target of the stator bar and the reproducible synchronous acquisition, interference identification and partition positioning methods.

[0050] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A partial discharge detection array for a hydroelectric generator stator bar, characterized by, The stator housing includes a stator frame housing (1), multiple monitoring UHF antennas (6) and at least one interference reference UHF antenna (7). The outer surface of the stator frame housing (1) is divided into a key monitoring area (14) at the end of the bar, a key monitoring area (15) at the groove of the bar, an interference ban area and a reference arrangement area (16). Multiple monitoring UHF antennas (6) are arranged in the key monitoring area (14) at the end of the bar, the key monitoring area (15) at the groove of the bar and the corresponding area of ​​the bar lead-out connection channel. The reference UHF antenna (7) is arranged in the reference arrangement area (16) and faces the strong interference source. The monitoring UHF antenna (6) and the interference reference UHF antenna (7) are connected in sequence to a synchronous acquisition unit (11), an interference suppression and identification module (13), a positioning analysis unit (12), and a monitoring terminal (23).

2. The hydrogenerator stator bar partial discharge detection array of claim 1, wherein, The key monitoring area (14) at the end of the stator bar is located on the outer side of the upper end, the outer side of the lower end, the outer side of the bar lead-out connection area, or the outer side of the neutral point bar connection area, and is projected onto the housing of the base. It extends 0.5D-2D to both sides along the axial direction, where D is the maximum external dimension of a single monitoring UHF antenna. The key monitoring area (15) of the bar groove is located on the projection area of ​​the groove ventilation opening, the core ventilation window, the air gap above the groove wedge, or the leakage sensitive position of the middle groove of the core on the machine base shell, and extends 0.5D-2D to both sides along the axial direction.

3. The partial discharge detection array for stator bars of a hydro-generator according to claim 2, characterized in that, The interference ban zone is a region that is less than 2D-5D away from a strong interference source or has an angle of less than 30 degrees between the direction directly opposite the strong interference source and the main sensitive direction of the monitoring UHF antenna (6). The reference arrangement area (16) is located near the source of strong interference, but avoids the location of the end air gap, slot opening and the direct line-of-sight path of the lead-out connection channel of the bar.

4. The partial discharge detection array for stator bars of a hydro-generator according to claim 3, characterized in that, The multiple monitoring UHF antennas (6) are respectively set in the upper rod monitoring layer (2) and the lower rod monitoring layer (3). The upper rod monitoring layer (2) and the lower rod monitoring layer (3) are both axially arranged strips extending circumferentially on the outer surface of the stator frame housing (1). The axial distance between the upper end bar monitoring layer (2) and the outer projection center line of the upper end face of the stator core or the upper end winding is not greater than D, and the axial distance between the lower end bar monitoring layer (3) and the outer projection center line of the lower end face of the stator core or the lower end winding is not greater than D. The monitoring UHF antenna (6) is set in the overlapping area of ​​the corresponding monitoring layer and the key monitoring area (14) at the end of the bar or the key monitoring area (15) at the groove of the bar.

5. The partial discharge detection array for stator bars of a hydro-generator according to claim 4, characterized in that, The circumferential angle between any two adjacent monitoring UHF antennas (6) is set to 30 degrees to 120 degrees; The axial spacing between the upper bar monitoring layer (2) and the lower bar monitoring layer (3) is set to 2D-10D, and the upper bar monitoring layer (2) and the lower bar monitoring layer (3) are offset by 10-60 degrees in the circumferential direction.

6. The partial discharge detection array for stator bars of a hydro-generator according to claim 5, characterized in that, The monitoring UHF antenna (6) and the interference reference UHF antenna (7) are fixed to the outer surface of the stator frame housing (1) by an insulating mounting base (9); Both the monitoring UHF antenna (6) and the interference reference UHF antenna (7) include antenna elements (20), which are disposed inside the radome (17); The monitoring UHF antenna (6) and the interference reference UHF antenna (7) are provided with a metal shielding shell (18) on the circumferential or opposite side of the strong interference source; a vibration damping sealing gasket (19) is provided between the insulating mounting base (9) and the wire lead-out position of the double-layer shielded transmission cable (10). A vibration damping sealing gasket (19) is provided between the contact surface of the insulating mounting base (9) and the stator frame housing (1).

7. The partial discharge detection array for stator bars of a hydro-generator according to claim 6, characterized in that, The monitoring UHF antenna (6) and the interference reference UHF antenna (7) are connected to the synchronous acquisition unit (11) through a double-shielded transmission cable (10); The double-shielded transmission cable (10) is laid along a path away from strong interference sources and avoids being laid parallel to high-current cables for long distances.

8. The partial discharge detection array for stator bars of a hydro-generator according to claim 7, characterized in that, A pre-conditioning unit (22) is provided at the antenna lead-out end of the monitoring UHF antenna (6) and the interference reference UHF antenna (7), and the distance between the pre-conditioning unit (22) and the corresponding antenna lead-out end is not greater than 1D; The pre-conditioning unit (22) includes at least one of a limiting protection circuit, a bandpass filter circuit, and a low-noise amplifier circuit.

9. A method for detecting partial discharge in the stator bars of a hydro-generator, characterized in that, The partial discharge detection array for the stator bars of a hydro-generator, based on any one of claims 1-8, includes the following steps: S1. Establish axial-circumferential installation coordinates with the generator shaft direction and the frame circumference direction, and conduct surveys on the installation area of ​​the stator frame outer surface, the sensitive area of ​​partial discharge signal leakage of stator bars, and the distribution of strong interference sources on site. S2. Divide the key monitoring area at the end of the antenna bar, the key monitoring area in the slot of the antenna bar, the interference prohibition area, and the reference arrangement area, and determine the installation coordinates, layer, and orientation of each antenna; S3. Complete the fixing of the insulating mounting base, antenna installation, laying of double-shielded transmission cables, and single-point grounding connection. S4. Perform clock synchronization, cable delay calibration, amplitude and phase consistency calibration, and establish reference interference templates for each channel; S5. Collect pulse signals from each channel and use the synchronization response relationship between the interference reference UHF antenna and the monitoring UHF antenna to suppress on-site operational interference; S6. Perform arrival time difference localization and zonal mapping analysis on the screened candidate pulses, and output the suspected discharge stator bar region and early warning results.

10. The method for detecting partial discharge of stator bars in a hydro-generator according to claim 9, characterized in that, S5 includes: When the interference reference UHF antenna receives pulses of the same shape before or simultaneously with multiple monitoring UHF antennas, and the normalized cross-correlation coefficient is not less than 0.6, and the pulse repeatedly appears in the direction corresponding to the strong interference source, it is determined to be field operation interference. When multiple monitoring UHF antennas exhibit a stable spatial time of arrival, the normalized cross-correlation coefficient between the interference reference UHF antenna channel and the monitoring UHF antenna channel is less than 0.6, and the earliest arriving channel or the channel with the largest amplitude is located in the key monitoring area at the end of the stator bar or the key monitoring area in the slot of the stator bar, it is determined as a candidate signal for partial discharge of the stator bar, and the suspected discharge bar partition is determined by combining the stator bar area corresponding to each monitoring UHF antenna.

Images