CN1204410C - Ultrasonic reflection detecting device and mehtod for diagnosis of insulation state of stator for large electric generator - Google Patents

Abstract

The present invention discloses an ultrasonic reflection detecting device and a method thereof for the diagnosis of the insulation state of stators for a large electric generator, which is used for measuring ultrasonics characteristic parameters of the stator insulation for the large electric generator. The insulation aging state is diagnosed by detecting insulation internal defects. The detecting device of the present invention comprises couplant agents, an ultrasonic straight beam probe, an ultrasonic wave generating and receiving device, a data collecting card and a notebook computer, and all component parts are mutually connected through coaxial cables or data transmission lines. The present invention can measure the ultrasonics characteristic parameter of the stator insulation of motors (300MW, 18kv)which are used within 23 years under background noise of a generator site 90dB(A), and measured minimum size of the insulation defects is 0.9mm. The volume of the main body part of the present invention relates to 150mm*150mm*100mm, the weigh is 2.5kg, and the aims of small type and portability are achieved. The device has the advantages of strong interference proofing performance, high accuracy, fast data processing, portability, etc., and is particularly for the on-site detection of the aging condition of the stator insulation of the large electric generator.

Description

Ultrasonic reflection detection device and method for large generator stator insulation state diagnosis

1. Technical field

The invention belongs to the technical field of motors, and relates to a diagnosis technology of motor stator insulation aging state, in particular to an ultrasonic reflection detection device and method for diagnosing the insulation state of a large generator stator.

2. Background technology

After searching, so far, there is no literature report on the use of ultrasonic reflection method for large-scale generator stator insulation detection, and there are no other hardware systems and methods for on-site diagnosis of large-scale generator stator insulation aging state using ultrasonic reflection method. The document report of software system, and the document relevant to the present invention also has only the prophase research article that the inventor of this application publishes before this application, and one is " the research of supersonic velocity of epoxy mica stator insulation of large electric machine ", mainly discusses Using the A-type pulse-echo method ultrasonic testing system, the influence of different insulation parts of the stator bar of a large motor on the detection of ultrasonic velocity, and the variation of wave velocity with insulation aging are studied. The second is "Study on the Aging Characteristics of Stator Insulation of Large Motors Based on Partial Discharge and Ultrasonic Method"; it mainly carried out multi-factor accelerated aging tests on the replacement wire rods of Jiangsu Jianbi Power Plant No. 7 (18KV, 300MW), and the different aging stages of the wire rods The results of partial discharge and ultrasonic sound velocity tests were carried out.

At present, the commonly used method for diagnosing the aging state of stator insulation of large generators is partial discharge measurement. The application of ultrasonic reflection detection technology in insulation detection has ultrasonic detection devices for internal defects of composite insulation such as bushings, transformers, switch cabinets and cables. This device includes displacement sensor, ultrasonic sensor, reference displacement element, displacement electronic component, ultrasonic flaw detector, RS232 interface, PC and color display, etc., and can perform color C-scan on defects.

Although partial discharge measurement is a commonly used method for diagnosing the insulation state of large generator stators, this method is easily affected by field electromagnetic waves and power system harmonics, and its accuracy is affected to a certain extent.

The ultrasonic reflection method used in the detection methods and systems of bushings, transformers, switch cabinets and cables, etc. has the following deficiencies: 1. The frequency of the ultrasonic sensor is 5-15MHz. For the stator insulation of large generators with a large attenuation coefficient, the frequency is so high The ultrasonic wave has been attenuated before the useful signal is detected, so the existing detection methods and systems are not suitable for the detection of large generator stator insulation. 2. What is obtained on the display of the ultrasonic flaw detector is the ultrasonic wave after wave detection, and only shows part of the waveform greater than or less than zero. This distorted waveform cannot study the changes in important parameters such as the frequency of ultrasonic wave propagation in the material, so it is lost. Information on the microstructure or texture changes of many materials. 3. This device can only detect insulation defects, and cannot evaluate the aging state of non-defective insulation before defects occur. 4. Too many components of the device, coupled with the use of ultrasonic flaw detectors, make the entire detection device heavy and unsuitable for on-site detection applications.

3. Contents of the invention

In view of the defects or deficiencies in the above-mentioned prior art, the present invention aims to develop an ultrasonic reflection detection device suitable for the diagnosis of the insulation state of a large generator stator and a method for diagnosing the insulation state of a large generator stator using the device. This detection method can achieve the following purposes: 1. It is suitable for the status diagnosis of the stator insulation of large generators; 2. It can detect the ultrasonic reflection full wave that propagates in the stator insulation and is emitted at the stator insulation-copper conductor interface or at the insulation defect. Waveform, to ensure all the information of the microstructural changes of the insulating material carried in the ultrasonic waves; 3. Not only can it detect insulation defects, but it can also diagnose the aging state of the (non-defective) insulation before the insulation defect occurs, so as to predict sudden and rapid development. The appearance of the most dangerous insulation crack; 4. The entire detection device meets the requirements of on-site detection.

The essence of sound wave propagation is the interaction of medium molecules, so the propagation of sound waves (such as ultrasonic propagation parameters and sound wave propagation paths) depends to a large extent on the microscopic changes inside the medium. During the aging process of the stator insulation of large generators, the insulation swells, the insulation material becomes loose, and microscopic defects such as air gaps, delamination, shelling and cracks appear, so the propagation parameters or propagation paths of ultrasonic waves propagating in the stator insulation may be caused by insulation varies with the degree of aging.

Based on the above theories, the technical solution adopted by the present invention is an ultrasonic reflection method detection device for the diagnosis of the insulation state of a large generator stator, including a couplant, a straight ultrasonic probe with a frequency of 0.8 MHz, and a full-wave waveform output Ultrasonic generating and receiving device, a notebook computer, characterized in that the device also has a dual-channel sampling rate of 20Ms/S data acquisition card, wherein the notebook computer has special software; ultrasonic straight probe and ultrasonic generating and receiving device Between, the ultrasonic generation and receiving device and the data acquisition card are connected to each other through the coaxial cable, and the data acquisition card and the notebook computer are connected to each other through the data transmission line;

The ultrasonic generating and receiving device transmits a synchronous electric pulse with a frequency of 500kHz. On the one hand, the synchronous electric pulse is transmitted to the ultrasonic straight probe by the coaxial cable, and the piezoelectric chip in the probe is excited to vibrate to generate ultrasonic waves. The frequency of the ultrasonic wave is determined by the frequency of the ultrasonic straight probe. On the other hand, the synchronous electrical pulse is used as the scanning trigger signal of the data acquisition card after being triggered and delayed; the ultrasonic wave generated by the ultrasonic straight probe is vertically incident into the stator insulation of the test sample through the coupling agent, and propagates in the stator insulation; when the ultrasonic wave is in the stator insulation When a defect is encountered, it will be emitted at the interface, and the reflected wave will propagate backward in the stator insulation and be received by the ultrasonic straight probe that emits ultrasonic waves; after being received by the ultrasonic straight probe, the ultrasonic wave becomes an electrical pulse signal, which is generated by the ultrasonic wave and then received by the ultrasonic straight probe. After signal conditioning such as attenuation and amplification of the receiving device, it is digitized by the data acquisition card and sent to the special software of the notebook computer through the data transmission line, and the real-time display, storage and analysis of the ultrasonic data are completed by the software.

Another feature of the device of the present invention is that the coupling agent is vaseline or silicone grease.

The ultrasonic generating and receiving device is a flaw detector capable of outputting ultrasonic full waves.

The method for diagnosing the insulation state of a large generator stator using the above-mentioned ultrasonic reflection detection device for diagnosis of the stator insulation state of a large generator is characterized in that it is carried out in the following manner:

1) Carry out multi-point measurement of the stator insulation of different slots of the generator to be diagnosed, and judge whether the reflection interface type of the ultrasonic full-wave waveform is an insulation-copper interface or an insulation-air interface;

2) The ultrasonic full-wave waveform judged to be reflected by the insulation-copper interface is used to count the minimum and average values of the ultrasonic propagation parameters of the stator insulation for each slot;

3) The ultrasonic full-wave waveform judged to be reflected by the insulation-air interface is used to count the existence rate of defects in the stator insulation of each slot;

4) The minimum value and average value of the ultrasonic propagation parameters of the stator insulation obtained above and the defect existence rate of the stator insulation are respectively compared with the minimum ultrasonic sound velocity, average ultrasonic sound velocity and The existence rate of defects is compared, so as to achieve the purpose of diagnosing the insulation state.

Under the background noise of 90dB(A) at the generator operating site, this device can measure the changes of the ultrasonic characteristic parameters of the stator insulation of the generator (300MW, 18kV) after 0-23 years of operation, and the minimum size of the detected insulation defect is 0.9 mm for effective insulation state diagnosis. The integration of the ultrasonic generating and receiving device (6) and the data acquisition card (7) makes the main part of the system small and light, with a volume of about 150mm×150mm×100mm and a weight of 2.5kg. This system has the advantages of strong anti-interference, high accuracy, fast data processing, and portability. It is especially suitable for on-site diagnosis of the aging state of the stator insulation of large generators.

4. Description of drawings

What Fig. 1 shows is the ultrasonic pulse reflection method stator insulation detection device of the present invention;

In the figure, the representations of each symbol are: 1. The measured stator bar; 2. Coupling agent; 3. Ultrasonic straight probe; 4. Coaxial cable; 5. Ultrasonic generating and receiving device; 6. Data acquisition card; 7. Data transmission line; 8. Notebook computer.

Fig. 2 is a flowchart of the special software of the present invention.

5. Specific implementation

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments completed by the inventor according to the technical solution of the present invention.

Referring to the accompanying drawings, the ultrasonic reflection method detection device for the diagnosis of the insulation state of the large generator stator of the present invention includes a coupling agent 2 of vaseline or silicone grease, a frequency of 0.8MHz, an ultrasonic straight probe 3 with a diameter of 15mm, a Ultrasonic generating and receiving device 5 outputting full-wave waveform, a data acquisition card 6 with a dual-channel sampling rate of 20Ms/S, a notebook computer 8 with special software, ultrasonic straight probe 3 and ultrasonic generating and receiving device 5 The room, the ultrasonic generation and receiving device 5 and the data acquisition card 6 are connected to each other via a coaxial cable, and the data acquisition card 6 and the notebook computer 8 are connected to each other via a data transmission line;

1. The coupling agent 2 is to reduce the attenuation of the ultrasonic energy by the gas between the ultrasonic straight probe 3 and the measured sub-wire rod 1;

2. The frequency and diameter of the ultrasonic straight probe 3 must be suitable for the on-site inspection of the insulation of the stator bar of a large generator. One of the three spare ultrasonic straight probes with different frequencies and diameters can be selected to meet the needs of generator stators with different capacities. The need for ground insulation testing of wire rods with different thicknesses;

3. The ultrasonic straight probe 3 itself is equipped with a coaxial cable 4 integrated with the ultrasonic straight probe, and two 3m and one 15m long spare cables and connectors are also provided to meet the needs of various test distances on site;

4. Inside the virtual frame is an integrated ultrasonic generating and receiving device 5 and a data acquisition card 6, with a volume of about 150×150×100mm and a weight of 2.5kg;

5. Ultrasonic generating and receiving device 5 is a flaw detector capable of outputting full ultrasonic waves;

6. The data acquisition card 6 is a virtual oscilloscope, and its trigger signal is the electric pulse signal that the ultrasonic wave generation and the receiving device 5 produce to excite the ultrasonic straight probe 3 to generate the ultrasonic wave, so the data acquisition card 6 is controlled by the notebook computer 8 through the data transmission line 7, It can display the transmitted wave of the system ultrasonic wave and the reflected wave when propagating in the insulation in real time, and the accuracy of the propagation time has reached 0.5ns.

The working principle of the ultrasonic reflection method detection system for the diagnosis of the stator insulation state of a large generator is as follows: the ultrasonic generating and receiving device 5 transmits a synchronous electric pulse with a frequency of 500 kHz, and the synchronous electric pulse is transmitted from the coaxial cable 4 to the ultrasonic straight probe 3 on the one hand. The vibration of the piezoelectric wafer in the excitation probe generates ultrasonic waves, and the frequency of the ultrasonic waves is determined by the frequency of the ultrasonic straight probe 3; the synchronous electric pulse is used as the scanning trigger signal of the data acquisition card 6 (virtual oscilloscope) after trigger delay on the other hand. The ultrasonic wave generated by the ultrasonic straight probe 3 is vertically incident into the stator bar (insulation) of the test object 1 through the coupling agent 2, and propagates in the stator insulation. When the ultrasonic wave propagates in the stator insulation and encounters a defect (insulation-air interface) or a copper conductor (insulation-copper conductor interface), it will be emitted at the interface, and the reflected wave will propagate backwards in the stator insulation, and will be emitted by the The ultrasonic wave is received by the ultrasonic straight probe 3 . After being received by the ultrasonic straight probe 3, the ultrasonic wave becomes an electric pulse signal. After signal conditioning such as ultrasonic wave generation and attenuation and amplification by the receiving device 5, it is digitized by the data acquisition card 6 and sent to the special software of the notebook computer 8 through the data transmission line 7 to complete the ultrasonic wave. Real-time display, storage and analysis of data and other processing.

The flow chart of this special software is shown in Fig. 2.

The method for diagnosing the insulation status of large generator stators with ultrasonic reflection detection technology is as follows: use the ultrasonic reflection detection system for the diagnosis of large generator stator insulation status, and conduct multi-point measurement of the stator insulation of different slots of the generator to be diagnosed, and judge the ultrasonic completeness. Whether the reflective interface type of the wave waveform is an insulation-copper interface or an insulation-air interface. The ultrasonic waveform judged to be reflected by the insulation-copper interface is used to count the minimum and average values of the ultrasonic propagation parameters of the stator insulation for each slot; the ultrasonic waveform judged to be reflected by the insulation-air interface is used to count the defect existence rate of the stator insulation for each slot . These stator insulation ultrasonic parameters obtained are compared with the threshold values of corresponding ultrasonic parameters of different insulation aging states in the database of the special software of the notebook computer (8), so as to achieve the purpose of diagnosing the insulation state.

Claims (4)

1. An ultrasonic reflection detection device for the diagnosis of the stator insulation state of a large generator, including a couplant [2], a straight ultrasonic probe [3] with a frequency of 0.8 MHz, and an ultrasonic generator and receiver capable of outputting full-wave waveforms Device [5], a notebook computer [8], it is characterized in that, the device also has a data acquisition card [6] with a dual-channel sampling rate of 20Ms/S, wherein the notebook computer [8] has special software; The probe [3] and the ultrasonic generating and receiving device [5], the ultrasonic generating and receiving device [5] and the data acquisition card [6] are connected to each other via the coaxial cable [4], and the data acquisition card [6] and Notebook computers [8] are connected to each other via data transmission lines [7]; The ultrasonic generating and receiving device [5] transmits synchronous electric pulses with a frequency of 500kHz. On the one hand, the synchronous electric pulses are transmitted from the coaxial cable [4] to the ultrasonic straight probe [3], which excites the vibration of the piezoelectric chip in the probe to generate ultrasonic waves. The frequency is determined by the frequency of the ultrasonic straight probe [3]; on the other hand, the synchronous electric pulse is used as the scanning trigger signal of the data acquisition card [6] after the trigger delay; the ultrasonic wave generated by the ultrasonic straight probe [3] is passed through the coupling agent [2] It is vertically incident into the stator insulation of the test product [1] and propagates in the stator insulation; when the ultrasonic wave propagates in the stator insulation, it will be emitted at the interface when it encounters a defect, and the reflected wave will propagate in the reverse direction in the stator insulation, and will be emitted by the The ultrasonic straight probe【3】receives the ultrasonic wave; the ultrasonic wave becomes an electric pulse signal after being received by the ultrasonic straight probe【3】, and after the ultrasonic generation and receiving device【5】attenuates and amplifies the signal conditioning, it is digitized by the data acquisition card【6】, Through the data transmission line [7], it is sent to the special software of the notebook computer [8], and the real-time display, storage and analysis processing of the ultrasonic data are completed by the software. 2. The ultrasonic reflection detection device for the diagnosis of insulation state of large generator stators according to claim 1, characterized in that the coupling agent [2] is vaseline or silicone grease. 3. The ultrasonic reflection detection device for diagnosis of insulation state of large generator stators according to claim 1, characterized in that the ultrasonic generating and receiving device [5] is a flaw detector capable of outputting full ultrasonic waves. 4. The method for diagnosing the insulation state of a large generator stator using the ultrasonic reflection method detection device for the diagnosis of the insulation state of the large generator stator according to claim 1 is characterized in that, it is carried out in the following manner: 1) Carry out multi-point measurement of the stator insulation of different slots of the generator to be diagnosed, and judge whether the reflection interface type of the ultrasonic full-wave waveform is an insulation-copper interface or an insulation-air interface; 2) The ultrasonic full-wave waveform judged to be reflected by the insulation-copper interface is used to count the minimum and average values of the ultrasonic propagation parameters of the stator insulation for each slot; 3) The ultrasonic full-wave waveform judged to be reflected by the insulation-air interface is used to count the existence rate of defects in the stator insulation of each slot; 4) The minimum value and average value of the ultrasonic propagation parameters of the stator insulation obtained above and the defect existence rate of the stator insulation are respectively compared with the minimum ultrasonic sound velocity, average ultrasonic sound velocity and The existence rate of defects is compared, so as to achieve the purpose of diagnosing the insulation state.

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