1 Overview The monitoring of the operation status of hydropower generating units of hydropower stations is an important way to improve the safety and reliability of the unit operation, reduce maintenance costs and improve economic benefits. The main parameters reflecting the operating state of the unit are temperature, vibration, swing, stator and rotor current, voltage and so on. The monitoring of temperature and electricity has been paid more and more attention. It is generally found in the computer monitoring system of hydropower stations, and there are mature technologies, and the monitoring of vibration and swing is not in the monitoring of many hydropower plants. However, in the operation of the hydro-generator set, due to various reasons (such as electrical, mechanical and hydraulic factors), the pendulum and vibration of the unit may be too large or even exceed the standard, and sometimes the resonance may be induced and the vibration of some components may be intensified. In severe cases, the safe operation of the unit will be jeopardized. Therefore, it is necessary to monitor the swing and vibration of the hydro-generator unit during operation.
The vibration problem of the hydro-generator set is different from that of the general power machine. The vibration of the unit is due to the action of the fluid (water flow through the runner), the mechanical and electromagnetic interactions, and the vibration of the unit is often mechanical. The coupling vibration of electric and fluid is very complicated to study the vibration of the unit according to the coupling relationship of the three. It is difficult to establish a mathematical model for analysis and calculation. In practice, it is often caused by the typical experience accumulated by hydropower stations. The vibration source is divided into mechanical, hydraulic and electrical factors, and the different types of vibration caused by the three vibration sources are analyzed and calculated.
In recent years, based on PC microcomputers, the system of monitoring and analyzing the vibration and swing of the unit by using vibration sensors has been successively introduced, and significant economic and social benefits have been achieved. Such as the VIMOS system in Sweden, the COMPASS system in Spain, and the IMPULS system in Norway. There are also many units in China that are researching and developing unit vibration monitoring systems. On the basis of absorbing the characteristics of relevant devices at home and abroad, we have developed an online monitoring and analysis system for the vibration of hydroelectric generating sets. It takes the industrial PC as the main body, takes the vibration signal processing and analysis software as the core, and connects with the vibration, swing and pressure pulsation sensors installed in the tested part to form the unit vibration online monitoring and analysis system. Through the periodic monitoring of the unit vibration, it is possible to continuously monitor the changes of the unit vibration on-line, so as to provide a scientific basis for the safe operation and system scheduling of the unit to achieve AGC and AVC functions. At the same time, the vibration online monitoring and analysis system can correctly provide the slow change process of the unit defects, and provide a reliable information basis for the state maintenance.
2 system configuration and composition 2.1 hardware system composition The overall simplified block diagram of the vibration monitoring and analysis system hardware is shown in Figure 1.
To meet the requirements of 0.4/ 11 ± 5 kV. The transformer with this voltage ratio is selected as the main transformer, and its output voltage is higher than the output voltage of the main transformer using the common transformer. Therefore, the operating voltage of the generator can be reduced back to its rated value, and the operating power factor of the generator is also Can be restored to the rated value. It not only improves the operating conditions of the generator and the main transformer, but also generates reactive power.
2.2 The rural hydropower stations that have been put into operation are a good way to increase the number of windings on the high-voltage side of the transformer for such old power plants that have already been put into operation. Generally, the number of turns of the original winding is increased to 10, and after the number of turns is increased, the taps of the 3rd gear (5, 0, 5) should be changed as required.
The increase in the number of turns of the high-voltage side winding of the transformer should be carried out as follows. The sling measurement is first performed, and the increased enthalpy value is finally determined depending on the spatial margin of the measurement result. If the space position can be installed with 10 turns of the original winding turns, it is limited to 10 of the original number of turns. If the space position can not be installed 10 of the original winding turns, it should try to use the space position to strive to increase the number of turns. If the spatial position margin is too small and it is difficult to increase the number of winding turns, the step-up transformer with a voltage ratio of 0.4/11±5 kV should be re-selected for the main transformer of the power station.
3 Conclusion Rural hydropower stations can use remedial measures according to their specific conditions, which can overcome the shortcomings of power station's reactive power shortage, improve the operating conditions of generators and main transformers, and improve the safety and economy of rural hydropower stations.
In addition, the author suggests that the relevant research and production units should develop a series of step-up transformers of 10 kV voltage level to meet the needs of rural hydropower stations, and also fill the blank of the series of transformers.
[Author] Zhao Lingqi, male, senior engineer (Editor: Xu Zhanguo) alarm contact output 4-way relay output fast high-precision A/D conversion card IPC610P industrial computer transmitter signal pre-processing board downstream water level transmitter upstream water level transmitter Active power transmitter vibration sensor swing sensor pressure pulsation sensor The entire hardware system consists of PC industrial computer, display, printer, A/D converter, signal pre-processing board, communication conversion module, relay alarm output module, swing, vibration sensor It is composed of pressure pulsation sensor, power transmitter and upstream and downstream water level transmitter.
Among them, 6 swing sensors (ie, eddy current contact sensors) are used to monitor the large axis swing of the upper, lower and water guides, respectively. 4 vibration sensors can be selected (the magnetoelectric speed sensor or piezoelectric type can be selected according to the actual situation). Acceleration sensor) is used to monitor the vibration of the genset frame and the turbine top cover. 2 pressure sensors are used to monitor the pressure pulsation in the draft tube. In addition, in order to facilitate the analysis of the relationship between vibration and output, working head and downstream water level, it is also necessary to pass the active power, upstream water level and downstream water level of the unit through their corresponding transmitters (these transmitters are already in the monitoring system of the power station). Installation) Introducing the vibration monitoring and analysis system.
Since the detected vibration signals are useful, and some may be superimposed interference signals, some signals may be strong, and some signals may be weak. Therefore, it is usually necessary to perform some conditioning on the detected signals. The signal pre-processing board is used to complete the work. At the same time, since the vibration signal requires fast sampling and high detection accuracy, the vibration signal acquisition requires the use of a fast and high-precision A/D conversion card.
For the active power of the unit and the upstream and downstream water levels, it is relatively slow signal. Therefore, the ADAM Adam module of Taiwan Advantech Co., Ltd. (ie 8 A/D transmitter ADAM 4017) can be used for A/D conversion and then passed. The Adam module ADAM 4520 (ie RS232/ RS485 communication conversion module) realizes communication with the industrial computer. For the vibration over-limit signal, the Adam module ADAM 4060 with 4 relay outputs can be output as an alarm signal.
The PC industrial computer is the core part of the unit vibration monitoring and analysis system. It can be used as the whole system of the IPC610P industrial computer of Taiwan Advantech Co., Ltd. (usually equipped with more than 16M memory, 1.2 G or more hard disk, Pentium microprocessor with a frequency of 166 MHz or higher). The data processor is equipped with a display of 14 inches or more as a real-time display of the vibration of the unit, and a printer as a graphic output tool.
2.2 Selecting the sensor The correct selection of the vibration sensor is a prerequisite for ensuring reliable and correct operation of the unit vibration monitoring and analysis system. According to the results of expert research, the vibration of mechanical equipment can generally be measured by direct measurement or indirect measurement, but the indirect measurement method may cause signal distortion and certain errors. Therefore, in most cases it is advisable to use a direct measurement method. The eddy current sensor can provide a reliable unit large-axis swing state parameter than the speed sensor or the acceleration sensor. Therefore, it is very effective to directly monitor the swing of the large shaft by using the eddy current sensor. Therefore, the slewing sensor can be selected from an eddy current type contact sensor. In this regard, there are many stereotyped products available at home and abroad. A variety of eddy current sensors such as the 3300 and 3301 series produced by the famous American Bentley Company, the PR6422 and PR6423 of the German Phillips Company, and the SD05 series of the German Schenck Company are widely used. There are various products such as 8505 developed by Tsinghua University's Fine Instrument Department, 85811 series products developed by Beijing Vibration Instrument Factory, and CWYD0 series products produced by Zhuhai Tianrui Company (namely, the 608th Research Institute of the former Aerospace Department).
For the vibration of the fixed parts of the unit, a magnetoelectric speed sensor or a piezoelectric acceleration sensor can usually be used for direct measurement. When measured with a speed sensor, the absolute motion of the measured vibrating component relative to the earth or inertial space can be measured. Therefore, the speed sensor is usually called an inertial sensor (or a seismic sensor, which can also be called an absolute sensor). The measured signal is the vibration speed of the component to be tested. After integration, the vibration amplitude of the vibration component can be obtained. The signal measured by the acceleration sensor is the acceleration of the vibration of the component under test. After one integration, the vibration velocity can be obtained. After the second integration, the vibration amplitude of the component to be tested can be obtained. Speed ​​sensors and accelerometers have their own characteristics, and they are used in mechanical vibration measurement. The magnetoelectric speed sensor is characterized in that the sensor body does not need a power source, has a simple structure and high sensitivity, can measure a small vibration output signal, has stable electrical characteristics, is free from external noise interference, and has no special requirements for the rear power supply, and has a limited dynamic range. The size and weight are larger than the acceleration sensor, and the spring member is relatively easy to fail. The piezoelectric accelerometer has the advantages of small size, light weight, high sensitivity and wide frequency range, and thus has been widely used. However, since the piezoelectric accelerometer is composed of electromechanical conversion elements, its performance changes with time or other factors, so the sensitivity, frequency characteristics, and dynamic linear range are recalibrated once after a certain period of use. In this respect, the acceleration sensor of Danish BK Company is an international famous brand product. The domestic Jiangsu Yangzhou Radio 2 Factory, Beijing Vibration Instrument Factory and Beidaihe Radio Factory also produce a variety of piezoelectric acceleration sensors and the Institute of Engineering Mechanics of the State Seismological Bureau. Tsinghua University's Fine Instrument Department has developed the 891 and DP seismic low-frequency vibration speed sensors. Therefore, the vibration measurement of the fixed parts of the unit can be selected according to the actual situation using an acceleration sensor or a speed sensor. The pressure pulsation of the draft tube can be selected with the relevant pressure transmitter.
In addition, special attention should be paid to the frequency response and dynamic range of the sensor when determining the specific types of sensors. Practice has shown that the frequency of the vibration and the fault diagnosis of the hydro-generator set is usually between 1/4 and 10 times. Therefore, the frequency response range of the selected sensor should be greater than the vibration of the device under test. The frequency range requires high detection accuracy.
3 software system 3.1 system signal and data processing flow The vibration and analysis system signal and data processing flow diagram is shown in Figure 2. The signal detected by the unit vibration sensor, the swing sensor and the pressure pulsation sensor is conditioned by the signal processing board, and then converted into a digital signal by a fast high-precision A/D conversion card and sent to the industrial computer. The unit active power, upstream and downstream water level signals are also sent to the industrial computer after A/D conversion at low speed (relative to high-speed A/D conversion). The industrial computer mainly performs data processing and analysis on the detected signals, including digital filtering, digital integration, FFT spectrum analysis, frequency domain time domain analysis, vibration waveform and large swing trajectory graphics processing and display, vibration and Swing amplitude amplitude water wheel generator vibration monitoring and analysis system Cai Wei by Chen Guangda Cheng Yuanchu Xu Hanke Cai Tianfu real-time display print storage alarm output low speed A / D conversion data processing digital filtering digital integral FFT spectrum analysis frequency domain time domain analysis alarm logic drawing expert Processing system high-speed A / D conversion signal pre-processing unit active power upstream water level downstream water level slow signal fast signal vibration sensor swing sensor pressure pulse sensor display, and over-limit alarm logic processing and print output.
3.2 System Software The software of this vibration monitoring and analysis system is modularized according to function. The functional modular structure of the whole software system is shown in Figure 3. When the system is started, you can select continuous or controlled measurements through the options window, as well as the channel rate (before commissioning).
The entire software system is actually a complex expert processing system. After the software system various data processing, FFT spectrum analysis and frequency domain time domain analysis of the vibration signal, according to the spectrum characteristics, amplitude time characteristics and three-axis large axis swing trajectory waveform processing and drawing for display and printout And alarm the over-limit signal.
When the system is in continuous monitoring, the next level of function modules can be selected through the keyboard, and so on, so that the spectrum characteristics, time amplitude characteristics and three-axis large-axis swing of the unit vibration, swing and pressure pulsation can be observed through the display. Track maps, etc.
4 System function The main functions of this vibration monitoring and analysis system are continuous monitoring and controlled measurement.
4.1 Continuous monitoring Continuous monitoring is the main function of the system to monitor the vibration of the unit during operation. It can be used to monitor and display the amplitude of the swing at each guide bearing of the unit, the vibration amplitude of the generator frame and the turbine top cover, the pressure fluctuation amplitude of the draft tube, and the three-axis swing of the display and printout. Trajectory, pendulum, vibration, spectral characteristics of pressure pulsation and time domain value characteristics.
4.2 Controlled Measurements There are two types of controlled measurements, where controlled measurement 1 refers to the monitoring of the operating conditions of interest or the vibration of the unit during a certain period of time under human control. When this function is selected, the system will automatically scan and collect the unit's vibration, swing information and draft tube pressure pulsation and form a data file, which can be displayed, stored or copied for off-line analysis.
Controlled measurement 2 refers to recording the vibration of the unit within a preset period of time (that is, the number of records can be set by the number of records) (generally, it is known in advance that the vibration of the unit is stronger, and the Measured, and at this time, the recorded file (not the data file) is collected, but the recorded file can be converted into a data file by reading back, and then converted into the observed recording waveform by the oscilloscope function. When you save the copy, you can perform offline analysis.
5 Conclusion The system is a vibration monitoring and analysis system designed and optimized based on the vibration monitoring and analysis system of the unit at home and abroad. It has complete functions, good work stability, convenient channel rate, and can be used as long-term real-time continuous monitoring, as well as a variety of detection functions such as controlled measurement of specific vibration conditions. Cooperating with the monitoring system, it can be used as the unit condition monitoring device of the unattended (small-management) power station, providing reliable guarantee for the safe operation of the power station and providing a reliable theoretical basis for the state maintenance of the unit, thus having broad application prospects.
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