Monitor And Diagnose Of Cavitation In Hydroturbine

In recent years,large-scale hydropower project make the important role in the entire electrica network on account of large percentage of the annual average electric energy production.As a result ,the accident of the hydroturbine will result in the most serious economic losses.Stability is an important condition for ensuring the safety and reliability of hydroelectricity generating units. Cavitation is one of the main factors affecting the stable operation of the generating units.Therefore it is necessary to carry out cavitation monitoring for timely adjustment of the unit operation to take effective measures to reduce the emersion of the cavitation, for example compulsory gas supply maybe is a effective method to alleviate vibration and pressure pulsation of hydroturbines.Now, there are a variety of monitoring methods in the cavitation monitoring of the hydraulic turbine, and the ultrasonic cavitation signal monitoring is now better monitoring methodology, its effectiveness has been confirmed by many experiments. The main principle of the monitoring system is:By the sensor which isinstalled on the appointed situation of the turbine,sample the special signal which is relative to the cavitation,and distinguish and process by comfortale arithmetic todistill the information about the cavitation,analyse the relationship between thedegree of the cavitation and it,so as to accomplish the purpose of monitoring thecavitation by monitoring this information.This dissertation mostly researches the noisy and ultrasonic characteristic from theory and experimental ways. The experiment includes the choice of experimental scheme,the collecting and processing of signal etc. Through wiping off noise from signal, time domain and frequency domain analysis,wavelet analysis,wavelet package analysis,the law of cavitation noise intension and frequency distributing are found.