| Partial discharge (PD) in Gas Insulated Switchgear (GIS) is one of the important factors for the fault, and therefore the on-line monitoring PD in GIS has been being researched at home and abroad in order to guarantee the safe operation of GIS. At the same time, mathematical model and calibration of the discharge quantity of Ultra High Frequency (UHF) signals are still an advanced problem to be studied. Therefore, on the basis of analysis of the researches about PD detection in GIS, establishment of mathematical model and calibration of the discharge quantity of UHF PD signals, combined with experiments of equivalent source, a Gaussian mathematical model of typical insulation defects are established. The inner relationship between UHF PD signal and its discharge quantity is studied deeply, a theory and method for calibration of discharge quantity is proposed in this paper in order to calibrate discharge quantity by the UHF PD waveform. At the same time, the complex threshold algorithm of complex wavelet transform is studied and used in de-noising of UHF PD signals. The main achievements are as follows.â‘ Based on technique of the sensitivity test, by improving the experimental procedure, combining with multiply parameters adjustment, experiments of equivalent source is established which could acquire PD waveform of PD source directly. At the same time, according to the features of PD of insulation defects in GIS, four types of insulation defects of GIS are devised and a lot of PD data are acquired by various PD experiments of equivalent source. Meanwhile, the waveform features of different types of insulation defects under different experimental conditions are studied deeply.â‘¡Gaussian mathematical model is established for all types of PD of simulation insulation defects by analysis of data from experiments of equivalent source. Gaussian mathematical model have identical expression for four types of PD of simulation insulation defects and every parameter in this model has physical meaning. The mathematical models are verified by waveform error analysis and spectrum error analysis.â‘¢Gaussian mathematical models of typical defects are used in source separation of multi-signals, study of propagation features of UHF signal in GIS, de-noising of PD signals and so on. These applications verify the correctness of these Gaussian mathematical models. At the same time, algorithm of complex threshold of complex wavelet transform is proposed in this paper, which could de-noise PD signals in different noise level.â‘£Combined with antenna theory, electromagnetic field theory and IEC60270, relationship between UHF signal and its discharge quantity is studied. And then, UHF signals and signals from method of IEC 60270 are acquired for four types of PD of simulation insulation defects at the same time. The relationship between UHF PD signal and its discharge quantity is studied deeply and a theory and method for calibration of discharge quantity by waveform of UHF PD is established.A new theory and method of mathematical model and calibration of discharge quantity by waveform of UHF PD are established by completing studies above. The purposes of these studies is to lay a foundation of studies of UHF monitoring and the developing of the UHF PD online monitoring system and solve the problems of mathematical model and calibration of discharge quantity.
|
PDF Full Text Request