Simulation Research Of Partial Discharge Propagation Characteristics In Large Power Transformer

Large power transformer partial discharge (PD) on-line monitoring technology is a hot topic in high voltage insulation detection and diagnosis domain. For PD signals generated in field power transformer is very faint, attaching to propagation in power transformer internal windings and between different dielectrics, which made sampling & extracting signals severe attenuation and aberration. It is a huge difficulty for PD on-line diagnosis, moreover tends to mis-judge and unable to early-warn in time, and then leads to a severe failure in power transformer.According to the problems existed in field large power transformer PD on-line monitoring system, this paper researches the PD propagation characteristics based on pulse current method and ultra-high-frequency (UHF) detection method respectively. The main results are obtained as following:Utilizing simulation software Saber, based on PD pulse current method, the transient models are established for power transformer windings, power transformer and its external network, and on-line detection system. The propagation frequency characteristics of PD signals are studied. The advanced model of power transformer winding based on PD signals propagation is put forward for the first time. Through theoretical calculation and simulation analysis for transformer winding brand-new model, the relations between winding frequency characteristics and winding parameters are discussed. Meanwhile the influence of current transducer (CT) performance parameters to pass-band is analysed. Then, the paper studies the influence of the complex external network to PD signal propagation characteristic.The primary exploration of large power transformer PD UHF detection method is discussed. UHF and ultra width frequency (UWF) sensing technique and PD signal characteristic is analysed. Varieties of propagation modes of electromagnetic (EM) wave excited by PD signal in power transformer is studied and the UHF detection measurement system is established. Through high frequency EM field analysis of finite element analysis (FEA) software ANSYS, assuming transformer oil-tank is a high frequency cavity, and PD excited point source EM wave is equivalent to radicalization current source of dipole antenna, PD EM wave signal propagation in power transformer is simulated and calculated.