Yang Jinggang

A system using fluorescent fiber for partial discharge detection in transformer

It is a new method to monitoring partial discharge(PD) signals by optical effect. PD generated physical phenomena of optical effect and fluorescence optical fiber sensing certain wavelength of the light signal characteristics, so we developed a system using fluorescent fiber sensors for detecting PD signals. This paper introduced the principle of optical signal caused by PD detected by fluorescent fiber, and it also gave out the main parameters and the system components of sensors. We can set up a test platform to simulate the PD in transformer oil in the laboratory. Compared to the test results measured by ultrahigh frequency method, we can get the conclusion that the PD pulses detected by these two methods mainly occurred around the positive and negative frequency voltage peak under the needle-plate defects in oil. Moreover, it had a good consistency in the number of discharge pulses and phases. The fluorescence optical fiber sensor can be easily embedded in transformer winding insulation, so it had a wide application prospect on the PD online monitoring in the complex insulation structure.

Research on the correlation between UHF signal energy and discharge quantity of partial discharge

In order to research on the correlation between discharge quantity and ultra high frequency (UHF) signal accumulated energy of the partial discharge (PD) from metal particles defections in oil of transformer, The thesis utilize 50 Ohm non-inductive resistance to measure current pulse and UHF electromagnetic wave; that two type of PD signal from artificial transformer defection, then have concluded the correlation between discharge quantity and UHF signal accumulated energy is a quadric curve. Meanwhile, when the weight of the particles and the voltage increasing, the discharge quantity and the energy receiving by antenna will increase too. The result shows that we can get discharge quantity by calculating UHF signal accumulated energy and in accordance with IEC60270 standard, this provides a valuable method of using UHF to do quantitative analysis for PD.

Research on decomposition characteristics of SF 6 under partial discharge at different gas pressures

In order to obtain the decomposition characteristics of SF<inf>6</inf> under partial discharge (PD) at different gas pressures, an experiment platform was established and PD decomposition experiments of SF<inf>6</inf> at different gas pressures was carried out in 96 hours. In the experiments, gas chromatography and gas chromatography-mass spectrometry were adopted to quantitatively determine the characteristic components of decomposition. The variation of these characteristic components at different gas pressure and the role of gas pressure in this process was analyzed on the basis of experiment results. It is concluded that, the generation rate of some characteristic components (such as CO<inf>2</inf>, SO<inf>2</inf>, SOF<inf>2</inf>) significantly declines with the increasing pressure. Among them SOF<inf>2</inf> has the most significant change, while the generation rate of SO<inf>2</inf>F<inf>2</inf> only reduces slightly. This troubles the diagnoses based on the signal characteristic ratio c(SOF<inf>2</inf>+SO<inf>2</inf>)/c(SO<inf>2</inf>F<inf>2</inf>). Therefore, To use a new characteristic ratio, c(SO<inf>2</inf>F<inf>2</inf>+SOF<inf>2</inf>+SO<inf>2</inf>)/c(CO<inf>2</inf>) was proposed which is not obviously affected by pressure.