Study On Partial Discharge Test Of The High Voltage Power Transformer

It's essential to do the partial discharge (PD) test regularly for the long-term and steadily operation of the power transformer. But in the test, there still exist some disadvantages, need to be solved. For example, there are a lot of noises in the outdoor test. It makes the data inaccurate; also, transformer substation always been located outlandish, generator group is too large for transporting. The main points of this paper are design of the variable-frequency power sources for the PD test, and extract the PD signal from the test data, at last, make an accurate orientation for the PD point.Firstly, study on the principle of the PD and research its characteristics, then design the variable-frequency power sources can fulfill these need. Traditional PD test adopt motor-generator as the test power. But with the development of the power electronic technology and the compactness, voltage/frequency regulative etc, the variable-frequency power sources is widely used in the power system. This paper introduces the research and design of this kind of power sources. Improving the filter of the rectifier, and using high definition three-phase programmable SPWM controller to adjust output of the inverter. In this circuit, the less the switch element used, the better output wave is. The aim of the whole design is to reduce the harmonic, restrain the interference effect for the test.Secondly, in the respect of PD signal test, this paper introduces an adaptive thresholding filter method based on wavelet transformer. It based on the db wavelet group, using the adaptive thresholding to filter the test data. Through the compartment of this test, db2 is the most match wavelet to extract the PD signal from the data. And the result of this test proves that after the data is decomposed, reconstructed, filtered, we can get the pure PD signal without interference.At last, for convenience of the repairman in the field, the time-delay method based on energy transformation is used to orient the position of the PD source. The method is widely used in earthquake, geological prospecting and so on. Compare with other methods, such as ultrasonic orientation, chromatography, its advantages are easy to install, simple reconstruction.The test result prove that, the adaptive thresholding filter method based on db2 wavelet transformer can usefully solve white noise, period noise, narrow band noise disturbing in PD measurement, and get the pure PD signal. After extracting the PD signal, the date is used to orientation by the energy transformation method, and the result is relatively accurately oriented the position of PD source. But the design of the variable-frequency power source is still in simulation stage. Need to do the further research in the future.