Selection of Waveform for DC-steep Pulse Field in Transformer Oil Purifying

In order to research a new method to purify transformer oil and to select a better pulse waveform as power supply,firstly,we analyzed the force of colloid impurity in transformer oil,then,we measured permittivity of different aging oil,finally,we analyzed the difference of amplitude-frequency characteristics between the square-wave pulse and exponential decay pulse.These analysis and measurements reveal that time varying electric field has an effect on colloid and can separate it from oil molecule;only the electric field with wide frequency bandwidth can deal with different kinds of colloid,the amplitude-frequency characteristic of exponential decay pulse decays slowly and then exponentially decays with short rising time,and wide pulse width is rich in both low and high frequency.Furthermore,the analysis and tests confirm that the fast rising and wide width bipolar exponential decay pulse is the most ideal waveform for power supply pulse,which will improve the efficiency of oil purify obviously.