A Preliminary Study Of Purifying Dirty Transformer Oil By DC Superimposed Microsecond Pulse Electric Field

As the power transformer insulation and cooling medium, the performance oftransformer oil has a direct bearing on the safe operation of the transformer and thepower system. Transformer oil will continue aging under various factors-like electrical,thermal, and magnetic etc-after long-time running, and insulation and coolingperformance will continue to decline, threatening the security of the power system.Conventional transformer oil purification methods, such as filtration pressure oil filter,oil purifier method, can improve the performance of the transformer oil to some extent,but all of them have their own limitations. In this paper, using dc steep pulse compositeelectric field purifying transformer oil, can effectively remove the impurities such ascolloid in the transformer oil, to improve the effect and efficiency of oil purification.This paper introduces the theory of transformer oil aging, analyzes the impact of itsproducts on aging transformer oil properties. On this basis, analyzes the theory ofdielectric polarization and the force of charged particles in oil under the action of theelectric field, analyzes the basic principle of dc superposition microsecond pulse electricfield purifying transformer oil.Then select exponential decay pulse waveform as thepulsed electric field pulse through the transformer oil dielectric constant frequencyspectrum waveform amplitude measurements and frequency analysis of several.In determining the desired pulse waveform, a pulse machine is designed based on aseries circuit of IGBT,3IGBT is a set of switches in series, designs the parameters ofdevice according to the requirements of pulse forming circuit. The conventional IGBTdrive circuit is improved, the use of optical fibers providing a high voltage isolationbetween the control circuit and the high voltage circuit, the use of self-createdelectrically powered drive circuit, the drive circuit to avoid the power supply voltageisolation problems. Analyzes the reasons of the uneven pressure for IGBT series andchoses the passive type RCD snubber circuit designed according to the actual situationas dynamic voltage circuit, calculate the static and dynamic voltage circuit parametersof each device, and use Pspice software to simulate the circuit. According to theexperimental design needs absolutes DC pulse superposition circuit, and simulates theverification. Respectively, for a variety of structures electric reactor electric fielddistribution simulation conducted to determine the electric field and the type of reactordesign and production. Using the developed of the DC superimposed microsecond pulse electric fieldgenerator and reactor to test program designed to find the optimal parametercombination absolutes, and the influence of the electric field is superimposed effect of asingle parameter of absolutes. Experimental results show that the performance ofdifferent parameter combinations absolutes dirty transformer oil had improved to acertain extent, the optimal parameter combinations are absolutes DC voltage10kV,absolutes time of12h, the pulse voltage amplitude6kV, pulse width14μs; Purifierresults obtained with decreasing pulse width increased with increasing the amplitude ofthe voltage pulses has decreased after an increase. Experimental results indicate that thedevelopment of a DC electric field superimposed microsecond pulse generator and areactor can be applied to the purification of contaminated transformer oil, and a bettereffect purifier can be further studied.