Space charge injection behaviors and dielectric characteristics of nano-modified transformer oil using different surface condition electrodes

Abstract

Electrodes are damaged by external forces, mechanical wear, and electrochemical corrosion during long-term operation in power systems, resulting in rough electrode surfaces. Space charge injected into the liquid by a rough electrode under a strong electric field causes electric field distortion and leads to breakdown. Moreover, the charge injection is associated with the energy barrier at the electrode-liquid interface. The combined effect mechanism of nanoparticles and electrode surface condition on the insulating characteristics of transformer oil was investigated using various surface condition aluminum plate electrodes. The breakdown voltages and space charge patterns in pure transformer oil and Al2O3 nano-modified transformer oil under impulse voltage were measured in this study through Kerr electro-optic field mapping measurement. The test results indicate that the breakdown voltage of nano-modified transformer oil depends on voltage polarity and electrode surface conditions and the charge injection shows the same mode in pure transformer oil using different surface condition electrodes, but the magnitude of charge injection differs considerably. Due to nanoparticle’s ability of shielding space charges of different polarities and the charge injection of different surface condition electrodes, they have different effects on the breakdown process of transformer oil between different surface condition electrodes. An interfacial model was formed to explore the mechanism of the effect of nanoparticles and electrode surface conditions on the insulation performance of liquid dielectrics and analyze the breakdown process using the space charge injection behaviors.

Interface Charge Characteristics in Polymer Dielectric Contacts: Analysis of Acoustic Approach and Probe Microscopy

“…[40,107,197,198] During long-term operation, the electrode material and surface roughness can change the interfacial states of the electrode/dielectric/electrode structure due to defects and electrochemical corrosion. [199] Figure 11a illustrates the interface charge density and electric field at the cathode/polyethylene interfaces, [190] which reveals that the interface charge density reaches a maximum with time for both semiconductor and metal electrode structures. Additionally, the interface charge accumulation at the Au electrode contact is lower than that of the semiconductor and Al contact.…”

Surface Electrons: Theory and Electrohydrodynamic Applications

“…Несмотря на то, что в электрогидродинамике много нерешенных проблем, особенно в плане ресурса работы ЭГД систем [8], интерес к этой тематике как в русских изданиях [24][25][26][27][28], так англоязычных [29][30][31][32][33][34][35][36][37][38] не ослабевает. Одним из путей решение этой проблемы является использование электроноакцепторных (ЭА) примесей, способных присоединять ПЭ на эмиттере и разряжаться на коллекторе, например, раствор ТМ+I.…”

“…В растворах ТМ+I при индифферентных электродах наблюдается униполярная инжекция отрицательных ионов за счет реакции(28), которая сопровождается квадратичной ВАХ.5. Полученные выражения для коэффициентов инжекции ξ c , η c , η x , η es в (20), (34),(35) Кишинев: Штиинца, 1977. 320 с.…”

Effect of surface modification of electrodes on charge injection and dielectric characteristics of propylene carbonate

“…where ɛ 0 and ɛ r are the vacuum dielectric constant and the relative dielectric constant, respectively, and x is the gap distance between the plates. According to (6), the distribution of space charge at different positions between the plates can be determined. Different work functions of aluminium, copper, and stainless steel result in different barrier heights at the interface between the plate and liquid.…”

“…These approaches including directly altering the physical and chemical properties of liquid dielectrics such as through the use of nanoparticle modified liquid dielectrics [2][3][4], which can introduce potential wells or holes, capture fast-moving electrons, and inhibit the development of streamers [5]. Besides, through an indirect action on the space charge injection, the surface of the electrode material can also be modified to change the surface chemical characteristics and physical morphology of the electrode and inhibit charge injection [6], and thus change the impulse insulation characteristics. Notably, nanoparticles easily form deposits and do not easily form stable nanofluids for power grid main equipment.…”