Optimisation of the dielectric strength of a non-uniform electric field electrode system under positive DC voltage by insertion of multiple barriers

AbstractNow days, the establishment of spacers is in wide usage in three-phase Gas Insulated Busduct (GIB) for providing mechanical support and better insulation to the conductors. The region of the intersection of SF6 gas, enclosure end and the spacer is one of the weakest links in GIB, so the major concentration is done on minimization of electric field stress at this junction by using Functionally Graded Material (FGM) technique. The other incidents of insulation failures are due to several defects like depression, delamination etc. reduces the dielectric strength of the spacers. In this paper, an FGM post type spacer has been designed for a three-phase GIB under depression and further electric field stress at Triple Junction (TJ) is reduced by introducing a metal insert (MI) nearer to the TJ. Several filler materials are used as doping materials for obtaining different permittivity values using FGM technique to achieve uniform electric field stress. Simulation is carried out for the designed spacer at various operating voltages with different types of FGM gradings. The effect of depression with different dimensions and positions is analyzed before and after inserting MI to the FGM post type spacer in three-phase GIB.

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Simulations of High Non-Uniform Electric Field in Dielectric Barrier Electrode System

Walailak Journal of Science and Technology (WJST) ◽

10.48048/wjst.2021.12953 ◽

2021 ◽

Vol 18 (14) ◽

Author(s):

Pitchasak CHANKUSON ◽

Mudtorlep NISOA

Keyword(s):

Electric Field ◽

High Voltage ◽

High Intensity ◽

Dielectric Materials ◽

Electrode System ◽

Ozone Production ◽

Uniform Electric Field ◽

Electrode Geometry ◽

Dielectric Barrier ◽

Fine Mesh

An electric field in the dielectric barrier electrode system is necessary for ozone production because ozone is produced by the electric discharge of O2 under a high-intensity electric field. The gas discharge plasmas contain energetic particles, such as electrons, ions, atoms, and radicals. The recombination of the O atom and O2 in the plasma will form O3. In this paper, the dependence of DC electric field formation on electrode geometry and the gap between electrodes and dielectric materials were examined by using computational modeling. Thus, a set of electrode geometry, gap distance, and dielectric material were obtained for high-intensity and uniform electric field generation. The COMSOL Multiphysics software was used for the modeling. Among the electrode geometries of plate-plate, pin-plate and mesh-plate, the mesh-plate generated high-intensity and uniform electric field. In the modeling, dielectric materials, including quartz, mica, alumina, and water, were compared. The highest intensity of electric field occurred on the water surface. HIGHLIGHTS When the gap distance between two parallel electrodes is less than 100 mm, the electric field in the gap is constant, independent of the space A high-intensity and uniform electric field is generated in the gap between the dielectric and grounded electrodes when a fine mesh high-voltage electrode is utilized With the fine mesh electrode, the electric field is about two times higher than the conventional plate electrodes, whereas the electric field uniformity was about 90 %. Therefore the barrier discharge will be initiated with lower high voltage GRAPHICAL ABSTRACT

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Research of Discharge Characteristics of CO2 Gas in Small Distance

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.860-863.2194 ◽

2013 ◽

Vol 860-863 ◽

pp. 2194-2198

Author(s):

Quan Wang ◽

Huan Wang ◽

Qiong Xiang

Keyword(s):

Electric Field ◽

Breakdown Voltage ◽

Dielectric Strength ◽

Small Distance ◽

Uniform Electric Field ◽

Key Indicator ◽

Discharge Device ◽

Power Frequency ◽

Gas Insulation ◽

Insulating Properties

In order to find a new kind of insulates gas to substitute for SF6 gas, a discharge device has been development with shifter electrodes and adjusts distances automatic. Uniform electric field, non-uniform electric field had been achieved in this discharge device. The power-frequency voltage-withstand test of CO2 gas has been taken in these three kinds of electric field. In this test, data of breakdown voltage were obtained under different pressure and distances of electrodes with 99.99% purity of CO2. It can be seem from these data that the value of breakdown voltage is positive correlation to pressure and distances of electrodes. Whats more? For uniform electric field, the dielectric strength meet the requirement of power-frequency voltage-withstand of 110kV gas insulation device when the distance of test electrodes no less than 30mm. For non-uniform electric field, the dielectric strength of gas insulation of CO2 gas has little difference until the pressure increased to 0.5MPa. According to the data of power-frequency voltage-withstand test it can be conclude that the 0.5MPa is a key indicator to improve the insulating properties.

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Study of the effect of cellulose fibers on the electrical strength of transformer oil

Vestnik IGEU ◽

10.17588/2072-2672.2020.4.023-033 ◽

2020 ◽

pp. 23-33

Author(s):

O.S. Melnikova ◽

M.V. Prusakov ◽

A.A. Zholobov

Keyword(s):

Electric Field ◽

Breakdown Voltage ◽

Breakdown Strength ◽

Dielectric Strength ◽

Cellulose Fibers ◽

Electrode System ◽

Transformer Oil ◽

Electrical Strength ◽

Abrupt Decrease ◽

Transformer Insulation

The electrical strength of transformer oil is the first parameter in transformer insulation tests. Such tests are carried out in a standard discharger according to the values of breakdown voltage. An abrupt decrease in electrical strength occurs when oil is contaminated with mechanical impurities. The greatest influence on the electric field is exerted by highly conductive cellulose fibers. The field between the electrodes may be severely distorted bya «bridge» of such fibers. At the same time, the influence of such particles is not taken into account in the tests. The problem is to experimentally determine the effect of such impurities on the breakdown strength. Thereby, this research poses and solves the problem of determining the dielectric strength of transformer oil in a standard discharger in the presence of cellulose fibers.To simulate electric field strengths, the ANSYS software package has been used. The basis of the 3D model was a standard measuring cell for determining breakdown voltage, which takes into account the boundary conditions in the form of a cube in which the electrode system is located, and the values of the electric field strength in the center of the electrode system.The electric field tension between the electrodes has been calculated, taking into account the influence of increased conductivity of cellulose fibers. It has been found that the electrical strength of oil gaps of moistened fibers with a length of more than 200 μm is significantly reduced, which is not taken into account when testing transformer oil for breakdown in a standard cell. This leads to inaccuracy in determining the electric strength of transformer oil in existing equipment.The results of the study can be used by operational services to improve the assessment of the quality of transformer oil used in power transformers as insulation. The results also can be used to study the mechanisms of electrophysical processes occurring in liquid dielectrics in the presence of fibers.

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