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

Vestnik IGEU ◽  
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.

scholarly journals Effect Of Phenol Addition To Transformer Oil Breakdown Voltage

2020 ◽  
Vol 8 (2) ◽  
pp. 77-81
Author(s):  
Amelya Indah Pratiwi
Keyword(s):  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Transformer Oil ◽  
Insulating Oil ◽  
Transformer Insulation ◽  
Is Failure ◽  
Insulation Oil

The failure of transformer insulation often occurs due to various kinds of things, one of which is failure in the oil isolation caused by the condition of oil that has been dirty or has been contaminated with other particles in the transformer. Phenol is a chemical that can purify or cleanse particles or impurities that are in used transformer oil, so that it can increase the breakdown stress on used insulation oil. Phenol contains acid which can attract particles and impurities in the transformer oil which results in a decrease in the breakdown strength of the insulating oil. The results of testing of used isolation oil by adding phenol as much as 10, 15 and 20 ml showed an increase in the value of breakdown voltage with a distance of 2.5 mm ball inlet electrode. Translucent stresses that meet the SPLN standard 49-1: 1982, that is ≥ 30 kV at intervals of 2.5 mm were obtained by adding 20 ml of phenol to the volume of used 400 ml transformer oil

scholarly journals Method of calculating the electric strength of oil channels of the main insulation of power transformers

Vestnik IGEU ◽  
2020 ◽  
pp. 48-55
Author(s):  
O.S. Melnikova ◽  
V.S. Kuznetsov
Keyword(s):  
Breakdown Voltage ◽  
High Voltage ◽  
Breakdown Strength ◽  
Dielectric Strength ◽  
Transformer Oil ◽  
Electric Strength ◽  
Power Transformers ◽  
Statistical Characteristics ◽  
Voltage Distribution ◽  
Design Features

The most damage-sensitive unit of power transformers is the main insulation of the oil barrier type. The breakdown of such insulation occurs as a result of the breakdown of the oil channel near the high voltage winding. In accordance with traditional methods of calculating the dielectric strength of insulation, the value of the breakdown strength is determined by empirical formulas depending on the selected width of the oil channel. The existing methods do not consider the influence of the oil channel volume, of the electric strength the statistical characteristics of the oil, the design features of the insulation of power transformers, and do not contain recommendations for creating design models. Thus, to improve the calculation accuracy, it is relevant to develop the evaluation method of dielectric strength of the main insulation of power transformers taking into account the volume and parameters of the breakdown voltage distribution of transformer oil, design features. The research results of the breakdown tension in oil channels with different volumes of transformer oil were used. To improve the accuracy of the calculation and taking into account the design features, the model of the main insulation of power transformers was made in the ANSYS program. Boundary data and assumption of linear stress distribution of transformer coils were considered. A method for calculating the dielectric strength of oil channels of the main insulation of power transformers, considering the volume and parameters of the breakdown voltage distribution of transformer oil was proposed. Unlike the existing methods, when calculating the minimum breakdown strength in the model of the main insulation, the design features of power transformers are taken into account and assumptions are justified to improve the accuracy of the calculation. In accordance with the methodology, the parameters of the dielectric strength of the transformer oil in the oil channel of the high voltage winding of the transformer were calculated. It was concluded that with increase of relative value of breakdown tension, dielectric strength of oil channel is decreasing, and it corresponds to physical sense of breakdown. The method for calculating the dielectric strength of transformer oil can be used when choosing the main insulation of power transformers in design.

scholarly journals Electric field bridging pattern of pre-breakdown and breakdown condition in transformer oil

2020 ◽  
Vol 19 (3) ◽  
pp. 1210
Author(s):  
Nur Badariah Ahmad Mustafa ◽  
N H Nik Ali ◽  
H. Zainuddin ◽  
Marizuana Mat Daud ◽  
Farah Hani Nordin
Keyword(s):  
Electric Field ◽  
Electrical Power ◽  
Major Axis ◽  
Dielectric Strength ◽  
Minor Axis ◽  
Transformer Oil ◽  
Support Vector ◽  
Electrical Power System ◽  
Feature Descriptors ◽  
Axis Length

Transformer is considered as one of the most important equipment in electrical power system networks. However, most problems occurred in transformer were related to the defects and weakness of the insulation systems. The oils used in transformer act as coolant and insulation purposes hence maintaining the dielectric strength of the transformer. In this work, electric field bridging pattern is observed from pre-breakdown and breakdown condition. The electric field bridging formation was recorded in the experimental setup and images were captured per frame. 193 images were randomly chosen from the whole video frames where 102 images were the pre-breakdown images and 91 images were the breakdown images. This system comprises of four stages: (i) a preprocessing stage to mark the electrodes tips and background subtraction; (ii) a segmentation stage to extract the electric field bridging formation in region of interest; (iii) a feature extraction stage to extract electric field bridging using feature descriptors, <em>area</em>, <em>minor-axis </em>and <em>major-axis length  </em> (iv) a classification stage to identify the pre-breakdown and breakdown condition. System performance was evaluated using support vector machine (SVM), <em>k</em>-nearest neighbour (<em>k</em>-NN) and random forest (RF) and SVM provided the most promising accuracy that was 99%. The results show that the combination of three feature descriptors, <em>area</em>, <em>minor-axis </em>and <em>major-axis length </em>are the best features combination in identifying the transformer oil condition. In future work, further studies will be conducted to investigate the pattern of pre- and post-breakdown due to some similarity found in image pattern. Due to that, more feature descriptors will be identified to find a unique pattern between pre- and post-breakdown condition

scholarly journals Preparation of Three Types of Transformer Oil-Based Nanofluids and Comparative Study on the Effect of Nanoparticle Concentrations on Insulating Property of Transformer Oil

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Qi Wang ◽  
Muhammad Rafiq ◽  
Yuzhen Lv ◽  
Chengrong Li ◽  
Kai Yi
Keyword(s):  
Thermal Properties ◽  
Comparative Study ◽  
Breakdown Voltage ◽  
Breakdown Strength ◽  
Transformer Oil ◽  
Standard Methods ◽  
Maximum Value ◽  
Negative Impulse ◽  
The Difference

Nanofluids have the potential to become the alternatives of conventional transformer oil for their exquisite electrical and thermal properties. Three kinds of nanoparticles with distinct conductivities, namely, nonconductive nanoparticle Al2O3, conductive nanoparticle Fe3O4, and semiconductive nanoparticle TiO2, with different concentrations from 5% to 40% w/v were selected and suspended into transformer oil to develop nanofluids. The lightening impulse breakdown strengths of the oil samples with and without nanoparticles were measured according to IEC standard methods. The positive impulse breakdown strength indicated that breakdown strength is first increased up to the maximum value at certain concentration and then starts decreasing. The results of negative impulse breakdown manifested that the breakdown voltages of nanofluids with different concentrations were less than the breakdown voltage of pure transformer oil. Different effect mechanisms of dielectric and conductive nanoparticles were also used to describe the difference among three prepared nanofluids.

PD Characteristics in Transformer Oil under AC Condition

2014 ◽  
Vol 492 ◽  
pp. 186-189
Author(s):  
Ji Chong Liang ◽  
Tian Zheng Wang ◽  
Kang Ning Wang ◽  
Jun Hao Li
Keyword(s):  
Electric Field ◽  
High Voltage ◽  
Applied Voltage ◽  
Partial Discharge ◽  
Electrode System ◽  
Transformer Oil ◽  
Pulse Burst ◽  
Transformer Oils ◽  
Pattern Display ◽  
Insulation Condition

Partial discharge (PD) detection is a technique widely used for high voltage equipment insulation condition assessment. The metal protrusion is a situation that often appear in transformer. Metal protrusion will cause the electric field concentration and lead to partial discharge. In this paper, PD characteristics in transformer oils are examined under AC conditions, using a needle-to-plane electrode system. The PD activity in transformer oil is confirmed as appearing in pulse burst form and the PD number and amplitude will increase with the applied voltage increase. The PRPD pattern display behavior typical of corona PD in oil.

Investigation on Voltage Breakdown of Natural Ester Oils Based-On Zno Nanofluids

2015 ◽  
Vol 1119 ◽  
pp. 175-178 ◽  
Author(s):  
Wittawat Saenkhumwong ◽  
Amnart Suksri
Keyword(s):  
Power System ◽  
Breakdown Voltage ◽  
Palm Oil ◽  
Breakdown Strength ◽  
Mineral Oil ◽  
Transformer Oil ◽  
Slow Process ◽  
Zno Nanofluids ◽  
Voltage Breakdown ◽  
Natural Ester

Transformer is one of the major component, which is the most important device in power system. Their lifetime depends upon liquid insulation that help transfer the heat out of its winding inside of transformer. Transformer oil uses mineral oil that is the most commonly used has very slow process on decomposition and non-biodegrade. This paper presents the investigation on breakdown voltage of two types of natural ester oils, including palm oil and soy bean based-on ZnO nanofluids. Nanofluids that use nanoparticles modified by use of surfactant that are suspended by process of sonication. Different fraction of nanoparticles were investigated from 0.1% - 0.5% by weight. The breakdown voltage were measured according to ASTM D877. The voltage breakdown strength increased significantly when nanoparticles were added in oils. The obtained results will enable transformer industry to develop liquid insulation dielectric for use in transformer in the future.

scholarly journals Probing the Use of Silane-Grafted Fumed Silica Nanoparticles to Produce Stable Transformer Oil-Based Nanofluids

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7649
Author(s):  
Muhammad I. Qureshi ◽  
Basit Qureshi
Keyword(s):  
Breakdown Strength ◽  
Plasma Reactor ◽  
Dielectric Strength ◽  
Transformer Oil ◽  
Amino Silane ◽  
Fumed Silica Nanoparticles ◽  
Air Atmosphere ◽  
Silane Coating ◽  
Hydrophobic Silane ◽  
Tan Δ

In this experimental investigation, hydrophobic silane-grafted fumed nano-silica was employed in transformer oil to formulate nanofluids (NFs). A cold-air atmosphere-pressure plasma reactor working on the principle of dielectric barrier discharge was designed and utilized to functionalize the surface of these nanoparticles. A field emission scanning electron microscope (FE-SEM) coupled with energy-dispersive X-ray (EDX) module and Fourier transform infrared (FTIR) spectroscopy were used to scan surface features of new and plasma-treated nanoparticles. The study revealed considerable changes in the surface chemistry of nanoparticles, which led to good dispersibility and stability of nanofluids. The measurements of AC breakdown voltages (AC-BDV) of nanofluids so prepared were conducted according to IEC-Std 60156, and a significant improvement in the dielectric strength was achieved. A statistical analysis of these results was performed using Weibull probabilistic law. At a 5% probability of failure, modified nanofluid remarkably exhibited a 60% increase in breakdown voltage. The dielectric properties such as variation of εr and tan δ in temperature of up to 70 °C were measured and compared with untreated fluid. Results exhibit an increase in tan δ and a slight decrease in permittivity of nanofluids. The analysis also revealed that while unpolar silane coating of NPs increased the breakdown strength, the polar-amino-silane-coated NPs in oil resulted in a drastic reduction. Details of this antagonistic trend are elaborated in this paper.

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