Influence of electrical and thermal ageing on the mineral insulating oil performance for power transformer applications

2020 ◽  
Vol 62 (4) ◽  
pp. 222-231
Author(s):  
C Ranga ◽  
A Kumar ◽  
R Chandel
Keyword(s):  
Power Transformer ◽  
Stress Test ◽  
Oxidation Stability ◽  
Chemical Properties ◽  
Mineral Oil ◽  
Thermal Ageing ◽  
Test Cell ◽  
Transformer Oil ◽  
Power Transformers ◽  
Solid Dielectrics

In the present work, a new electrothermal combined stress test cell has been designed and fabricated to conduct accelerated electrothermal ageing. The fabricated test cell includes all possible real working conditions of the transformers. The effects of accelerated electrothermal ageing on the performance of power transformers with thermally upgraded Kraft (TUK), Nomex-910 and Nomex-410 solid dielectrics in conjunction with mineral oil have been investigated. The accelerated electrothermal ageing has been performed for a temperature range of 100°C to 220°C, along with 10 kV electrical stress. Subsequently, several electrical, thermal, mechanical and chemical properties of transformer oil and different paper dielectrics have been determined. It has been observed from the diagnostic test results that Nomex impregnated mineral oil samples have better electrothermal performance as well as oxidation stability when compared to the thermally upgraded Kraft oil samples. Therefore, Nomex insulating materials in conjunction with mineral oil are suggested as alternative solid dielectrics for power transformers in order to achieve better oxidation stability, improved thermal performance for long service runs and reduced operating and maintenance costs. It is envisioned that the present experimental study will be very beneficial to utility managers and end-users of power transformers.

scholarly journals Experimental Investigation on Vegetative Oils under Accelerated Thermal Ageing against Their Dielectric Strength

2017 ◽  
Vol 7 (3) ◽  
pp. 1588
Author(s):  
Siti Sufiah Abd Wahid ◽  
Mohd Fikri Hilmi Mohd Taib ◽  
Yanuar Z. Arief ◽  
Mohd Hafizi Ahmad ◽  
Noor Azlinda Ahmad ◽  
...  
Keyword(s):  
Power Transformer ◽  
Research Work ◽  
Dielectric Strength ◽  
Mineral Oil ◽  
Thermal Ageing ◽  
Transformer Oil ◽  
Accelerated Ageing ◽  
Insulation Material ◽  
Low Dielectric ◽  
High Dielectric

Insulation is one of the most important parts in high voltage apparatus such as power transformer. Most power transformer use liquid insulation material, known as power transformer oil. Petroleum-based oil so called mineral oil has been used for many years as power transformer oil. This is due to its high dielectric field strength, low dielectric loses and good long-term performance. This research work has been carried out to investigate the effect of thermal accelerated ageing on electrical properties for several vegetative-based oils. The oil samples that have been used in this research work are soy bean-based oil (FR3) and commercial palm-based oil (PFAE). As comparison, Hyrax mineral oil has also been investigated. The results revealed that vegetative-based oils have as well as dielectric strength compared with mineral oil.  It was found that the dielectric strength for all oil samples decreased when undergo the thermal accelerated ageing process.

scholarly journals Alternative liquid dielectrics in power transformer insulation: a review

2021 ◽  
Vol 23 (3) ◽  
pp. 1761
Author(s):  
Bokang Agripa Tlhabologo ◽  
Ravi Samikannu ◽  
Modisa Mosalaosi
Keyword(s):  
Power Transformer ◽  
Chemical Properties ◽  
Fire Risk ◽  
Mineral Oil ◽  
Acid Number ◽  
Gas Analysis ◽  
International Standards ◽  
Liquid Dielectrics ◽  
Transformer Insulation ◽  
Natural Ester

Transformer liquid dielectrics evolved where mineral oil has been the dominant choice until emergence of synthetic esters and natural esters. Natural ester-based oils have been under extensive investigations to enhance their properties for replacing petroleum-based mineral oil, which is non-biodegradable and has poor dielectric properties. This paper focuses on exposition of natural ester oil application in mixed transformer liquid dielectrics. Physical, chemical, electrical, and ageing characteristics of these dielectrics and the dissolved gas analysis (DGA) were reviewed. Physical properties include viscosity, pour point, flash and fire point which are vital indicators of heat insulation and fire risk. Chemical properties considered are water content, acid number, DGA, corrosive sulphur, and sludge content to limit and detect degradation and corrosion due to oil ageing. Electrical properties including breakdown voltage were considered for consistent insulation during overload and fault conditions. These properties of evolving alternative dielectrics were reviewed based on ASTM International standards and International Electro technical Commission standards for acceptable transformer liquid dielectrics. This review paper was compiled to avail modern methodologies for both the industry and scholars, also providing the significance of using mixed dielectrics for power transformers as they are concluded to show superiority over non-mixed dielectrics.

Effect of Waste Vegetable Oil on Cooling Performance and Lifetime of Power Transformers

2020 ◽  
Author(s):  
Ehsan Ebrahimnia-Bajestan ◽  
Mohammad Arjmand ◽  
Hani Tiznobaik
Keyword(s):  
Magnetic Energy ◽  
Power Transformer ◽  
Mineral Oil ◽  
Power Transformers ◽  
Cooling Performance ◽  
Mineral Oils ◽  
Waste Vegetable Oil ◽  
Lower Viscosity ◽  
Insulating Liquid ◽  
Main Factor

Abstract During the operation of a power transformer, a large amount of heat is generated due to the electrical and magnetic energy losses in its core and windings, causing a temperature rise in transformers. This generated heat is known as the main factor for aging the electrical insulating system of a transformer. In this research, we numerically studied the ability of a vegetable-based oil — as an alternative coolant for the petroleum-based oils — on the cooling performance of a power transformer. The studied oil was a biodiesel produced from waste cooking vegetable oils, having lower viscosity compared to traditional mineral oils. We also calculated the aging rate of the transformer in the presence of the biodiesel. The results indicated that compared to the mineral oil, the average hotspot temperature of the transformer is 3 degrees lower when the biodiesel was used. The life expectancy of the transformer with the vegetable-based oil was also significantly longer than the case with mineral oil. In conclusion, this study provided a sustainable way to use an eco-friendly material produced from a waste resource as an alternative insulating liquid for the cooling of power transformers.

Research of Ageing and Life Assessment Methods of Power Transformers in Nuclear Power Plants

2012 ◽  
Vol 614-615 ◽  
pp. 1109-1115 ◽  
Author(s):  
Cheng Feng Yang
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Assessment Method ◽  
Thermal Ageing ◽  
Degree Of Polymerization ◽  
Transformer Oil ◽  
Life Assessment ◽  
Power Transformers ◽  
Analysis Method

The effective methods of the ageing and life assessment for large and medium-sized power transformers used in nuclear power plants are analyzed and described, including the thermal ageing life assessment method for transformer solid insulation, the gas analysis method of CO and CO2 in the transformer oil, the average degree of polymerization method, furfural content analysis method, and the analysis method based on the insulation ageing-related electrical parameters. The analysis results show that the methods used can reasonably assess the remaining life of the transformers. These methods have important reference value to the ageing and life management for the large and medium-sized power transformers in nuclear power plants.

Transformer Mineral Oil Mixtures Characterization by Isothermal Charging Currents

2013 ◽  
Vol 664 ◽  
pp. 632-637
Author(s):  
Tahar Toudja ◽  
Hocine Moulai ◽  
Azzeddine Nacer ◽  
Abdeslem Beldjillali ◽  
Nadia Saidi ◽  
...  
Keyword(s):  
Power Transformer ◽  
Physicochemical Characteristics ◽  
Field Application ◽  
Transformer Oil ◽  
Oil Mixtures ◽  
Physicochemical Methods ◽  
High Voltage Insulation ◽  
Solid Dielectrics ◽  
Good Agreement

This work aims at the characterization of power transformer oil mixtures by using dc charging currents measurements for long field application times. The principle of this approach is inspired from the technique of measurements carried out on solid dielectrics used in high voltage insulation. It will be applied to characterize mixtures between two compatible oils of different provenances and ages. The obtained results are conclusive and reinforce those obtained by classical physicochemical methods of characterization. For the purpose, we intent to link between the space charge behavior in the insulation and its several characteristics. Moreover, in addition to the fact that the obtained results are in good agreement with the physicochemical characteristics, the charging currents reported at room temperature enabled us to determine the mixture resistivity and charge carriers' mobility.

scholarly journals Study on the increase in power supply reliability for the consumers of electricity

2021 ◽  
Vol 939 (1) ◽  
pp. 012011
Author(s):  
A Rakhmatov
Keyword(s):  
Water Management ◽  
Chemical Composition ◽  
Power Supply ◽  
Power Transformer ◽  
The State ◽  
Transformer Oil ◽  
Power Transformers ◽  
Degree Of Damage ◽  
Physical And Chemical ◽  
Supply Systems

Abstract The issues of increasing the reliability of power transformers used in power supply systems for agriculture and water management were discussed in this article.The degree of damage to the insulation of power transformers by the physical and chemical composition of the transformer oil and insulation of other parts was also investigated, materials on the assessment of the state of insulation by the degree of damage to the insulation of individual units of the power transformer were presented.

Condition Monitoring of High Voltage Transformer using Dissolved Gas Analysis Methods

2021 ◽  
Vol 9 (VI) ◽  
pp. 1759-1770
Author(s):  
Dayyala Ravi
Keyword(s):  
Power Transmission ◽  
Power Transformer ◽  
Accurate Method ◽  
Mineral Oil ◽  
Gas Analysis ◽  
Transformer Oil ◽  
Dissolved Gas ◽  
Voltage Transformer ◽  
Transformer Protection ◽  
Dissolved Gas Analysis

Power transformer plays a significant role in the entire power transmission network; thus, transformer protection requires more attention for fault free electric supply. when the mineral oil and insulation inside the transformer is subjected to high thermal and electrical stresses, gases are created by the decay of mineral oil and cellulose. Different gases create different faults, Identification of faults inside the power transformer before they occur reduces its failure rate during its service period. For Knowing the fault condition of power transformer, Dissolved Gas Analysis (DGA) is proven to be as accurate method based on combination of concentration of gases like CO, CO2, H2, C2H6, C2H4, C2H2 etc., Dissolved gas analysis is the most important test in determining the fault condition of a transformer and it is the first indicator of a problem and can identify deteriorating insulation and oil, overheating hot spots, partial discharge and arcing. For developing this DGA Techniques, the MATLAB GUIDE interface can be used for making easy interaction between the user and software developed. This software is designed using some conditional statements and logical functions to get the type of faults in transformers based on the concentration of gases in transformer oil. The faults in transformer using dissolved gases analysis are detected using methods such as key gas, Roger’s methods, IEC ratio, Doernenburg ratio, Duval triangle and the Combined DGA methods. In this paper, these four methods of dissolved gas analysis (DGA) are presented and explained briefly.

Characteristics of Mineral Oil-based Nanofluids for Power Transformer Application

2017 ◽  
Vol 7 (3) ◽  
pp. 1530 ◽  
Author(s):  
I. H. Zakaria ◽  
M. H. Ahmad ◽  
Y. Z. Arief ◽  
N. A. Awang ◽  
N .A. Ahmad
Keyword(s):  
Electrical Properties ◽  
Breakdown Strength ◽  
Power Transformer ◽  
Atmospheric Pressure Plasma ◽  
Mineral Oil ◽  
Transformer Oil ◽  
Before And After ◽  
Cold Atmospheric Pressure Plasma ◽  
The Stability ◽  
Physical Changes

Trends in the field of nanomaterial-based transformer oil show most of the conducted works have focused only on the transformer oil-based nanofluids but limited studies on the stability of transformer oil-based nanofluids. Since mineral oil-based nanofluids still can produce the sedimentation, thus the cold-atmospheric pressure plasma method is proposed to functionally modify the Silicon Dioxide (SiO<sub>2</sub>) nanofiller in order to enhance the electrical properties of the mineral oil-based nanofluids. The AC breakdown strength oil samples before and after modification were measured. It was found that the plasma treated nanofluids have higher AC breakdown voltage compared to pure oil and untreated nanofluids. Also, Fourier Transform Infrared (FTIR) Spectroscopy has been used in this study to analyse the physical changes of oil samples. It is envisaged that the added silica nanofiller has significant effect on electrical properties of the transformer oil-based nanofluids which would enable to the development of an improved class of liquid dielectric for the application of power transformer.

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