scholarly journals Gassing Tendency of Fresh and Aged Mineral Oil and Ester Fluids under Electrical and Thermal Fault Conditions

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3472 ◽  
Author(s):  
Luc Loiselle ◽  
U. Mohan Rao ◽  
Issouf Fofana
Keyword(s):  
Degradation Rate ◽  
Power Transformer ◽  
Uv Spectroscopy ◽  
Mineral Oil ◽  
Gas Analysis ◽  
Partial Discharges ◽  
Mineral Oils ◽  
Dielectric Fluids ◽  
Insulating Liquids ◽  
Fault Gas

Operational factors are known to affect the health of an in-service power transformer and to reduce the capabilities and readiness for energy transmission and distribution. Hence, it is important to understand the degradation rate and corresponding behavioral aspects of different insulating fluids under various fault conditions. In this article, the behavior of mineral oil and two environmentally friendly fluids (a synthetic and a natural ester) are reported under arcing, partial discharges, and thermal fault conditions. Arcing, partial discharges and thermal faults are simulated by 100 repeated breakdowns, top oil electrical discharge of 9 kV for five hours, and local hotspots respectively by using different laboratory-based setups. Some physicochemical properties along with the gassing tendency of fresh and aged insulating liquids are investigated after the different fault conditions. UV spectroscopy and turbidity measurements are used to report the degradation behavior and dissolved gas analysis is used to understand the gassing tendency. The changes in the degradation rate of oil under the influence of various faults and the corresponding dissolved gasses generated are analyzed. The fault gas generations are diagnosed by Duval’s triangle and pentagon methods for mineral and non-mineral oils. It is inferred that; the gassing tendency of the dielectric fluids evolve with respect to the degradation rate and is dependent on the intensity and type of fault.

scholarly journals Influence of Aging on Oil Degradation and Gassing Tendency for Mineral oil and Synthetic Ester under Low Energy Discharge Electrical Faults

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 595 ◽  
Author(s):  
L. Loiselle ◽  
U. Rao ◽  
I. Fofana
Keyword(s):  
Molecular Weight ◽  
Uv Spectroscopy ◽  
Mineral Oil ◽  
Gas Analysis ◽  
Low Energy ◽  
Liquid Volume ◽  
Mineral Oils ◽  
Laboratory Setup ◽  
Aging Conditions ◽  
Electrical Faults

The intent of this work is to understand the influence of low energy discharge electric faults in mineral oil and synthetic esters on liquid degradation and gassing tendency at different aging conditions (based on acidity values). A low energy discharge electric fault has been created by continuous discharge of 9 kV for five hours on the liquid surface using a suitable laboratory setup. Liquid degradation is reported by adopting UV spectroscopy, turbidity, and particle counter measurements. The gassing tendency is understood by dissolved gas analysis using Duval’s triangle and Duval’s pentagon methods for mineral oil and non-mineral oils accordingly. It is observed that the influence of low energy discharges on liquid degradation is higher in mineral oils than synthetic esters. The fault gasses in mineral oil are involved with electrical and thermal faults accompanied by stray gassing whereas only partial discharge activity is noticed for synthetic esters. Importantly, the existence of low energy discharge faults like corona discharges will involve a generation of excess high molecular weight products as compared to low molecular weight products that are soluble in liquid volume.

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.

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.

scholarly journals Electrostatic Charging Tendency Analysis Concerning Retrofilling Power Transformers with Envirotemp FR3 Natural Ester

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4420 ◽  
Author(s):  
Maciej Zdanowski
Keyword(s):  
Mineral Oil ◽  
Volume Density ◽  
Point Of View ◽  
Pipe Material ◽  
Mineral Oils ◽  
Insulating Liquids ◽  
Electrostatic Charging ◽  
Tendency Analysis ◽  
Insulating Liquid ◽  
Natural Ester

Natural and synthetic esters are liquids characterized by insulating properties, high flash point, and biodegradability. For this reason, they are more and more often used as an alternative to conventional mineral oils. Esters are used to fill new or operating transformers previously filled with mineral oil (retrofilling). It is technically unfeasible to completely remove mineral oil from a transformer. Its small residues create with esters a mixture with features significantly different from those of the base liquids. This article presents electrostatic charging tendency (ECT) tests for mixtures of fresh and aged Trafo EN mineral oil with Envirotemp FR3 natural ester from the retrofilling point of view. Under unfavorable conditions, the flow electrification phenomenon can damage the solid insulation in transformers with forced oil circulation. The ECT of the insulating liquids has been specified using the volume density of the qw charge. This parameter has been determined using the Abedian–Sonin model on the basis of the electrification current measured in the flow system, as well as selected physicochemical properties of the liquids. It was shown that ECT is strongly dependent on the type of insulating liquid and pipe material, as well as the composition of the mixtures. The most important finding from the research is that a small amount (up to 10%) of fresh and aged mineral oil is effective in reducing the ECT of Envirotemp FR3 natural ester.

Review on Dissolved Fault Gases in Monitoring Bio-Oil Filled Transformer

2016 ◽  
Vol 818 ◽  
pp. 69-73
Author(s):  
Siti Soleha Ab Ghani ◽  
Nor Asiah Muhamad
Keyword(s):  
Corn Oil ◽  
Power Transformer ◽  
Mineral Oil ◽  
Gas Analysis ◽  
Small Scale ◽  
Dielectric Fluid ◽  
Hydrocarbon Gases ◽  
Large Power ◽  
Distribution Transformers ◽  
Oil Monitoring

The combination of solid insulation (usually cellulose paper) and liquid insulation (usually mineral oil) yield good dielectric properties at fair cost. However, arising concerns on environmental effect of mineral oil when leakage and its risk of fire has force researches for alternative fluids. One of the suitable options for replacement of mineral oil is biodegradable oil that is plant-based, high biodegradability, non-toxicity and high fire point. Some refining and modification to crude vegetable oils resulting to suitable transformer dielectric fluid such as BIOTEMP®, ENVIROTEMP® FR3 and PFAE (palm fatty acid ester). Application of these oils in small scale distribution transformers give positive feedback so far, hence, led to development of biodegradable oil-based large power transformer. Monitoring of the oil for power transformer is important to ensure its reliability and avoid unnecessary cost of failure. Dissolved Gas Analysis (DGA) is one of the methods for oil monitoring of transformer. This method analyzes oil condition to detect incipient faults so that relevant actions can be made before actual failures occur. This paper will review the hydrocarbon gases or known as faults gases for monitoring and faults diagnosis for mineral and biodegradable oil-filled transformer. Past works about DGA on biodegradable oil such as sunflower, soybean, and corn oil are analyzed. Any different on gases production of oil through different tests will be discuss further in this paper.

scholarly journals Optimization of Various Natural Ester Oils Impregnated Nomex Paper Performance in Power Transformer Applications under Different Ageing Conditions

2019 ◽  
Vol 8 (3) ◽  
pp. 6245-6251 ◽  
Keyword(s):  
Vegetable Oil ◽  
Vegetable Oils ◽  
Power Transformer ◽  
Well Being ◽  
Mineral Oil ◽  
Mustard Oil ◽  
Mineral Oils ◽  
Time Frames ◽  
The Impact ◽  
To Receive

Vegetable oils are being considered as the potential replacements to mineral oils because of their better natural execution and for their high fire point. In spite of the fact that these fluids have been utilized as a part of appropriation transformers, it is as yet a huge advance to receive vegetable oils in control transformer because of high cost and abnormal state of well being and unwavering quality required in benefit for these units. Vegetable oils such as honge oil (HO), neem oil (NO), mustard oil (MO), punna oil (PO) and castor oil (CO) offer the reasonable option for mineral oil. It is expected that the greater part of the un-matured oil could fulfil the base necessity of dielectric protection fluids in the transformer. This paper concentrated on the impact of maturing on the electrical and physicochemical properties of HO, NO, MO, PO and CO. Fixed maturing tests have been set at 90°C for 30 days, 60 days and 90 days. Prior to the maturing procedure, the examples were dried in a vacuum broiler under the pressure of 0.8kPa at 85°C for 48 hours keeping in mind the end goal to evacuate the dampness content in the oils. At that point, the oils were impregnated with the Nomex paper and keep on ageing for choosing the span time. The electrical properties (relative permittivity, dielectric misfortunes, resistivity and breakdown quality), mechanical properties (thickness and elasticity) and substance properties (dampness and corrosiveness) of the oils were estimated all through the maturing time frames. It can be reasoned that the research center quickened warm maturing test uncovers that every single vegetable oil in this examination are safe towards oxidation in light of the steady thickness and low corrosiveness estimations of vegetable oils all through the maturing term even with the nearness of oxygen. The AC breakdown voltages of vegetable oils can in any case conform to the prescribed furthest reaches of new Vegetable oil set by ASTM 6781 even after subjected to maturing. From the results, it may be concluded that the proposed vegetable oils can be used as the alternatives for mineral oil.

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