scholarly journals Streaming Electrification of Nycodiel 1255 Synthetic Ester and Trafo EN Mineral Oil Mixtures by Using Rotating Disc Method

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6159
Author(s):  
Maciej Zdanowski
Keyword(s):  
Molecular Diffusion ◽  
Mineral Oil ◽  
Electric Power System ◽  
Point Of View ◽  
Power Transformers ◽  
Main Element ◽  
Insulation System ◽  
Rotating Disc ◽  
Synthetic Ester ◽  
The Impact

Power transformers are the main element of an electric power system. The service life of these devices depends to a large extent on the technical condition of their insulation system. Replacing mineral oils with natural or synthetic ester (retrofilling process) may increase the efficiency and operational safety of transformers, and also limit their adverse environmental impact. It is technically unfeasible to completely remove mineral oil from a transformer. Its small residues form a mixture with fluid ester, with different physicochemical and electric properties. Streaming electrification is one of the phenomena which, under unfavorable conditions, may damage the insulation system of a forced oil cooled transformer. It is necessary to run prophylactic tests for the ECT (electrostatic charging tendency) of insulating liquid mixtures from the point of view of transformer retrofilling, which is being used more often than before. The article presents the results of studies on selected physicochemical, and electrical properties, and the ECT of mixtures of fresh and aged Trafo EN mineral oil with Nycodiel 1255 synthetic ester. In this regard, the density, the kinematic viscosity, the conductivity, and the relative dielectric constant were measured. The molecular diffusion coefficient was determined using Adamczewski’s empirical dependency. The streaming electrification was tested in a rotating disc system. The impact of the rotation time, the diameter, and the disc’s rotation speed on the amount of the electrification current generated were analyzed. In addition, the co-relation between the electrification current and the composition of the mixture was determined using fresh and aged mineral oil. On the basis of the electrification model, the volume density of the qw charge was calculated, which is a parameter defining the ECT of insulating liquids. Based on the results, it was concluded that the synthetic ester is characterized by a higher susceptibility to electrification than the mineral oil. However, combining synthetic ester with a small amount (up to 20%) of fresh or aged mineral oil significantly reduces its ECT, which is beneficial from the point of view of retrofilling power transformers.

scholarly journals Kinetic Assessment of Mechanical Properties of a Cellulose Board Aged in Mineral Oil and Synthetic Ester

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4150
Author(s):  
Cristina Fernández-Diego ◽  
Alfredo Ortiz ◽  
Isidro A. Carrascal ◽  
Inmaculada Fernández ◽  
Carlos J. Renedo
Keyword(s):  
Mechanical Properties ◽  
Kinetic Models ◽  
Mineral Oil ◽  
Power Transformers ◽  
Fiber Direction ◽  
Insulation System ◽  
Synthetic Ester ◽  
Aging Study ◽  
Kinetic Assessment ◽  
Materials Used

In oil-immersed power transformers, the insulation system is constituted of a dielectric oil–solid combination. The insulation oil generally used is mineral oil; however, this fluid has started to be substituted by natural and synthetic esters due to their higher biodegradability and flash point. The introduction of a new fluid in the insulation system of power transformers requires kinetic models that can estimate the degradation rate of insulation solids. The aim of this work was to go further in quantifying through different kinetic models the deterioration suffered by a commercial cellulose board (PSP 3055), which is one of the solid materials used in the insulation system of oil-filled transformers. The aging study was extended to cellulose board specimens immersed in two different oils (mineral and synthetic ester). It was obtained that there is a lower degradation when synthetic ester is used in the insulation system. Additionally, it can be concluded that the use of mechanical properties to quantify the degradation of the cellulose board through kinetic models provides information about the different behavior shown by PSP 3055 when different fiber direction angles are considered.

Electrophysical properties of mixtures of mineral oil and synthetic ester dielectric liquid

2021 ◽  
Vol 14 (2) ◽  
pp. 132-141
Author(s):  
M. N. Lyutikova ◽  
S. M. Korobeynikov ◽  
A. A. Konovalov
Keyword(s):  
Dielectric Loss ◽  
Breakdown Voltage ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Kinematic Viscosity ◽  
Mineral Oil ◽  
Flash Point ◽  
Power Transformers ◽  
Synthetic Ester ◽  
Insulating Properties

Power transformers are key equipment in power generation, transmission, and distribution systems. The reliability of power transformers is based on the performance of the insulation system, which includes solid cellulose insulation and a liquid dielectric. Modern power engineering requires liquid insulation to have excellent insulating properties, high fire resistance, and biodegradability. Mineral oil that has been in use for over 100 years does not meet certain requirements. Therefore, various methods of enhancing the insulating properties of the oil are currently being considered, including mixing it with other liquid dielectrics, which have excellent properties. Synthetic and natural esters are considered as alternative fluids.This article discusses the possibility of enhancing the insulating characteristics of mineral oil with a high content of aromatic hydrocarbons (for example, T-750 oil) by mixing it with synthetic ester Midel 7131. Assessment is given of insulating parameters of the resulting mixtures with an ester fraction in mineral oil from 0% to fifty%. The main characteristics of the mixtures are described, such as density, kinematic viscosity, flash point, dielectric loss tangent, relative dielectric permittivity, breakdown voltage, and moisture content. It is shown that with an increase in the proportion of ester, some parameters of the obtained insulating liquid improve (flash point, dielectric constant, breakdown voltage), while values of other parameters (density, kinematic viscosity, dielectric loss tangent) with an ester content of more than 10% in the mixture do not meet the requirements for mineral oils.

scholarly journals Effect of Moisture on the Thermal Conductivity of Cellulose and Aramid Paper Impregnated with Various Dielectric Liquids

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4433 ◽  
Author(s):  
Grzegorz Dombek ◽  
Zbigniew Nadolny ◽  
Piotr Przybylek ◽  
Radoslaw Lopatkiewicz ◽  
Agnieszka Marcinkowska ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Linear Equation ◽  
Heat Transport ◽  
Mineral Oil ◽  
Experimental Database ◽  
Synthetic Ester ◽  
Dielectric Liquids ◽  
Paper Insulation ◽  
The Impact ◽  
Natural Ester

This paper presents the effect of the impact of moisture in paper insulation used as insulation of transformer windings on its thermal conductivity. Various types of paper (cellulose and aramid) and impregnated (mineral oil, synthetic ester, and natural ester) were tested. The impact of paper and impregnated types on the changes in thermal conductivity of paper insulation caused by an increase in moisture were analyzed. A linear equation, describing the changes in thermal conductivity due to moisture, for various types of paper and impregnated, was developed. The results of measuring the thermal conductivity of paper insulation depending on the temperature are presented. The aim of the study is to develop an experimental database to better understand the heat transport inside transformers to assess aging and optimize their performance.

scholarly journals Study of the Dielectric Response of Ester Impregnated Cellulose for Moisture Content Evaluation

2018 ◽  
Author(s):  
A Graczkowski ◽  
J Gielniak ◽  
P Przybyłek ◽  
K Walczak ◽  
H Morańda
Keyword(s):  
Moisture Content ◽  
Dielectric Response ◽  
Mineral Oil ◽  
Operating Conditions ◽  
Power Transformers ◽  
Synthetic Ester ◽  
Measurement Results ◽  
Content Evaluation ◽  
Cellulose Insulation ◽  
Non Destructive

<p>Knowledge about moisture content in impregnated cellulose insulation is essential for power transformers when estimating remaining lifetime, planning operating conditions and drying procedure. Frequency dielectric spectroscopy (FDS) is non-destructive, convenient method to asses moisture content of insulation. It is important to study dielectric response of ester-cellulose insulation due to growing number of transformers using synthetic ester MIDEL 7131 as insulation fluid [1, 2]. The paper presents study of dielectric response of synthetic ester-pressboard samples with various moisture content (from dry to 5%) measured in wide temperature range (from 5 ˚C to 50 ˚C). Measurement results for pressboard impregnated with synthetic ester are compared to data of pressboard impregnated with mineral oil. The aim of presented work is to provide patterns of dielectric response of synthetic esterpressboard for accurate moisture content evaluation.</p>

Modeling and Validation of Hydro Cascade Operation Considering Price Uncertainty

2021 ◽  
Author(s):  
Maxime Libsig ◽  
Elena Raycheva ◽  
Jared B. Garrison ◽  
Gabriela Hug
Keyword(s):  
Market Price ◽  
Electric Power System ◽  
Point Of View ◽  
Computational Time ◽  
Price Uncertainty ◽  
Historical Simulation ◽  
Perfect Knowledge ◽  
System Operator ◽  
Price Uncertainties ◽  
The Impact

Abstract Most studies involving the use of hydropower in an electric power system tend to consider the point of view of the system operator even though under liberalized markets in Europe, the operation of hydro units is set by the owner to maximize their profits. Such studies also often neglect uncertainties related to hydropower operation and instead assume perfect knowledge of the system conditions over the simulation horizon. This paper presents a methodology to overcome the aforementioned limitations. We optimize the operational choices of a hydropower cascade owner with multiple linked hydro assets and the ability to participate in several energy and reserve markets while also accounting for the impact of market price uncertainties on the owner’s operating decisions. The versatile optimization model created includes a detailed representation of any selected hydro cascade’s topology, constraints to reflect the machinery characteristics, and a rolling horizon approach to account for the price uncertainties in the daily operating schedule. The model is first validated using historical data for a hydro cascade in Switzerland and a perfect-knowledge approach. Next, price uncertainty is added to improve the historical simulation results and find a trade-off between accuracy and computational time.

scholarly journals Application of Molecular Sieves for Drying Transformers Insulated with Mineral Oil, Natural Ester, or Synthetic Ester

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1719
Author(s):  
Mateusz Cybulski ◽  
Piotr Przybylek
Keyword(s):  
Molecular Sieves ◽  
Water Sorption ◽  
Sorption Isotherms ◽  
Mineral Oil ◽  
Drying Process ◽  
Insulation System ◽  
Synthetic Ester ◽  
Transformer Insulation ◽  
Natural Ester ◽  
Water Sorption Isotherms

A high level of moisture in the insulation system of power transformers is often the cause of their failure. This can be prevented by drying a transformer in its place of installation. In the article the application of molecular sieves (MS) in the drying process of the transformer insulation system was analyzed. The water sorption isotherms of 3A MS in mineral oil, natural ester, and synthetic ester at 35 °C were determined, which was not described in the literature before. An evaluation of the influence of temperature on the drying dynamics of electro-insulating liquids using MS was also carried out. The drying dynamics were tested at three temperatures, i.e., 35 °C, 50 °C, and 65 °C, which allowed to analyze the effect of temperature on a short-term or continuous drying process. The tests showed that 3A MS’s ability to adsorb water varied depending on the type of electro-insulating liquid. The determined water sorption isotherms, described by means of Langmuir adsorption model, make it possible to calculate the amount of MS needed for drying transformers with different liquid insulation. The research and analyses show the MS’s great potential for the drying of transformer insulation systems.

scholarly journals Effectiveness of management practices in the field of professional mobility of Russian youth

2020 ◽  
Vol 11 (4) ◽  
Author(s):  
Viktor Krivopuskov ◽  
Dmitry Mishchenko
Keyword(s):  
Young People ◽  
Labour Market ◽  
Management Practices ◽  
Professional Socialization ◽  
Management Strategies ◽  
Point Of View ◽  
Main Element ◽  
Professional Mobility ◽  
Low Efficiency ◽  
The Impact

This article analyzes and evaluates management practices in the field of professional mobility of Russian youth from the point of view of the effectiveness of the subjects of management of the system of professional mobility of youth (state, family, education, mass media, expert and professional communities). The study revealed that management practices in the field of professional mobility of young people are characterized by low efficiency and are mainly focused on eliminating the risks of professional mobility. Marked fragmentation of subjects of management system of professional mobility of youth in the conditions of crisis the main element of the system «education – labour market» and the crisis of the institution of education. Risks from the point of view of their detection and prevention is based on reducing the impact of environmental and activity-related risks in the process of professional self-determination and formation of young people not included in management strategies and programs, and even management practices focused on development of innovative methods and channels of professional mobility of young people (all-Russian competitions, projects) that have a real positive effect, have the character of local, fragmentary, not able to radically change the situation in this key area of life-realization of youth. In the end it is stated that a new approach is needed to the management of professional mobility of the youth, based on risk management professional mobility taking into account their nature, derived from the influence of environmental factors (global Informatization, «mobile turn», the crisis of the system of professional socialization, labour market, etc.), and activity expressed in the individualization of the social behavior of youth and a pronounced orientation at a multiple of professionalization and inter-occupational mobility.

The Impact of the Converter on the Reliability of a Wind Turbine Generator

2019 ◽  
Author(s):  
Gopal Singh ◽  
Santiago Lentijo ◽  
Kalpathy Sundaram
Keyword(s):  
Wind Turbine ◽  
Temperature Rise ◽  
Selection Procedure ◽  
Point Of View ◽  
Limiting Factors ◽  
Insulation System ◽  
Generator System ◽  
Wind Generators ◽  
Winding Insulation ◽  
The Impact

Abstract Temperature rise is one of the limiting factors in generator design. Bearings and windings failure are the two most prominent cause of generator failure in the wind turbine application. The generator is mostly converter-fed in the wind turbine application, and operation with converter brings specific challenges. Insulation of generator system should be designed in such a way to withstand these challenges. Two immediate problems with converter-fed wind generators are winding temperature rise due to harmonic losses and voltage peaks. Voltage peaks generated by converter can create a winding hotspot and eventually destroy the insulation system of generator winding, which leads to reducing the lifetime of the insulation system. Turbine availability study from a commercial point of view is presented. For selecting the winding insulation system, it is essential to know the environment generator is going to operate. Specific voltage peaks from different converter systems can damage windings insulation. Damage insulation brings the downtime of the turbine, which affects the LCOE and AEP of the wind turbine. The electrical voltage between motor terminals and ground can be generated due to the different converter output circuit, longer feeder cables (when converter being placed on the basement and not in the nacelle) on the and unfavorable grounding conditions. Paper discusses voltage peaks due to operation with converter and make a recommendation for the winding insulation system, for a particular case. A better selection procedure for a generator winding insulation system is recommended.

scholarly journals COUPLED ELECTROMAGNETIC-THERMAL SIMULATION OF A POWER TRANSFORMER BY 3D FEM

2020 ◽  
Vol 60 (5) ◽  
pp. 400-409
Author(s):  
Henrique Oliveira Henriques ◽  
Carlos Eduardo Vizeu ◽  
Paulo Cesar Souza ◽  
Mauricio Caldora Costa ◽  
Guilherme Gonçalves Sotelo ◽  
...  
Keyword(s):  
Power Transformer ◽  
Hot Spot ◽  
Computation Time ◽  
Electrical Energy ◽  
Electric Power System ◽  
Power Transformers ◽  
Economic Losses ◽  
Variable Load ◽  
3D Fem ◽  
The Impact

Power transformers are the most common equipment in an electric power system, which has been manufactured in the last decade. However, overheating can damage them, considerably reducing their operation lives, which may cause economic losses to the power utilities. The motivation of this paper is to investigate the time and power overload limits that a power transformer can be subjected to and how it will impact its temperature. Investments in the grid can be delayed if a transformer can support some overload during some momentary load demand increase. In this context, this paper presents a study of a 30/40MVA power transformer by 3D finite element method (FEM) for coupled thermal-electromagnetic simulations to investigate its thermal behaviour when it is submitted to its nominal load at a steady-state operation and a variable load during a period of one day. The simulations were performed with the commercial software packages Flux 3D and AcuSolve, for electromagnetic and thermal modelling, respectively. The modelled equipment was based on a power transformer installed in the Light Serviços de Eletricidade S.A, the utility that supplies electrical energy to the city of Rio de Janeiro, in Brazil. Since the literature doesn’t present many works simulating coupled thermal-electromagnetic power transformers in 3D-FEM, this paper has the goal to bring new contributions to this field. Three study cases were modelled, and some simplifications in transformer’s geometry were made in some of them to reduce the computation time usually required for such a simulation. The obtained results are presented and compared with the measured values for the temperature in the hot spot of the transformer and in the top of the oil, to investigate the impact of these simplifications in the calculated results.

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