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>

scholarly journals Assessment of Concentration of Mineral Oil in Synthetic Ester Based on the Density of the Mixture and the Capacitance of the Capacitor Immersed in It

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1839
Author(s):  
Hubert Moranda ◽  
Jaroslaw Gielniak ◽  
Ireneusz Kownacki
Keyword(s):  
Mineral Oil ◽  
Power Transformers ◽  
Scientific Achievement ◽  
Similar Measurement ◽  
Drying Process ◽  
Mixture Density ◽  
Synthetic Ester ◽  
Capacitance Method ◽  
Oil Concentration ◽  
Cellulose Insulation

This research was carried out during the realization of a project with the aim of developing a method of drying cellulose insulation in power transformers by using synthetic ester. Unfortunately, during the drying process, the ester is systematically contaminated with mineral oil, which reduces its water absorption. Information on the oil concentration in the mixture is needed in two cases: when deciding how to treat the mixture, and during the treatment. The article presents two methods: (1) based on the measurement of the mixture density, and (2) based on the measurement of a capacitor immersed in the mixture. The most important scientific achievement of the work is the proof, by way of experiment, of the existence of a relationship between the concentration of mineral oil and (1) the density of the mixture, and (2) the capacity of the capacitor immersed in it. These relations are presented in the form of equations for which the error calculus showed that the uncertainty of measurement for both methods did not exceed 3 p. %. Due to the similar measurement error of both methods, the authors recommend the capacitance method as easier to use, especially online.

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 A New Concept of Applying Methanol to Dry Cellulose Insulation at the Stage of Manufacturing a Transformer

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1658 ◽  
Author(s):  
Piotr Przybylek
Keyword(s):  
High Temperature ◽  
Moisture Content ◽  
Power Transformers ◽  
Technical Challenge ◽  
Moisture Contents ◽  
Percentage Points ◽  
Time Period ◽  
Drying Techniques ◽  
Heating Up ◽  
Cellulose Insulation

A decisive technical challenge for transformer manufacturers is correctly drying the cellulose insulation. During the production of a transformer, it is necessary to reduce its insulation’s moisture content from about 8% to less than 1% in the shortest possible time period. The drying of insulation is a time-consuming process, and for high-power transformers, it can last up to three weeks. Several drying techniques are used during the production of a transformer, and all of them require heating up the insulation to a high temperature and applying a vacuum. Unfortunately, the use of a high drying temperature above 100 °C can cause a decrease in the degree of cellulose polymerization by over a dozen percentage points. This paper presents a new concept for drying cellulose insulation that does not require heating insulation and applying a vacuum. In this solution, methanol is used as the drying medium. The research results showed the possibility of drying cellulose insulation by means of methanol with different initial moisture contents. The possibility of completely drying pressboard of various thicknesses for a sufficient period of time was also proven. The paper also presents a new concept of both the device and the procedure for drying cellulose insulation by means of methanol.

Tribological Studies on Oscillating Bronze Bearings Lubricated With Environmentally Adapted Lubricants (EALs)

2004 ◽  
Author(s):  
Jan Ukonsaari ◽  
Elisabet Kassfeldt
Keyword(s):  
Surface Layer ◽  
Mineral Oil ◽  
Tribological Performance ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Bearing Surface ◽  
Bearing Material ◽  
Sliding Bearings ◽  
Synthetic Ester ◽  
Tin Bronze

Different compositions of bronze materials are used for sliding bearings in various applications including those involving oscillatory motion and moderate temperatures. The compatibility of new environmentally adapted synthetic esters with different contacting surface materials is important to ensure good tribological performance. The present work deals with tribological studies on oscillatory journal bearings manufactured with three different compositions of bronze materials lubricated with EALs under boundary lubricated conditions. Under certain operating conditions, dissolution of alloying constituents from the bronze bearing material dissolute into the synthetic ester lubricant occur leading to the formation of a copper enriched bearing surface layer. Tin-bronze with synthetic ester lubricant showed more stable friction values and roughly ten times better wear results than the harder aluminium- and manganese-bronze and also outperformed the mineral oil under the same conditions.

Effects of slide-roll ratio and lubricant properties on elastohydrodynamic lubrication film thickness and traction

2001 ◽  
Vol 215 (3) ◽  
pp. 301-308 ◽  
Author(s):  
J Lord ◽  
R Larsson
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Mineral Oil ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Thickness Reduction ◽  
Lubrication Film ◽  
Synthetic Ester ◽  
Lubricant Films ◽  
Two Factors

With tribology research aimed at decreasing energy consumption, two factors are inherently in focus: lubricant film thickness and traction. These factors are effectively decoupled and depend on lubricant properties which are sometimes contradictory-favourable for one factor and disadvantageous for the other. The film thickness ought to be maximized to reduce the number of asperities in contact and thus wear, whilst the traction should be minimized in order to reduce energy losses. In this experimental investigation the tested lubricants were investigated to see whether they possess beneficial properties for forming thick lubricant films under severe operating conditions while maintaining low traction forces. This is done by experimentally studying the film thickness reduction due to thermal and rheological effects for a fully flooded electrohydrodynamic lubrication (EHL) contact. The base oils tested were a naphthenic mineral VG150, a synthetic poly-α-olefin VG68 and a synthetic ester VG46. It was found that the synthetic ester maintained a relatively thicker lubricant film during sliding than the poly-α-olefin and mineral oil. The film thickness reduction for the mineral oil was greater than for the poly-α-olefin.

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.

Improved method for measuring moisture content of mineral-oil-impregnated cellulose pressboard based on dielectric response

Cellulose ◽  
2018 ◽  
Vol 25 (10) ◽  
pp. 5611-5622 ◽  
Author(s):  
M. Zhang ◽  
J. Liu ◽  
J. Lv ◽  
Q. Chen ◽  
P. Qi ◽  
...  
Keyword(s):  
Moisture Content ◽  
Dielectric Response ◽  
Mineral Oil ◽  
Improved Method

Tribological Studies on Oscillating Bronze Bearings Lubricated With Environmentally Adapted Lubricants (EALs)

2004 ◽  
Vol 128 (1) ◽  
pp. 181-187 ◽  
Author(s):  
Jan Ukonsaari ◽  
Elisabet Kassfeldt
Keyword(s):  
Surface Layer ◽  
Mineral Oil ◽  
Tribological Performance ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Bearing Surface ◽  
Bearing Material ◽  
Sliding Bearings ◽  
Synthetic Ester ◽  
Tin Bronze

Different compositions of bronze materials are used for sliding bearings in various applications including those involving oscillatory motion and moderate temperatures. The compatibility of new environmentally adapted synthetic esters with different contacting surface materials helps ensure good tribological performance. The present work deals with tribological studies on oscillatory journal bearings manufactured using three different compositions of bronze materials lubricated with EALs under boundary lubricated conditions. Under certain operating conditions, alloying constituents from the bronze-bearing material dissolute into the synthetic ester lubricant, thereby leading to the formation of a copper enriched bearing surface layer. Tin-bronze with synthetic ester lubricant showed more stable friction values and roughly ten times better wear results than harder aluminium- and manganese-bronze as well as outperforming the mineral oil under the same conditions.

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