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

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.

PROPERTIES IMPROVEMENT ON POLYESTER FABRIC USING POLYVINYL ALCOHOL

Polyethylene terephthalate is one of the important synthetic ester polymeric material used in widespread areas. In textile industry, this fibrous material finds use in most of the garment and apparel applications due to its ease of handling, maintenance, and drying and competes with cotton materials. However, due to the maximum hydrophobic behavior, this textile material gives number of issues like accumulation of statics, negligible moisture content, poor comfort and aesthetic characters. Hence, in order to use this polyester material in the general textile industries particularly for garment and apparel productions, it is necessary to increase to some extent of its hydrophilic character by the application of some suitable chemicals like polyvinyl alcohol. In these context, in this work an attempt is made to treat the polyethylene terephthalate fabric with sodium hydroxide followed by polyvinyl alcohol so as to increase the aesthetic properties. The output received after the polyvinyl alcohol treatment on this fabric gives the good results expected for the garment applications.

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

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.