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This article describes the influence of thermal properties of materials to properties of electrical insulating systems (EIS) in electrical rotating machines. Multi-component composite materials combine the advantage of the individual materials, and allow generate new materials with better properties than those of individual components (the synergistic effect). The objective of this experiment is to...
Technological progress creates new challenges, especially in the areas of energy savings, environmentally friendly materials and sustainable development. These challenges exist for electroinsulating materials, including electroinsulating fluids. Finding substitutes for the petroleum-based fluids used in electrotechnics is not a simple task. It involves the geopolitical location of the manufacturer...
Electrical technology diagnostics is a branch of science examining the actual state of electrical machinery under the operation when using two basic accesses. The first and older one is an “off-line diagnostics”. It means a device or an appliance subjected to diagnostic process need to be for example disconnected from circuit, turned off or stopped. An on-line diagnostics — diagnosing a device during...
An influence of thermal and voltage treatments on properties of high-temperature electrical insulating material based on mica and silicone binder was analyzed. Tested material is intended for an operation at extremely high temperatures along with electric field stress. The main aim was to describe the high temperature and electric field influence on the material inner structure. Thermal treatment...
The stator wedge supporting material is used for diagnosing the state of the main insulation in rotating machines. The stator wedge is placed in a stator slot, and the material is aged using the same degradation conditions experienced by the bar winding insulating system itself. The possibility of easy replacement of the supporting material without causing any damage to the whole insulating system...
The working life of electrical machines is primary affected by the insulation system quality. Diagnostics methods help to understand the momentary state of insulation and to avoid the possible damage or electrical breakdown of machines through the repair or insulation rewinding. Partial discharges testing belongs to one of the high applicable test method of insulating materials within electrical machines...
Power transformers are reliable high performance electrical machines. The reliability of the power transformer is directly linked to the electrical insulation reliability. Well known and long time used paper-oil insulation system stands on the threshold of a new era. Due to the international agreements and environmental requirements it is compulsion to substitute petroleum based oils with synthetics...
Power transformer service availability is influenced by a condition of insulating and cooling medium - by transformer oil properties. The transformer is subjected to many untypical situations arising casually or due to changed operation conditions. Between the casual phenomena belongs e.g. an unbalanced loading, which causes phases overload etc. These situations reflect on the properties of cooling...
Insulation liquids are mainly used in oil filled transformers for their cooling and insulating properties. Besides a testing of electrical properties, there is also important to monitor oxidation stability and activation energy as the factors which can decide on an application possibility of the insulating liquid. The main aim of this paper is to describe the influence of temperature aging on the...
Power transformers are inconsiderable group of the electrical appliances with two components insulation system. One of the components - liquid insulating medium plays two roles- insulating and cooling. It can be mineral as well as synthetic based liquid. Second component is an organic based solid insulation usually of cellulose character. Organic materials of this structure are sensitive to an operational...
Insulating system of power transformers is mostly composed of two basic components: insulation oil and cellulose paper (oil-paper system). These components are of an organic nature and thatpsilas why they become very sensitive to operation degradation conditions (temperature, oxidation, moisture etc.). Aging of these components can endanger the failure free operation of the transformers. The main...
Composite insulating materials have their important place in high-voltage insulating technology. The quality and high reliability of electrical devices is much affected by the curing level of these materials. Curing level is quantified by so-called degree of conversion and there are several possibilities how to determine this degree in practice. Attention is given mainly to kinetic analysis based...
Poly(ethylene:vinyl acetate) (pEVA) and polyether urethane-urea (PEUU) are widely used i.a. as materials for electric cable insulation, hence they contain various fiame-retardants for this purpose. Two flame-retardant filled pEVA samples are compared with PEUU sample without flame-retardant. Thermal effects accompanying the burning of these materials are examined by differential scanning calorimetry...
During the last few decades, partial discharge measurement and analysis have been considered one of the most important test methods for evaluating the quality of electrical machines and insulating systems. Test methods based on potential free capacitive and/or inductive couplers have taken place as well as methods based on the galvanic circuit with measuring impedance. These potential free couplers...
The construction of electrical devices operating under the extreme temperatures requires the knowledge of their particular components behavior during the processing and operation of these devices. The minimum amount of volatile release is one of the requirements imposed on these materials. Thermal analyses (especially Thermogravimetry TG and Differential Thermal Analysis DTA) are considered to be...
A condition of oil-paper insulating system is principal diagnostic indicator for failure-free operation of power transformers. This insulating system is thought to be one of the key components of the whole machine. During the operation of the transformer ageing of the insulating system appears, which may cause changes of its important electrical and mechanical properties. Many factors work simultaneously...
Monitoring of the properties and applicability of high-voltage insulating systems containing epoxy resins require knowledge of curing degree of these resins. This curing degree is considered to be the key parameter for quality of materials used for these systems. Application of differential thermal analysis (DTA) for evaluation of curing degree of three-component composite materials (glass fabric,...
Industrial controls have experienced dramatic changes in the past twenty years. Especially advances in adjustable speed drive technology are very well observable. This technology produces repetitive pulses with the high level of voltage rise fronts (slew rates). However, this technology is an advantage for a drive control; the voltage waveforms generated by power frequency converters may affect significantly...
The construction of electrical devices operating at extremely high temperatures requires insulating systems with appropriate thermal properties. Insulating materials based on mica and silicone binder are usually used for this purpose. For these materials, it is necessary to understand their behavior under operating temperatures, as well as the specific properties which characterize their behavior...
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