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This paper focuses on evaluating the influence of thick films on the electrical properties of ceramic substrates, especially their dielectric strength. Dielectric strength is one of the most important parameters of the substrates used in power electronics. Increasing the thickness of the conductive films on these substrates is necessary to achieve sufficient current capability. The glass phase of...
Natural oils are divided into vegetable and mineral oils. Compared with vegetable oils, the mineral oils show better dielectric properties, however, they can be dangerous for the living environment and their flammability is higher. The vegetable oils are composed of natural ester molecules with a triacylglycerol structure. The mineral oils are a mixture of hydrocarbons produced from crude oil. Recently,...
The difficulty with the insulation oils is well known and it has been dealt with several years by now. Using the mineral oils as a transformer insulating fluid represents a thread to the environment. With a considerable amount of research, the biodegradable insulating fluids based on natural esters were developed and used as a replacement for mineral oil. Their main features are biodegradability,...
The insulating liquids for power transformers are still evolving area. The current trend is to move away from currently used mineral oil because it poses a threat to the environment and use the renewable, biodegradable nature ester oils instead. These oils are now well known but what keeps them from widespread usage are unbalanced properties. In some areas these natural oils excel (fire point, sulfur...
Natural oils are divided into vegetable and mineral oils. Compared with vegetable oils, the mineral oils show better dielectric properties, however, they are rather dangerous for the living environment and their flammability is higher. The vegetable oils are composed of natural ester molecules with a triacylglycerol structure. The mineral oils are a mixture of hydrocarbons produced from crude oil...
Because of the financial savings and with respect for the environment, several efforts are made to replace AC voltage long distance transmission lines for DC voltage transmission lines. This may lead to increases of charging of insulation materials. The main aim of this paper is to describe the space charge accumulation in insulation material and its effect on local overloading of insulation material...
Composite insulation systems are inseparable part of most electrical installations. Strongly inhomogeneous structure of these systems is the main problem which may lead to defect during operation life. Main aim of this paper is to introduce novel composite material designed for insulating system of high voltage equipment. This material is composed of epoxy resin matrix with dispersed magnesium oxide...
This paper describes the assessing the lifetime curves of composite insulation under different kind of voltage stress. This covers several areas that are important for using the electrical insulation properly. First one is the composite insulation. The use of this kind of insulation is rising, new types of composites are being invented and investigated with the aim for the best achievable properties...
The world of diagnostics has to keep up with the needs and possibilities today's world requires and offers. Everybody want the desired information in a cheap way and with minimum delay. The world of diagnostics is no different. Online diagnostic tools can cover these demands. Proper usage of tools like CBM (Condition Based Maintenance) can save us lots of money otherwise spend on unnecessary maintenance...
This paper deals with diagnostic of composite insulation material which are currently used in high voltage appliances e.g. in large rotating machines — turbo or hydro generators. This composite is consist of calcinated mica paper, polyethylene terephthalate (PET) foil and epoxy-novolac resin. The insulation composite material with inhomogeneous structure was subjected to accelerated thermal aging...
Electrical insulation system is an important part of electrical equipment with high requirements — accuracy, quality, reliability and environmental protection. In power and distribution transformers is the most common electrical insulating system oil-paper system. The liquid component of the insulation system is used as a cooling and insulating medium as well. The most commonly used liquid insulating...
The world of diagnostics has to keep up with the needs and possibilities today's world requires and offers. Everyone want to have the information they desire at the moment and, of course, at minimal cost. The world of diagnostics is no different. One tool that offers that is the online diagnostics. It has many benefits that allow, with proper usage of tools like CBM (condition based maintenance),...
Natural esters are candidate fluids for transformer insulation system. Recently the most common insulation system in power transformers is paper-oil system. Oil generally mean petroleum based insulating fluid. As there are efforts to preserve sustainable development, crude oil products should be eliminated and replaced by natural products, which are easily biodegradable. In past it was shown that...
Until now not much attention was paid to behavior of insulating materials under different voltage stresses. For decades, the applied research was done generally under AC voltage. As power electronics was involved in drives and dominated instead of DC drives, new troubles with lifetime occurred. The great influence of higher harmonics does not affect operating parameters only but also it limits the...
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