The measurement of oil-paper insulation systems in the frequency domain provides novel diagnostic methods for quality control of materials and highvoltage power transformers. The first task is to measure and to analyse the dielectric behaviour of oil-paper insulation systems and their dependency on material quality, moisture content and ageing products in oil, paper and pressboard. Furthermore,...

Reliability of electrical energy networks depends on quality and availability of electrical equipment like power transformers. Local failures inside their insulation may lead to catastrophic breakdowns. To prevent destroying events power transformers are e.g. tested on partial discharge (PD) activity. As testing is just snapshot information about transformers condition, permanent online monitor...

Incipient fault diagnosis of a power transformer is greatly influenced by the condition assessment of its insulation system oil and/or paper insulation. Dissolved gas-in-oil analysis (DGA) is one of the most powerfull techniques for the detection of incipient fault condition within oil-immersed transformers. The transformer data has been analyzed using key gases, Doernenburg, Roger, IEC and Duv...

The number and diameter of strands to minimize loss in a litz-wire transformer winding is determined. With fine stranding, the ac resistance factor can be decreased, but dc resistance increases as a result of the space occupied by insulation. A power law to model insulation thickness is combined with standard analysis of proximity-effect losses to find the optimal stranding. Suboptimal choices ...

In transformers the main consequence of harmonic currents is an increase in losses, mainly in windings, because of the deformation of the leakage fields. Higher losses means that more heat is generated in the transformer so that the operating temperature increases, leading to deterioration of the insulation and a potential reduction in lifetime. This paper includes the effects of non-sinusoidal...

Power transformers are the most complex, important and critical components of the transition and distribution power systems. Insulation system is the key component of life extension, better availability and higher reliability of a transformer. In order to achieve both decreasing operational cost and reliable service conditionbased maintenance is needed. Monitoring and diagnostic methods and tec...

Power transformers are important and expensive components in the electric power system. The knowledge of the actual status of the transformer insulation behavior, load tap changer performance, temperature, and load condition is necessary in order to evaluate the service performance concerning reliability, availability and safety. Systems abnormalities, loading, switching and ambient condition n...

The Hot Spot Temperature (HST) value depends on the ambient temperature, the rise in the top oil temperature (TOT) over the ambient temperature, and the rise in the winding HST over the top oil temperature. In this paper a new semi-physical model comprising of the environmental variables for the estimation of HST and loss of insulation life in transformer is proposed. The winding hot-spot tempe...

Transformer is one of the most important and costly apparatus in a power system. The reliable and efficient fault free operation of transformer has a decisive role in the availability of electricity supply. In recent years, there has been growing interest in the condition assessment of transformer insulation. In this paper we concerned about the condition monitoring of transformer, benefit of c...

Abstract: Mineral oil is widely used as liquid insulation in high voltage equipment. Due to environmental considerations, recently natural esters have been considered as naturally friendly liquid insulation candidates for high voltage transformers. In this experiment, transformer insulation paper was subjected to get accelerated aging test with copper strip in natural ester in a hermeneutical h...