one of the major problems that may occur in the differential protection systems of power transformers is mal-operation of the protection relays in sake of internal fault detection, because of similarity between this current and inrush current. this paper presents a novel approach for discriminating inrush current from internal fault in power transformers based on improved gravitational search a...

The study introduces the detailed sequence of operations necessary to determine the selfand mutual inductances of power transformers from numerically simulated open-circuit and bucking experiments. Parameters of a welding style transformer are compared to those of a normal step-down transformer of equivalent ratings. The investigation identifies the different patterns of magnetic flux circulati...

This paper presents a novel approach based on the back-propagation neural network (BPNN) for the insulation diagnosis of power transformers. Four epoxy-resin power transformers with typical insulation defects are purposely made by a manufacturer. These transformers are used as the experimental models of partial discharge (PD) examination. Then, a precious PD detector is used to measure the 3-D ...

Usually, harmonics are the base point when engineers start to analyze waveform distortion. Frequencies of these voltage and current waveforms are integer multipliers of the base frequency of power system (50 Hz or 60 Hz). If it is not the case then these are named as intermediate harmonics. The sinusoidal waveforms of voltage characterize the ideal power system with the highest clarity of base ...

Transformers are generally considered to be the costliest assets in a power network. The lifetime of transformer is mainly attributable condition its solid insulation, which turn measured and described according degree polymerization (DP) cellulose. Since determination DP index complex time-consuming requires taken out service, utilities prefer indirect non-invasive methods determining based on...

In this paper, multilayered coreless printed circuit board (PCB) step-down power transformers for DC-DC converter applications have been designed, manufactured and evaluated. A set of two different circular spiral step-down transformers were fabricated in the four layered PCB. These transformers have been modelled with the assistance of high frequency equivalent circuit and characterized with b...

This work investigates the use of a specially designed cylindrical metal cell, in order to obtain complex permittivity and tanδ data of highly insulating High Voltage (HV) transformer oil samples. The data are obtained at a wide range of frequencies and operation temperatures to demonstrate the polarization phenomena and the thermally stimulated effects. Such complex permittivity measurements m...

Due to the relatively large availability and reduced price, the mineral transformer oils are widely used as electrical insulating liquids. However, mineral oil drastically degrades over time in service. New efforts were made to improve mineral oils characteristics, and other types of liquids like vegetal oils are proposed. This paper deals with new comparative tests on mineral and vegetal oils ...