The development of power electrical systems causes attention to accuracy of protection elements and measurement values. So we need some new measuring devices with high accuracy for power transmission lines. One of these devices is Optical Current Transformer (OCT). Optical current transformers are suitable for power system protection and can replace the magnetic current transformers. In this pa...

(Received: October 30, 2011; Accepted: December 8, 2011) Abstract: This paper presents a novel technique for transformer differential protection to prevent incorrect operation due to inrush current. The proposed method in this paper is based on time-frequency transform known as the Wavelet transform. The discrete Wavelet transform is used for analysis the differential current signals in time an...

This article presents a novel technique to distinguish between magnetizing inrush current and internal fault current of power transformer. An algorithm has been developed around the theme of the conventional differential protection method in which parallel combination of Probabilistic Neural Network (PNN) and Power Differential Protection (PDP) methods have been used. Both PNN and PDP method ar...

In this paper, the properties of the physical and chemical materials, such as low loss amorphous HB1 core, high temperature resistance winding and insulation vegetable oil have been developed for use in liquid-immersed power transformer. The measured results of magnetic properties with different ferromagnetic materials core were obtained. Considering winding property for operation above 95°C co...

Internal Turn-Turn faults (TTF) are the most common failures in power transformers, which could seriously reduce their life expectancy. Although common protection schemes such as current-baseddifferential protection are able to detect some of the internal faults, some other minor ones (such as TTFs andshort circuit near the neutral point) cannot be detected by such schemes. Likewise, these rela...

-Protective systems require a faithful reproduction of primary current on the Current Transformer (CT) secondary side. Saturation is a common problem in a steel core CT. Saturation problem causes dreadful effects in the protection systems. This paper presents a simple solution towards detection and compensation of current transformer saturation problems. This paper describes a method in which C...

Transformer differential protection may be of malfunction at the emergence of inrush current, and it will affect the normal operation of the transformer. So the paper puts forward a new application of wavelet energy spectrum entropy-neural network theory in transformer microcomputer protection, in which the multi-resolution analysis of wavelet transform and information entropy technology are co...