Microprocessor-Controlled Differential Protection of a Power Transformer.

Document Type : Research Studies

Authors

1 Department of Electrical Engineering., College of Eng., University., of Basrah., Irag.

2 Department of Electrical Engineering., College of Engineering., University of Basrah., Irag.

Abstract

 The paper presents a developed algorithm or a digital filter for the Fast computation of the fundamental and higher harmonics of the differential current of a differential protected power transformer. The derived algorithm is based upon the discrete Fourier transform ( DFT). An estimation technique is used in the algorithm to compare the magnitude of the second-harmonic of the differential current with its fundamental content. Then a microprocessor trip command is given or blockad depending on the result of comparison. 
The proposed computation algorithm has been coded on a microprocessor unit. Necessary prephirals have been built to link the microprocessor to a complete differential protection scheme on a single-phase power transformer. The whole protective set-up is put into working order for test. 
Laboratory experimental investigations of performance of the protective scheme showed accurate discriminative operation of the relaying circuit for different abnormal conditions. The algorithm is simple, fast and highly discriminative and can be implemented in power system protection. 

Main Subjects