Phase Comparison Protection of Parallel Power Lines

Abstract

The known transverse protections of two parallel power transmission lines are briefly analyzed. A protection that is free from their shortcomings but retains their inherent advantages is suggested. It detects a faulty line from the ratio of the phase angle shifts between the current equal to the difference of currents in the same phases of the first (second) and second (first) lines and the current in the same phase of the first (second) line). It is shown that the cascade action zone of the proposed protection is no more than 11 % of the line length due to monitoring the presence of current in the lines and the ratio of the modulus of the difference between the absolute values of the currents in the same phases to their sum. The technique for choosing the protection actuation parameters is described. The protection operation algorithm is formulated and written in switching algebra symbols. Its implementations using microprocessor and semiconductor devices are given. The protection operation in different modes is analyzed by mental and computer simulations. Time curves constructed in the MatLab environment confirm the protection performance. The results of comparison of the suggested protection with the most advanced ones of the known protections are presented.