Authors : Saleh A. Al-Jufout and Emad S. Addasi
Abstract: This study presents, a theoretical approach to develop a digital protection method against 3-phase short circuits on radial electrical power systems that decreases the fault clearance time and thus, increases the stability of the system. The criterion used in this proposed, protection method is the inclination angle of the envelope of the short-circuit current. The concept of the current envelope has been introduced and its change during 3-phase faults has been analyzed. The inclination angle has been calculated and its use as a criterion for protection against 3-phase faults on radial electrical power systems has been discussed. The suggested protection method has been developed with the use of mathematical modelling of the radial electrical power system. The mathematical model has been represented as a system of differential equations for currents and a system of algebraic equations for bus voltages. This model has been formulated in a rectangular coordinate system and has been developed for both steady-state and transient analyses. The curves of the envelope of the short-circuit currents during the first 2 milliseconds after the fault instant and the time grading diagrams of the proposed protection method have been illustrated.
Saleh A. Al-Jufout and Emad S. Addasi , 2009. Instantaneous and Time-Overangle Protection Against Three-Phase Faults on Radial Electrical Power Systems. International Journal of Electrical and Power Engineering, 3: 69-75.