Quadrilateral relay based distance protection scheme for transmission lines under varying system conditions

Quadrilateral relay provides flexible protection during high fault resistance of ground and phase faults. This is advantageous for protection of phase-to-earth faults on short lines, non-effectively earthed systems and feeders with extremely high tower footing resistance. It also provides fault impedance coverage for both phase to phase and phase to ground faults. The proposed work intends the development of a numerical quadrilateral distance relay that can retain its function even under a major change in system configuration. The proposed relaying scheme is analyzed by coding the relay logic and simulating the system with transmission network in MATLAB/Simulink. Different factors influencing the performance of quadrilateral relay are studied and verified. It is observed that the scheme is adaptive to the system variations and mal trips are reduced.