A Backup Protection Technique for Three-Terminal Multisection Compound Transmission Lines

This paper presents a backup non-iterative protection technique for three-terminal multisection compound untransposed double-circuit transmission lines using synchronized phasor measurement units. The proposed technique is based on a distributed line model taking into account the mutual couplings between the two circuits. Synchronized voltage and current measurements in the phase domain are utilized for fault detection, classification, and location. The proposed technique can discriminate internal transmissions lines faults from other load change conditions or external faults and identify correctly the faulty branch and fault type, as well as determine accurately the fault location. The proposed algorithm is tested under different fault resistances, different fault locations, different fault inception angles, different fault types, non-linear high impedance faults, evolving faults, and synchrophasor errors, as well as transmission line parameters errors. Extensive simulation studies carried out using MATLAB software show that the proposed protection technique yields acceptable performance for all simulated cases.