Digital protective relaying algorithms for double circuit lines protection

This paper presents digital relaying algorithms for double circuit lines protection using synchronized phasor measurement units. Most of the double-circuit lines in Taiwan are built in the same tower and they are generally untransposed. Therefore, this paper focuses on the design of relaying algorithms for untransposed double circuit fines. The basic principles are extended from those of a single-circuit line. The functions of the developed algorithms include fault detection, internal and external faults discrimination, and faulted-circuit identification. Both of two-terminal three voltages and six currents in the two protected circuits measured by PMUs are used in the algorithms. EMTP/ATP simulator is used to verify the performance of the proposed algorithms. Some typical responses of the algorithms are reported.