False Trip in Double-Circuit Lines Due to Improper Time-Settings of the Teleprotection System

One of the main advantages of double-circuit lines is to improve the reliability of transmission systems by providing redundant paths between two substations, so that the power flow can remain established after clearance of a fault on either of the parallel circuits. Accordingly, false tripping of healthy circuit is undesirable since it imposes an N-2 contingency on the power system. This paper presents the results of laboratory tests performed on a commercial teleprotection system (TPS), and shows that improper settings of the TPS could cause false tripping in double-circuit lines by increasing the pulse-width of teleprotection commands. Then, an actual event occurred in a 230kV double-circuit line is analyzed, in which a healthy circuit is tripped during the transient interval of fault clearing process in its adjacent circuit. Performing simulation studies in the PSCAD/EMTDC program, it is shown that the mentioned false trip is prevented using the proposed modifications in the TSP settings.