A Graphical Tool to Examine the Coordination Details of Directional Overcurrent Protections as a Function of Fault Location

This letter describes a novel graphical tool that was developed to check the coordination details of directional overcurrent protections (67) as a function of the fault location. The tool considers transient configurations due to sequential trips at both line-ends, and shows three important issues of coordination for each fault location: a) separation between operation times of main and backup 67s; b) currents seen by each 67 prior to and after the trip of the first circuit breaker; c) possible loss-of-sensitivity of backup 67s due to the pickup setting or due to direction of current. A previously developed simulator performs the calculations, using 1000 fault locations for each protected line, and it is complemented by the proposed graphical tool.