Dynamic Zone Selection for Busbar Protection Based on Graph Theory and Boolean Algebra

This article presents a method based on graph theory and Boolean algebra, to obtain dynamic zone selection for busbar protection applications. The solution is an offline software-based tool capable of calculating logic equations for any bus configuration in terms of the status of switching devices. Therefore, the equations can be set up and executed in real time when using existing relays. The method accounts for normal bus-switching sequences, in-service transfer, bypassed current transformers, breaker substitution, and paralleled buses. One of the main benefits is that neither logic equations nor switching analysis are required as inputs when using this method. The obtained logic equations can be set up in most existing bus relays in a straightforward manner. The method was tested in two bus arrangements, and the results have proven its effectiveness.