Increasing sensitivity for transformer protection using incremental differential

Abstract

This study presents a new protection element that can increase transformer differential sensitivity. The new element, called incremental differential, takes the differential currents, operation and restraint currents and, using a new mathematical approach, it can be more sensitive than the standard differential. The study presents the mathematical calculation and how the incremental differential handles with the errors involved in the differential protection. It also presents the algorithm response for some fault cases, always comparing the element to the standard differential algorithm. As the new element is simple in a mathematical concept, the protection element was developed inside a commercial relay just using the manufacturer programming language and the users' available programming area. The contributions of this work are the method to increase sensitivity using the same variables already available in differential relays, and the possibility to use the algorithm in a field installed relay