Setting and Testing of Power Swing Blocking and Out of Step Relays Considering Transient Stability Conditions

This paper reviews the behavior of electrical systems when they are subjected to oscillations which can cause that one or more synchronous machines loose synchronism with each other. The paper makes a detailed reference to power swing blocking and out of step relays whose operation has to assure adequate protection under these conditions. A thorough procedure is discussed to set out of step relays based on transient stability studies. The procedure is illustrated with a case study using power system stability software and then the settings were implemented in a numerical relay for real testing.