An enhanced zone 3 algorithm of a distance relay using transient components and state diagram

Summary form only given. Zone 3 of a distance relay is used to provide the remote back-up protection in case of the failure of the primary protection. However, the risk of mal-operation under stressed conditions such as heavy loading, voltage and transient instability is quite high. Zone 3 is used in combination with the derivatives of the voltage, and current, etc, to prevent mal-operation. At times, the impedance characteristics that restrict the tripping area of relay are used to avoid mal-operation due to load encroachment. This paper presents a novel zone 3 scheme based on combining the steady-state components (i.e. 60 Hz) and the transient components (TCs) using a state diagram that visualizes the sequence of studies that emanate from the sequence of events. The simulation results show that the novel zone 3 distance relay elements using the proposed method operate correctly for the various events.