Abstract
The share of inverter based renewable resources (IBRs) in power systems is rising rapidly. However, these resources pose challenges to conventional line protection algorithms. The current control features embedded in IBRs limit the magnitudes of the fault current and modulate the phase angle. Consequently, the fault impedance seen by the relays becomes significantly different, leading to their potential malfunction. To address this issue, an adaptive setting-based distance relaying algorithm is proposed for Zone-1 that calculates the fault path current to modify the boundaries of the quadrilateral relay. It estimates the equivalent grid-side voltage and impedance from the prefault measurements and expresses fault sequence currents as a function of local measurements using the voltage relations of sequence circuits. Upon the occurrence of a fault, the algorithm determines the magnitude and phase angle of the fault loop current by combining fault sequence currents according to the fault type. These calculations allow for the adaptive adjustment of quadrilateral relay boundaries for accurate Zone-1 decisions. Key advantages of the proposed technique include immunity to grid impedance magnitude and variations in IBR impedance from prefault to fault. Testing of the adaptive setting method on IBR-connected lines under diverse fault types and resistances confirmed its accuracy.
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