Adaptive criteria of estimating power system separation times based on inter‐area signal.

This paper presents an online protective scheme of estimating critical inter‐area angle for controlling the inter‐area oscillations based on evaluating the rate of changes of rotor angle oscillations as an adaptive tripping index (ATI)‐based protective zone. For this purpose, by using wide area measuring system technology, oscillatory signals Δδ and Δω are measured which based on correlation coefficients criteria, coherent groups are identified which based on evaluating oscillating areas, inter‐area signals ΔδCOI‐AB and ΔωCOI‐AB are provided. In the case of evaluating an inter‐area oscillation, the proposed ATI scheme is activated which the first zero crossing point (ZCP0) of δCOI‐AB is determined as the critical criteria for estimating unstable situation. The proposed ATI approach consists of two adaptive protective zones ATI1 and ATI2 to estimate inter‐area oscillatory and inter‐area transient instabilities, respectively. The proposed ATI is an online and non‐model‐based scheme which evaluates the system dynamic stability through two straight and sinusoidal‐based adaptive zones. The effectiveness of the proposed ATI approach is evaluated on three different test systems IEEE 39‐bus, modified IEEE 39‐bus with converter‐based low inertia sources and a practical Iran nation power grid with presenting positive effects of damping inter‐area oscillations through different operational and topological conditions. [ABSTRACT FROM AUTHOR]