Protection information based transient stability margin assessment of splitting islands

Abstract Transient stability of islands after splitting is significantly affected by fault factors such as fault clearing time, fault location and fault type. Reasonable application of these fault factors obtained by protection information allows operators assess transient stability margin (TSM) for islands in a more accurate and effective fashion. This paper presents a protection information based transient stability margin assessment method for islands after splitting to evaluate the effect of fault factors on their TSM. First, analytical expressions for state vectors of generators and algebraic vectors of network that consider fault factors are derived. On the basic of this, the transient energy function of islands with 4th order synchronous generator model and first order approximation exciter dynamic model is developed to determine energy of islands under different fault factors. The corresponding critical energy of islands is determined by the boundary of stability-region-based controlling UEP (BCU) method. Next, the analytical expressions for TSM of islands are derived, which could quickly determine TSM of islands after splitting and critical splitting time of system using protection information. Finally, An IEEE 68 bus system and a practical power system are carried out to demonstrate the validity and effectiveness of the proposed transient stability margin assessment method.