Impact of sizes of islands on the stability of a faulted power system

Abnormalities to any power system create oscillations to electrical quantities such as frequency, power factor, voltage and current. Most of them lead to fall of system frequency and sometimes systems are faced unwanted blackout due to extreme abnormalities. Systems can be protected through planned and proper islanding from complete blackout even in case of extreme abnormalities. Islanding operation not only helps stabilizing a faulted system but also supports power supplies to critical and important loads, in extreme emergency. But the islanding systems are weaker than integrated system so the stability of islands is the prime concern when integrated systems are separated to islands. In this paper, Bangladesh power system (BPS) has been considered as the test case and a frequency based auto load shedding (ALS) scheme has been developed. The developed ALS has been applied to two different sizes of island with higher and lower inertia constant namely Dhaka Island (the largest and generation rich island with higher inertia constant of BPS) and Khulna-Barisal Island ( a load rich island with lower inertia constant) to validate the effectiveness of the developed technique. Various types of abnormalities to the test islands have been simulated and compared with CYME PSAF (Power System Analysis Framework).