Abstract:
Under frequency load shedding has been widely used to restore the power system frequency
following a severe generation demand unbalance due to a disturbance. If system frequency is not
counteracted properly system will be led to major blackouts. This frequency decline may be
corrected by shedding certain amount of load so that system is back to stable state. This dissertation
discusses on designing of new under frequency load shedding scheme align with the development
of Sri Lankan power system. Further, due to present network configuration after certain power
System failures some part of the system isolates from the main system and operates in islanding
mode. This islanding operation fails at all the times due to unbalance of the generation and load.
This dissertation also discusses in what way to overcome above situation by rearranging 33 kV
Load Shedding Feeders in the Sri Lankan network.
Whole Sri Lankan power system has been modeled using the PSS®E (Power System Simulator for
Engineers) software. PSS®E dynamic model was validated considering an actual generator tripping
occurred in the system. The Existing Load Shedding scheme was simulated using this model and
identified its drawbacks. Proposed a new Load Shedding scheme and discussed the system
improvements with simulations. The observations and results obtained from the simulations
comprise frequency plots before and after applying the proposed new load shedding scheme.
Further, identified possible islanding operations and analyzed the stability of them with proposed
load shedding scheme. Finally rearrange the 33 kV load shedding feeders in the Sri Lankan
network to facilitate islanding operation by analyzing the stability of the islands using simulation.
This new load shedding schemes with rearranged 33 kV load shedding feeders will improve the
Power System reliability and have a definite positive effect on customers which in turn improve the
wellbeing of the people and economy of the country.
