Proper setting of underfrequency load shedding relays in industrial plants

Underfrequency relays are the most reliable tools for load shedding in active power generation deficiency conditions especially industrial power systems. In this paper, a new algorithm is proposed to set underfrequency load shedding relays based on transient stability studies (frequency dynamic study). The proposed algorithm utilizes a comprehensive transient stability module to find out the unwanted events which are not safe for the operation of the plant and the load shedding actions are unavoidable. Underfrequency load shedding relays are set in such a way that the power system preserves the electricity in service for critical loads and frequency is maintained in permissible limits. The application of the proposed method on a test case is described and the results and related discussions are presented.