On estimation of rate of change of frequency for relay settings during power export to grid from a CPP

Amendments in the Indian Electricity Act in 2003, has opened up the Power Industry to make profitable business. Further, the acute shortage of power in India, can only be addressed by increasing the power generation and allowing smaller capacity distributed generation systems to interconnect to the grid. A captive power plant (CPP) associated with the fertilizer manufacturing sector is contemplating pumping its spare generation to the grid. This requires a study and settings of relays for protection of equipment associated with the CPP. On connecting to the grid the faults within the network may lead to either overloading or over speeding up of CPP generators. This requires a protective mechanism to isolate and island. This in turn is possible using quick response relays which are based on change in frequency or changes in load angle. By studying the related machine and system parameters, the effort is made to evolve the settings of such frequency based relay for the CPP under study. Using the swing equation as the basis along with related system parameters of the CPP and grid, the process of evolving the settings of Rate of Change of Frequency (RoCoF) and Vector Surge Relay (VSR) is discussed in this paper.