This paper describes problem of fast frequency variation control in large interconnected power system. Interconnection of the large power system with different philosophy of frequency control can cause ineffective and sometimes nonselective behavior of frequency automation. Paper presets results of analysis of frequency control using spinning reserve. Optimal distribution of the primary reserve can be based on cooperative game theory method. Severe system disturbances can result in fast frequency drop, which makes fast governor and boiler response impossible. If the governor action cannot activate spinning reserve quickly enough to restore the system to its normal operating frequency, underfrequency load shedding (UFLS) serves as a lastresort tool to prevent the system from collapse. Application of smart metering and communication can improve efficiency of emergency automation during underfrequency condition. A new load shedding method is suggested. Simulation of frequency behavior was conducted for existing load shedding system and a new one.