This study presents, two load shedding scheme that are simulated on IEEE-14 bus systems are voltage dependent priority based approach and voltage and frequency based NVSI methods. The frequency-based method is designed to consider the rate of change of frequency to estimate the power loss and thereby trigger the load shedding when the frequency or rate of change of frequency exceeds the corresponding thresholds. A novel method voltage and frequency-based load shedding scheme is designed to estimate the real and reactive power losses using frequency. After estimating the power loss, the buses are indexed using the Novel Voltage Stability Index (NVSI) to select the load buses for load shedding. The loads to be shed at each of the buses are determined using the improved self adaptive harmony search(ISAHS) algorithm. Simulation results of voltage and frequency based NVSI method are presented in comparison with voltage dependent priority based approach.