Abstract: Provided is an apparatus and method for calibrating a signal, which extracts a plurality of signal samples from sine-wave input signals; calculates a real root of a DC component calculating condition derived using simultaneous equations for values of the signal samples; calculates a value of a DC component from the simultaneous equations by using the calculated real root; and removes the DC component by applying the calculated value of the DC component to the sine-wave input signals, wherein the number of signal samples extracted in the signal sample extracting step is set according to the number of unknown quantities of the simultaneous equations.

Abstract: Provided is a system for determining the area of vulnerability for estimation of voltage sages including: a system information reader reading information on a power system; a unit for determining the area of vulnerability calculating a voltages at a target bus corresponding to ends of a fault line by using the system information and a first residual voltage equation that is a voltage relationship between points in the fault line in the power system where a fault is simulated and the target bus where a voltage change due to the fault occurs, calculating a voltage at the target bus corresponding to a point between the ends when the voltages at the target bus corresponding to the ends are not higher than a predetermined voltage threshold, deriving a second residual voltage equation that is an approximate quadratic interpolation equation for the first residual voltage equation by using the voltages at the target bus corresponding to the ends and the point between the ends of the fault line, calculating the voltag