Disclosed embodiments relate to a system for correcting an error, which can correct the error of a measurement device and a transformer data unit through calibration using an emulator even if the measurement device and the transformer data unit are connected in a random combination. In some embodiments, the system for correcting an error includes a measurement device connected to a secondary output line of a transformer to measure current that is output from the transformer, a transformer data unit configured to determine a usage rate and an overload state through calculation of a load amount for a capacity of the transformer in accordance with the current that is measured by the measurement device, and an emulator connected to the measurement device and the transformer data unit to perform error correction between the measurement device and the transformer data unit through performing calibration at least once.