Abstract: Disclosed herein is a method of compensating for the distorted secondary/ current of a current transformer. The method includes steps (a), (b) and (c). At step (a), the saturated section of the current transformer is detected. At step (b), fault current generated during a fault in a power system is represented using an AutoRegressive (AR) model, with the fault current being assumed to be a combination of a Direct Current (DC) offset component, a fundamental wave component and harmonic components. At step (c), coefficients of the AR model are estimated and the secondary current during saturation of the current transformer is compensated, based on the secondary current data sampled in the unsaturated section.

Abstract: A method for preventing the unwanted maloperation of a protective relay system that is caused by the imprecise detection of an actual secondary current value resulting from a measured secondary current being distorted comprises the steps of calculating difference values for sampled secondary currents; comparing absolute values of the difference values with a predetermined critical value, and determining a saturation starting moment of a current transformer when one of the absolute values exceeds the predetermined critical value; obtaining a magnetizing current at the saturation starting moment using the difference values if the saturation starting moment is determined, and obtaining a magnetic flux value in a steel core of the current transformer from a magnetization curve using the magnetizing current; calculating a magnetic flux value at a time after the saturation starting moment using a secondary current value measured at that time and the magnetic flux value obtained at the saturation starting moment so

Abstract: Disclosed is a relaying method for protecting a transformer by using a difference of current. A decision function, related to the rate of change of a primary current, a secondary current, or a differential current, is used for determining whether a detected abnormal current is due to the inrush or internal fault.

Abstract: The present invention relates to a method for preventing the unwanted maloperation of a protective relay system that is caused by the imprecise detection of an actual secondary current value resulting from a measured secondary current being distorted.

Abstract: The present invention relates to a relaying method using the ratio of induced voltages or the ratio of flux linkage increments. The protective relaying method for power transformers with one or more phases includes the first step of obtaining primary and secondary voltages and currents of the transformer; the second step of calculating induced voltages, induced voltage differences, ratio of primary and secondary induced voltages, or ratio of primary and secondary induced voltage differences from the currents and the voltages; the third step of calculating at least one predetermined decision parameter derived from at least one predetermined equation; the fourth step of deciding whether an internal winding fault occurs by comparing the decision parameter to the induced voltages, the induced voltage differences, the ratio of primary and secondary induced voltages, or the ratio of primary and secondary induced voltage differences.

Abstract: Disclosed is a relaying method for protecting a transformer by using a difference of current. A decision function, related to the difference of a primary current, a secondary current, or a differential current is used for determining whether a detected abnormal current is due to the inrush or internal fault.

Abstract: Disclosed is a method for detecting saturation of a current transformer. The method determines whether or not a change of a secondary current generated in a current transformer is due to the saturation of the current transformer.

Abstract: Disclosed is a method for detecting saturation of a current transformer. The method determines whether or not a change of a secondary current generated in a current transformer is due to the saturation of the current transformer.

Abstract: The present invention relates to a relaying method using the ratio of induced voltages or the ratio of flux linkage increments. The protective relaying method for power transformers with one or more phases includes the first step of obtaining primary and secondary voltages and currents of the transformer; the second step of calculating induced voltages, induced voltage differences, ratio of primary and secondary induced voltages, or ratio of primary and secondary induced voltage differences from the currents and the voltages; the third step of calculating at least one predetermined decision parameter derived from at least one predetermined equation; the fourth step of deciding whether an internal winding fault occurs by comparing the decision parameter to the induced voltages, the induced voltage differences, the ratio of primary and secondary induced voltages, or the ratio of primary and secondary induced voltage differences.