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.