Turn-to-earth fault modelling of power transformer based on symmetrical components

In this paper, a new approach to simulate transformer turn to earth fault, by using symmetrical components approach, has been presented. In the suggested novel modeling technique, the transformer turn to earth fault is simulated as a new healthy transformer with new short circuit (SC) impedance. This SC impedance is considered as the SC impedance of the transformer with the fraction part of the transformer winding through which the turn to earth fault occurs. The SC impedance of the reminder part of the transformer winding is added to the transmission line impedance or load impedance as external impedance. Hence, by using this suggested modelling technique, the system of turn to earth fault transformer is represented with a new system of a new healthy transformer, and the turn to earth fault is represented as an external line to ground fault. The values of the turn to earth fault current from this novel modelling technique (using the symmetrical components approach) were compared with those obtained by Electromagnetic Transient Program/Alternative Transient Program (EMTP/ATP). Finally, a suggestion method to estimate general information about the SC impedance of a three-phase three-winding transformer at different percentages of turn to earth fault is discussed.