A New Technique for Power Transformer Protection Based on Transient Components

This paper presents a new protection technique for discrimination between internal faults and external faults in power transformers based on the transient components of the transformer's currents. The three phase transient currents of the transformer are converted to the modal current components using Clarke's transformation to produce the ground mode, areal mode 1 and areal mode 2. These different modes produce useful information which can be used to discriminate between internal faults and external faults by applying the Fault Discrimination equation suggested by the author. The proposed technique is evaluated via an extensive simulation study for a 132/15 KV – 155 MVA power transformer using Alternative Transient Program (ATP). It can be seen from the obtained results that the new approach is very successful in discriminate between internal faults in addition to inter-turn faults and external faults.