A Laboratory Emulation of a Percentage Differential Protection Relay for a Single Phase Transformer Using PLC

The electrical transformers in the electrical network are one of the most important and expensive elements, which explains the presence of a large number of protection devices installed on them, and among these protections is the differential protection, the subject of our paper. This paper attempts to emulate the conventional electro-mechanical differential relay available in the laboratory of our department with an automated system based on the PLC techniques and replacing the current transformers by Hall Effect current type transducers. The authors studied the principles of operation of the conventional differential relay and designed an embedded system to emulate the operation of the old one. This system was tested in the laboratory by implementing it on a single-phase transformer; the results were good especially its response which was faster than that of the conventional one. Better differential protection for transformers, generators and lines may be achieved by applying this system.