Microcontroller based line differential protection using fiber optic communication

Transmission lines protection is one of the important priority of protection engineer as their tripping will lead instability in the grid which may result in cascade tripping. This will put the grid in stressed condition due to increased angular separation between different nodes. Now a days, Carrier based protection scheme for the transmission line is being adopted for most of the transmission line which is based on carrier signal exchange from both ends of lines. Carrier based protection is having faces various limitations such as communication signal loss, introduction of noise, employment of old technology, bandwidth limitations, data speed and associated challenges. This paper presents the differential protection for transmission line from internal faults. It focuses on the design of one such system comprising of microcontroller based line differential protection using fiber optics communication. A working model was designed that employs microcontroller and fiber optic communication for the differential protection of line. In the implemented scheme, received signal is compared with a reference signal using microcontroller. Any received value below the threshold is an indication of internal fiber damage. Differential current beyond a fault current threshold value indicate the fault in the transmission line. Major activities carried out involved are fabrication of connections; algorithm development for fault calculation, serial data transfer algorithm, display, conversion to fiber media.