Distance Protection Scheme for a Digital Substation

The protection system in a digital substation is of high importance in the context of larger and larger interconnected power systems. The IEC61850 standard enables easier operation of protection and control in substations. A special case of the distance protection scheme for a 220kV overhead line- autotransformer block in the Romanian Power System is proposed and implemented in simulation environment. The distance protection relays installed at the edges of the studied transmission line are designed in digital technology. The protection relays have enabled the polygonal characteristic equipped with five independent zones for each fault impedance loop. The DigSilent Power Factory simulation showed that the distance protection relays installed at the ends of the studied line achieve the rapidity criterion for several types of short-circuit faults and different locations of the fault.