  Over-Current (OC) protection is one of the pervasive protections in
solar-based DC microgrids. Fast operation is a key advantage of its popularity.
On the other hand, utilizing OC in DC microgrids has some challenges that are
not in AC grids. Some of these challenges are related to the grounding approach
of the DC microgrid, and others are related to the high rise time of the fault
current in DC microgrids. Considering these challenges, an adaptive OC scheme
with high selectivity and speed is presented in this paper. The proposed scheme
is communication-assisted and relies on IEC 61850 protocol. In this scheme,
different setting groups for each OC relay are defined, and based on the grid
and fault conditions, a setting group is selected. This option is performed
considering the data transferred via communication level using IEC 61850
protocol between relays. To evaluate the efficiency of the proposed scheme,
simulations using MATLAB software and the experimental tests using OPAL-RT
real-time simulator and Zenon software are presented.
