Satisfying fault ride-through requirements, solar photovoltaic (PV) plant remains connected to
the grid even during a fault. With the current limiting feature, the plant current during a fault
becomes comparable to its rated current. This imposes challenges to conventional local data
based protection methods employed in the relay on PV side. In such a situation, the selectivity
of a protection scheme is crucial for maintaining an uninterrupted supply to customers. In this
article, a q-axis component-based protection scheme is proposed for the distribution system
with a PV plant. The method extracts the second-order harmonic components of q-axis voltage
and current at relaying points for fault detection and direction identification. Using this
direction information at both ends of a line segment is protected, internal and external faults
are discriminated. The performance of the proposed method is tested on a 14-bus distribution
system for various fault cases. A comparative analysis with existing techniques shows the
strength of the proposed method. Hardware-in loop testing using OPAL-RT simulator as a
system and Arduino NANO microcontroller as relay validates the performance of the proposed
method in real-time.