Resolving the impact of distributed renewable generation on directional overcurrent relay coordination: a case study

Two approaches are proposed to solve the directional overcurrent relay coordination problem associated with the installation of distributed renewable generation (DRG) in interconnected power delivery systems (IPDS), depending on the existing system protection capability (adaptive or non-adaptive). For adaptive protection systems, the first proposed approach introduces a procedure to select the optimal minimum number of relays, their locations and new settings. This procedure is restricted by the available relay setting groups. For non-adaptive protection systems, the second proposed approach implements a practice to obtain optimal minimum fault current limiter values (FCL) to limit DRG fault currents and restore relay coordination status without altering the original relay settings. An integration of the proposed two approaches is evaluated for IPDSs possessing both protection systems. Three scenarios are assessed for different numbers of DRGs, and DRG and fault locations using an optimisation model implemented in GAMS software and a developed MatLab code. The obtained results are reported and discussed.