Adaptive overcurrent relay coordination for off-peak loading in interconnected power system

Due to the substation automation, the supervisory control and data acquisition (SCADA) system is spreading that the protective relay settings can be modified through the network automatically. This work presents an overcurrent relay coordination decision for switching the relay settings to adaptive the off-peak loading in interconnected power system. Overcurrent relays (OCR) including directional and non-directional protective relays are widely applied in power system as main protective devices as they are reliable, cost effective and selective. Usually, the OCR protective coordination is coordinated at the time of maximum load and normal power supply, which may not be adaptive, as generating and load power are decreased significantly during the off-peak period of time compare to peak load that insufficient currents caused cascade lagging to activate OCRs. An example of single-ring interconnected power system was tested to demonstrate the coordination and confirm that the proposed approach method is practical during the off-peak time.