Inverse time directional overcurrent relays optimal coordination using nonlinear programming and cuckoo search algorithm improved by lévy flights

The integrity and robustness of Electrical Power Systems are safeguarded by relay-controlled protection schemes. These relays have to identify and locate system anomalies and alert system operators, triggering alarms, signals or commands. In this context, primary protection relays must act during faults, while backup protection should only act in case of non-operation of the primary protection. The backup protection needs to have a delay in its operation time due to the selectivity conditions, which are guaranteed through coordination with the primary protection. Using inverse time directional overcurrent relays, a coordination problem arises to obtain the optimal configuration so that faults can be quickly eliminated wherever they occur, even when the relay closest to the fault fails. This optimization is defined as a problem of minimizing the relays operating time under selective conditions. This paper proposes the use of the Cuckoo Search Algorithm modified through the application of Lévy Flights to solve this coordination problem. The proposed method was tested for three different test systems, showing that it reaches solutions with equal or better qualities than those reported in specialized literature, using its nonlinear formulation, where both the time multiplier and tap settings must be parameterized.