Overcurrent relays optimization is a topic associated with the coordination of overcurrent relay protection in active distribution networks. Proper settings of overcurrent relays and minimizing their operating time, while maintaining selectivity, become significant challenges for distribution network operators worldwide. Lately, the passive operation of distribution networks has been greatly altered by the integration of distributed energy resources. Therefore, the protective settings of all existing and new relays must be thoroughly verified before connecting new generation units since contribution fault current can have a significant impact on addressing the optimization problem of overcurrent relay protection. The solution to the optimization problem is typically achieved by minimizing the operating time of primary relays. However, it has not been fully explored whether the fault location has a significant effect on these solutions. Therefore, this doctoral thesis examines the optimization problem of overcurrent relays from a practical perspective through different fault locations. Additionally, a new method is proposed to optimize the settings of directional overcurrent relays in active distribution networks considering the thermal equivalent of short-circuit current. A modified genetic algorithm is employed as the optimization algorithm to simultaneously minimize the operating time of primary relays and maximize the time safety margin between the operation of backup relays and the thermal stress curve of their corresponding protected elements. In other words, the main objective optimization function to be minimized is defined as the sum of the operating times of all primary relays and the sum of the reciprocals of thermal discrimination times. The latter part is necessary as the protection engineer needs to ensure that the operating time of the backup relay is far enough from the thermal stress curve of the protected element. For each solution, the algorithm ensures proper coordination between primary and backup relay pairs throughout the network. Simulation is conducted for a closed-loop radial medium-voltage distribution network, and the results are presented in detail from multiple perspectives to demonstrate the effectiveness of the proposed approach. The main advantage of this optimization algorithm is that it can indicate whether the existing protective system can operate safely below the thermal stress curves of the protected elements or if additional protection measures are required. In conclusion, the impact of changes in the configuration of the distribution power network on the optimal settings of overcurrent relay protection has been investigated.