This paper represents detailed results of developing a huge applied software program of Overcurrent and Earth Fault relays coordination in high voltage substations. The paper introduces an effective structure which can be potentially used in power system study tools. It has been developed by using the programing language, Vb.net and connection to the database, Microsoft Access. According to the proposed structure, private databases are produced for different regions of grid while keeping accessibility to other regions. This will in turn help the boundary substations to be evaluated by system operators from different authorized study groups simultaneously. Data layer relations of the developed solver are discussed together with various block diagrams, representing connections between the entities. This relationship as well as managing coordination algorithm has been figured out by using a program of 22000 lines of code and the software program has been verified in practice on a large power system grid in a regional electric company for about 10 years.