This paper summarizes the features and advantages of the renowned Real-Time Digital Simulator (RTDS) called OPAL-RT Simulator. Alongside with its applications in the electric power system for the system design, analysis and testing. This comprehensive study also includes a brief description of its software, hardware, I/O system, modeling, Hardware-in-the-Loop and other prospects. Tremendous advancement in the storage capacity and computational speed of the modern computer system has done for the last few decades. Assimilating this advancement, this simulation tool has designed with unique features like real-time model-in-the-loop, Hardware-in-the-loop. Also for moderate operational and maintenance cost, OPAL-RT Simulator has become more prevalent to the researcher. There are immense scopes of experimental research in power systems analysis. This is the prime reasoning for describing the necessity and significance of OPAL-RT simulator in this work. In addition, a semi-simulation experiment of a PV system is presented using RT-LAB software. Two of the most salient tools of OPAL-RT are 1) RT-LAB and 2) ARTEMIS, which were applied in power electronics are also summarized.