Wide-area protection (WAP) is a new concept applied using wide-area multi-source information. WAP utilizes the Phasor Measurement Units (PMUs) widely installed in networks. PMUs are mainly installed in transmission systems. Recently, Wide-Area Monitoring, Protection, Automation, and Control (WAMPAC) applications increased due to the growth of the PMUs in the electric network. PMUs provide an overview of the transient processes in the network by delivering synchronously measured data of the voltage and current with high-speed rates and an accurate, common time reference. WAP applications vary, such as protection for interconnection lines, backup protection, and enhancement of conventional protection systems. The main objective of this thesis is to design and simulate wide-area protection (WAP) for the transmission system of Oman Grid. The developed WAP system shall be a backup to conventional protection on high-voltage lines. The Wide Area Backup Protection (WABP) shall be able to detect faults on the high-voltage transmission lines using the data received from PMUs available at the select networks. The proposed WABP technique uses Positive Sequence Voltage Magnitudes (PSVM) and Positive Sequence Current Angles (PSCA). The Omani Grid is simulated in DIgSILENT PowerFactory software. Additionally, the WABP algorithm is carried out using DIgSILENT Programing Language (DPL). The proposed WABP technique is simulated and validated in DIgSILENT PowerFactory software using the IEEE 14 bus test system and a selected part of Oman Grid. Moreover, the Real-Time Digital Simulator (RTDS) and Real-Time Simulation Software Package (RSCAD) are used to evaluate the proposed design in EEE 14 bus test system. Two 7SL86 Siemens PMUs are used in the experiment as Hardware in-Loop (HIL) with RTDS to validate the PMU's response during different fault scenarios. The proposed WABP technique detected all types of faults inside the selected protection zones. Furthermore, it was stable for external faults.