Current differential based wide area protection (WAP) has recently been proposed as a technique to increase the reliability of protection systems. It increases system stability and can prevent large contingencies such as cascading outages and blackouts. This paper describes how power differential protection (PDP) can be used within a WAP and shows that the algorithm operates correctly for all types of system faults whilst preventing unwanted tripping, even if the data has been distorted by CT saturation or by data mismatches caused by delays in the WAP data collection system. The PDP algorithm has been simulated and tested on an Iranian 400kV transmission line during different fault and system operating conditions. The proposed operating logic and the PDP algorithm were also evaluated using simulation studies based on the Northern Ireland Electricity (NIE) 275 kV network. The results presented illustrate the validity of the proposed protection.