An experimental evaluation of a power differential relay is conducted and the results are described. The experimental setup consists of a generator connected to the network via a transmission line protected by the power deferential relay. The relay input signals, fundamental active and reactive powers, are locally computed from the complex product of the current and voltage phasors at each end on sample-by-sample basis. The relay setting is refined and it is examined for different internal and external fault conditions as well as during power swings. Response of the active and reactive power detectors is evaluated in the time domain. Test cases provide evidence of the efficacy of the proposed technique.