This study presents a new protection scheme for a series compensated transmission line, which prevents maloperation of distance relay during severe stressed conditions. The proposed method depends on the calculation of the net angular difference of positive sequence phasors of voltage and current signals acquired from phasor measurement units (PMUs). For fully observable power system network, the minimum number of PMUs required with a maximum number of system observability redundancy index has been identified by the suggested method using binary chemical reaction optimisation technique. The validity of the suggested technique has been confirmed by generating different severe stressed conditions along with faulty situations by modelling IEEE-39 bus system using RTDS/RSCAD software. The proposed technique offers effective discrimination between severe stressed conditions (symmetrical/asymmetrical power swing, load encroachment, voltage instability) and faulty situation even against wide variation in fault type, fault resistance, fault inception angle, degree of compensation and location of the series capacitor (middle or both ends). The accomplished results disclose higher discriminating capability between severe stressed conditions and faulty situation of the proposed technique in comparison with those of the several existing techniques.