Abstract This paper presents a new algorithm, using phasor measurements, that allows real-time analysis and correction of contingencies in power systems. The focus is specifically on overloaded lines. Contingency indicative phasor limits are investigated using current magnitude and voltage angle. These limits are applied to a rotating phasor chart. An algorithm which predicts sensitivity is applied to an off-line system in order to determine the buses that need to be monitored. An online system with available phasor measurement unit (PMU) data is used to verify the phasor chart obtained using off-line data. The chart is completed for on-line PMU data, and compared with the off-line chart for further verification.