Transmission lines are the backbone of any power grid, responsible for delivering generated power to consumers. They are typically protected by local protection systems that may fail under stressed operational conditions, leading to cascading failures. This paper introduces a two-stage wide-area protection scheme (WAPS) to offer more secure and reliable protection functions. It includes a fault-detection algorithm for large-scale power systems that detects active-power flow reversals regardless of current magnitudes as the first stage. Active power is calculated from real-time measurements transmitted by phasor measurement units (PMUs). PMUs are optimally positioned to monitor each transmission line from a single terminal. A solution for the optimal location problem in the IEEE 39-bus system is presented. In the second stage, a fault-identification algorithm initializes two metrics to identify the faulty line. The phasor values are averaged over two windows centered on the detected event time to compute these metrics, thereby removing the influence of measurement fluctuations during the transient period. The performance of the proposed algorithms is extensively validated through simulations of various faults and disconnect scenarios in a MATLAB/SIMULINK model of the IEEE 30-bus system. The results confirm the detection algorithm's ability to distinguish between fault and stressful conditions and accurately identify the event time. The outputs show that the fault identification algorithm can detect faulty lines across a wide range of fault resistances and remain unaffected by transient spikes and measurement noise.
Vrtal et al. (Sat,) studied this question.