Ensemble decision trees for phasor measurement unit-based wide-area security assessment in the operations time frame

This study proposes ensemble decision trees for phasor measurement units (PMUs)-based wide-area security assessment to provide early warnings of deteriorating system conditions. In the proposed technique, the wide-area response signals in real-time operation are captured after 1 and 2 s fault clearing time, from the respective monitoring buses where PMUs are placed. These wide-area post-disturbance records are processed in time and frequency domains for extracting selected decision features such as the peak spectral density of the angle, frequency and their dot product evaluated over the grid areas called as wide-area severity indices (WASI). WASI are used as input features to train the random forests (RFs) to build effective predictor for early warnings in security assessment. The RF-based learning not only provides high performance accuracy but is also effective in valuing the importance of, and the interaction among, the various WASI input features, for developing the reliable predictor. The RF has been successfully tested for classifying both system-wise and area-wise NERC-compliant contingencies, using 55 196 cases (76 stable) from system operations studied on the Hydro Que bec network providing 99.9 reliability.