Validation of the sensitivity based Thevenin Index on large systems

Monitoring the long-term voltage stability of the power grid is necessary to ensure its secure operation. This paper presents a new Wide-Area Measurement (WAMS) based Voltage Stability Index, called the Sensitivity based Thevenin Index (STI), that is calculated using sensitivities. The novelty of this index is that it is the first WAMS based method whose value is equal to the Local Thevenin Index (LTI) measured locally at the Phasor Measurement Units (PMU). The wide-area nature of the STI makes it very robust to measurement noise and provides the control-center with a method to verify the LTI received from a PMU. This ensures that the operator can take the proper control actions, even when the PMU transmits spurious or noisy LTI. Validating results are presented for the IEEE 30 Bus and the MATPOWER 3120 Polish Summer systems, verifying that the STI can be used to validate the LTI measured at the PMU locally in a quick manner and establishing the robustness of the STI to measurement noise.