Which of the following would constitute a reportable disturbance for DCS evaluation?

A reportable disturbance for DCS (Disturbance Control Standard) evaluation is typically defined by the magnitude of the disturbance and its potential impact on the reliability of the power system. In this context, the threshold for what constitutes a reportable disturbance tends to center around large generation losses, as these can significantly affect system stability and reliability.

A loss of 950 MW from a generating unit falls within a critical range that is often considered significant enough to trigger a DCS evaluation. The evaluation aims to ascertain the effects of such a loss on the overall grid, and whether it posed any risk to system reliability, making it essential to assess and report.

In contrast, while a 600 MW unit loss and an 850 MW unit loss are substantial, they do not reach the same level of concern for system reliability compared to a 950 MW loss. The 1000 MW loss would typically also trigger a report, but the question narrows it down to the specific evaluation of significant losses and their reporting thresholds.

Thus, the 950 MW loss is viewed as a substantial disturbance warranting closer examination and reporting due to its size and potential ramifications on the grid's stability.