What Is GADS:

Unplanned outages of generating units can undermine reliability by reducing available capacity. They can also introduce instability by reducing frequency and depriving the system of inertia, voltage support, and ramping capability. In some cases, the loss of a large unit in one part of the interconnection can cause generators in other parts of the system to trip, further affecting reliability.

The NERC Generating Availability Data System (GADS) collects performance and availability information from conventional generating units. WECC uses this information to measure outage rates, including frequency (outages per unit) and duration (weighted by capacity). Tracking outages caused by equipment issues, human error, and fuel-supply issues allows WECC to identify and monitor vulnerabilities in the power system. 

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In this section of the report, the information is not shown by region or BA. This section shows how the Western Interconnection is doing overall, so the map and regional functions are not present. However, in this section, the use of statistical significance is introduced.

The chart on the right shows the historical data that is selected by the filters and a trend line over the last five years. The summary box shows the change per year, a p-value (a statistical measure showing the significance of the trend), and a flag that shows whether something is significant.