On Oct. 23, 2007, the North American Electric Reliability Council's Board of Trustees approved the collection of the Phase I Transmission Availability Data System (TADS) data beginning in calendar year 2008. TADS will collect transmission outage data in a common format for:

• AC circuits ≥200kV overhead and underground)
• Transformers with ≥200 kV low-side
• AC/DC back-to-back converters with ≥200 kV AC on both sides
• DC circuits with ≥ ±200 kV DC voltage

NERC will use the information to develop transmission metrics that analyze outage frequency, duration, causes, and many other factors related to transmission outages. NERC will also issue an annual public report showing aggregate metrics for each NERC region, and each transmission owner reporting TADS data will be provided a confidential copy of the same metrics for its facilities.

While TADS is not intended to provide determinative performance measures, it will be used to quantify certain performance aspects. In addition to collecting simple transmission equipment availability, TADS will collect detailed information about individual outage events that, when analyzed at the regional and NERC level, will provide data that may be used to improve reliability. Specific equipment outages will be linked to disturbance reports filed with NERC, enabling better association of transmission outages with load and generation outages. Additionally, outages by one transmission owner will now be tracked to outages of other transmission owners so that any relationship between multiple outages can be established.