Transmission Availability Data System (TADS)
On October 23, 2007, the NERC Board of Trustees (Board) approved the collection of the Phase I TADS data, beginning in calendar year 2008. On October 29, 2008, the Board approved the collection of Phase II TADS Non-Automatic Outage Data, beginning in 2010. TAD collects transmission outage data in a common format for: 
  1. Bulk Electric System AC Circuits (Overhead and Underground)
  2. Transmission Transformers (No Generator Step-up Units) 
  3. Bulk Electric System AC/DC Back-to-Back Converters 
  4. Bulk Electric System DC Circuits
TADS efforts began in 2006 with the formation of the TADS Task Force under the NERC Planning Committee. This task force designed TADS and the associated processes for collecting TADS data. On June 30, 2009, the task force issued its first reports for data collected in 2008. On July 1, 2009, the task force was retired and replaced with the TADS Working Group. This change recognized the ongoing design and oversight of TADS that is more appropriately assigned to a working group than a task force. NERC will use the information to develop transmission metrics that analyze outage frequency, duration, causes, and many other factors related to transmission outages.
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.
All TADS-related material is available for download from the TADS Working Group.
Key TADS documents may also be downloaded below:

For more information, please contact


 TADS News

The 2018 version of the TADS Workbook has been posted. The version removes an erroneous space in the "P-P Fault" option from the Fault Type pick list.

Deadlines for Data Submission Into WebTADS Are:

  • February 15, for the prior year 

  • May 15, for Quarter 1, January 1 – March 31

  • August 15, for Quarter 2, April 1 – June 30

  • November 15, for Quarter 3, July 1 – September 30  

  • February 15, for Quarter 4, October 1 – December 31


 Program Contacts

expand Grouping : webTADS Application Updates ‎(3)
expand Grouping : Key TADS Documents ‎(8)