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 uses the information to develop transmission metrics that analyze outage frequency, duration, causes, and many other factors related to transmission outages.

In 2020, the TADS Working Group became the TADS User Group (TADSUG).  The TADSUG performs the same functions as the TADSWG.  However, it no longer reports into the NERC Committee structure. Instead, it reports to the NERC Performance Analysis Department.

While TADS is not intended to provide determinative performance measures, it is 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.

All TADS-related material is available for download from the TADS User Group.

For more information, please contact


 TADS News

TADS Training (In-Person) - October 18-19, 2023​

 Data Submission

Deadlines for Data Submission into WebTADS are:

Reporting Deadline*Period of Operation to Report
February 15​Any updates for the prior year
May 15​Quarter 1: January 1 - March 31
​August 15​Quarter 2: April 1 - June 30
​November 15​Quarter 3: July 1 - September 30
​February 15​Quarter 4: October 1 - December 31

*When a deadline falls on a weekend or holiday, reporting will be extended through the following business day.

collapse Grouping : Key TADS Documents ‎(2)
TADS_Reporting_Workbook.xlsxTADS Reporting Workbook1/1/2024
2024_TADS_DRI.pdfTADS Data Reporting Instructions1/1/2024
collapse Grouping : webTADS Application Updates ‎(9)
TADS_Multi-Owner_Inventory_Update_Instructions.pdfTADS Multi-Owner Inventory Update Instructions11/2/2022
TADS_Application_Update_web-TADS_20220819.pdfTADS Application Enhancements August 20228/26/2022
TADS_CO_19.pdfTADS Application Enhancements November 202011/19/2020
TADS_Change_Order_16.pdfTADS Application Enhancements February 20205/11/2020
TADS_Application_Update_Change_Order_11.pdfTADS Application Enhancements July 201810/31/2018
TADS Application Update Change Order 9 Phase II.pdfTADS Application Enhancements February 20173/1/2017
TADS Application Update Change Order 9 Phase I.pdfTADS Application Enhancements November 20162/6/2017
Proposed Element Inventory and Quarterly Data.pdfTADS Section 1600 Request: Comments and Responses Proposed Element Inventory and Quarterly Data12/1/2012
TADS_Section_1600.pdfTADS Section 1600 Request: Comments and Responses Proposed Outage Data Collection for BES Elements Operated at Less Than 200 kV12/1/2012