Case Study: Deployment of On-line DSA System at ERCOT

The use of DSATools™ by the Electric Reliability Council of Texas Inc. (ERCOT) demonstrates how the software can provide real-time information to improve grid security and optimize system operation for electricity market benefits.

The ISO has experienced voltage and transient stability problems related to high power flow transferred from remote generation sites to large load centers.

To assist operators in addressing these issues, ERCOT installed the on-line DSA system in 2000 and upgraded it in 2012. The system consists of two functional modules: voltage security assessment (using VSAT) and transient security assessment (using TSAT).

Running every 15 minutes, the on-line DSA system performs voltage security assessment for seven study scenarios and transient security assessment for one study scenario. Each study scenario calculates the stability limit on the pre-defined transfer interface, which is the maximum active power (MW) transferred through the interface before voltage or transient instability happens. The calculated stability limits provide system operators with a measure of reliability margin from the current operating condition to potential instability, and an approach to use the market tools to prevent the system from getting close to an unstable state.

Prior to the use of the on-line DSA system based on DSATools™, power transfer limits on ERCOT’s West-to-North interface were based on annual off-line engineering studies. The on-line VSAT and TSAT modules automatically determine the transfer limits every 15 minutes using the real-time system data. ERCOT estimated that by using the on-line TSAT technology alone, it saved US$27 million in 2011 in congestion management cost[1].

[1]Source: presentation made by ERCOT President and CEO Trip Doggett on April 9, 2012 to the Texas Renewable Energy Industries Association.