December 19, 2003—PJM Interconnection has implemented a reliability-related system that provides the widest picture of the status of the transmission grid in North America.
The new computer program provides PJM system operators with a model of current conditions on an extensive area of the transmission system. It uses a mathematical formula to estimate the current state of the transmission system. The huge program, called a “state estimator,” models the electric transmission grid from Minnesota to the Atlantic Ocean and from Tennessee and the Carolinas to New England. In all, the state estimator gives PJM operators the status of nearly a third of the Eastern Interconnection, which includes most of the transmission and generation systems in the U.S. and Canada east of the Rocky Mountains.
A state estimator is a standard power system operations tool. But, the new PJM state estimator is one of the largest, most thorough systems of its kind. It monitors PJM’s current area, transmission systems slated to become part of PJM and neighboring systems beyond. It is important to look beyond PJM’s region because changing conditions in neighboring systems can affect reliability.
A state estimator continuously monitors incoming data from meters at thousands of locations around the high-voltage grid and processes it through a mathematical model to determine the reasonableness of data, correct bad data and estimate missing or unavailable data.
The new state estimator program models 45,000 nodes compared with 11,000 nodes in the old state estimator program. It receives data from 46,837 telemetry points compared with 22,600 points on the old system. All of that data is processed, analyzed, corrected and used to estimate the state of the transmission system on a minute-to-minute basis. The system operates so quickly because data is processed on eight computer processors operating in parallel.
The results are used to consider 3,000 potential events that could compromise reliability. This “what if” analysis looks at what would occur on the transmission system if those events occurred. If the analysis shows that an event could cause a problem, PJM tells certain generators to start or increase or decrease output to reduce the flow of electricity on a particular transmission line.
For more information, visit PJM.
