Electric Reliability Council Of Texas (ERCOT) Practice Test

Transmission congestion happens when the grid’s ability to move electricity from generators to loads is limited by the physical capacity of the transmission network, with flows coming up against the network’s limits. This means the system is near the points where lines or other facilities can no longer safely carry more power, i.e., approaching thermal or load-based limits and thus at risk of violating security constraints. When this happens, certain paths become constrained and the operator may need to take actions to relieve the constraint. That’s why the statement describing the system as approaching thermal or load-based limits and at risk best captures congestion. If the system were within all security limits or had excess capacity, there would be no congestion. Economic constraints alone don’t define congestion; it’s the physical limits of the transmission network that create the constraint.