Transmission Loading Relief (TLR) and hour-ahead ATC

In open-access electricity markets, the reservations of transmission services are based on data resulting from the offline computation of Available Transfer Capability (ATC). When ATC data is inaccurate or misused, security violations can emerge and cause operators and operations planners to invoke Transmission Loading Relief (TLR) procedures. The paper illustrates the relationship between TLR and ATC, and presents possible approaches to reducing the need to invoke TLR procedures while improving the utilization of the transmission system.