LEW HANES: You mentioned that it is necessary to plan for contingencies.  One contingency that you mentioned relates to TLR's.

BILL MELTON:  The security coordinators across the interconnection call the TLR's. They are aware of system problems based on running case studies concerning interfaces using the worst single contingency on their respective systems. Take, for example, the TVA - Southern Company interface. The Bowen-Sequoyah 500-kv line is the interface's worst contingency so the Security Coordinator runs a case study and outages this line to see how it will impact the capability of that interface.  If they see they cannot solve the case with the resources available using local procedures, they might go into a TLR situation.  This might involve cutting or curtailing  schedules that cross that interface to bring that interface back to a controllable situation in case we lose that line.

Everything has to be based on that first contingency.  If you ran the system without taking into consideration the contingencies, then when that contingency happened, there would be no planned recovery from that contingency situation.