Lotdys Analysis Of August 1973 Gulf Coast Area Power System Disturbance

This paper presents results of research sponsored by EPRI on long term power system dynamics conducted by General Electric under contract RP764-2 with support from Southern Company Services, Inc. An analysis of a major power system disturbance was made by digital computer simulation of the interacting dynamics of power plants, electrical transmission systems, and connected customer loads. The incident under examination occurred on Tuesday morning, August 7, 1973 in the southern Alabama and Mississippi and western Florida portions of the Southern electric system and resulted in the formation of an electrical island. The seven minute simulation of the Gulf Coast area electrical island was made to: 0 Test and validate the computer program LOTDYS, 0 Explore the effect of alternate simulation data to improve the accuracy of the simulation, 0 Provide further insight and information on this specific incident, 0 Identify and make improvements in analytic methods and data acquisition and estimation methods. The simulation of the disturbance was compared to disturbance records and a good match over a two minute period was obtained between the records and the simulation results. This match was obtained by use of conventional electrical system data supplied by Southern Company Services and typical data for load and prime mover characteristics obtained from a prior EPRI long term dynamics project.(l) In the period after one minute of island operation, the effects of steam plan safety valves and boiler fire trip and restart were found to be significant; LOTOYS was modified to add models of these effects in order to obtain a match to plant pressure chart records. In the period following the first two minutes of the island operation, operator actions and changes in connected customer load were found to be significant; a fair match was obtained by incorporating assumed manual run back of generation and assumed values of load pickup rate.