Integrated approach to transfer limit calculations

Operators and planners of transmission systems must deal with new concerns brought about by open access to the transmission grid and an increase in the number of power wheeling transactions. This problem is compounded by additional regulatory and environmental concerns that have limited the amount of new transmission facilities that have been constructed in recent years. As a result, the question of how much additional power can be safely wheeled across a system has taken on new urgency. In addition, the requirements and methods for calculating transfer limits have evolved from an early emphasis on overload (using linear DC load-flow models) and transient stability limits to include voltage and voltage stability limitations. Utilities typically apply different methods and computer programs to determine transfer limits caused by each failure phenomenon. The various limit reports must then be consolidated in a time-consuming process. This article presents an integrated method for determining the transfer limits on a specified transmission interface due to low voltage, voltage collapse, and thermal overload constraints resulting from branch outages