Corrective Control of Flow in a Power System by Line and Bus-Bar Switching.

A method is developed for selecting and ranking all possible lines for corrective control to relieve power system overloads. The means to achieve this goal is by rerouting the flows in a power system by changing the topology by way of network switching. The control action is of a passive nature. This characteristic is very useful especially when the system lacks active overload control measures. The method uses the non-iterative DC approximate model to represent the system resulting in a very fast computational time. The near optimal ordered triangular factorization is used to get the sparse bus reactance matrix, which generates only the relevant terms of the bus reactance matrix. This offers a decrease in execution time and considerable reduction in core memory requirements for a digital computer. The method is based on obtaining linear sensitivity factors (line and generation outage distribution factors), which give the amount of change in the flow of each line due to the removal of some other line in the system. These factors are calculated using relevant elements of the bus reactance matrix and line reactances. Special treatment for substation circuit breakers makes it possible to use bus-bar splitting for corrective action. The method was implemented by a FORTRAN IV computer program. The program is designed to be suitable for on -line applications. This will enable the system operating engineer to make quick and accurate decisions during emergencies to bring the system to a secure state of operation. The method was tested on two systems. Test results show the effectiveness of the method in selecting all possible switching strategies for correcting a given overload situation within a remarkable response time. Calculation accuracy was demonstrated by the test result to be acceptable for practical applications.