Abstract
Generally, improving voltage stability against the power demand increase tends to increase short circuit capacity. In this paper, two methods are proposed in order to obtain the appropriate system separation points which minimize the short circuit capacity increase and the voltage stability decrease.
Considering the Q-ε network which expresses the relation of voltage and reactive power, the voltage sen-sitivity is equivalent to the element of the system impedance matrix. A fast calculation procedure for the change of the impedance matrix element due to bus connection changes has been proposed. It can be applied to the calculation of both the voltage sensitivities and the short circuit capacities. The results give the information on the most appropriate separation points among the designated candidates, against the short circuit capacity problem and voltage stability consideration.
The second method proposed uses a linear programming technique with variable line impedances and the objective function of minimizing the short circuit capacity subject to bus voltage dip constraints. This gives the information on the preferable separation points in large and complicated systems. Some practical procedures are also given.
