In a recently published paper of the authors („On an Exact Transformed Decoupled Load Flow”︁: Electr. Power a. Energy Syst. 13 (1991) no. 1, pp. 28‐32) the method of an exact transformed decoupled power flow (ETD) was presented which can almost achieve the speed of a decoupled power‐flow computation while maintaining the benevolent performance of a Newton power flow in ill‐conditioned cases. The present paper introduces this method to an optimal power‐flow solution. It can be shown that a speed‐up of about the factor three is achieved as against a standard Dommel/Tinney version.

In order to speed up on‐line security assessment, a fast and accurate technique for on‐line generator outage simulation is presented in this paper. A linearized active power‐flow model is built up. After the generator outage, the active power of lost generator is distributed among the remaining units according to the frequency‐response characteristics (FRC) of individual units and loads taking into account the speed control actions of the unit governors. A linearized model of the automatic voltage regulator (AVR) and excitation system are used to derive the proposed steady‐state relation between the bus‐angle correction, obtained from the solution of active model using the redistributed power mismatch, and the corresponding changes in the voltage magnitudes. The quadratic power‐performance index for every generator outage is computed and the results are subsequently sorted in decreasing order according to the severity of effects. The proposed method is verified by applying it to a test system to show the ability of the proposed method to find the accurate solution and decrease in the computation time and memory storage required.