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A Genetic algorithm is applied to the problem of determining the optimal hourly schedule of power generation in a hydro thermal power system. A multi-reservoir cascaded hydro-electric system with a non-linear relationship between water discharge rate, net head and power generation is considered. The water transport delay between connected reservoirs is also taken into account. The main control parameters that affect the genetic algorithm performance are discussed and a summary of the theoretical basis of the genetic algorithm method is presented. It is shown that a multiple step genetic algorithm search sequence can provide the optimal hourly loading of the system generators.

Nodal admittance matrix models are obtained for Wye-connected three-phase transformers with various grounding impedance configurations. The derivations have been performed using computational symbolic algebra, avoiding the necessity for simplifying assumptions. An original model for the general case of a Wye-Wye transformer, with grounding impedances on both primary and secondary neutrals, is given. It is shown that this model does not correspond to the simple combination of the previously known formulae for cases where neutral impedance occurs on either the primary side only or the secondary side only. It is also demonstrated that the new model simplifies to the well-known limiting cases for solid grounding and no grounding. A model is also given for multiple transformers sharing a single neutral grounding impedance. Index Terms--Grounding impedances, neutral grounding, nodal admittance matrices, three-phase transformers.

This letter describes a robust state estimator based on the solution of a mixed integer program. A tolerance range is associated with each measurement and an estimate is chosen to maximize the number of estimated measurements that remain within tolerance (or equivalently minimize the number of measurements out of tolerance). Some small-scale examples are given which suggest that this approach is robust in the presence of gross errors, is not susceptible to leverage points, and can solve some pathological cases that have previously caused problems for robust estimation algorithms. Index Terms--Mathematical programming, robustness, state estimation.

This letter presents a comparative study between two methods for estimating the uncertainty interval in power system state estimation. Constrained nonlinear and linear formulations are proposed to estimate the tightest possible upper and lower bounds on the states. The study compares the performance of these methods in terms of estimating the bounds of the uncertainty interval. In addition, an assessment of time performance for both methods is carried out with varying measurement redundancy levels. Index Terms--State estimation and measurement uncertainty.