Security-constrained OPF: influence of fixed tap transformer fedloads

The behavior of the conventional security-constrained optimal power flow (OPF) solutions is studied in the presence of loads not controlled by under load tap changing (ULTC) transformers. modified versions of the AEP/IEEE 30 bus system with exponential-type load models were used to create a variety of test situations. The study reveals that with loads not controlled by ULTC transformers, the solution to a conventional security-constrained OPF can be different from its practically observed version. This conclusion is similar to that obtained for OPF neglecting contingencies. In the present case, since the voltages are usually higher than for OPF neglecting contingencies, it follows that an increase in fuel costs, power demand, and total and net revenue can be expected in more cases than in the previous study. Moreover, limit violations in the present case are observed mainly during contingencies