Correctability of voltage violations in on-line contingency analysis

This paper focuses on determining the correctability of bus voltage violations during the contingency selection process. The present day strategy in the contingency selection function consists of flagging the worst contingency cases for further detailed analysis, when preventive and/or corrective actions are obtained. The worst contingency cases are the ones which bear a large severity or performance index (PI). However, one must take into account that contingencies with a large PI may be easily correctable, whereas contingencies with small PI, that had not even been flagged, may be noncorrectable. Thus, the selection process should flag not only those contingencies with large PI but also those that are not easily correctable. In a previous paper, it was shown that correctability of line overloads can be determined using a first order sensitivity approach with an acceptable increase in contingency selection time. In this paper, the correctability of voltage violations is addressed. Because of the nonlinearities, the algorithm used requires more calculations than the correctability of real power violations, but the additional time needed for the selection process is still quite acceptable for on-line purposes. The paper describes the algorithm, and provides test and timing results