| Recent changes in the economical, political, and environmental aspects of the power system industry have driven utilities to operate the grid under an increasing number of stressful conditions. Deregulation policies have caused the transmission system and especially the interties to be used in a manner other than it was originally designed. Regulatory uncertainty at both the state and federal level has impeded transmission investment and prevented necessary system coordination on a regional scale. Environmental activism has exacerbated this situation by creating a public reluctance to permit and build new generation stations and transmission lines. Utilities have responded to this new environment by operating under reduced safety margins in order to sustain profitability without increasing rates. This operating environment has made the power system vulnerable to voltage collapse related blackouts and wide area disturbances.;This research explores the use of an inverse-time under-voltage load shedding scheme for voltage collapse prevention. In particular, issues associated with configuring relays in predominantly inductive loaded systems and voltage-regulated environments are explored. For the highly inductive system, a methodology is developed to determine relay parameters that take into account local and global voltage problems. A voltage slope control method and a sensitivity index is developed to address situations where local distributed resources provide reactive power compensation at sufficient levels to create the potential for instability to occur at close to nominal voltage. The IEEE 30 Bus test power system and several smaller test systems are used to investigate these concepts. |
