Voltage Control in Southwest UtahWith the St. George Static Var System

PacifiCorp commissioned the St. George static VAr system (SVS) with a continuous rating of -35 to +100 MVar (transient rating -70 to +278 MVar) in June of 2006. This paper presents the Southwest Utah area transmission system, the requirements for voltage support, the planning and dynamic performance studies used in rating and verifying performance of the SVS, and provides an overview of the design and coordinated control strategy. An overview of the SVS stability model with integrated "smooth" and "stepped" susceptance control is also discussed.The St. George SVS is connected to the 138 kV bus of the St. George substation to enhance voltage control and dynamic VAr support for major disturbances in the Southwest Utah 138 kV and 345 kV transmission systems. The SVS coordinated control strategy employs local and remote shunt reactive devices to reduce SVS reactive steady-state output and to regulate the voltage at the local St. George 138 kV bus and at the remote Red Butte 138/345 kV substation