Optimizing Non-Utility Generating Facility Reactive Power Capability

In optimizing the reactive power export and import capability, critical decisions need to be made early in the design process of an non-utility generator (NUG) station in order to achieve an optimum range of desired operating conditions for the facility. While these decisions are well documented in ANSI standards, factors such as grid voltage changes, ISO regulations, and NUG design market timing will impact the selection process of the equipment specified. As a result, the NUG operation can vary considerably depending on the settings of plant electrical equipment variables. This article addresses a case study of an NUG station designed with two gas turbine generators and one steam turbine generator operating in a combined cycle mode and connected to an existing grid system. This article is based on generator step-up (GSU) transformers with fixed raps that can only be adjusted when the transformer is de-energized (no load). The effects of equipment selection and plant operation settings are examined for optimizing the reactive power capability of the station based on projected operating conditions.