Next-Generation Synchronous Condenser Installation at the VELCO Granite Substation

As part of the Northwest Reliability Project (NRP), the Vermont Electric Power Company, Inc. (VELCO) upgraded its transmission system with a next-generation synchronous condenser-based Reactive Power Device (RPD) located in the Granite 230 kV / 115 kV station. The Granite RPD consists of four (4) synchronous condensers, four (4) 115 kV, 25 MVAr shunt capacitor banks, and a control that coordinates condenser volts/vars, 115 kV shunt capacitor banks, 115 kV bus voltage, and autotransformer tap settings. Each synchronous condenser is rated 13.8 kV, +25/-12.5 MVAr continuous and incorporates a digital voltage regulator (EX2100*) and brushless excitation system. The Granite RPD was placed into commercial operation in November 2008 and represents the first new conventional utility synchronous condenser-only installation provided by GE in more than 30 years. This paper describes the overall project starting with VELCO's planning issues, how synchronous condensers are able to meet the system requirements, and a description of the supplied synchronous condenser equipment.