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.