T&D World Magazine

Vermont Electric Power to Install Four Synchronous Condensers

In the first project of its kind in the New England area in more than 30 years, Vermont Electric Power Company (VELCO) has chosen GE Energy to install four synchronous condensers at its Granite substation located in Williamstown, Vermont.

VELCO will be using the synchronous condensers to provide both steady state and dynamic support (VAR and voltage control) to the critical transmission corridor located in and around the Granite substation. The addition of the condensers will help to improve the system's efficiency and reliability, allowing VELCO to meet growing customer demand on the transmission grid in this area. The condensers and excitation systems are designed to provide low-voltage ride-through capability for 115 kV or 230 kV faults to aid in overall system stability.

The four condensers form the core of the Granite reactive power device, a system designed to maximize the available dynamic range of the condensers by coordinating condenser operation with 115-kV shunt capacitor banks and two autotransformer tap changers.

"VELCO selected our synchronous condensers because the turnkey solution was able to meet its strict specification requirements for fault performance as well as facilitate control compatibility with nearby HVDC and STATCOM installations," said Dan Heintzelman, president of GE Energy's services business.

"When the Northwest Reliability Project is complete, the Granite substation will be one of our most important stations for supporting network reliability and our new synchronous condenser installation will provide vital reactive power support for the New England transmission grid," said John Donleavy, president and CEO, VELCO.

GE Energy's units are each nominally rated at +25/-12.5 MVAR, for a total of +100/-50 MVAR. Each machine will be controlled with a state-of-the-art excitation system consisting of GE's EX2100* digital control and brushless exciter. Also included under the terms of the contract is a joint VAR controller that will coordinate both 230 kV tap changers, four 115 kV shunt capacitor banks and the voltage reference for each condenser's automatic voltage regulator. It will do so while maintaining 115 kV and 230 kV voltages within desired limits. The condensers are scheduled for commercial operation at the end of 2007.

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