SeaWest Wind Power operates a 183-turbine wind-farm connected to PacifiCorp's Foote Creek Substation. With a current maximum output of 135 MW, the Wyoming Wind Energy Project delivers reliable, renewable power to a 230-kV transmission system in the southern part of the state.

Until recently, however, operators regulated voltage at the windfarm's remote location using switched capacitor banks (on the 230-kV transmission system as well as on the substation's 34.5-kV collector bus). As is typical with wind turbines, step-voltage changes caused by capacitor switching events can cause accelerated wear and tear in gear boxes between the wind turbines and the induction generators. Frequent capacitor switching — essential to regulating voltage — can damage the gear mechanisms.

Following a thorough evaluation of major vendors of voltage-regulation devices, PacifiCorp selected GE Industrial Systems and American Superconductor to provide a dynamic VAR device for smoothly regulating voltage while also controlling the Foote Creek 34.5-kV capacitor banks.

Installed in October 2002, the +/- 8 MVA dynamic VAR device (D-VAR^™ voltage-regulation system), monitors the 34.5 kV bus voltage and regulates the voltage smoothly by ramping its VAR output over several seconds, as required. If positive dynamic VAR output is not enough, the D-VAR simultaneously switches on a 34.5-kV capacitor bank and reduces its dynamic VAR output by the same amount. The result is a nearly invisible change in VAR support level, with no step-change in voltage and no related gear box wear.

If needed, the D-VAR system once again ramps up its output to support voltage. This smooth ramping and instantaneous offsetting of switched capacitors can continue across all nine capacitor banks in the substation. The D-VAR control system may be easily expanded to control additional capacitor banks in the future.

The D-VAR system also detects step-voltage changes due to the switching of large remote 230-kV capacitor banks and instantaneously offsets them. This provides PacifiCorp and SeaWest with additional means of managing step-voltage changes that could damage wind generator gear mechanisms
Circle 180 on Reader Service Card or visit freeproductinfo.net/tdw