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Synchronizing on West Point

Could local generators be used either to regulate voltage or control the power factor on distribution systems in New York?

Fortnightly Magazine - February 2006

that NY-ISO staff work with the owners of synchronous condensers to identify the unique issues associated with operation and cost-recovery needs, and develop a proposal that allows fair compensation for service provided to the New York market.

The concerns expressed in this draft report certainly are valid. The New York Power Authority (NYPA) recently took a 40-MVAR synchronous condenser out of service because it was not economical to operate. Dynamic reactive power reserves are shrinking. As loading has increased and transmission systems have been “propped up” with more and more capacitor banks, and as less transmission capacity is available, the voltage collapse curve has become steeper. The power voltage curve “nose” has become very sharp, and voltages will fall immediately when there is no reactive power available to support more load or transfer. This is shown in Figure 1. 1

Opportunities to Supply Reactive Power From West Point

The United States Military Academy has a 1,500-kW diesel generator and two steam turbine-driven 1,250-kW generators. The turbines are older non-condensing turbines used only in the winter, and the exhaust steam is used to heat campus buildings. The generators are vintage 1973 and operate at 1,800 rpm.

These generators would be ideal for use as synchronous condensers because they are connected to the turbines with removable couplings. In addition, there is a newer 1,500-kW steam turbine. These generators are installed with switchgear connecting them to the West Point distribution system, and they could be controlled either to regulate voltage or control the power factor on the West Point distribution system.

A critical point, however, is that reactive power does not travel well, and there are some locations where it is needed and some locations where it is not.

The local transmission operator at West Point is Orange and Rockland. Orange and Rockland has two capacitor banks on the 34.5-kV line that feeds West Point, and they usually operate only one. The second one is only connected during a heat wave when load is unusually high, and has been used only once in the last two years. Orange and Rockland has no need for reactive power from West Point.

Economics for the Local Supply of Reactive Power

For the purposes of discussion, let us assume that West Point is in a load pocket, an area of potential voltage susceptibility, that Orange and Rockland has grown weary of replacing capacitor switches and load tap changers, and that Orange and Rockland is looking for an alternate method of supplying dynamic reactive power and regulating local voltage. In this case, it may be possible to supply dynamic reactive power from West Point as a service. As mentioned above, we have a total of 5.5 MW of real power available from the four generators.

To supply reactive power when the generator is running, all we need to do is to control the generator excitation to provide the appropriate phase angle, either for voltage regulation or power factor correction. The problem is that the turbine generators are running only during the winter, and the diesel generator is only running during