The adverse effects of excitation system VAr and power factor controllers

The trend toward automation of today´s power stations has prompted an increased demand for excitation systems having voltage regulators with the ability to automatically regulate generator reactive power (VAr) output or power factor (PF). While not really a new type of control, automatic VAr and PF controllers are appearing in the specifications of more and more power plants and generator voltage regulators. This paper provides a functional description of voltage, VAr, and PF controllers and regulators, along with an example demonstrating the superior steady-state voltage support performance on a transmission system by regulating voltage, rather than VArs or PF. The paper concludes that VAr/PF controllers or regulators should generally not be specified or utilized on excitation controls for voltage supporting generator applications