What happens when a generator is under excited?

When a generator is under excited, it operates in a mode where it absorbs reactive power (VARs) from the grid instead of supplying it. This state occurs when the field excitation is insufficient to produce the necessary magnetic field strength for generating adequate reactive power. As a result, the generator draws VARs, which can lead to a scenario where it experiences a lagging power factor, affecting the overall stability and voltage regulation of the power system.

Understanding this behavior is essential in managing power system operations, as under-excited generators can contribute to voltage support issues and can be a critical factor in maintaining system reliability during peak demand or disturbances.