What impact does phase angle exceeding 90 degrees have on a power system?

When the phase angle in a power system exceeds 90 degrees, it indicates a situation where the current and voltage are no longer synchronized. This misalignment can lead to instability within the system. Specifically, as the phase angle approaches 180 degrees, power transfer capability diminishes, potentially resulting in conditions that can incite oscillations.

In a stable power system, the phase angle is maintained within a certain range to ensure effective power delivery and system reliability. However, once the phase angle escalates beyond 90 degrees, it can create a scenario where small disturbances or changes in load lead to significant oscillatory responses. This can further exacerbate system instability, creating challenges in maintaining regular and safe operation within an electrical grid.

Understanding this behavior is critical for engineers and operators working with transmission systems in order to prevent cascading failures and to maintain proper system dynamics.