Which of the following best describes the consequence of allowing a power angle to exceed 90 degrees?

• A. Increased generation efficiency.
• B. Risk of losing synchronism between generation and load areas.
• C. Improved voltage stability.
• D. A reduction in operational costs.

Answer: (B)

Allowing a power angle to exceed 90 degrees poses a significant risk of losing synchronism between generation and load areas. The power angle, which is the angle between the voltage and current phasors in an alternating current (AC) system, is a critical factor in maintaining system stability. When this angle exceeds 90 degrees, it indicates that the generators are not properly supplying the load, leading to an unstable condition known as loss of synchronism.

In a synchronous system, all generators operate in lockstep, meaning their outputs are coordinated, and the system remains stable. However, when the power angle grows larger than 90 degrees, the torque on the generators can become negative. This means the generators will start to operate outside their intended performance range, potentially leading to destabilization. If the condition continues, it can result in generators losing synchronization with the system entirely, which can cause widespread outages or cascading failures.

In contrast, increased generation efficiency, improved voltage stability, and a reduction in operational costs are not directly associated with the issue of excessive power angles. Maintaining a power angle below 90 degrees is crucial for achieving operational performance and reliability in power systems, making the aforementioned consequence of exceeding this threshold particularly critical to understand for anyone involved in system operations and