What causes angle instability in a power system?

• A. A shortage of reactive reserve.
• B. A loss of generator excitation.
• C. Exceeding voltage limits.
• D. A loss of magnetic bonds.

Answer: (D)

Angle instability in a power system refers to a situation where the rotor angles of generators in the system begin to diverge approximately due to system disturbances or inadequate control actions. One of the significant causes of angle instability is the loss of magnetic bonds. Magnetic bonds refer to the interactions and connections between the magnetic fields produced by generators and the system’s power grid, which are critical for maintaining synchronization.

When there is a loss of these magnetic bonds, either due to equipment failures or sudden changes in system conditions, the coordinated behavior of generators is disrupted. This can lead to a situation where the power system becomes unsynchronized, further increasing the risk of angle instability. Essentially, all generators must operate in a synchronized manner; if this synchronization is lost, it results in instability, prompting divergences in angle.

The other options, while relevant to different aspects of power system stability, do not directly lead to angle instability in the way that the loss of magnetic bonds does. For instance, while a shortage of reactive reserve is crucial for voltage stability, it does not primarily impact angular relationships between generators. A loss of generator excitation can indeed affect stability but is more closely related to voltage stability issues and does not address the direct cause of angle detachment. Exceeding voltage limits