In a three-phase system, a voltage unbalance greater than ___ from the average voltage should be investigated.

In a three-phase system, a voltage unbalance greater than 2 percent from the average voltage is a critical threshold that warrants investigation. This percentage is significant because voltage unbalance can lead to a variety of issues, such as increased heating in motors, reduced efficiency, and potentially shorter equipment life.

The 2 percent threshold is recognized in industry standards as the maximum allowable unbalance to prevent harmful effects on connected equipment. Specifically, when the variation in the phase voltages exceeds this percentage, it can cause non-uniform currents in motor windings, leading to mechanical failures or operational inefficiencies.

This is particularly important in three-phase systems where load balance across the phases is crucial for maintaining operational stability and longevity of electrical equipment. Thus, identifying and rectifying any voltages that exceed this threshold is essential for the safety and reliability of the electrical system.