Typically, a phase loss is caused by a blown fuse, thermal overload, broken wire, worn contact or mechanical failure. Phase loss protection refers to safeguarding the power system when a phase is lost in a three-phase AC supply. Phase Imbalance: Voltage or current between the three phases becomes uneven, even if all. The most important feature offered by a solid-state overload relay (SSOLR) is phase loss protection. When a phase loss causes a significant current increase in the remaining phases of the motor circuit, there is a major increase in rotor current that can cause motor damage.