In electrical engineering, "Zero Sequence" refers to a specific type of current or voltage that occurs in three-phase systems. It represents the component of the system where all three phases are equal in magnitude and phase angle, effectively acting as a single-phase system. This condition often arises during unbalanced loads or faults, such as a ground fault, where one phase is affected while the others remain stable. Zero sequence currents can lead to issues in power systems, including overheating and equipment damage. To manage these effects, protective devices like ground fault relays are used to detect and mitigate zero sequence conditions, ensuring system stability and safety.