What does a ground fault relay primarily detect?

A ground fault relay primarily detects ground faults, which occur when there's an unintended connection between an energized conductor and the ground or an extraneous conductive body that can cause current to flow outside of the normal circuit paths. Ground faults can lead to hazardous situations such as electric shocks, equipment damage, and even fires.

These relays monitor the current flowing through the system and are designed to identify imbalances that occur when a fault condition exists. When it detects that the current entering a circuit is not equal to the current leaving it—indicative of a ground fault—the relay activates, typically shutting down the circuit to prevent further hazards.

The other options refer to different electrical issues: overvoltage conditions pertain to voltage levels that exceed the normal operating range, short circuits involve a direct connection between two points of a circuit potentially causing excessive current flow, and phase imbalance indicates a situation where the currents in the three phases of a three-phase system are unequal. While important in electrical systems, they are not the focus of what a ground fault relay detects.