Phasetoground

Phase-to-ground fault is a type of short circuit in electrical power systems in which one live conductor makes contact with the earth or a grounded object. It is one of the most common fault types in power distribution and transmission networks, alongside phase-to-phase faults. Such faults can occur due to insulation failure, damaged cables, moisture, or contact with conductive objects after a fault.

During a phase-to-ground fault, current returns to the source through the earth, the grounding system, or a grounded neutral. The magnitude of the fault current depends on system grounding and earth resistance; solidly grounded systems can produce large fault currents, while high-impedance or unearthed (IT) systems may exhibit lower, slower-appearing faults. The fault causes voltage to collapse on the faulted phase, arcing, heating, insulation damage, and potential harm to equipment. It poses safety risks to personnel and can ignite fires.

Protection against phase-to-ground faults relies on protective relays and devices such as overcurrent protection, earth-fault protection, residual current devices, and circuit breakers. Coordination and proper grounding reduce fault currents and aid in rapid clearance. In distribution networks, fault-location and isolation schemes aim to minimize outage and equipment damage. Regular maintenance of insulation and grounding systems, along with insulation coordination, helps prevent such faults.