🔍 Key Concepts

• Ungrounded 3‑phase systems and what happens to line-to-ground voltage when a single ground fault occurs • How current returns to the source in a fault condition – is there a complete circuit path in figure A for one fault vs. two faults? • Difference between faults on same phase vs different phases in an ungrounded system and how that affects phase-to-phase current flow

💭 Think About

• Look at figure A and trace the current path for a single ground fault from the phase conductor, through the fault, along the common equipment grounding conductor, and back toward the source. Is there a full loop back to the source? • Now imagine there are two separate ground faults: first put them on the same phase, then put them on two different phases. In which case do you actually create a phase-to-phase fault path that can drive high current and trip a breaker? • Compare figure A (ungrounded) with figure B (grounded neutral). In which figure does even a single ground fault clearly complete a circuit back to the source neutral and therefore cause substantial fault current?

✅ Before You Answer

• Verify whether an ungrounded 3‑wire source has its neutral or any phase intentionally tied to ground in figure A. • Check which condition actually creates a low-impedance path between two different phase conductors through the equipment grounding conductor. • Confirm when a breaker trips: it must see overcurrent. Ask yourself: in which choices would the ground fault(s) realistically produce high enough current to be detected by an overcurrent device in an ungrounded system?