Final answer:
The correct answer is option 3) Ground fault.
Step-by-step explanation:
In three-phase equipment, the observation of half the expected arc can be indicative of a ground fault. A ground fault occurs when there is an unintentional electric path to the ground. This usually happens when the current escapes from its intended circuit, which can be due to damaged insulation or conductive dust, moisture, or other conductive materials that enable the current to flow outside its intended path. Ground faults are dangerous as they can lead to electrical shock, equipment damage, and fire hazards.
A ground fault circuit interrupter (GFCI) or ground fault interrupter (GFI) is a device designed to detect such faults. It monitors the difference in currents between the live/hot and neutral wires. If the GFCI detects that the current flowing out through the hot wire is not fully returning through the neutral wire, it implies there is leakage, commonly referred to as earth leakage, and the GFCI will trip to cut off the power to prevent hazards.
The three-wire system provides a safer environment by incorporating an earth/ground wire that offers a low-resistance path back to the source. This system, coupled with circuit breakers or fuses, helps protect against thermal overload and electric shock by disconnecting the circuit when excessive currents occur due to faults such as short circuits or ground faults.