Touch Potential on Ungrounded systems

[NickParker]

What is the purpose of equipment grounding on the first line-to-ground fault? What will happen to the person touching the metal enclosure assuming the single-line-to ground fault happened inside the metal enclosure if there is no equipment grounding? Will he be electrocuted? should touch potential be calculated? or since the fault current does not return back to source, the touch potential is irrelevant for the first line-to-ground fault in ungrounded systems?

 

[bacon4life]

Rather than truly being ungrounded, typical "ungrounded" systems are actually grounded through the shunt impedance of the circuit. A person forming a ground path to the first phase on such a system will carry a small amount of mostly capacitive current. Even though the amount of current flow is small compared to faults currents in solidly grounded systems, the capacitive current can be orders of magnitude larger than the human body can withstand.