Resistance Ground <600V System

[ron]

Is anyone aware of a graphic that would help explain the limited ground fault current of a resistance grounded system, during a fault, and how it would effect an electrician while working on the faulted equipment if touched?
I was trying to draw myself a four line diagram to indicate fault current through a worker that may be different then a solidly grounded system. Clearly during a fault on a resistance grounded system, the system is still energized and hopefully in an alarm condition, requiring electricians to make the diagnosis while the equipment is "hot".
Would you consider a resistance grounded system more dangerous to a worker than a solidly grounded system?
I've seen lots of solidly grounded system that have high impedance arc faults, that didn't trip the upstream circuit breakers too.
The graphic will be used for educational purposes within my office.
We design systems that are critical in nature, and can sort of be considered similar to a batch industrial process.

 

[don_resqcapt19]

Unless you can limit the ground fault current to a very low value, there is no difference in the shock effect for some one touching an energized conductor. There is a significant change (for the better) in the arc flash/blast effect for a ground fault on a resistance grounded system.
Don

 

[LarryFine]

Ron, to put it simply, the neutral-to-ground resistance is in series with a fault, which is why it limits current. Whether it affects an electrical shock depends on the relative resistances of the neutral resistor and that of the body parts in the pathway.

In order to really reduce the shock potential (pun intended), the neutral resistor would have to be at least equal to the person (which would halve the current), or better yet, several times higher than the person. This is simple series-resistance voltage dividing.

Ohm's law tells us that the higher resistance drops the higher voltage. Unfortunately, that's usually the body.