Volume I - DC Corrections Needed

Thread Starter

Unregistered

Joined Dec 31, 1969
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I just read through volume 1 DC "Shock Current Path" and I think it's pretty good in overall, however, I noticed two little mistakes. Figures 4 and 6 and their respective descriptions are not completely correct. The reason is the following:

If you have a voltage source and the voltage source is NOT grounded and a person would stand on ground and touch the positive pole (for DC, or the phase for AC) of the voltage source, then it depends on the potential that the ground is at whether the person would get shocked or not, since it is the potential difference between two points that drives the current. If say the voltage source is +230V and the ground is at +20V (in the real world the ground would probably be more close to 0V) the person will still feel a current that depends on the person's resistance and the remaining potential difference of +210V!
 

Dave

Joined Nov 17, 2003
6,970
The point illustrated in figures 4 and 6 is that the person is open circuit with respect to the voltage source. As can be seen in figure 5, when the voltage source is grounded, the person is shorted and the shock path is then a function of the resistance of the person and load.

I guess the question is, is there a point of clarity with the diagram as illustrated.

Dave
 

Thread Starter

Unregistered

Joined Dec 31, 1969
0
Well, let's see, maybe my above description wasn't completely clear. I've seen that you are making a point about the person being open circuit with the voltage source.

However, I'm arguing that this does not matter since it is the potential difference between two points that drives the current. Therefore, it depends on the potential difference between the ground of the person and the ground of the voltage source whether the person will get shocked or not; so I'm arguing that it is NOT safe to stand on the ground and touch the phase of a voltage source even if the voltage source is NOT grounded. It's a gamble, you could be fine (if the potential of the ground is somewhat close to the plus potential of the source) but it could also work out really bad for you (if the potential of the ground is much lower or higher than the plus potential of the source). To be really sure, one would have to measure the potential difference between the respective grounds. Hope this makes sense?
 

thingmaker3

Joined May 16, 2005
5,084
so I'm arguing that it is NOT safe to stand on the ground and touch the phase of a voltage source even if the voltage source is NOT grounded. It's a gamble, you could be fine (if the potential of the ground is somewhat close to the plus potential of the source) but it could also work out really bad for you (if the potential of the ground is much lower or higher than the plus potential of the source). To be really sure, one would have to measure the potential difference between the respective grounds. Hope this makes sense?
This is certainly good advice. I see nothing in the text to the contrary, however. The text specifically describes ground faults as a potential hazard.

Perhaps a line of text could be added admonishing the reader to avoid touching power lines altogether until they have proper training and equipment?
 
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