Dog pee

Merry Christmas
Russell Ensslin

Russell Ensslin

Member
Location
Olivehurst California
MH uses an example of a dog meeting its demise while peeing because a municipality thought that driving ground rods at lamp posts would clear a fault. Similarly, a military person was electrocuted while showering because electrical installers believed a ground rod at the shower was equivalent to an EGC back to the source.

My questions are;
“Were the victims in series or in parallel? How was the circuit completed? Had an effective EGC been properly installed, would the victims still have experienced shock during the duration of the operation of the OCPD?

Can I get permission from MH to use his examples for a presentation to my company team?
 
It is not really that they though that a ground rod would clear the fault, it that the installations were likely made under the NESC (National Electrical Safety Code, the utility code) and they do not use EGCs in utility systems.

The victim is between an ungrounded conductor and some conductive thing that provides a path to the grounding conductor of the system...it is a parallel circuit just like any other load.

If there is an effective ground fault current path, there is a shock hazard equal to the voltage drop on the effective ground fault clearing path until the OCPD clears the circuit.

You would have to ask Mike for the permission, however I assume any slides he has as free stuff would be fair game.
 
Russell Ensslin said:
How was the circuit completed?
Click to expand...
From power panel's breaker, to the light fixture on the lamp post, to the short circuit connection that energized the lamp post itself, to the hand of the person (let's leave the dog out of this discussion) touching the lamp post, through that person's body and through their feet, to the dirt under their feet, through the dirt itself (yes, dirt can conduct electricity), to the building's grounding electrode system, through the grounding electrode conductor to the power panel's neutral bar, and finally through the main bonding jumper, and that completes the circuit.
 
If the graphic or video or whatever Mike Holt puts on the internet as a freebie, then imo, it is fair game. Make sure you give credit to Mike Holt when you use it. I was also told I could do this by a member of his team and I assume it was meant for all. When I got his spreadsheet Mike told me directly to spread it around. Pun intended.

If you used the material in an event where you are paid money then I would think you could be in trouble. In that case, I would ask permission.
 
charlie b said:
Absolutely! But the OCPD would react and open the circuit so quickly that the victim would probably not feel anything.
Click to expand...

IMHO if the victim was in the 'circuit' at the moment the fault occurs, there is a significant chance that they will feel something, especially for a high impedance outdoor circuit where clearing time might be measured in seconds.

However most likely the fault will occur and the OCPD will react when no-one is in a position to get shocked, even if it takes many seconds to trip. In the situations were people were shocked or killed by energized objects (manhole covers, lamp posts, etc.) how long was the object energized before someone came along and touched it?
 
Winnie, my comment was in response to the question in which the EGC was properly installed. The tripping time would be in milliseconds, and the victim would probably feel nothing.
 
Russell Ensslin said:
MH uses an example of a dog meeting its demise while peeing because a municipality thought that driving ground rods at lamp posts would clear a fault. Similarly, a military person was electrocuted while showering because electrical installers believed a ground rod at the shower was equivalent to an EGC back to the source.

My questions are;
“Were the victims in series or in parallel? How was the circuit completed? Had an effective EGC been properly installed, would the victims still have experienced shock during the duration of the operation of the OCPD?

Can I get permission from MH to use his examples for a presentation to my company team?
Click to expand...
Likely the victims found themselves across two points of different potential. Doesn't have to be nominal operating voltage, say it was a 120 volt supply involved and for whatever poor bonding reasons you had maybe 25 volts between shower water supply piping and actual earth, drain piping or whatever - user of the shower is at shock/electrocution risk.

Dog peeing on the light pole- maybe there is a ground fault energizing the pole to say 120 volts, there probably is some continuity from either ground rod or even just concrete base of the pole that will allow some current to flow and lower that voltage, but not enough current to open overcurrent protection. In that case there would be voltage gradients surrounding the pole. A small dog may not stand across much gradient but larger dog would be more subject to higher voltages. The dog maybe not a great example - more common with large livestock would be a water tank with electric heater to keep it from freezing, subject this to similar fault as I described above and housing of this water tank is energized to 120 volts. Again probably voltage gradient around the base of this most will sit on a concrete pad which will help enhance ground continuity some but not enough to function like an EGC either. Now have a cow with ability to have their back feet say six or seven feet away while they touch the tank with their mouth- they are spanning a much bigger voltage gradient in the earth surrounding the tank than we as humans typically would if we walked up and touched it, plus they are not wearing any shoes so no extra electrical insulation on their feet to help them any. People that touch it maybe get a tingle, the cow just falls dead as soon as they go to drink from it because they were subjected to a lot more current through their body.
 
charlie b said:
Winnie, my comment was in response to the question in which the EGC was properly installed. The tripping time would be in milliseconds, and the victim would probably feel nothing.
Click to expand...

I strongly agree for typical circuits inside of a building.

I somewhat disagree for outdoor lighting circuits, exactly the situation where someone might mistakenly believe that a ground rod could substitute for an EGC.

For these situations you might have a properly installed circuit with proper EGC that has a a far end impedance of several ohms and a bolted fault current well into the magnetic trip range of a typical breaker. It might take several seconds for the breaker to clear the fault, and during that time the circuit conductors and EGC will form a voltage divider; for a 120V circuit wired with equal size hot and egc, the fault voltage will be 60V until the OCPD clears.

-Jonathan
 
winnie said:
I strongly agree for typical circuits inside of a building.

I somewhat disagree for outdoor lighting circuits, exactly the situation where someone might mistakenly believe that a ground rod could substitute for an EGC.

For these situations you might have a properly installed circuit with proper EGC that has a a far end impedance of several ohms and a bolted fault current well into the magnetic trip range of a typical breaker. It might take several seconds for the breaker to clear the fault, and during that time the circuit conductors and EGC will form a voltage divider; for a 120V circuit wired with equal size hot and egc, the fault voltage will be 60V until the OCPD clears.

-Jonathan
Click to expand...
really long circuit runs can have same issues even if indoors. Type of indoor environment involved can lessen chance of victim having grounded objects within reach or a grounded floor to stand on though.

Wet indoor location however could be very similar to an outdoor location in many ways.
 
You must log in or register to reply here.
Top