How Long Does Before Being Killed? 3

[coloradog1]

Most people know that current determines how damaging getting shocked can be. A question was recently asked which I do not know the answer to. The question is, how long does the current have to exist before someone sees the effects.

For example, 100 to 200 mA can be fatal. But how long does this current have to pass through the body? What if it exists for only 1-2 cycles?

I believe a GFCI trips in less than 2 cyles. Since this device protects people, it would seem that 2 cycles of 100mA may not kill someone.

Any help is appreciated. I would also appreciate any references that can be provided.

Thank you

 

[jghrist]

IEEE Std 8-2000, IEEE Guide for Safety in AC Substation Grounding give a duration formula for allowable body current:

I_B = 0.116/sqrt(t_s)

for a 50 kg body weight

I_B in amps, shock duration t_s in seconds

 

[NAZ55]

Just wanted to correct a typo. It's IEEE Std 80-2000

 

[burnt2x]

transposed: for a 50 kg body-
t_(s) =(0.116/I_B)²

 

[ScottyUK]

Lots of other factors such as the path it takes through the body are (were?) believed to be significant. For example a current passing hand to shoulder on one arm is less likely to be fatal that one passing hand to hand across the torso. How does the equation accomodate those variables, or is it an equation for a specific case? I hadn't realised there even was an equation - thanks for the info.


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If we learn from our mistakes I'm getting a great education!

 

[radug]

You should also check IEC 60479. There is an article which compares both of them. I attach it.

 

[magoo2]

If you google Charles Dalziel, you'll find a lot of info on this topic. He was a professor who did a fair amount of experimentation with animals and with some of his students.

 

[cuky2000]

See the enclosed information extracted from different sources.

I hope this help.

 

[Sanditech]

The IEE regs for LV portable equipment states 400ms maximum dissconect time. For the simple reason that it is less than the time span of a heart beat, if the heart is held in shock for a time greater than a heart beat it will most likely go into a cardiac arrest.
Bit of hard luck if you have just done a 500m sprint and then touch a live conductor. So never rush to job is my advice.

 

[electricuwe]

A 100 mA GFCI may be helpful for fire protection, but it is definetly not a device suitable for protection against electric shock.

 

[itsmoked]

Most GFIs for house hold outlets is 5mA max. Is it not?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Keith,

30mA in the UK, 10mA in high risk areas.


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If we learn from our mistakes I'm getting a great education!

 

[alehman]

5mA in the U.S.

 

[itsmoked]

I guess you English blokes are working the population control issue with your 240V and 10mA GFI.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[marks1080]

Any specific answer to your question depends on the person being shocked. A persons skin does have a relatively high resistance, but once the skin breaks down (burns away) the resistance drops dramatically.

2 cycles @ 100 - 200mA probably wouldn't be fatal. But again, depends on the indivule.

Also, sweaty skin can make a huge difference in the amount of time it takes for the outer skin to break down.