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#27678 - 07/30/03 11:28 AM Megger Death  
Spark Master Flash  Offline
Member
Joined: Jul 2003
Posts: 141
Las Vegas, Nevada, USA
I'm wondering just how deadly meggers are, if anybody here has ever heard of anybody being killed or shocked hard using a megger and if the low amperage isn't dangerous while the high voltage is trying to kill him. Also, I've read online that a long cable can hold megger-induced voltage for a long time and that you have to ground it for "a few minutes" after a megger test. That seems excessive to me - a few minutes of grounding?

I'm thinking about buying a megger (not sure whether to get 500v or 1000v). Anything you can tell me about megger dangers or accidents involving them will be appreciated. I like to learn from other people's mistakes!

So...exactly what will happen to me (and in what order) if I grab both leads and someone cranks 1000v through me? Is the duration too short to kill me? If it can kill me, what body part fails first that causes death? Has anybody here got experience being zapped by one of these things?

Thanks in advance for sharing your wisdom and experience.


"When in doubt, short it out"

Work Gear for Electricians and the Trades

#27679 - 07/30/03 11:36 AM Re: Megger Death  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
I believe the megger is set to give off about a milliamp.


#27680 - 07/30/03 01:07 PM Re: Megger Death  
ThinkGood  Offline
Member
Joined: Aug 2002
Posts: 1,081
Milwaukee, WI
I once asked a similar question as a reply in this thread .

I'm sure the others here can add a whole lot more from personal experiences, etc.

Quote
...cable can hold megger-induced voltage for a long time...

If you have wire connectors on the ends, do they hold all the voltage in? [Linked Image]


#27681 - 07/30/03 02:32 PM Re: Megger Death  
George Corron  Offline
Member
Joined: May 2001
Posts: 717
Lorton, Va USA
Spark Master,
HOW do you call yourself "Spark Master" if you've never 'experienced' a megger? [Linked Image]

They are set for milliamps. An old teacher of mine used to have the class hold hands and the student at the front and rear of the line had to grab a lead......... fun. I'm pretty sure they would not allow this anymore. Not deadly (Personal Opinion) unless you have a health condition, such as a pacemaker, but not something to play with arbitrarily.

Most 1000 volt meggers have a 500 volt switch nowadays, so buy the 1000 and get both. DC meggers are better for longer runs.

Because of capacitance in conductors (remember, a capacitor is a conductive material, wrapped in an insulative material, wrapped in a conductive material - can you say cable in conduit boys and girls?) so it WILL hold a charge and WILL require grounding out. You only have to ground it for a brief period, or wait a few minutes (up to an hour) for the charge to dissipate on it's own.

Yup, I can tell embarrassing stories about this, but won't [Linked Image]

You will find a megger to be one of the most useful tools you'll ever own. Fluke makes a great one that is volt meter, ohm meter, capacitance checker all in one, a bit pricey, but great. I disdain that they taught this in my apprenticeship but seem to not teach it anymore, real pity.

Also, if you're a geez (THANK you veddy much) you may want to look at the old amprobe wind ups, no batteries to go bad. I don't trust that 'lectricity, got's ta have my windup. OK, I own both.

Of course, NOBODY beats Biddle for the meggers, AND the training. Both a bit pricey, but I recommend them highly.

Good luck, and........... wear gloves. [Linked Image]

[This message has been edited by George Corron (edited 07-30-2003).]


#27682 - 07/30/03 03:10 PM Re: Megger Death  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,303
how many joules is the average megger ? i wonder if one could defib (in a pinch) with a one?

Steve (aka... any port in a storm) sparky

[This message has been edited by sparky (edited 07-30-2003).]


#27683 - 07/30/03 04:12 PM Re: Megger Death  
US Coreman  Offline
Member
Joined: Mar 2003
Posts: 36
Illinois, USA
Her's where I show my ignoarance, but aren't joules a measurement of stored/generated then discharged energy? I know all our strobe power supplies and things like defibrilators and "thumper" partial discharge cable fault locators, ( http://www.hipotronics.com/ ) by example are devices expressed in joules. But my megger can apply a fairly steady voltage into a cable under test, but does so at a maximum 5 milliamp output.

If you are talking about the voltage that capactively builds up and can lay stored on a long cable run, I guess that would be applicable, but would vary with a number of factors including the length of the run and the amount of energy wou were able to dump into the cable in the first place.


[This message has been edited by US Coreman (edited 07-30-2003).]


#27684 - 07/30/03 05:47 PM Re: Megger Death  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
A joule {pronounced 'jewel'} is equal to 1 watt·second of energy, or 1/3600 of a watt∙hour [NOT kilowatthour.] CF Dalziel and his noted Dalziel's Equation are pertinent in electric-shock response.

[Small aside — there are portable DC insulation-test sets that produce 160kV.]


#27685 - 07/30/03 06:05 PM Re: Megger Death  
Spark Master Flash  Offline
Member
Joined: Jul 2003
Posts: 141
Las Vegas, Nevada, USA
People tell me "It's the amp load that will kill you, not the voltage".

If I say, "Okay then, grab onto the hot lead of 4160", they say, "Well...at high voltages, the voltage alone will kill you."

Can somebody explain this?

When I hear these two statements, there seems to be a big gray area of how much voltage and how much amperage it takes to hurt me. How much voltage/amperage does it take to hurt somebody? 480 at 1 amp? 120 at 5 amps? 4160 at 0 amps?

Thanks again


"When in doubt, short it out"

#27686 - 07/30/03 06:57 PM Re: Megger Death  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Most of the modern electronic meggers will deliver a maximum of a few milliamps into a short-circuit. The current likely to flow through your body if you grab hold of the probes will obviously be less due to your body's resistance.

Quote
People tell me "It's the amp load that will kill you, not the voltage".
If I say, "Okay then, grab onto the hot lead of 4160", they say, "Well...at high voltages, the voltage alone will kill you."

Can somebody explain this?


It's not the high voltage in itself which would kill you, but rather the high current flow which results from that high voltage.

It is the current which does the damage during an electric shock. How much harm is done depends upon the intensity of the current, which parts of the body it flows through, and for how long. As the current and the duration are increased, so there is more chance of burns. Current passing through the vital organs of the body (e.g. the heart) is far more dangerous than that passing between, say, two fingers on the same hand.

Ohm's Law applies to the human body just as to metallic conductors. Thus at higher voltages you will get more current for any given value of body resistance.


#27687 - 07/30/03 10:29 PM Re: Megger Death  
ThinkGood  Offline
Member
Joined: Aug 2002
Posts: 1,081
Milwaukee, WI


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