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Registered Member #1361
Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305
I have seen people saying a 15kv 30ma NST is dealy, and others saying its not. What is the truth? I know it is dealy if you purposly make it conduct through your heart, but what about something like touching it?
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
Is 450 VA - 15 kV 30ma "deadly" - more like a "serious shock hazard". I'm guessing that if the conditions were right - it could pose a serious danger to a small child and could cause death. I'd think - dangerous - is the optimal word here. Potential danger is very real --- it NOT NOT NOT a kids toy!
I have a 2 kVA 14.4 KV Westinghouse PT unit. I consider this DEADLY!!
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
It's good practice, when making adjustments to any 'hot' HT circuit, to work always with one hand in your pocket, or behind your back, so you don't get a hand-to-hand across-the-body shock, which are generally thought to be the most dangerous.
Remember that it's not the voltage in itself, but the ability of the voltage to drive a current through the resistance of your body, that is dangerous. You may survive contact with a very high voltage source with which you just have a brush contact, but be killed outright by a much lower voltage source better coupled to your skin by larger surface area of contact, and by moisture such as sweat.
It's safest to assume that a shock from an NST will kill you, so you don't take foolish chances.
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Of the 3 known TC deaths only the one where a baby died was a home a TC and presumably a NST. Ventricular fibrillation threshold in the heart is I gather about 30mA across the chest. Above that at about 100mA asystole intervenes which should restart itself unlike VF. I am not sure whether those figures were AC or DC though.
Defibrillators which I have used in my job of the older unipolar type, are rated in Joules. One typically uses 200J from a cap charged to about 5kV 32uF through a limiting inductor. I have got the chest resistance as low as 50ohms between the paddles with extensive skin prep and electrode gel.
Registered Member #1361
Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305
Well of course im not gonna go and put each hand on a terminal, i make sure it is off and unplugged every time i touch it, and use a long chicken stick if i need to move any electrodes, along with having the power cord in my hand ready to unplug, and wearing shoes. Ive only been shocked by a dual ignition coil circuit, and even that was scary, you could fell the AC pulses going through your body.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
lpfthings wrote ...
Well of course im not gonna go and put each hand on a terminal, i make sure it is off and unplugged every time i touch it, and use a long chicken stick if i need to move any electrodes, along with having the power cord in my hand ready to unplug, and wearing shoes. Ive only been shocked by a dual ignition coil circuit, and even that was scary, you could fell the AC pulses going through your body.
It's easy to get complacent, and not take all the safety precautions that you should, or trust to luck instead of method, or work when you're too tired to pay attention properly. I'm sure most of us have made a serious mistake with high voltage at one time or another, and found ourselves thrown backwards across the room. I certainly have.
Registered Member #1157
Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307
Electricity is kind of like that pet cobra that the snake charmers keep in those wicker baskets. If you take good care of the snake for all of its life, provide for it's every need, use it only when you need to, then it will still bite you if you aren't paying attention.
Why? Because it's a snake. It can't help being a snake, it just is a snake. It didn't have any hatred of you, it didn't feel for you at all. It was just acting like a snake. It gave you all the warnings, and you grew complacent and chose to take risks. The moment you let your vigil slip, it will bite you.
Same with an NST. The GFI NST's are probably "safer" than the NonGFI NST's, in that they will switch off if a serious ground fault is detected. However, I wouldn't rely on any built in circuitry to save me. I try to take every precaution. I treat my NST's like they are cobras' in my wicker basket.
That way, on the day I get a potential transformer, or even bigger with the Distribution Transformer, I am prepared and I have the safety routines already ingrained.
Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
my uncle mas making a jacoulbs ladder once and he accidentally touched the electrodes of a 12kv 30ma nst and he lived to tell the story but i still dont recommend doing this and i take various precautions when handeling a nst so as far as the deadly part i cant be positive but i could be very wrong but painfull yes and you probably will have some nice burn marks on your hand.
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Is a NST lethal?
