Instruction and Tools for Working Safely with High Voltage?

[MitchJi]

Hi,

I know a lot of this is basic common sense but its also basic common sense to know what you are doing when doing work that is potentially hazardous .

So any recommendations on how or where to get instruction or information (easiest, cheapest, quickest) on tools and techniques for safely working with high voltage packs and systems?


Thanks!

 

[bigmoose]

First having a clear and uncluttered workspace.

Remove your rings, watches and neck jewelry.
Tape over non necessary parts of your metallic tools.
Keep distractions away from you, like wifey, kids pets.
Focus on what you are doing, and think through what you do before you commit to action.

Pay particular attention to the potential of dropping small parts into/onto battery buss bars. Plasmaboy racing had an incident that turned the car into a plasma ball over a dropped washer. Nice story about it here http://www.plasmaboyracing.com/blog/?page_id=10

Mind the path from your left arm down through the right foot. That is the path that is the most susceptible to killing you. Around HV switchgear we were taught to keep the left hand in our pocket.

It is not the voltage that kills but the current. Obviously the voltage drives the current through your bodies impedance. Dry skin is pretty good, but hot humid weather and sweat drops that impedance.

 

[jonathanm]

Having suffered a few high voltage shocks, including one that threw me 10 feet across the room (not a fault of my doing I hasten to add) I have found the best thing is to know exactly what you are looking at (and touching).

Awareness is the biggest safety device.

Learn to quickly evaluate what is in front of you. what is connected where....what things are ground or 0v, what things are high V, how close they are, (could a slipped screwdriver or dropped screw short something) is there a fuse or a breaker, etc etc.

This process can happen very fast if you know what you are doing, but if you are not sure, take your time....check once, check twice, check as may times as you feel you need to, before you switch it on or touch it. There is no rush. Make sure you understand what is in front of your before you start poking around.

It's easy to get sloppy. I was recently working on some high voltage tube audio gear. while poking around in the low voltage part of the circuit, I suddenly became aware of how my arm was crossing over part of the high voltage circuit. Just turning the box by 90 degrees mitigated the risk factor in case the cat jumped up and startled me, or my chair collapsed or some other unforeseen random happening...

 

[liveforphysics]

Keep 1 hand in your pocket when possible. This makes it tough to take it through the heart.

Shrink wrap the shanks of your screwdrivers so just the very last 1mm of tip is uninsulated.

Wrap your wrenches with tape or big shrink so only the insides of the jaws are exposed.

I have a pair of high voltage linemans gloves that are a silicone inside liner with a leather outer cover to protect the liner. They are nice when working with really big things, but lack the dextarity needed for most fine work.

Don't assumed power is off until you check it. I've been bit by seeing a contactor was open and main fuse was out, but forgetting that pre-charge resistor was keeping the caps in the controller at pack voltage.

Wear long pants, rubber shoes, and stand on a rubber mat. Do anything and everything you can to avoid your body being grounded. You can only get shocked if you're making a circuit somehow, so avoid contact with things you don't need to be in contact with to do the job.


If its under around 150v, it can't really hurt you IMHO, just give you a little jolt. I take 100vdc across the chest roughly everyday at work and play, its not a big deal. We even have played games at work where you had to carry a 116vdc battery pack around by the terminals with one in each hand shocking you across the chest as you carried this 50lbs pack around. Lol.

 

[jbkeh]

If its under around 150v, it can't really hurt you IMHO, just give you a little jolt. I take 100vdc across the chest roughly everyday at work and play, its not a big deal. We even have played games at work where you had to carry a 116vdc battery pack around by the terminals with one in each hand shocking you across the chest as you carried this 50lbs pack around. Lol.

I am gobsmacked to the point of registering. A car battery can kill you if the contacts penetrate the skin into your salty wet interior.

http://www.physics.ohio-state.edu/~p616/safety/fatal_current.html

 

[jonathanm]

I'd heard this story before so I just looked it up to see if it was true.......

Sailor accidentally kills himself with multimeter:

http://www.darwinawards.com/darwin/darwin1999-50.html

 

[liveforphysics]

If you poke it through your skin, yeah, you can have some issues at any voltage. Don't poke it in your skin.

 

[bigmoose]

I forgot what I originally posted here... but a story about current and voltage. In 1975 I was working on an ion source for a Nuclear Accelerator. The source was floated at +50,000 Volts. The gas was fed through a teflon tube that went through a liquid nitrogen cold trap to remove volatiles. I reached for the tube in the process of refilling the cold trap. Unknowingly the cold trap had gone dry and the water vapor created a conductive path to the ion source. I watched a 1 to 2 inch spark jump to my right index finger. In an instant my body was blown off the 2 foot platform and into a gas manifold of about 10 K bottles.

I survived, lots of voltage, but the current was below the atrial fib level.

 

[rhitee05]

#1 safety rule: Don't do it!

#2 safety rule: Don't do it!

If you have to do it, the most important thing you can do is to prevent any shock that does occur from going through your heart. Thus, the one hand rule. Keep the other in your pocket or behind your back - even if you're leaning on your workbench you might accidentally touch something grounded.

Make sure all your tools are insulated. LFP made good suggestions. Don't think that one layer is enough. An insulated screwdriver is good. An insulated screwdriver while wearing rubber gloves is better. An insulated screwdriver while wearing rubber gloves while standing on a rubber mat is better still... You want a rubber/plastic/etc surface on top of your workbench, too.

Obviously keep water far, far away. But you shouldn't work if you're sweaty or have any kind of moisture on your hands, either. Any little bit of moisture will dramatically decrease the resistance of your skin and turn an "ouch" into a "big ouch" or worse.

 

[TylerDurden]

Oatnet's buildlog of the vw bus bus is instructive.

IIRC, Mr Mik's posts on Vectrix and Prius battteries are also good reference.

 

[wrobinson0413]

Don't use your tongue to check for voltage :lol:

Seriously, if you are not trained to work with high voltages then don't do it. Totally agree with the others on this. It only takes one mistake that could be your last. I have had a few brushes with 125VDC and it is way more painful than 120VAC.

 

[jonescg]

I've been bitten by 100 V DC across the chest, and contrary to what LFP does for "fun" I found it rather painful. In this instance it was pure negligence on by part - trying to get the cycle analyst to read a current draw while holding the twisted wire together with my fingers Fair to say, Darwin's theory on selection and adaptation still holds true :lol:

I have also been bitten by 240 V AC a few times, but only across one hand. I don't think I have ever had an instance where I created a ground path either AC or DC... except I have been bitten by 7000 V pulse (75 Joule electric fence). It involved a massive spark that burned the tip of my finger. Needless to say, I was fine as electric fences for stock are designed to be non-lethal. But holy frock it frocking hurt. It was like someone trying to rip my arm out of it's socket through my finger. Why did I touch an electric fence?

Cause someone told me it was off. And it wasn't.

So there you go. Test everything first, only do what needs to be done, do that PROPERLY and wear rubber gloves for anything up to 500 V.

My next bike is going to be 460-500 V

 

[jdb]

+1 on the rubber mat. If you expect to do a lot of this kind of work, you can buy EH-rated (electrical hazard) safety shoes. The EH rating doesn't seem to come with much of a price premium over other steel-toed work shoes, so it may be worthwhile upgrade even if you don't do that much electrical work. Taking your feet out of the picture makes it that much less likely to get a path through your core.

 

[tedcs]

I recommend:
1) Build a Tesla Coil and play around with the neon sign transformer a lot.
(This is best done while one is adolescent.)

2) Find a 480 volt circuit breaker panel which is energized.
Remove the cover.
Drop an open-end wrench across the bus bars.

3) For extra credit, build a "Quarter Crusher."

These activities give physical and visual experiences which have a degree of permanence.

4) Think before acting, pay attention, don't do hazardous work when tired.