Achtung! High Voltage!

[eccerr0r]

Curiosity of people these days... High Voltage, does this faze you?

Of course I'd rather work on the circuit dead instead of becoming dead from a mishap, I still work on CRTs even while they're powered up, etc.

Poll is: Do you work on high voltage stuff?

And yes I put my hand on a charged photo cap once... That felt... weird.

[ReeceyBurger123]

Re: Achtung! High Voltage!

I work on Tv's and other power devices with SMPS and other HVE been shocked by 240v quite a few times and by PFC buck voltage hurts yes and makes you go red in the face with fast heart beat lol ever since im extra careful

[stj]

Re: Achtung! High Voltage!

it's a rush.

btw, i'v been hit with about 14Kv
it's totally different from being hit with 240v.

[ReeceyBurger123]

Re: Achtung! High Voltage!

Bloody hell what did it feel like STJ ?

[stj]

Re: Achtung! High Voltage!

nothing, it just throws you backwards and makes your arm tingle.
the thing you crash into behind you - in this case a shelf is fucking painfull though!

[rhomanski]

Re: Achtung! High Voltage!

I have changed a circuit breaker with power on. Hold the screws with needle nose pliers and turn with your screw driver. Working behind a live breaker panel isn't fun but can be done if your careful. The feeder is the big problem, usually 10 gauge wire. Hard to move with needle nose and the screw.

I was working on the central computer on a P-3 once. You had to lay on your side next to the power supply and turn two tiny resisters to adjust the voltage to 5 volts. I was running the meter while the other guy was laying down. While I was counting down the volts an arc shot out right beside his face and hit the rack behind him. I jumped up and pulled the breakers. We, uh, replaced that power supply. It left a big old black spot where it hit the rack.

[goontron]

Re: Achtung! High Voltage!

nothing, it just throws you backwards and makes your arm tingle.
the thing you crash into behind you - in this case a shelf is fucking painfull though!

I've been chucked by 240v. Both phases, a neutral and two grounds. (NatGas line and mains) It put me through the wall. Once i came to, the look on the occupants of the neighboring apartment that i ended up in was hilarious!

I have changed a circuit breaker with power on. Hold the screws with needle nose pliers and turn with your screw driver. Working behind a live breaker panel isn't fun but can be done if your careful. The feeder is the big problem, usually 10 gauge wire. Hard to move with needle nose and the screw.

That reminds me of a light fixture replacement i did a couple weeks ago. I was replacing 3 sets of dead floro fixtures with LED lights LIVE with 208v. It was a commercial building and to replace the lights with the power off would take killing the lights for another 5 Businesses. AKA Not happening. I was working under the guidance of a licenced electrician BTW.

[ReeceyBurger123]

Re: Achtung! High Voltage!

nothing, it just throws you backwards and makes your arm tingle.
the thing you crash into behind you - in this case a shelf is fucking painfull though!

Lol

[japlytic]

Re: Achtung! High Voltage!

I've been quite comfortable with high voltages for at least 15 years despite getting the rare shock or tingle - and I have a purpose-built EHT probe.
In 2003, I started working on valve/tube equipment (with my first valve radio) and became quite comfortable working with high voltage equipment.
Some time later, I bought a secondhand 1000VA isolation transformer, which helped me work more safely on "mains side" circuitry.

[ratdude747]

Re: Achtung! High Voltage!

Doesn't faze me much, then again I have a BS in EET and I know how to in most cases work with such safely.

[redwire]

Re: Achtung! High Voltage!

During high school, I fixed CRT televisions and frequently had my arm in there to make measurements. I also liked frying stuff with car ignition coils. You learn pretty quick what not to do.

Recently I worked in substations 25kV-240kV and during switching operations, or rain/snow/fog... I got scared walking through the yard, corona is a bit unnerving.
Manually closing a disconnect with 72kV into a 10 mile long power line, there is so much line capacitance that the arcs are super loud until you gradually close the contacts.
That was the most scary HV work (utility industry) that I have done.

Funny thing is you must put ground chains on power lines when working on them. Mutual (capacitive) coupling from adjacent power lines is enough to charge up a de-energized line, enough to kill a person.
I was on a project where they energized a 240kV power line, but some idiot left the ground chains on. So switching into a short circuit! It almost took out the entire grid in the province. Massive overload until the protection relays tripped.

[ljintexas]

Re: Achtung! High Voltage!

I have taken hits from 120, 240, 277 and had 480 blow up about 10 ft from me..never been hit with 14KV..WOW~!

[stj]

Re: Achtung! High Voltage!

the 14k was DC, it's a lot safer because it throws you back.

AC can paralize you so you cant let go!!

[kc8adu]

Re: Achtung! High Voltage!

lots of hv and lots of zaps from it.still repair crt's.those always seem to get me.but no big deal.i dont want a taste of my amplifier power supply.4800v@1.5a!
it powers a 3cx3000a7.

[SteveNielsen]

Re: Achtung! High Voltage!

I haven't been zapped that much or with that much but I've made sparks and blown out a couple of multimeters working on tube guitar amps output circuits. I've worked on live CRTs and thankfully haven't been bit by them. One memorable zap was working in a TV shop in the 70s and touching an RF test point in an old tube set. Left a nice little burn on my finger. Other than the odd ac mains zap I've been careful or lucky, probably both. I turn things off unless I have to work on live gear.

[xelectech]

Re: Achtung! High Voltage!

I haven't been zapped that much or with that much but I've made sparks and blown out a couple of multimeters working on tube guitar amps output circuits. I've worked on live CRTs and thankfully haven't been bit by them. One memorable zap was working in a TV shop in the 70s and touching an RF test point in an old tube set. Left a nice little burn on my finger. Other than the odd ac mains zap I've been careful or lucky, probably both. I turn things off unless I have to work on live gear.

I once watched a spark jump about 3/4" from the flyback area of a crt into the tip of my thumb, then out the tip of my index finger 1/2" to the chassis - the higher the frequency (I think it was 15-something Khz) the closer to the bone the current travels, my hand felt a little weird for days afterwards.

[Topcat]

Re: Achtung! High Voltage!

I've been bit by enough flybacks to not be fazed too much. also done some high current 3-pahse industrial install back in the day.

[xelectech]

Re: Achtung! High Voltage!

I've been bit by enough flybacks to not be fazed too much. also done some high current 3-pahse industrial install back in the day.

I was once up on a ladder checking out a 3-phase breaker box and didn't have a tester with me. I saw another maintenance guy (the new guy) down on the floor and asked him if he had a test light with him, he said yes and tossed it up to me.

It was a 480 volt 3phase supply-box so to make sure I asked him if the tester was good for all voltages and he said 'sure'. I put the leads across one phase and it blew up in my hand !! I said 'I thought you said it was good for all voltages', the guy goes 'well the guy at the auto parts store said it was'. Still kinda cracks me up when I think about it.

[momaka]

Re: Achtung! High Voltage!

High Voltage, does this faze you?

Can't say it fazes me. But fascinate? - Certainly.

Got shocked several times, but none of them seriously.

First one was with a TV PSU board. The APFC bulk cap had not discharged at all due to a fault in the PSU. I was a bit of a rookie back then, so I thought it did like with other PC PSUs and didn't check the voltage. It did cross my mind, though. As soon as I dragged my hand across the board (was checking some parts with a multimeter), I pulled my hand quickly. Felt like getting a bee sting.

Second time was when repairing a PC PSU and was working on it with the cover off. Normally, I first plug in the power cable to the PC and then to the wall. But for some reason, I had the power cable plugged in the wall already. When I tried to plug the cable in the PSU, I was using one hand to hold the PSU plug on the exposed wire end - the exposed wires were all resting in the palm of my hand. Funny enough, I only felt a slight tingly sensation in my hand and nothing more. I guess my hand must have been very dry, since it was winter. Didn't realize what was happening until after I was done testing the PSU.

3rd time: installing a 208V plug for a machine at the shop where I used to work at. Told my boss/owner of the shop not to touch any of the turned-off circuit breaks. And what did he do? Turn them on because he needed to use some plug somewhere. Not knowing that, I went to work on the plug. First stripped the neutral wire and bent it into shape to fit on the plug screw. Next, I stripped the live wire and did the same thing. No problem again. Finally, I grabbed both the L and N wires to bring them closer together so I could fit them on the plug and... OUCH! 208V going through my thumb and exiting my index finger. Luckily, it was all only on my right hand. The floor was concrete and the shop was ground-level too, but I had shoes on, so no problem.

And most recently, I fixed a lamp for a family friend. Went to install back in her apartment, but we couldn't figure out which switch was for the light (there were 3 of them, and some of them were 3-way switches, so no telling which one is the ON and OFF position) and much less which breaker (15 breakers of "lights and plugs" isn't very helpful ). Normally, I bring my multimeter, but I had just forgotten it this time.

So, what did I do? Drawing back from the 3rd experience above, I put my shoes on and wired the Live wire to the lamp before the ground and neutral. Why? Because the lamp fixture has a metal body. Had I wired the ground, that could have been bad news for my right hand again. So after wiring L, I test-connected the neutral on the light figure. Lights turned ON, so I *was* working on a live wire the whole time . Anyways, I went down and started playing with the mysterious switches on the wall until I turned off the light. Next, I used my right hand as the "test subject" and put one finger on ground whilst quickly touching the live wire with the other. No shocks, so no power. Wired everything, and that was that.

the higher the frequency (I think it was 15-something Khz) the closer to the bone the current travels, my hand felt a little weird for days afterwards.

Actually, the other way around.
The skin effect states that electrons tend to travel closer and closer to the surface of the conductor as the frequency increases.

In other words, if you make the frequency really high, you won't get shocked/zapped at all. Rather you will get a burning feeling in your skin, because... well, that's what's going to happen to it.

[xelectech]

Re: Achtung! High Voltage!

Can't say it fazes me. But fascinate? - Certainly.

Got shocked several times, but none of them seriously.

xelectech: same here 8^) - but I never worked on high voltage high current circuits
and I'm pretty sure I don't want to, dangerous enough as it is...

(snip)

Actually, the other way around.
The skin effect states that electrons tend to travel closer and closer to the surface of the conductor as the frequency increases.

xelectech: I think the explanation is this; in a body, the bone marrow is a better conductor than the skin (unless you're all sweaty) and I guess there's some kind of capacitive coupling involved, the higher the freq., the more coupling, that allows the majoity of the current to follow the easier path. At least that's what I seem to remeber one of my electonics instructors saying, I could be wrong.

In other words, if you make the frequency really high, you won't get shocked/zapped at all. Rather you will get a burning feeling in your skin, because... well, that's what's going to happen to it.

I agree with the last part, which accounts for how Nikola Tesla was able to hang out
in his room with all that sparking going on - wonder what frequencys he was working with...