If you’re reading this sentence, there’s a pretty good chance that you interact with electricity more than just as an end-user. You’re a hacker. You aren’t afraid of a few volts, and your projects may involve both DC and AC voltage. Depending on what you’re working on, you might even be dealing with several thousand volts. And it’s you who Big Clive made the video below the break for.
“Familiarity breeds contempt” as the old saying goes, and the more familiar we are with electronics, the more cavalier we may tend to get. If we allow ourselves to get too lax, we may be found working on live circuits, skimping on safety for the sake of convenience, or jokingly saying “safety third!” far too often as we tear into a hazardous situation without scoping it out first.
Who better to bring us down to earth than Big Clive. In this video, he explains how electricity has the potential to impede the beating of our hearts, the action of our lungs, and even break bones. You’ll find a candid discussion about what electric shock does to a person, how to avoid it, and how to help if someone near you suffers electric shock.
Of course, if safety isn’t your thing, then maybe you’re ready to Shake Hands With Danger.
I once discharged a fully charged 8uF 15,000V capacitor into my hands. It was a loud explosion and my vision returned a few minutes later, dripping with sweat, quite sore, and still standing. It was from a Hipotronics destructive cable tester that another technician gave up fixing it and the wiring harness was tangled with the gravity operated interlock switch. Interestingly, I could find no burns on my body and lucky to be alive.
That a big part of the problem. I’ve personally been sent through a wall, typical framed drywall. Yet I still don’t observe as much safety as I really should. Often excuse it with mitigation. That’s how we get ourselves killed though.
There’s always the old game of catch with the new guy, tossing a charged capacitor across the room. One way or the other, you only catch it once.
Only once indeed. Don’t stick around a workplace like that. Practical jokes are harmless until someone gets it wrong and people get hurt. Sorry to be the internet safety police for today :-)
> “Familiarity breeds contempt”
Until it has contempt for you, then we become more respective. ;-)
I’ve seen 120V/10A circuit blow a hole in the cutting edge of lineman’s plier (someone turn the breaker back on before we started our work). I got zapped by a fly back transformer that was 2ft away (high humidity in the work area). Watched a set of wirewrap pins flame on a 12v/gnd short ( but the computer kept running).
My friends play with really high power (railroad) and they have some ‘interesting’ stories.
Always respect voltage, current, power. Even the low power stuff can burn you.
Came to express the same sentiment. In my first job out of school I was working on military radar and nav equipment. I was troubleshooting an RF power amplifier that used lighthouse tubes – they plug into coaxial sockets and the anodes are connected directly to aluminum radiating fins on the top that help cool the tube. I forgot to turn off the 400V B+ supply – put one palm on the grounded quarter-inch aluminum chassis, and reached in with the other to pull a tube. The only way to pull those is to grasp the radiating fins…
After that I just put my head on my bench for a few minutes. I was OK, and now I’m ALWAYS super careful about disconnecting power and discharging caps. I NEVER have that devil-may-care swagger I observe in some techs and electricians. I’m wary and respectful. Electricity can destructive and life-ending in a heartbeat – or lack thereof…
saftey?I’st,Second,third,no,no,no.training is only for repitive tasks
there is no cure for stupid.
be focused,observant,physicaly FAST,and listen quiet and close when old linesmen tell horror stories of encounters with phenomina.
Took a course that telco linemen need to take and was surprised that you must always check to see if a wooden pole is live. Up to that point I never considered that the AC on the pole could leak into the pole. Telco wiring – yes, wooden pole – no. They also explained that wooden ladders were a no-no. You must use fiberglass ladders and always check the pole/box/circuits before working on them.
I was interested so I looked it up, check out this study on conductivity of poles treated with various things:
https://www.diva-portal.org/smash/get/diva2:1076982/FULLTEXT02
I was brought up on 240-volt systems, so I do tend to treat electrical circuits with good deal of respect.
same here – it’s people from low voltage countries (ie the USA) that seem to have a casual attitude ie I’ve seen bare wires plugged into a power point!
I remember getting a few 230vac shocks as a child, fiddling with electronics. By all rights I should probably be dead, but apparently I’m lucky. I’m more diligent about switching things off and discharging them these days, or at least careful when working with things I need to test live. Saying that, it hasn’t stopped me working on things in the tens or even hundreds of kv since.
As a AV integrator I always get to play electrician because electricians and low volt don’t get along and seems like the electricians will go out of their way to cause problems.
Anyway, after getting hit with a TV flyback once I always triple check things to make sure it’s safe to touch. Make sure the circuit is off or device is unplugged and use a non-contact probe or discharge caps. Also check again and make sure it has no power. All depends what I’m working on. You see some crazy things in the low voltage world and have tons of stories.
Never mind the doom gloom and death… tell us about those blinky lights on the drawer units!
It’s the supercomputer panel: https://www.youtube.com/watch?v=bI_zgZz-V40
Wow, I actually worked at the gate level on a supercomputer and we had what I called the “man from UNCLE” lights that looked like that and actually worked. We had LED in panels arranged in groups of 16 for each register or bus we hooked to. As we single stepped the Processor Element, you could watch the data travel through the computer. We had bench top modules with the pattern but with switches on each bit to force it high, low, or pass. This was perfect for low speed diag..
In the early 80’s Red was the only cheap LED so no nice colors.
The more I think of it, that thing would be a hackers dream, all 74LS TTL DIPs in wirewrap sockets, about 10,000 of them. Only one hi-tech chip was was a 16bit x 16bit multiplier. (It was the Architecture that made it a supercomputer, the technology for speed would have come later). The LEDs were driven directly by the buss pin itself (7 internal busses) and attached the indicator panels were simply hooked into where ever using those old DIP clips with ribbon cables. To force a bit somewhere, we used a center off switch and just shorted it to gnd or +5v, 74LS chips don’t care. There were 52 x 50pin ribbon cables for each processor element.
Very reusable tech.
Sorry for off topic.
I’ve had my share of experiences – some more “throbbing” than shocking. But the most recent was trying to diagnose an issue with an industrial laser I put in 1 or 2 years earlier. Laser wasn’t firing but power definitely getting to it’s PSU. With everything off my friend (his kit) was taking the PSU off the machine so I could take a look. He got shocked. I thought I’d better discharge it before going any further. In the old days of CRT TVs you could discharge the tube’s HT with a well placed screwdriver, so that’s what I carefully went to do. I got shocked. Very unfairly, I felt. Until I realised that the screwdriver was not VDE rated, but wouldn’t have mattered it it was as the 45kV PSU could pass straight through the handle of any 10kV rated tools. High voltage but thankfully only mA so no real harm done.
I went to grab an old picture tube off the shelf in a storage shed at a repair shop I worked. The boss swore he put it there over a year ago.
The spark from the HV port went thru my clothes and hit me in the stomach. Needless to say I dropped the tube. That hurt.
That is (was?) a very low leakage high voltage capacitor with glass as a dielectric. I used a old big screwdriver with an alligator clip and wire to hook to ground to discharge tubes before working on them.
I did forget more than once.
Working on vacuum tube TV’s I took the 600v B+boost across my hand. You could see the tunnel it burned through my hand at both ends. Took a year to stop hurting. It arced an inch to get me.
The second anode of an old VTube CRT is a most excellent capacitor! Of course if it were not so, it would take the screen to light up a little longer. That was one of the complaints in those days. People want an instant image not one that took minutes to appear. That ultra HV was part of the solution. Back in the early 80’s when I was still fresh out of tech school and trying to do repair work, I had the misfortune to get too close to a damaged HV lead to the back side of the CRT( mice had been chewing on the insulation inside) I was holding the shielded lead to my Oscope and took a solid hit at around 35kv which sent me across the shop and sent my Oscope to a repair shop shortly after, when I was again able to speak, and function on my feet, breath normally. I’ve been around electrons most of my life working on TV, residential electrical wiring, industrial (welders) been lit up many times working with welders and eventually in high power wind turbines, that last one was incorrectly wired by a licensed electricial that connected the breakers backwards as in bringing the incoming source power in the bottom with no shielding. It was a good thing there was another disconnect switch in the system at the Watt meter/service lead to the building the 65kw 480 volt turbine was feeding into, the disconnect inside the tower base was where the mistake had been made. The electricians were not looking at the turbine as a source of power but another load on the power. Of course a sychronous generator would require a power input before it would produce, meaning the power would not matter which way it was coming in, it’s only a matter of connecting it safely. You don’t want an unshielded 480V 3 ph feed left unprotected inside a steel tower or place where if someone was working even though it appeared to be disconnected and safe but not safe. It truly is amazing as many of us survive working with electrons, many don’t.
Lots of equipment is transformer-less these days.
Very bitey, live switching supplies, in amongst the stuff you regularly deal with.
When I was a teenager I was playing with a very old oscilloscope I had been given. It included a mysterious banana post labeled “B+”, and a corresponding switch labeled “on/off”. I had no idea what it was for, so I put a resistor across B+ to ground, then turned the switch on. Magic smoke and a bright arc began to leave the resistor, and without thinking I grabbed the resistor with my fingers to prevent burning down my bedroom.
I was crouched down in front of the scope when my fingers made contact with B+. My bare feet were firmly in contact with a concrete floor in an occasionally damp basement. My legs shot up exactly as Clive described, (like a frog leg with a 9V battery) and I vaguely remember flipping backwards across my bedroom.
When I came to, the resistor was no longer flaming, and the room wasn’t burning. The only damage I really suffered were fairly minor burns on my fingers where I’d touched the resistor.
And then I read up on B+.
Safety third.
It doesn’t mean a cavalier attitude about safety. It recognizes that if safety were truly the first consideration, nothing would ever get done, because the safest course is to abstain entirely.
Safety should always be in the top 5, probably in the top 3, but never first.
240 volts is quite pleasant for a wheil, moreso than a freaking alu macbook OUCH! OUCH AGAIN! OUCH!
My work is installing 240 volt deep well pumps in the nearby lakes on or near the bottom. I have to flip off the breaker to the dock and the pump (all power heading into the water). Unfortunately sometimes the neighbors docks are very close and I cannot turn off their power without permission. So far I have been lucky, although shocked many times at my old fault. Fortunately my national tech support taught me to buy a Megohm meter and check the insulation resistance of the existing cables – – which more than 50% of the time test bad, so they have to be replaced, and sometimes these rich guys on million dollar properties don’t want to spend the money. That’s when I pack up my tools and tell them I cannot help them, I don’t need lawyers breathing down my neck . . .
Ohhh the irony! Big Clive lectures us on avoiding electrocution then goes right back to making cringe-worthy YouTube videos with complete disregard for dangerous mains power. Gotta love it.
I haven’t seen all of Clives clips but I can’t remember him ever “completely disregarding dangerous mains power”…
Got a sample?
“I haven’t seen all of Clives clips…” Yup, you obviously haven’t.
How about that example?
I watch a lot of Clive’s videos and he’s never cavalier with mains – he gets close sometimes but he’s clearly experienced and able to work safely even while appearing somewhat slapdash.
Certainly he’s not following approved practices and it’s not how you’d do it professionally, but he’s better than a lot of YouTubers and always knows (and usually explains) when he’s taking a risk or being a bit naughty.
This is right up my alley in my current projects at work, the newest Ground Fault Circuit Interrupters with self test. The ones I am working on are cord based models but are identical to the wall outlets.
I am recommending using one on your work benches if you work with exposed AC.
There is no way to keep you from making the connection with both Line and Neutral with your body, that is on you.
What a GFCI will prevent is you getting hurt touching the Line while GOUNDED. Feet on concrete, arm on benchtop, damp clothing to your grounded seat; being grounded is hard to avoid. Neutral is Grounded at the incoming breaker panel so you are pretty much at Neutral potential through ground, which is why you get shocked on one wire.
Now, since you are Grounded (not touching Neutral on the bench) and you touch the line, you divert some of the current away from neutral directly to Ground. L and N no longer have the same current in them since you are in parallel with the Neutral going back to the breaker box. If you divert more than 5mA, presumably through you, POP goes the GFCI.
If you are to short the G and N at your bench, that would defeat the fault path the GFCI senses. Modern GFCI also can sense when Ground and Neutral are shorted after the GFCI and trip. (BTW, that is a tough one to sense. I don’t know many people that actually fully understand how it works!)
To round it out, the self test is the circuit is required by UL to test itself 4 times a day. It actually tries to trip the relay and stops before the relay can react, (uSec). And the button actually creates a fault, so is a very valid test of the entire GF circuit.
Back to the bench. I just put an industrial version on my GFCI test bench. They are not a circuit breaker so when I pull 180A through it off my 208v 50A circuit (<30mS or my load starts on fire) it ignores me. But it tripped when I got bit by touching my test circuit while live once. It still bit me, but I didn't impale my hand on something reacting (the TV repair man's injury).
I put all this information here for experimenters' benches to assure you that if you put one on the bench and it trips, you actually have a problem at your bench. Otherwise it should just sit there quietly wait for you to mess up.
Note the new spec with self test isn't really required for what we all do, you can test it better manually once in a while as it is a more comprehensive test. The new ones are barely on the shelves and will cost more no doubt.
One more app note; the wall sockets now have a couple of connections marked "LOAD". You can put the outlet on your bench and wire your power outlets to the LOAD connections and the GFCI will protect the whole string.
There are some excellent youtubes explaining GFCI uses and the entire safety ground system in better detail, I just wanted to orient it to we experimenters on the bench, more than appliances.
There are a number of caveats to this post.
Firstly many countries use a MEN (Multiple Earth Neutral) system where the neutral in the power box is connected to earth by a copper stake in the ground. This is an unbalanced distribution scheme.
A GFCI (Ground Fault Circuit Interrupter) is very uncommon and shouldn’t be confused with the most common load imbalance breaker that has different names in different countries and even has over-simplified names like a RCD (Resetable Circuit Device), this has no earth connection and simply trips if there is more current in the active than there is in the neutral going to the load.
RCD means Residual Current Device and works exactly the same as a GFI.
Suspect you’ve got mixed with MCD (Miniature Circuit Breaker) which are just for overload protection (protects the wiring from overheating) and not personal protection from electric shock.
RCD/GFI are wired ‘downstream’ of the neutral/ground connection and thus the specific grounding type doesn’t matter. You can get ones that plug into outlets, ones that replace outlets and include a GFI, ones that go in the panel/fusebox between the breaker and the circuit wiring, and ones that replace the breaker (RCBO, does both GFI and Overload, but requires rewiring to add the neutral)
As for the OP not understanding why a neutral/ground short trips an RCD/GFI, it’s because the device operates when an imbalance between the currents in the active and neutral conductions reaches a certain threshold. Should the neutral and ground get shorted that means ALL current in the neutral is now split between the neutral and the ground. That will certainly be different to what’s flowing in the active (unless there is no current flowing at all).
I followed up after a broadcast engineer at a 5 MW ERP / 120 KW TPO UHF transmitter was working on a live transmitter and was electrocuted by a 23,000 V AC main power supply feed. The station was a major market hispanic station which was carrying the soccer World Cup games but the station had received a lightning strike about a week before which fried one of the 2 480V main feeds. The station had a new and inexperienced manager who had demanded that any transmitter outage would result in the engineer’s firing. The engineer was working (alone) on repairing burned out 480 V feeds to the outdoor transformers and was operating one of 2 transmitter cabinets in IF diplex mode and was attempting to use an insulated fiberglas screwdriver to switch a high voltage contactor plate to bring the second cabinet online to switch over to a 2 transmitter visual/aural diplex mode when the voltage arced the distance of the screwdriver and and went into his hand. He was on a metal ladder reaching over to the wall and holding on to a section of power conduit with one hand while stretching over to the contactor junction box with the other hand and the power went through his body through his arms and chest. Surprisingly, he survived and was able to walk to a house and get them to call for an ambulance. He sufferred permanent damage and heart issues. He tripped a 480V 250 A breaker with the flash over. I was called out on an emergency call to restore the transmitter to the air. Once I arrived at the site I was greeted by the station manager who got out of her Mercedes and was screaming at me that I had to run in there right now and turn everything on and get the station back on the air. I had a soda in my hand and I said that wasn’t going to happen and told her to stand outside and watch the power transformers for fire and said I was going to drink the Coke, think about this and slowly do what was necessary. I got them back on the air after about an hour. There were numerous things that contributed to the root cause of the injury but I rank the extreme and unreasonable pressure from the manager to be the primary cause of the issue. You can never compromise safety for pressure or shortcuts. There is no reason that the repair shouldn’t have had at least 2 people on the site and following all lock-out and tag-out procedures. If the station had to go off the air then ‘so be it’. The engineer was fired. He should have sued them until he ‘owned the station’.
I’ll never forget that the phases of a 500 kV switching station are kept far enough apart that you can drive a truck between them and not cause arcing …
Bah! If they made them closer, you wouldn’t be able to fit the truck in the first place.
My worst was a jolt from a 780 vdc solar string. 3rd degree burns on the finger the wires touched and my hand twitched for about 5 seconds after…
Nikola Tesla kept the left hand in pocket so main current doesnt go trough heart, says legend.
There was a guy who was able to touch high voltage, multiple times in Europe, and he suppose to sit on chair in America but no one wanted to insure sucha stunt. Some say he didnt have sweat glands or something. I started believing that I can do to. I touched live 220V couple times and felt nothing till the big one. I learned. Expect unexpected.