can i get killed by high voltage test set up - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: December 30, 2018, 04:01:54 pm
content: Hello guys This is High voltage(AC. freq= 50hz) test set up for testing ground insulation of Main pole and interpole coil of traction motors (dc series motor).The leakage current is set to 300mA (max).That is if any ground insulation fault is detected, this device allows max 200mA to pass before it's trips(probably Current sensing relay is used ).my question is Can i get killed by high voltage(as high as up to 8kV)??because if current is 200mA and voltage is 8KV, The power transferred to my body is (0.2 * 8000 = 1600 watt)

author: Buriedcode
author_rank: Super Contributor
timestamp: December 30, 2018, 04:09:51 pm
content: Your calculation is wrong as it won't transfer all "power" to you, as your body has resistance so will limit the current. Short answer is: yes that could kill you, much more readily than mains.Whilst many oft-quote the rather crude saying "its the volts that jolt and the amps that kill" it is the current that does the work, but the voltage that allows it to flow through a resistance. SO.. even if your skin has very high resistance, given high enough voltage, enough current can flow to stop your heart. V= IR. I = V/R. If R is fixed, if V goes up, so does I.What that lethal current/voltage is, varies greatly on the person and situation. Skin generally has a high resistances, but this drops considerably when hands are wet, sweaty (which contains a lot of salt) or clammy. The actual resistance from hand to hand, through the body, not including skin can be quite low indeed. 8kV @ 150mA could kill you several times over, but I have no doubt it one was to run horrible experiments, some would survive, some would die. Also note if it is particularly humid 10kV can jump a fair way, at least 10mm (I believe its more like 5mm in dry air).So yeah, take precautions.

author: khatus
author_rank: Regular Contributor
timestamp: December 30, 2018, 04:23:00 pm
content: I have found this chart from a youtube channel named RimstarOrghttps://youtu.be/9iKD7vuq-rY

author: BravoV
author_rank: Super Contributor
timestamp: December 30, 2018, 04:35:04 pm
content: Quote from: khatus on December 30, 2018, 04:01:54 pmYes.You don't need more complex words answer than my above word.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 30, 2018, 04:37:04 pm
content: The Electrical Safety DOE handbook is available free on-line. This may be a good read.

author: barry14
author_rank: Regular Contributor
timestamp: December 30, 2018, 09:08:41 pm
content: The previous answers have covered the dangers of this setup from an electrical point of view. I would like to point out that the mains on/off switch seems to violate normal practice which is to have a toggle switch flip up to turn on and flip down to turn off. In an emergency, it would seem that someone might delay in turning off the power since the natural action would be to try to flip the switch down to remove power.

author: GeoffreyF
author_rank: Regular Contributor
timestamp: December 30, 2018, 10:17:24 pm
content: Yeah - Duh, You bet.Voltages in the KV range also can form plasma arcs, break down the natural resistance of skin and some types of insulators. I will also say the knowledge you need to be safe with this kind of equipment is more than you can acquire by reading books or google pages. You should have some sort of practical experience with someone who has it.Finally, this type of equipment can store lethal charges in capacitors, which can last for a long period. If you don't know how to make the equipment safe, don't even attempt to take it apart.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 31, 2018, 12:16:32 am
content: Quote from: barry14 on December 30, 2018, 09:08:41 pmNot in countries where the domestic switches all work the other way round.Just about everyone knows that circuit breakers work "up is on", but toggle switches are much more likely to be treated like domestic ones.

author: IanB
author_rank: Super Contributor
timestamp: December 31, 2018, 12:26:49 am
content: Quote from: barry14 on December 30, 2018, 09:08:41 pmThis is only normal practice in the USA and American influenced regions. Elsewhere, down is on, up is off. My instinctive reaction to turn a switch off is to sweep it upwards. In America that would be a problem.

author: IanB
author_rank: Super Contributor
timestamp: December 31, 2018, 12:28:51 am
content: Quote from: IanB on December 31, 2018, 12:26:49 amI should add that where an emergency off switch is required, it is customary to provide a big red mushroom button that you push for off. This I think is universal.

author: fsr
author_rank: Regular Contributor
timestamp: December 31, 2018, 01:07:54 am
content: Yes, that's lethal. Ground fault interrupters trip around 5 to 30 mA. 200 mA thru your body can (and probably will) kill you.

author: Brumby
author_rank: Unknown
timestamp: December 31, 2018, 01:35:24 am
content: To the Op: If you have to ask the question, then, for your own safety, I would advise you to keep well clear of this item when in use.Working with elevated voltages requires a certain level of understanding to remain safe - and it is rather clear you do not have this.If high voltage stuff interests you, then I suggest you find a mentor who is competent and willing to sit by your side until you develop the knowledge and skills to work safely on your own.EVEN THEN -don'twork on your own. Have someone stationed near a kill switch, watching you. They don't need to be skilled in high voltage - only observant enough to know when to kill the power before the power kills you.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 31, 2018, 02:19:00 am
content: Working with high voltages isn't rocket science.You wouldn't start your motorbike, get up to highway speeds, then step off without expecting something bad to happen.The same goes for electrical safety.If you want to mess around touching wiring, make sure the thing is switched OFF!.The best way to do this is to switch the power off both on the device, & most importantly at the power source for the device.If it has a lead & power plug, turn off the power point (if it has a switch) & unplug the lead.If it is hard wired, identify the main safety switch (or circuit breaker) for the device on the appropriate power distribution panel, turn it off, & tag it, so nobody turns it back on.Having done that, do your "fiddling", step away from the device & only then restore power, warning everybody in the area of what you are doing.Obviously,experiencedpeople do work on some activated equipment, but in many cases, the accessible power supplies are not capable of supplying sufficient current (either low voltages, or in some cases, high voltage supplies with quite high internal resistance).

author: GeoffreyF
author_rank: Regular Contributor
timestamp: December 31, 2018, 03:31:05 am
content: Quote from: vk6zgo on December 31, 2018, 02:19:00 amActually it is high voltage science. People don't start a motor bike without knowing how to ride one.It's definitely not existential philosophy such as yours. You appear to believe that a thousand volts behaves like a hundred. You never mentioned capacitors in shut off equipment or what an Arc flash is. Do you know? You didn't say.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 31, 2018, 06:30:19 am
content: Quote from: GeoffreyF on December 31, 2018, 03:31:05 amIt also isn't something to run around shrieking in fear about.A thousand volts obeys Ohm's Law, just like any other voltage.Yes, indeed, capacitors in shut off equipment can store a lot of energy------- a very valid point.I didn't include a warning about that, because the OP was not playing around inside the equipment, which was being used to test other stuff, so I limited my advice to that.In a career of over forty years working on high powered Broadcast & TV Transmitters, including all the high voltage supplies used in Tube equipment (commonly of the order of 10kV), & the associated 3 phase Mains supply wiring to them, I have never run into a case of Arc Flash.Yes, it does happen, most often in the the power distribution industry, when people make mistakes, just as motorcycle accidents do, but it does not make basic advice about turning off Mains supplies to equipment invalid.Actually, people do "start motorbikes without knowing how to ride one".You can't get dual control motorcycles, so a learner is doing just that, & following the instructions of the person riding alongside them teaching them "to the letter".If a prospective rider was regaled with all the gruesome details of what could happen in a bike smash, they would never try to learn.

author: Brumby
author_rank: Unknown
timestamp: December 31, 2018, 08:06:23 am
content: Quote from: vk6zgo on December 31, 2018, 06:30:19 amThat statement unnerved me more than anything else written in this thread.You have been desensitised to the risks by having an extended exposure to such an environment - and you will have learned to approach things appropriately. The OP has shown no such knowledge and a thousand volts needs far more respect than ten, irrespective of Ohms Law.If anything, publishing warnings about safety are - even if felt to be excessive by some - is the responsible thing to do, especially when people are asking some fundamental questions thatclearly indicatethey havenext to no knowledge on the subject.If those warnings are indeed over the top, then letthemmake that judgement call - hopefully based onunderstandingand not on the cavalier suggestion of someone who has decades of experience.JMHO

author: IanB
author_rank: Super Contributor
timestamp: December 31, 2018, 08:11:57 am
content: The device posted at the top of the thread undoubtedly would be used in context in a controlled situation where the operators have been thoroughly trained in how to use it safely and correctly. No untrained person would be allowed near it.We have to suspect that the OP is not one of those trained people, and that perhaps the device is no longer in the original place where it was designed to be used.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 31, 2018, 11:13:27 am
content: Quote from: Brumby on December 31, 2018, 08:06:23 amIt is nonetheless, true!, & if you were "unnerved", I'm glad I don't have to work on high voltage circuitry with you!QuoteLooking back, you will find I was answeringGeoffreyF, who compared 1000v to 100v.Nobody mentioned 10v!Quite a few people have been electrocuted by 125 v------ quite close to his 100v!Almost certainly, thousands more than were ever electrocuted by 1000v!In my first posting in this thread, I also pointed out that some high voltage sources had high internal resistance, so could not source enough current to be fatalBy the same token, the US 125v supply has a very low source resistance, can supply a fatal shockQuoteMy suggestions were far from "cavalier".On the contrary, they were reasoned, & gave the OP some useable instructions on how to work safely withanytype of Mains supplied high voltage equipment.OK, I did not make the point about capacitors retaining charge, but the original posting did not refer to opening up the equipment shown.Quote

author: Brumby
author_rank: Unknown
timestamp: December 31, 2018, 11:41:47 am
content: OK. Some of my comment seems misdirected because I did not make the connection between what you said and who you said it to...However:Quote from: vk6zgo on December 31, 2018, 11:13:27 amYou really need to comprehend what was written.I was "unnerved" at your statement because it was advice given on a thread where the OP obviously hasNOfundamental understanding. Not for my sake - but fortheirs!This is why I respond as I do inthe Beginners sectionwhen potentially lethal voltages are being discussed, especially where there are participants that show their lack of knowledge. You don't have to worry about me - but I would rather a newbie be given excess caution until they learn enough to be able to competently assess the risks and make their own decisions.

author: Synthtech
author_rank: Regular Contributor
timestamp: December 31, 2018, 11:58:04 am
content: To the OP - unless you have a very specific and reasonable purpose for that piece of equipment and looking at the physical condition I would treat it like an unpredictable junk yard Rottweiler and assume that it bites. At the very least have it inspected for safety by a competent person before you energise it. It is dangerous enough in good working order, if it has a fault then it’s even more so.

author: fsr
author_rank: Regular Contributor
timestamp: December 31, 2018, 01:29:43 pm
content: Quote from: vk6zgo on December 31, 2018, 06:30:19 amAnd that means that a 1000 volts has 10 times the potential to kill you than a 100. Probably more, as this is AC and the skin acts as a capacitor, bypassing it's normal resistance.Beginners don't need to risk their lives working with HV circuits.That kind of equipment has to be used by following safety procedures, which were never mentioned, and likely unknown to Khatus.Who has even certified that the equipment is in working condition?If 8 kV get to you, that's it, your life very likely ends there. It's very easy for that kind of voltage to cause enough current thru the body to kill a person.

author: Zero999
author_rank: Super Contributor
timestamp: December 31, 2018, 07:17:19 pm
content: Quote from: 3roomlab on December 31, 2018, 12:36:06 amThat won't provide complete protection, as something could go wrong, passing the full current.