Electronics definitions of LV, HV, EHV and standards involved.  - Page 1
Forum section: electronics / general

author: station240
author_rank: Unknown
timestamp: April 05, 2014, 11:26:28 pm
content: Sorry if this reads like someone wanting help with their homework, but I think it's just a crazy situation that two related industries cannot agree. Besides I'm wondering how uniform the definitions as to what LV, HV etc is voltage wise.Some people with electrical/academic qualifications who I would not consider friends, believe that electrical and electronic industries around the world both consider 240V,415V etc to be Low Voltage, and that consumers and everyone else is an idiot. It's just silly that people cannot consider the industry they work in has such a huge problem.I mean it's reasonably common to see PCBs/Caps etc labelled as "CAUTION HIGH VOLTAGE" but electrical people consider this to be Low VoltageI've found the US Underwriters Laboratory consider anything in the electronics field above 50VDC to be high voltage, and below that is low voltage.However where the hell is the Australian standard for this ?What about the EU and other parts of the world what are their standards ?Surely someone on here would know which specific sections of the standards actually say.Anyway IMHO the electrical industry are wrong, you cannot go against the standards of the electronic industry and the belief of the general public and lethal voltages are "Low Voltage". Changing the signage on power transformers and electrical poles is easier than scratching off PCB screen printing, altering injection moulding dies, and a ton of documents and layouts.Would be a good chance to add some useful info like safe working distances and actual voltages. They don't need to worry about house switch boards as none of them seem to have any warnings unless solar power has been added. I cannot ever see it happening though.

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2014, 11:36:39 pm
content: I'm not sure what things are like in Australia, but in the UK I have never seen any indication that mains voltages are not dangerous.For instance a 415 V switch cabinet will have a "Danger: High Voltage" sticker on it with a hazard symbol in bright colours.A substation will have big warning signs that say things like "High Voltage. Keep Out! Danger of Death!" in big letters on the outside of the enclosure. There will be a fence or building to keep people far away.

author: notsob
author_rank: Frequent Contributor
timestamp: April 05, 2014, 11:50:52 pm
content: From AS3000-1991Definitions:Section 0.5.95a) Extra-low voltage -- not exceeding 32V a.c. or 115 V d.cb) Low voltage -- exceeding extra-low voltage, but not exceeding 1000 V a.c. or 1500 V d.c.c) High voltage -- exceeding low voltage.

author: gxti
author_rank: Frequent Contributor
timestamp: April 05, 2014, 11:52:21 pm
content: The problem is pretty much any voltage is enough to be dangerous if it's got current behind it. Try dropping a wrench on a car battery and tell me it's not worth some caution. And on the other hand, with suitable gloves and insulated tools there's not much risk working in an energized 240VAC electrical panel.So really the issue is that the technical definition isn't too helpful when it comes to safety matters. 480V may technically be low voltage, but that doesn't mean a "Danger High Voltage" placard is unjustified. Really I wish people would resist the urge to blurt out "But That's Low Voltage!" every time someone casually calls mains high voltage.

author: ajb
author_rank: Super Contributor
timestamp: April 06, 2014, 12:04:02 am
content: Some perspective is required. If you're a utility worker (or even an industrial electrician) who routinely deals with equipment running at 14kV or higher, then 240V is absolutely low voltage by comparison. The difference is not simply a matter of numbers, either, as the precautions and PPE required for the different ends of the voltage range will be different. Sure the lower end of the range can still be quite dangerous, especially when dealing with equipment that can produce extremely large fault currents, but as a simple matter of classification it is not at all wrong to call it low voltage in this respect.On the other hand, an for electronics technician that only ever deals with equipment in the 0-240V range, the whole multi-kV range is going to be almost entirely irrelevant. Sure there are some applications where a couple kV might be involved, but even then the hazards are substantially different from those faced by utility workers, as the voltage of the system is only one aspect of its potential (heh) to cause harm.Anyway, it's not at all unusual that different industries will use similar terms in different ways, and I'm not sure why that bothers you. I'm sure that whatever standards you dig up will define low and high voltage in whatever way suits their respective target industries, which is why well-written standards explicitly define such things ahead of time--or, even better, simply indicate the exact voltage range in question.

author: station240
author_rank: Unknown
timestamp: April 06, 2014, 12:07:11 am
content: Quote from: IanB on April 05, 2014, 11:36:39 pmYeah, I have a UK made 30 year old computer with "Caution: High Voltage" as a sticker applied to the top of the switch mode PSU transformer. Which definitely isn't driven off 1500V DC.Thanks notsob, a quck websearch only shows AS3000-1991 as an electrical wiring standard. The only time electronic(s) is mentioned is when it offers me a PDF of a document.I've also seen "Hazardous Voltages" warnings on some devices, which to be honest is a more through description.

author: han
author_rank: Frequent Contributor
timestamp: April 06, 2014, 12:17:00 am
content: In my opinion:High voltage classification is only for cable rating, transformer rating, ....But high voltage warning meant its high enough to kill you.

author: AlfBaz
author_rank: Super Contributor
timestamp: April 06, 2014, 02:07:17 am
content: Quote from: notsob on April 05, 2014, 11:50:52 pmIt's changed a littleAS3000 - 20071.4.98a) extra low voltage: Not exceeding 50VAC or 120V ripple free dcb) Low voltage: Exceeding extra low voltage but not exceeding 1000VAC or 1500VDCc) High Voltage: Exceeding Low voltageAS 3000 is available at most electrical whole sale places (the ones that sell circuit breakers, cables fuses etc) for around $160

author: station240
author_rank: Unknown
timestamp: April 06, 2014, 10:10:27 am
content: From what I can tell the source of this effort to change what the electronic industry defines as high voltage, comes from theLow Voltage Directive, when then filtered into the CE standards, and later into EU laws. Seems it was originally targeted at supply voltages (electrical) but has crept into appliances.Quote from: AlfBaz on April 06, 2014, 02:07:17 amYeah, sort of proves it's targeted at electricians, as electronics people rarely if at all visit those shops.That price ouch, still someone has to pay for standard groups, and it doesn't seem to be the government.I was involved in an international standards group many years ago (software related), its like watching paint dry and annoyingly as most of them are academics and don't do practical things in the industry nobody seems to bother with them any more. End result is things like the Australian electronics industry not seeming to have a standards body any more.

author: AlfBaz
author_rank: Super Contributor
timestamp: April 06, 2014, 11:09:09 am
content: Quote from: station240 on April 06, 2014, 10:10:27 amThe bastards have gotten greedy, I have a nice 2000 hardback version which cost around $40. The new $160 2007 paperback version makes beads of sweat form on your brow from the effort it takes to keep it openEDIT: at any rate it is the "wiring" rules, there's another standard for electrical equipment manufacturing I forget the number 38 or 48 hundred there abouts

author: station240
author_rank: Unknown
timestamp: April 06, 2014, 01:00:20 pm
content: I just realised what the real issue is, and it's a bugger.You have two transformers in metal boxes, lets call them A and B, both have mains cords which are clearly to plug into the wall but you need to fit the plugs first, which you do. One contains a 12V lighting transformer and is wired to AS3000 - 2007, the other contains a MOT and is wired to the yank UL standard. You don't know which is which.Both are labelled "Danger High Voltage", which one do you want to measure the output voltage on the bare wire ends with ?Yeah, 12V or a meter destroying 2000V.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: April 06, 2014, 01:11:34 pm
content: I don't put my meter on something labelled high voltage. In Australia that means > 1000V.It would be much better if the terminology was similar, across borders.BTW I think all AusNZ safety standards should be free in pdf format. It is just not very safe if you cant easily get the safety standards. Such as AS3000.But SAI Global seems to think otherwise. I suppose somebody is making money from it so it can't be changed.

author: AlfBaz
author_rank: Super Contributor
timestamp: April 06, 2014, 03:57:20 pm
content: Quote from: HackedFridgeMagnet on April 06, 2014, 01:11:34 pmAn even bigger imperative to have these standard freely available is the fact they are referred to in legislation/acts making them law which is hard to follow if not freely available

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 06, 2014, 04:52:58 pm
content: Quote from: gxti on April 05, 2014, 11:52:21 pmUse a high current warning for that.The convention I go by is high voltage for anything over 50V. The threshold between high voltage and extra high voltage varies, but more than the common mains voltage is a good mark to go by. I think it's a good solution around misleadingly calling mains "low voltage".