Electric shock...from being stupid. :/

[stillp]

BAS, that version of IEC 60038 is not only a breach of copyright, but is well out of date. The current (2009) edition doesn't define low/medium/high either.
However the IEC 60947 series "Low voltage switchgear and controlgear" states "This standard applies, when required by the appropriate product standard, to switchgear and controlgear hereinafter referred to as "equipment" and intended to be connected to circuits, the rated voltage of which does not exceed 1000 V AC or 1500 V DC".

 

[JohnW2]

My comment was 'in context', since it seems very likely that the ('high frequency') 700V a.c. to which plugwash referred will have been 700V relative to Earth, and not the pd between two phases of a multi-phase supply!

Plug encountered 700V at the output of an inverter, which as it had an ELV input was surely not referenced to earth.

You might well be right. I confess that I hadn't properly read (or, at least, 'absorbed'!) the earlier parts of his post, indicating where this 700V came from.

But as for definitions, it looks as though the IEC don't officially use any L/M/H labels.

Fair enough. As I said, BS7671 only recognises ELV, LV and HV which, between them cover all voltages from zero to infinite, with anything higher than LV being HV.

Kind Regards, John

 

[stillp]

Many of the standards that I work with recognise only ELV, LV (<1000 V AC/1500 V DC), and HV.

 

[JohnW2]

Many of the standards that I work with recognise only ELV, LV (<1000 V AC/1500 V DC), and HV.

As I said, that's what BS7671 does. One suspects that people decided that having an 'MV" slipped into the middle of that range does not really serve any particularly useful purpose.

The fact that 'LV' is seemingly misunderstood by the vast majority of the general public (and many of those supplying products, not only to the general public, but also to professionals!) is a different matter!

Kind Regards, John

 

[leeco]

Anyone watched this when it was on.

http://youtu.be/J4SW8bX37Ag

I have had 3 electric shocks in my time.

The 1st was my evil brother telling me to put my fingers in the light fitting in my bedroom when I was about 5

The other 2 was been careless when working on c/us

 

[ban-all-sheds]

The fact that 'LV' is seemingly misunderstood by the vast majority of the general public (and many of those supplying products, not only to the general public, but also to professionals!) is a different matter!

If you travel on the Tube you'll frequently see doors with a notice saying "DANGER - HIGH VOLTAGE".

I've often wondered what's really behind them.

 

[JohnW2]

As I said in my post it was a floating output* so you could touch it without getting a shock as long as you didn't touch both ends at once, my mistake was not realising that before the connection was established the terminals on the lamp I was connecting to were effectively the other end of the supply.

Yes, I now realise that - as I said to BAS, I didn't read your post carefully enough.

Not sure how you would count that, do you assume that it's centered with respect to earth? do you assume that one end is likely to get inadvertandly tied to earth putting the other end at 700V relative to earth?. I guess it's a situation the authors of BS7671 didn't really consider.

I wouldn't have thought so. If there were no explicit connection from the secondary of your transformer to earth, I think BS7671 would simply consider it as a floating situation - in which case there would have to be a pd of at least 1000V 'between 'the two ends' of the secondary before it ceased to be classified as 'LV'.

IIRC the transformer was intended to be used to convert 240V to 3V at 50Hz but we were using what was intended to be the secondary as the primary. We were driving it off some electronics powered from a 12V DC supply, I don't recall exactly what the frequency was but iirc it was substantially higher than mains frequency.

Sounds familiar! We used to regularly use transformers intended to have 240V primaries and 12V secondaries (or thereabouts) 'back-to-front' for 12V DC to 240V AC inverters.

Kind Regards, John

 

[ban-all-sheds]

And what some people do with pole transformers.

 

[JohnW2]

The fact that 'LV' is seemingly misunderstood by the vast majority of the general public (and many of those supplying products, not only to the general public, but also to professionals!) is a different matter!

If you travel on the Tube you'll frequently see doors with a notice saying "DANGER - HIGH VOLTAGE". I've often wondered what's really behind them.

Quite so - although, in that case, I suppose it's quite feasible that it really is what BS7671 would call HV.

I'm sure that, as far as the vast majority of the general public are concerned, there are just two things - low voltage (which you would call ELV), which is 'safe' and high voltage (everything above what you would call ELV), which could harm or kill them - and I suspect that will always remain the case, regardless of 'official definitions'or Standards.

Kind Regards, John

 

[conny]

When I was a teenager I tried to light a ciggy from a coiled element of an electric fire using the silver paper from the fag packet.

 

[deadshort]

DS