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Old 31st Jul 2013, 10:25 am   #21
dominicbeesley
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Default Re: Live Line Neutral etc etc

This discussion, is very interesting and I'm intrigued. I'm half tempted to stump up the money and buy a copy of BS1363!

The suggestion that the terminology be changed is not a sensible idea. People can and do still change plugs frequently - (sometime badly). Usually, because the moulded on plug won't fit through a gap in a cupboard. I hope this will continue to be the case for many years and not get stamped out by the H&S or vested interest brigade. L,N,E are very sensible markings and have served well - whether L is for "line" or "live" doesn't matter so long as people know that is where the bitey wire goes! As to the use of "phase" in a single phase supply it makes no sense to me - phase relative to what?

I've just had a look at a couple of Electrical Engineering books from the mid to late thirties and neither mention live, line, phase or neutral with one just referring to "circuit" for either and earth for earth.

A related question: in DC circuits what was the general practice? Positive Earth, Negative Earth, Balanaced? I know 1363 plugs and sockets are for AC only but did they ever get used in DC areas?
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Old 31st Jul 2013, 11:19 am   #22
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Default Re: Live Line Neutral etc etc

Quote:
Originally Posted by dominicbeesley View Post
A related question: in DC circuits what was the general practice? Positive Earth, Negative Earth, Balanaced? I know 1363 plugs and sockets are for AC only but did they ever get used in DC areas?
I recall DC mains in certain East Midlands housing-estates up until around 1970: they were connected positive-earth and used "Dorman&Smith" fuse-as-the-live pin plugs&sockets. The "live" pin was -200V.

Each pair of semi-detached houses had a single mains incomer from the road - a thick armoured cable overwound with a sort of tarred hessian which ran up the wall on the front of the house to a large cast iron junction box - from this a pair of smaller individually-clipped cables ran off to each house.

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Old 31st Jul 2013, 12:33 pm   #23
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Default Re: Live Line Neutral etc etc

There seems to be only confusion and opinion on this subject, great for discussion but not at all definitive. I obviously started a bit of a rabbit!

It looks like my internal pedant will just have to put up with the fact that there's probably no definitive answer and from a practical point of view it doesn't matter anyway. I'll stick to "line" for the same reason as Hugh in post #17
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Old 31st Jul 2013, 2:22 pm   #24
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Default Re: Live Line Neutral etc etc

Quote:
Originally Posted by dominicbeesley View Post
A related question: in DC circuits what was the general practice? Positive Earth, Negative Earth, Balanaced?
Both were used - approximately half the generator output suppliedto positive-earth consumers, and about half to negative-earth.

So that meant that many "live chassis" radios really did have to be live with respect to earth.
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Old 31st Jul 2013, 5:11 pm   #25
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Quote:
approximately half the generator output suppliedto positive-earth consumers, and about half to negative-earth
As most customers used about the same amount this made the 0V conductor carry less current and could be smaller (cheaper!).
 
Old 1st Aug 2013, 12:56 am   #26
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Default Re: Live Line Neutral etc etc

Quote:
Originally Posted by dominicbeesley View Post
As to the use of "phase" in a single phase supply it makes no sense to me - phase relative to what?
Many, many moons ago I was advised (probably not by anyone who was a subject matter expert), that the use of “phase” was chosen so that the three wires could be P, N, E, and thus align with DC practice of Positive, Negative and Earth. I suspect that that explanation was a post facto rationalization.

But “phase” and “line” are not really the same. For example, in a star-connected three-phase system, the line-to-neutral voltage is the same as the phase voltage, but the line-to-line voltage is √3 times the phase voltage. In a delta-connected system, the line-to-line voltage is the same as the phase voltage.

Neutral conductors are I think, supposed to connect to a neutral point, such as the star point of a star connected three-phase system or the centre point of three-wire single-phase system or the centre point of a three-wire DC system. On that basis a two-wire single phase system, supplied from single-phase transformer, does not have a true neutral point to which a neutral conductor could be connected. If one side is grounded, which is usually the case, then I guess it would be viewed as being a “pseudo-neutral”. The case would seem to arise in practice in rural areas, supplied by either a two-wire single-phase 11 kV primary (tapped from a three-wire three-phase 11 kV system) or by 11 kV SWER, and with transformers that have simple 230 V secondaries, and not the 230/0/230 V split types.

Cheers,
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Old 1st Aug 2013, 10:15 am   #27
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Default Re: Live Line Neutral etc etc

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Originally Posted by G6Tanuki View Post
Over in the US they colloquially refer to "phase" as "Hot" which is kind of appropriate given the thermal state the flat pins on their 110V plugs/sockets often end up in when you try to draw significant current.
Just to point out the US does not and never has used 110V. It is 120V, often quoted as 117V to take account of volt drop.
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Old 2nd Aug 2013, 9:09 pm   #28
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Default Re: Live Line Neutral etc etc

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Just to point out the US does not and never has used 110V. It is 120V, often quoted as 117V to take account of volt drop.
Actually the US domestic voltage was nominally 117.5 Volts, this has now been changed to 120 Volts.

Most people still refer to it is as 110 Volts and 220 Volts across the phases. In my house, which is right next to the transformer, the voltage measures as high as 125 Volts in off peak times, and has never gone below 120 Volts at peak times.
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Old 2nd Aug 2013, 9:58 pm   #29
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Default Re: Live Line Neutral etc etc

I read somewhere, not sure it it was a thread on this forum or elsewhere, that you can roughly date US equipment, or publications that mention mains electricity, by the stated mains voltage. The progression I have noted is 110 - 115 - 117.5 - 120. I understand that this was deliberate policy with a view to increasing the power deliverable via the supply network, and the increase was staged at intervals long enough that most of the apparatus designed for the lower voltage would only experience one increment of increase before it was replaced. I do remember a US chemistry book published in the late 1950's that mentioned 117.5V, and the table of world voltage power supplies of the 1968 [6th] edition of the ITT Reference Data for Radio Engineers gives the US mains votage as 120/240V.

A US-type 2 pin plug bought from Maplins a few years ago is marked with a voltage rating of 150V.

Last edited by emeritus; 2nd Aug 2013 at 10:14 pm.
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Old 4th Aug 2013, 6:40 pm   #30
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Default Re: Live Line Neutral etc etc

As far as i am aware the use of live and neutral actually dates from the 1930s when it was decided to use this terminolgy because it was applicable to both AC and DC supplys and was nice and simple for mr or miss jo public to understand rather than a mixture of phase for AC and negative or positive main for DC. obviously radio and tv engineeers and electricians of the time would have known the difference but not jo or jayne public same as now really
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Old 5th Aug 2013, 3:33 am   #31
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Default Re: Live Line Neutral etc etc

In Australia the terms used are "Active", "Neutral" and "Earth".
The word "Phase" is only used where a 2 or 3 phase supply is used and then it is usually identified such as "A Phase", "B Phase" or "C Phase". Similarly, when colours are needed, we use "Red", "White" and "Dark Blue" to indicate the 3 phases.

The colours for a single phase to neutral supply are "Brown" for the active, "Light Blue" for the neutral and "Green, Yellow or a combination of Green/Yellow" to indicate the earth.
Some older cables had "Red" for the active and "Black" for the neutral and "Green" for the earth conductor.

Cheers, Robert.
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Old 15th Aug 2013, 3:35 pm   #32
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Default Re: Live Line Neutral etc etc

Spain; Main plugs have 2 pins exactly the same size. Earth connection is external. Can be plugged in both ways.
Which means live & neutral have a 50/50 chance of being reversed.

Last edited by AC/HL; 15th Aug 2013 at 9:18 pm. Reason: Irrelevant bits removed
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Old 16th Aug 2013, 2:37 am   #33
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Default Re: Live Line Neutral etc etc

My first holiday in Spain was at a fairly new rented apartment in the mid-1970's. One of our party got a shock from the fridge. Recalling a hint I had read in a US magazine, without getting up from the sofa I told them to remove the plug and put it in the other way round. No more shocks!

All the sockets were 2 pin with 4mm pins protected by 6A circuit breakers, except the kitchen water heater, which was connected via a US-type 2 pin socket via a substantial rubber plug and protected by a 10A circuit breaker.

Last edited by emeritus; 16th Aug 2013 at 2:43 am.
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