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Okay, so there was something else happened on Friday, I didn't mention it at first because my pride was massively wounded, but I got a belt (my first, and hopefully last). It happened because I didn't isolate properly - I'd been isolating all day properly, but then towards 3pm on Friday I was getting fed up, my head was frazzled, and I only isolated at the switch, totally forgetting that light 5 had a permanent feed for an emergency fitting. Yes, stupid, and it has certainly humbled me.

Thing is, and I'm probably being thick as they come, I can't understand how I got a zap. Here's a diagram of how the wiring is, I'm not sure where light 3 comes from, whether it's from 1 or 2 as I haven't opened then part up. Lights 1 and 2 were still connected but turned off at the switch. Light 2 also has a permanent feed as that's emergency, but that's upstream on the circuit. Lights 3, 4, 5 and 6 were all disconnected fully (click adapter). As you can see, line moves 3 to 4 to 5 to 6, neutral does some fudged stuff. Anyway, switched line off, permanent line not isolated, but no loads past light 2 (as far as I can tell). I removed the neutrals at click adapter #3, and as I did my thumb bridged the gap between them and I got a belt.

So, someone please tell me I'm being stupid and that it's really obvious why seperating the neutrals on a dead circuit gave me a tingle. I know permanent line was still live at light 5 but there was no load connected to it. Likewise, permanent line was still live at light 2 but that's upstream and so that should have still had a neutral connection present.

I'm eager to get back up there and see exactly what the hell is going on, but I'm not allowed to until an LA spark comes out and signs the incident off.

Voltage dropped cables.PNG - EletriciansForums.net
 
Sounds like you have another circuit borrowing the neutral from this one, a circuit which is still live. Can be hazardous on lighting circuits which have crossed neutrals.

That was my initial thought, when it happened the first words out my mouth were "f****** lazy t**** borrowing a neutral" (yes I see the irony in calling them lazy when I didn't isolate properly). But I still can't see why that would be the case. I've got a dodgy neutral hence why lights 4, 5 and 6 aren't working, so any load behind this (borrowing the neutral) surely wouldn't work either. I will get to the bottom of it when I'm allowed back on the job, but it's driving me insane.
 
Your neutral issue is still showing 210v so this will still give you a belt. When you can carefully disconnect the neutral at the board and see if it is live with the protective device off.
 
Thinking this is an "emergency lighting" only thing ?
(If was normal lighting in off state - Bor Neutral was only way)
Seeking a charging opportunity, if they are "self sustaining".
Floating neutral will also seek out any cpc. -
 
Unless you had the emergency light fully disconnected then the charging circuit will have been live. Disconnecting the neutral upstream of it will cause the black wire from the emergency light to cease to be neutral and rise to line voltage.
 
I think HT's point was that all the lights on the affected section were unplugged from the Click fittings, so although the PL was present at the Click, there was no load, not even the EM charging load, to complete the circuit to the floating length of neutral to give him a shock w.r.t. the good section. I too would have been surprised to get a shock if all were as per his sketch.

Unfortunately we are dealing here with a section of circuit that is known to be faulty or incorrect, although we don't yet know how, where or why. So it is a leap of faith to assume that the circuit will behave in the way we expect. With luck, the cause of the shock path will be revealed at the same moment the original fault is found. Not much point guessing with so many variables.
 
Noting this is a big assembly hall with long cable runs perhaps this is the 'real' circuit (and you could add some insulation resistance too if you are feeling artistic(!)...) These capacitors are charged to +350V and the -350V every cycle.
Voltage dropped cables.PNG - EletriciansForums.net
 
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Thanks all, I appreciate all the ideas being bounced around. It's out of my hands now, I'm not allowed to touch it until a council spark comes and takes a look. At the moment I feel a bit foolish, and just hope tomorrow he has the same findings as me thus far. I've really enjoyed working on electrics this past 5 years or so but this has really humbled me, and I don't know how I'll feel should something be found that i really should have spotted at first sight.
 
I wouldn't worry about it. The wiring doesn't sound very straightforward.
 
Most of us have been there and spent hours and days thinking if only I'd......... but we don't have the benefit of hindsight. As I said earlier lighting circuits can be a minefield even if you do use safe isolation procedures, few weeks time will all be forgotten about.
 
I think HT's point was that all the lights on the affected section were unplugged from the Click fittings, so although the PL was present at the Click, there was no load, not even the EM charging load, to complete the circuit to the floating length of neutral to give him a shock w.r.t. the good section. I too would have been surprised to get a shock if all were as per his sketch.

In which case my guess would be an, as yet, undiscovered load on the circuit. A light in a cupboard or something like that,which may turn out to be the location of the original problem.
 
It would be nice to get to the bottom of this fault,but,i would like to tip my hat,to the OP,for a refreshingly open and candid post.
The man that never made a mistake,never made anything,and it is job stories,such as this,which can keep even experienced hands,from forgetting the hazards which abound.

Marconis drawing,reminded of a large council workshop,where the spark had shut-down the power,and removed the main DB.....before discharging what may have been,an entire floor of broken florries,via his left thumb...

There was no site power,apart from a couple of small generators,and he was on for blaming the contractors for back-feeding,before it dawned on him...Believe nothing you hear...and only half of what you see ;)
 
PEG's #36 and ROHT's anecdotes are great ways to warn and train people. When I was brought in to sort out the mess after a contractor was electrocuted by 11kV I introduced these 'tool box' talks for my technicians. I was always on the lookout for folk with a tale to tell which rammed home the point of 'no short cuts to safety'. Much, much better than a dry lecture on the subject. It's the setting and context which provides the engagement and learning. As humans we remember stories which is indeed how folk passed on information and learning in those days when they could not read or write or there was no paper or books.

One of my 'favourites' is the computer technician who shorted out the live 5Volt busbars of a Ferranti FM1600B computer with his gold wedding ring - yes he had done the training, there were warning signs for very high current and to remove hand and arm metal jewellery, he had checked busbar connections hundreds of times before but on this occasion he lost a finger, because ......
 
Hi All, late to the party I know, but here’s 20p from me :) .

Recently, I investigated an EICR C2 fault for high leakage. I did find the fault wiring with the usual application of time and patience to work through a couple of false starts (well no one’s perfect, not me anyway). I ended up with house global IR of about 90 meg Ohm and a leakage of about 6mA. Which made me think - why is it so?

Of course it’s the capacitance to earth of the L conductor and a direct consequence of running the CPC together with the Lives. But how much leakage is reasonable? I got a new 100m roll of 2.5/1.5 and just connected it up - 1mA earth leakage. Add up 10 circuits and even with no loads we see another reason why we don’t remove the Earth on a live installation...

I’ve added the hurt graph to illustrate - blue is ok, green is not good, yellow makes me bellow and red I may not be posting again.

Voltage dropped C9AEB4B3-6CD5-46FD-8896-7D143374C0CB - EletriciansForums.net

Voltage dropped 2944F81E-BCD0-4E67-A3AF-0739ACF87D8A - EletriciansForums.net
 
Right then chaps, sorry I didn't post yesterday but council sparks came out Monday and got to the bottom of it. Bottom line is, it was a loose neutral causing the fault in 3 lights.

So, to talk through the actually wiring of it, all lights on the bank are fed from a single switched line, with the exception of 2 & 5 that have an additional perm line for emergency. Lights 1-3 are fed by 1 neutral, lights 4-6 are fed by another totally separate neutral (independent all the way back to the board). Other banks are seemingly wired the exact same, 1 line 2 neutrals, so this looks original wiring instead of bodged repair. The loose neutral was at a junction box upstream from lights 4-6, hence why only these 3 lights were faulty.

So, I got a belt, and I think the reason is, I separated the neutral after light 3, what I thought was the link from 3 to 4. Because I'd left the emergency connected and had only isolated at the switched line (wrongly thinking light 2 was upstream and therefore wouldn't be affected by me breaking the neutrals). Instead of breaking 3-4 neutral link, I broke 3's neutral back to the DB and hence the belt. Yep, it's my own fault - safe isolation would have prevented it, and I've learned a massive lesson.

However, anyone know why it may be wired in such a way?
 

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