In article ,
says...
Tweaking some lighting, I turned off the mcb for the LX circuit and
opened a pendant fitting. Double-checked with a neon 'driver - not live,
is says. Unscrewed one of the neutrals. As I do so it sparks quite
impressively. Why?

(I chickened out and turned off the whole house supply in the end. Wife
really enjoyed that on a Sunday evening...)

It was a pretty common pendant arrangement - four cables - incoming
L/N/E feed. Outgoing feed. Cable to switch. Cable for pendant fitting.


A spark must means there's current flowing - but where from? I did
wonder whether the 12v transformers for the halogens might have caused
it?


There is current returning through that neutral block from one of the
other lights upstream of that fitting. Disconnect the neutrals, and one
will be at 0v (near enough), and the other will be live, as there's no
voltage drop across the 'on' light, because no current flows. I learned
very early on that you can get quite a belt from a neutral that way!