Why are all the other cores becoming live??? (Video)

[ppelec100]

Can someone please help me understand what the hell is going on here???

This 3c E was in flexi conduit and the same problem was happening as shown in the video. I have pulled it out to do it like this for testing purposes.

I have tried with 3 different pieces of 3c E. all tested open between all cores on continuity. All cores tested >1049 on IR. But when putting only the brown core in all other cores are live.

I realised the problem when the emergency light was permanently on.

Only the brown core should be live but for some reason all cores are live???!!!

My testers are completely fine.

 

[davesparks]

Can you explain what you xactly you mean by putting only the brown core in all the others are live?
A picture might help.

What are you measuring voltage with?

 

[ppelec100]

Can you explain what you xactly you mean by putting only the brown core in all the others are live?
A picture might help.

What are you measuring voltage with?

Oh, I attached a video but it didn’t seem to upload.

I’ve fixed it now, I called my old employer he came round as he was local. He mentioned that it was just induced voltage running through the cables which is why the other cores were coming up live.

Scenario: surface back box has feed in and feed out. Putting a 1g switch there for the under stairs light. When I used the 3c & E to feed the light from that switch the light was staying permanently on, so when I tested it, the black (SL) was staying permanently live, pulled it apart and left only the brown core connected to the brown feeding in and out and the other cores out, on the other side all cores out but I was getting a voltage on all cores of the 3c & E

I was testing it with kewtech voltage continuity tester

 

[Simon47]

As you've found out, there's capacitive coupling between cores which will induce a voltage into other cores when one (or more) is fed with AC. How much you measure will depend on the impedance of the tester - if it's high enough then you'll measure a significant voltage.
Of course, back in the days of incandescent lights it wasn't a problem. These days the available current is enough to make many LED lamps glow dimly, or for those with more than just a bunch of emitter chips and some current limiting components may make them flash (current charges up capacitor, when voltage gets high enough the switch mode controller tries to start up, LED flashes before voltage collapses, rinse & repeat).