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I'm not sure what you mean by a loop 'enclosing' the toroid.
I'll use klugesmiths drawing to explain. Imagine the red torus to be a CT, i.e. a toroidial winding and the blue torus a wire loop. The wire loop then "encloses" the CT. Not enclosed would be the case if the blue torus is removable from the red one.
A convenient way to see whether a conductor is linked magnetically to the core is to see whether the conductor encloses (that word again) the flux that's in the core.
There might be flux outside the core. That depends on the u of the core and geometry. If there is, then it can go through a loop, induce voltage there and therefore the loop will be coupled. For a high u core that might be negligible.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
If Klugsmith's red ring is the flux-carrying core of the CT, and the blue ring a wire loop, then I'd say the blue ring *links* the red ring, or the blue ring *encloses* the flux in the red ring. The blue ring does not enclose the toroid, or at least, I find that description ambiguous.
Flux outside the red ring? Let's KISS with the ideal case of infinite permeability and say there's no flux outside the red ring. In the real case, the flux outside the red ring will be negligible. It certainly won't turn an earth wire loop that doesn't link the CT flux into one that does.
AFAICS from the picture, the earth tail loops do not link the flux in the CT core, because they go up and back again. The three phase conductors, red, blue and yellow, do link the CT flux, as they go through once.
Registered Member #61276
Joined: Mon Nov 07 2016, 08:44AM
Location:
Posts: 6
From what I see the CT is for a ground fault device. The routing of the ground leads is to prevent a sharp bend at the bottom. - I'm afraid not. the routing is purely because the installer thought they conductors had to run through the CT
Not seen, but of interest, is how the single cables enter the (presumed) steel enclosure . - see pdf from 1st post. and attached pic. they come from the gland. also tied to the copper screen.
Are the individual cables secured with a non ferrous connector? Cables of ampacity in the hundreds will heat iron ring surrounds to an extent to , melt or compromise the cable insulation. - copper lug I assume.
I am not an inspector, but have installed cables to boxes, low and high voltage. An inspector might grumble the box is too small to cramp the CT like that as shown in pdf, the pic is only part of the compartment, below floor is where cable made off.
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11kV termination earthing through core balance CT
