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Selk
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Single Core Cables in Trefoil in Conduit/Pipe

11/25/2019 7:48 AM

We have installation of 9 single core cables (3 x r-y-b trefoil groups, 10kV Cables) laid directly buried under ground without any pipes/conduits. On transition from underground to above ground to connect to the motor terminals,

Can I use each trefoil group in a conduit/pipe till the motor terminal. Are there any disadvantages in it?. The installation is in IEC Land.
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redfred
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#1

Re: Single Core Cables in Trefoil in Conduit/Pipe

11/25/2019 9:37 AM

The only disadvantage I'm aware of is the sizing of the pipe/conduit. Twisting cables into a trefoil makes them stiffer than each cable individually run, so installation may be difficult. Going up one or two pipe diameter sizes from the minimum for thes cables loose should mitigate this.

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raghun
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#4
In reply to #1

Re: Single Core Cables in Trefoil in Conduit/Pipe

11/26/2019 12:13 AM

Considering the trefoil formation will nullify the flux, metallic conduit that will be robust and supports the cables can be safely used.

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PWSlack
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#2

Re: Single Core Cables in Trefoil in Conduit/Pipe

11/25/2019 12:22 PM

...as would choosing a material for the <...conduit...> that is non-conductive.

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redfred
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#3

Re: Single Core Cables in Trefoil in Conduit/Pipe

11/25/2019 12:28 PM

IEC Land? Is this where glaciers are melting?

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JWthetech
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#5
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Re: Single Core Cables in Trefoil in Conduit/Pipe

11/26/2019 2:42 AM

Thankfully they melted on Lon Gisland. Giving you 300 yrs of great tasting freshwater.
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redfred
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#6
In reply to #5

Re: Single Core Cables in Trefoil in Conduit/Pipe

11/27/2019 12:54 PM

Close, but it's actually Lawn Guy Land.

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SolarEagle
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#7
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Re: Single Core Cables in Trefoil in Conduit/Pipe

11/27/2019 1:25 PM

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7anoter4
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#8

Re: Single Core Cables in Trefoil in Conduit/Pipe

11/28/2019 3:17 AM

If you are in IEC World I'd prefer three-core cables instead of single core. The problem with single core it is the unbalance between currents and a mistake in cable grouping [let's say r,r,b instead of r,y,b ] could produce current difference between conductors of a same phase and induce current in conduit.

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7anoter4
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#9

Re: Single Core Cables in Trefoil in Conduit/Pipe

11/29/2019 12:30 PM

See also-for instance:

https://pdfs.semanticscholar.org/e84e/444ab5899f91301f7e738dbd92b01e8d0a23.pdf

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