Single or Multicore

[Aii02]

Dear All
a fellow engineer and i had a long arguement about what type of mv cable to use for transformer connections,i.e. from traqnsformer to transformer or transformer to panel.
i argued that multicore cables can be used up to a feasable size, yet he argued the only single core cables can be used in transformer connections.
so what do you think?

 

[davidbeach]

I've done both over the years, can't see how it could matter.

 

[waross]

I agree with David.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Aii02]

so there is no standard of type of cables used for transformers?

 

[7anoter4]

I agree, of course, there is not such a standard [as far as I know] and I don’t see what could be the reason for such a requirement.
There are some advantages of three-phase cable:
Less reactance –important if a voltage drop is involved-usually does not.
No shield induced voltage built-up –since the 3 phase shields are in contact and transposed [one may ground both ends without derating].
There are some disadvantages:
-the cable is heavy and more rigid and it could be hard to pull it -through ducts, mainly.
-the terminating are more complicated [ a little] for rated voltages above 15 kV.

 

[waross]

These days I see a lot of transformers connected with three conductor TECK cable. (An armored and jacketed construction)
This would be for transformers in the 1000KVA range. Primary voltage from 4160 Volts to 25,000 Volts, secondary voltages 480V, 600V or 4160V.
parallel multi-core cables may be used for the secondary. Larger transformers may have bus duct Flexi-bus or Husky-Bus on the secondary.
This seems to be an engineering standard in a particular industry in a particular geographic area. I have seen primaries with three single conductors, each in a separate steel conduit. I have seen parallel single conductors.
It depends on the size, the voltage, the industry and the preference of the designer.
In general I know of no reason to use only single conductor cables for transformer connections.
There may be specific installations where it is desirable to use only single core cables but I can't think of any just now.

Bill
--------------------
"Why not the best?"
Jimmy Carter