Parallel Conductors x 4

[skhan855]

Hi,

I need to take advice if its ok to install 70mm2 - 3 core non armored cable carrying 380 volts each in parallel of 4 cable to have load of 600 Ampere?

Each cable have capacity to carry 192 Amperes so 4 would be 768 Ampere!!

What should be installation technique? is gap of 20 CM enough between each cable?

Regards
Salman Khan

 

[Dennis Alwon]

Where are you running this cable? Underground, in a tray or where. I am not sure spacing is required as long as they not atop each other. The strapping should keep a small gap.

 

[Besoeker]

Hi,

I need to take advice if its ok to install 70mm2 - 3 core non armored cable carrying 380 volts each in parallel of 4 cable to have load of 600 Ampere?

Each cable have capacity to carry 192 Amperes so 4 would be 768 Ampere!!

What should be installation technique? is gap of 20 CM enough between each cable?

Regards
Salman Khan

I assume you are using Table 4D2A from BS7671.
For 3ph ac trefoil on a perforated tray, reference method 11, each conductor gives 196A.

 

[skhan855]

Hi
I plan to install between wall as a sandwich.

 

[Julius Right]

If the space between walls is well ventilated and cable insulation is xlpe [or epr] a single
three-core cable ampacity [at 30oC air] is 194 A[method 40 Table 4E2A column 5.
If the clearance between horizontal cable is 2*De or more no derating is required.
The distance between the two walls has to be at least 10*De=360 mm [approx.].
Since the actual current will be 150 A[4*150=600 A] the conductor temperature will be not more than 70oC then no overheating damage of connected with breaker will occur.
I think the 30oC ambient air is good for U.K. For Pakistan 40oC could more actually.
In this case a derating factor of 0.91 has to be employed.

 

[Tony S]

As they are 3c cables 20cm separation should be OK and not requiring any derating.

Where the problem lies is the location and ventilation. The cables need to be ≥ 50mm below the surface of the wall otherwise S type RCD protection is required. If there is insulation in the wall or poor ventilation then derating has to be applied. You need to look in BS7671 for the derating factor.

 

[Julius Right]

If the space between walls is field than A1 or A2 method is to be taken into consideration.
I’d prefer IEC 60364-5-52 instead of BS7671 since BS7671 does not differentiate between A1 and A2 -that means with and without conduit.
So according to IEC 60364-5-52 Table 52-3 (52H) pos.3 [A1] and Tb.A.52-5 (52-C4) column 1[A1] for 3*70+35 179 A and for 3*185+95 324 A. If the air temperature is 40oC a factor
of 0.91 it has to be employed then 179*0.91=163 A and 324*.91=295 A.
If clearance between cables is 7-8 cm for 3*70+35 and 14 cm for 3*185+95 then no
reduction factors for groups of more than one circuit is required.