5 conductors per phase parallel run 3

[MD88]

Hello,

I've got a 2500A, 600V run to put in, and I'd like to use 15x1c-350MCM 100% spaced as per CEC Table 1 (Canadian project). My question is what would be the optimal conductor and phasing arrangement to minimize the inductive reactance differences. Any tips or references would be much appreciated.

Thanks

 

[dpc]

Are these in 5 conduits - I'm not Canadian? As long as you are running three phase conductors (ABC) in each conduit, there should minimal inductive interaction between conduits. A bigger issue might be mutual (thermal) heating of conductors.

 

[MD88]

No, not in conduits - specifically for the thermal reasons you mentioned. The intent would be to use cable tray and/or maple spacer blocks to maintain 100%+ spacing around the cables in order to use the free air rating of the single conductors.

 

[davidbeach]

As a single layer you'd want A-B-C-A-B-C-etc. and not something like A-A-A-A-A-B-B-etc.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[itsmoked]

Maybe you're overthinking this?

These thirty 400MCM cables were jammed into five PVC conduits buried in dirt out to a 1.5 megawatt Cat generator.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[FacEngrPE]

If using cable tray, a trefoil arrangement might be appropriate.

, the arrangement is not quite free air, but is low impedance.

 

[MD88]

Yeah, I don’t want to trefoil, just because I’d need to up the cabling. I’m thinking

ABCCBA
ABCCBA
ABC

for the 15 conductors, using maple blocks to maintain 100% space.. any comments on that?

 

[che12345]

Dear Me. MD88 (Electrical)(OP)21 Jan 23 21:17
"....Yeah, I don’t want to trefoil, just because I’d need to up the cabling. I’m thinking ABCCBA ,ABCCBA , ABC ..."
1. I am of the opinion as advised by learned Mr. davidbeach (Electrical)20 Jan 23 22:45
" As a single layer you'd want A-B-C-A-B-C-etc. and not something like A-A-A-A-A-B-B-etc.". The major disadvantage is the distance d =dia. d of each cable, it takes up a wide width. It would be undesirable if d=2dia. d . Of cause you can have multiple layers.
2. Re-consider have it in trefoil formation ABC - d- ABC- d-etc where d-1x ABC dia or 2x ABC dia. - Unless this trefoil formation is under rated for your application, it can be a good proposition; as it needs a smaller duct/less cost and room.
BTW: In LV where large no. of parallel cables, trefoiled formation method is widely practised.
Che Kuan Yau (Singapore)

 

[unclebob]

A_B_C_A_B_C_N_N
_C_A_B_C_A_B_N_N
A_B_C_N

That looks good? Found that too...

http://www.advcablebus.com/downloads/advancedcablebuscatalog.pdf

 

[che12345]

@ "... Mr. unclebob (Electrical)22 Jan 23 03:36
A_B_C_A_B_C_N_N
_C_A_B_C_A_B_N_N
A_B_C_N
That looks good? Found that too....."
I am confuse. If [3x (3ph+N) = 12 ], [ 4 x (3-ph+N] = 16 } . Both cases do NOT indicate 15.
I am thinking it is [5 x (3-ph) = 15 ], i.e. No N.
Singapore (Singapore)

 

[jghrist]

You can calculate the reactance by phase for different spacings using equations for parallel three-phase circuits. We designed an installation of 4 kV cable bus which included changing the phase arrangements of an existing cable bus system and installing a parallel cable bus system. Each had 4-750 kcmil copper cables per phase and was 700-800 ft long. Cable spacing was 3.2" inches vertical and 3" horizontal. The existing system had the arrangement:

A A B B C C
A A B B C C

Calculate reactance was 0.0318 ohm/1000 ft for each phase

Changing the phase arrangement to

A C C C A A
B A B B C B

had calculated average reactance of 0.0142 ohm/1000 ft

Changing the phase arrangement to

A C B B C A
A C B B C A

had calculated average reactance of 0.0178 ohm/1000 ft


If you purchase a cable bus system, the supplier can optimize phasing arrangements for lowest reactance and phase current balance. See

http://www.mphusky.net/images/brochures/cablebusbrochure2015.pdf.

In our project, we purchased the cable bus from MPHusky and used their recommended phasing arrangement, matching the last arrangement above. MPHusky's calculate reactance was 0.0172 ohm/1000 ft

 

[Padlock01]

Perhaps one should follow the attached arrangement.

 

[7anoter4]

I don't know what CEC says. However, NEC art.392.80 allows, for single core cables installed in triangular or square with a maintained free airspace of not less than 2.15 times one conductor, for 350 mcm copper 90oC insulated [EPR or XLPE] 464 A .For 5 parallel conductor it is not enough [it is less than 2500 A]. But 400 mcm it is better[503 A].
If the cables will be installed in single lay close each-other the phase order has to be ABCCBA...See:
for instance:

https://www.researchgate.net/public...ce_of_Current_Distribution_in_Parallel_Cables

However, according to NEC art. 392.80 A 2b and Tb 310.15(B)(17) the ampacity it is only 370.5 for 350 mcm copper.
Another limitation:
According to Art. NEC 110.14 Electrical Connections.(A) Terminals.(1) Equipment Provisions.
unless the equipment is listed and marked otherwise[that means 90oC],(b) Termination provisions of equipment for circuits for 350 mcm permissible will be only 335 A. for 75oC [Tb 310.15(B)(16) ]

 

[7anoter4]

If you intend to use marple blocks then it could be

https://unitedwc.com/maxiamp-cable-bus/

or jghrist proposal for MPHusky. We used MPHusky 750 mcm 4 cables per phase but short length, 25 years ago.

 

[Sn00ze]

explore a stacked solution if you are (rightfully) concerned about realstate.

 

[waross]

Google "Husky Cable Bus"

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[davidbeach]

Welcome back.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[waross]

Thank you, David.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[dpc]

Bill! Good to see you back.

Dave

 

[Amit Bajpayee]

five conductors per phase in a parallel run, it means that each phase of the three-phase system is transmitted through five electrical wires, with each wire carrying a portion of the electrical load.

Having multiple conductors per phase in a parallel run provides several benefits, including:

Increased reliability: With multiple conductors, there is a reduced risk of power failure in the event of a conductor failure.

Improved power transmission efficiency: Multiple conductors can reduce electrical losses, improve voltage regulation, and provide more stable power transmission.

Increased capacity: Multiple conductors per phase allow for a larger amount of electrical power to be transmitted.

It's important to note that the number of conductors per phase in a parallel run may vary based on the specific requirements and conditions of each application, including the available space, budget, safety concerns, and electrical power requirements.

https://agnisolar.com/