Closed Loop Distribution Scheme

[rba10]

I recently worked on a job with a 4kV circuit that had two A-phase loops. Most often these loops have an open point at one end or the other and I understand the benefit being the flexibility in that the load can be fed from either end. In this particular case, however, each of the loops were closed in on both sides.

So my question is, what is the benefit of having both ends of a loop closed? I think I have an idea but I'm not sure.

 

[jghrist]

Neglible advantage:

Load currents will split between the two ends to minimize conductor losses.

Non-neglible disadvantage:

1. Fault current will split between the two ends to increase tripping time in fuses or overcurrent relays at ends. This may allow upstream devices (that see total fault current) to trip faster.

2. Faults will result in loss of entire loop instead of just half.

 

[apowerengr]

On heavily loaded circuits sometimes owner's choose to close loops because one end can't handle the load by itself.