Short answer
Feeder reconfiguration loss reduction moves normally open points so that load is shared more evenly between feeders. Because resistive losses scale with the square of current, two feeders carrying equal loads lose less than the same total carried unequally. In an illustrative pair of 11 kV feeders carrying 6 MW and 2 MW with 0.5 Ω lumped resistance per phase each, losses are about 165 kW; moving the open point so each carries 4 MW reduces them to about 132 kW. The new configuration must remain radial, use only permitted switches and supply paths, and keep every substation transformer, distribution transformer and line within its limits. Voltage at the ends of the reconfigured feeders also changes and must be checked. Loss-driven reconfiguration is a planning or operational optimisation and should not be confused with fault restoration logic.
Why balancing reduces losses
| Case | Feeder 1 | Feeder 2 | Losses |
|---|---|---|---|
| Before | 6 MW, 315 A | 2 MW, 105 A | ≈ 165 kW |
| After | 4 MW, 210 A | 4 MW, 210 A | ≈ 132 kW |
Ploss = 3 I^2 R
Illustrative example. Two 11 kV feeders with lumped resistance 0.5 Ω per phase each; loads 6 MW and 2 MW at unity power factor. Values chosen for demonstration.
Currents: 6,000 / (1.732 × 11) ≈ 315 A and ≈ 105 A.
before ≈ 3 × 0.5 × (315^2 + 105^2) ≈ 165 kW
After moving 2 MW: both ≈ 210 A.
after ≈ 3 × 0.5 × 2 × 210^2 ≈ 132 kW
Savings of about 33 kW, 20 %. Real feeders have distributed loads, so savings are calculated by load flow.
Constraints
| Constraint | Check |
|---|---|
| Radial topology | No loops, every load supplied once |
| Permitted switches | Only switches approved for routine operation |
| Substation transformer | Loading of receiving transformer, including emergency margin |
| Distribution transformers | Unchanged load, but voltage changes |
| Lines and cables | Thermal ratings |
| Voltage | End-of-feeder limits |
| Protection | Settings valid for new topology; see adaptive protection when a feeder is reconfigured |
Transformer losses
Feeder reconfiguration need not change the customers assigned to each distribution transformer, but changed terminal voltage can change current and losses. Recalculate loss duty where voltage, tap or excitation changes; do not assume every distribution-transformer loss remains fixed. Substation transformer load losses change with feeder allocation and should be included. Loss accounting at transformer level is covered in technical and nontechnical losses at a distribution transformer.
Model quality
- Switch states in the model must match the field; hidden parallels distort results; see normally open points without hidden parallel sources.
- Load allocation to transformers should be calibrated; see calibrating transformer load allocation with AMI data.
- Time variation: the best configuration at peak may not be best over a year; time-series studies help; see quasi-static time-series studies.
Separate from restoration
Fault restoration uses different objectives and time limits. A configuration chosen for losses must still allow restoration options, but the two analyses are separate.
Where this reasoning stops. Lumped resistance oversimplifies; savings come from load flow over representative periods.
Practical takeaway
Evaluate reconfiguration options with load flow over time, accept only radial permitted topologies, check every transformer and line against limits, and recheck voltages and protection before adopting the change.