Self-Healing Smart Grid: Fault Isolation & Restoration

Fault Setup

Fault location Segment 3 (A2–A3)

Automation

Automatic self-healing (FLISR)

Tie-switch restoration delay 2.5 s

Backup feeder (B) loading 55%

Grid Status

Grid nominal — both feeders closed, tie switch open (normal radial configuration).

Customers without power

0 / 830

Restoration time

—

Service restored

100%

How it works

Real distribution networks are normally run radially: each feeder is a tree fed from one substation, with a normally-open tie switch linking the far end of one feeder to a neighboring feeder as a backup path. A smart grid's FLISR system (Fault Location, Isolation and Service Restoration) automates what used to take a truck roll:

Trip — an overcurrent relay at the substation opens the feeder breaker within milliseconds of a fault, protecting equipment upstream.
Locate & isolate — reclosers/sectionalizers along the feeder use fault-current signatures to pinpoint the faulted segment and open just the switches bracketing it, typically in 1–3 s.
Reclose upstream — the substation breaker recloses, restoring everything between it and the fault immediately.
Backfeed downstream — the normally-open tie switch closes, re-energizing customers beyond the fault from a neighboring feeder, if that feeder has spare thermal capacity: P_spare = P_rated,B − P_load,B ≥ P_downstream,A. If not, automation must leave the tie open to avoid overloading feeder B, and a crew is dispatched instead.

Radial rule:     exactly one closed path from source to every load
FLISR condition: close tie  iff  P_rated,B − P_load,B ≥ P_downstream,A
Without FLISR:   restoration ≈ manual crew dispatch, 30–90+ min

This is the same architecture used by utilities' ADMS (Advanced Distribution Management Systems, e.g. from Schneider Electric, GE and Siemens) to shrink outage duration from tens of minutes to a few seconds for everyone the topology can reach — the segment actually holding the fault still needs a physical repair before its switch can reclose.

Energized De-energized Fault / open switch Backfeed from Feeder B

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.