Case studies · Recurrent faults
Same fault twice in six days, and a dead squirrel found within hours
A breaker trip interrupted more than 1,200 customers twice. DFA linked the two faults within a minute, and the report took the crew to one pole.
- Where
- Overhead feeder, United States
- DFA reported
- Recurrent fault, within a minute of the second trip
- Customers
- More than 1,200 interrupted each time
- Found
- A dead squirrel on the phase A recloser
- Outcome
- Fixed within hours; no further faults
What DFA reported
A fault tripped the substation breaker and momentarily interrupted more than 1,200 customers. It began on phase A and pulled in phase B about ten cycles later. The breaker reclosed and, as usual, nobody acted. Six days later a near-identical fault tripped the breaker again. Within a minute DFA linked the two events and posted a recurrent-fault report.
What the crew found
The report's fault current, the way the fault spread from one phase to two, and extra trips of single-phase reclosers pointed the crew to one pole with single-phase reclosers. There they found a dead squirrel on the phase A recloser and damage on the phase B insulator, and fixed both within hours.
Why it matters
No further faults followed. Each recurrence would have interrupted every customer on the circuit, and a carcass on a pole can draw birds and cause more faults for weeks.
Keep reading
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A hanging branch tripped a recloser six times without an outage. DFA grouped the faults into one report, and a targeted patrol found it.
Two blinks in 18 days, and a failing arrester found within four spans
On a 125-mile circuit with about 20 unmonitored reclosers, DFA showed which recloser was working and cut the search area by 76%.