Case studies · Protection
70 needless blinks in 54 weeks, from a recloser tripping on load
In a winter storm a hydraulic recloser tripped 26 times with no fault on the line. DFA showed why, and the utility bypassed it.
- Where
- 12 kV rural circuit, United States
- DFA saw
- 26 trips in 5.5 hours with no fault
- Cause
- Heating load near 11 MW on a 6.5 MW circuit
- History
- 70 needless momentary interruptions in 54 weeks
- Outcome
- Recloser bypassed; replacement moved up
What DFA reported
During the January 2024 winter storm, heating load on a 12 kV rural circuit reached just under 11 MW, against a 2023 peak of 6.5 MW. DFA saw a hydraulic recloser on a single-phase lateral trip 26 times in five and a half hours, reclosing 1.6 seconds later each time, with no fault present. It was tripping on overload.
What the crew found
DFA's records showed 44 more overload interruptions on the same circuit and phase in 13.5 hours in late December 2022: 70 needless momentary interruptions for every customer downstream in 54 weeks. None of the utility's AMI, DMS or SCADA systems had flagged it. The utility bypassed the recloser and moved up its replacement.
Why it matters
The utility runs an advanced FLISR system, but its hydraulic reclosers report to nothing. DFA saw them from the substation.
Keep reading
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