Case studies · Protection
A circuit lockout explained, and the grass fire it started found
SCADA showed the whole circuit locked out. DFA said why, and the crew went to the predicted span and found arc marks and burned grass.
- Utility
- Mid-South Synergy
- DFA reported
- Breaker lockout caused by conductor slap
- Circuit
- Long, rural 25 kV
- Found
- Arc marks in the predicted span
- Outcome
- Span modified so it cannot slap again
What DFA reported
A tree caused a phase-to-phase fault far out on the circuit, where a mid-point recloser should have isolated it. Instead the fault current swung conductors together closer to the substation, and the substation breaker tripped repeatedly and locked out the whole circuit. SCADA showed the lockout. DFA identified the cause as fault-induced conductor slap and reported the current of each fault in the sequence.
What the crew found
The co-op entered those currents into its circuit model, which predicted a specific span. The patrol found arc marks on the conductors in that span and a burned patch of grass beneath it; a customer had reported the fire at the same time. It had burned out on its own.
Why it matters
The co-op modified the span. Conductor slap tends to recur in the same span for years, and every episode is a whole-circuit interruption and a possible ignition.
Keep reading
1,100 operations in 33 minutes, from reclosers that never locked out
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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.
A glowing substation switch, found within two hours
No calls, no SCADA alarm, normal meters. DFA reported series arcing, and a lineman found the failing switch before two days of storms.