Case studies · Protection
1,100 operations in 33 minutes, from reclosers that never locked out
Twelve episodes on ten reclosers at six utilities. None of the utilities knew, and no customer complained.
- Where
- Six utilities, from small cooperatives to a large investor-owned utility
- Scope
- 10 reclosers at 6 utilities
- Worst case
- About 1,100 operations in 33 minutes
- Customer complaints
- None
- Who knew
- Nobody, until DFA
What DFA reported
A line recloser set to lock out after a few trips should never reclose dozens of times. DFA has documented twelve episodes in which hydraulic reclosers did exactly that. In the worst, a recloser on a 25 kV circuit operated about 1,100 times in 33 minutes. Another pumped 740 times, then six months later about 320 times in 22 minutes, 13 of them in a single minute.
What the crew found
Each utility was unaware, and none of those contacted had received a single customer complaint. DFA recorded every operation from the substation, with the phase and the current.
Why it matters
Every reclose into a fault is another ignition chance, another interruption for customers beyond the recloser, and more damage at the fault and inside the recloser. One recloser did it twice, six months apart.
Keep reading
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.
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.