Ohio, United States
Haverly 132 kV
Pre-dawn flight under full load. A transformer bushing at 94.6 °C, 58 K above the phase next to it.
4
ha
Area covered
18
min
Flight time
3
flagged
Anomalies found
95
°C
Hottest reading
Findings
T2 HV bushing, phase B: 94.6 °C, delta-T 58 K, priority 1
Disconnect switch jaw on bay 3 at 41 °C
Cooling fan bank 2 not running
Debrief
Substation flights run before sunrise so solar loading does not mask electrical heat. The plan held 15 m from energised conductors at all times.
The bushing was reported to the control room within the flight. The utility took T2 out of service the same afternoon.
Fifty-eight kelvin on one phase. We would have found it at the next ground survey, in eleven months.
Mark Ellison, protection engineer
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