Substation Clearances: 15KV to 115KV
Minimum electrical clearances for outdoor air-insulated substations per NESC Rule 235 and IEEE Std 1427. Includes phase-to-ground, phase-to-phase, fence, roadway and walkway clearances by voltage class.
| voltage class | bil basis kV (kV) | clearance over roadway ft (ft) | clearance over walkway ft (ft) | clearance to fence ft (ft) | min phase ground clearance in (in) | min phase phase clearance in (in) | nesc rule | standard |
|---|---|---|---|---|---|---|---|---|
| 25KV | 150 | 18 | 12.5 | 8 | 9.5 | 9.5 | NESC_235 | IEEE Std 1312 / NESC 2023 |
| 38KV | 200 | 18 | 12.5 | 8 | 13 | 13 | NESC_235 | IEEE Std 1312 / NESC 2023 |
| 69KV | 350 | 20 | 14 | 10 | 18 | 21 | NESC_235 | IEEE Std 1312 / NESC 2023 |
| 115KV | 550 | 21.5 | 15.5 | 10 | 25 | 29 | NESC_235 | IEEE Std 1312 / NESC 2023 |
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