Quick Hits

EPISODE 11 — Impedance Grounded Systems — Part II Finale (270.36)

Slide 1 — Hook "Closing out Part II with a system type unique to medium/high voltage work: impedance grounding."

Slide 2 — What & when

• Impedance grounded systems use a grounding impedance device (typically a resistor) to LIMIT ground-fault current instead of letting it flow solidly to ground.

• Only permitted when: qualified persons handle all maintenance/supervision, ground detectors are installed, and the system does NOT serve line-to-neutral loads.

Slide 3 — Key installation details

• The impedance device sits between the grounding electrode conductor and the impedance grounding conductor (tied to the system neutral point, or a grounding-transformer-derived neutral point if there's no natural neutral point).

• The impedance grounding conductor must be insulated for the max neutral voltage (bare only allowed if inaccessible and well-separated from ungrounded conductors).

• System neutral points can ONLY connect to ground through the impedance device — no other ground connection.

• An impedance bonding jumper (unspliced, min. 8 AWG copper/6 AWG aluminum) runs from the first disconnect/OCPD to the grounding-electrode side of the impedance device.

Slide 4 — Quiz + CTA Q: "Which of these is a REQUIRED condition for using an impedance grounded system per 270.36?" A) The system serves line-to-neutral loads B) Only qualified persons maintain/service the installation C) No ground detectors are needed D) The system must be over 5000V

✅ Answer: B — 270.36 requires qualified-persons-only maintenance, ground detectors installed, AND no line-to-neutral loads.

CTA: Follow for more daily quick-hit study notes 📚⚡ — Part II done! Part III (Grounding Electrodes) starts next episode.

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