Q. When installing a high-impedance grounded neutral system for a 480V, 3-phase electrical system, the following question arises. Where is the proper location for the grounding impedance (resistor)?

  1. Between the equipment bonding jumper and the system neutral.
  2. Between the main bonding jumper and the system neutral.
  3. Between the transformer secondary and the first disconnecting means.
  4. Between the grounding electrode conductor and the system neutral.

Answer: D

As per 250.36(A), “The grounding impedance shall be installed between the grounding electrode conductor and the system neutral. Where a neutral is not available, the grounding impedance shall be installed between the grounding electrode conductor and the neutral derived from a grounding transformer.”

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at necexpert@aol.com.