Grounding Systems Flashcards

What is the minimum length of a ground rod electrode required by the NEC?

Answer: 8 feet

NEC 250.52(A)(5) requires ground rod electrodes to be at least 8 feet in length and must be installed to make contact with the soil.

An equipment grounding conductor run in a conduit with ungrounded conductors must be sized based on which NEC table?

Answer: Table 250.122

NEC Table 250.122 is used to size equipment grounding conductors based on the ampere rating of the overcurrent device protecting the circuit.

What is 'touch potential' in grounding system analysis?

Answer: The voltage between a grounded structure and a point on the earth's surface within arm's reach

Touch potential is the voltage difference between a grounded metallic structure and a point on the earth's surface that a person standing nearby could simultaneously contact.

Which of the following is required when a grounding electrode conductor is run exposed along a wall?

Answer: It must be protected from physical damage where subject to it

NEC 250.64(B) requires that a grounding electrode conductor exposed to physical damage be protected by conduit, armor, or other approved means.

What does the term 'bonding' mean in the context of NEC grounding requirements?

Answer: Permanently joining metallic parts to form an electrically conductive path

Bonding is the permanent joining of metallic parts to ensure electrical continuity and the ability to safely conduct any fault current.

In a corner-grounded delta system, which conductor is grounded?

Answer: One phase conductor

In a corner-grounded delta system, one of the three phase conductors is connected to ground, which must be identified with green color coding.

What is the minimum size copper conductor permitted for a grounding electrode conductor where connected to a rod, pipe, or plate electrode?

Answer: 6 AWG

Per NEC 250.66(A), the grounding electrode conductor need not be larger than 6 AWG copper when the electrode is a rod, pipe, or plate.