Which example qualifies as a primary normal ground electrode?

A primary normal ground electrode is an important component in electrical systems, as it provides a low-resistance path to earth for electrical faults and helps stabilize voltage levels. Among the options provided, a 15-foot metal underground water pipe with bonded joints qualifies as a primary normal ground electrode because it meets the required criteria for effectiveness.

The bonding of the joints in this case ensures that the entire metal water pipe system is electrically continuous and provides a reliable grounding path. This is crucial because unbonded joints can create potential differences in the system, leading to ineffective grounding and safety hazards.

Additionally, water pipes are recognized as suitable grounding electrodes under the National Electrical Code (NEC), especially when they are metal and properly bonded. The length and material of the pipe also contribute to its capacity to function effectively as a ground. In this context, the 15-foot length ensures compliance with the NEC requirements for minimum lengths needed for grounding electrodes.

In summary, the characteristics of the 15-foot metal underground water pipe with bonded joints make it a suitable and effective primary normal ground electrode, ensuring safety and compliance in electrical installations.