LMS Substation 3-2 Practice Test

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According to the National Electrical Code® (NEC), what is required if a single electrode has a resistance to ground greater than 25 ohms?

No additional electrodes are needed.

One additional electrode is required.

When a single electrode has a resistance to ground greater than 25 ohms, the National Electrical Code® (NEC) stipulates that at least one additional grounding electrode is necessary. This requirement is in place to ensure adequate grounding and reduce the resistance to ground, which is critical for safety. Proper grounding minimizes the risk of electric shock, helps prevent damage from electrical surges, and contributes to the overall performance of the electrical system.

The NEC recognizes the importance of maintaining low resistance to ground for effective grounding systems. If the resistance exceeds the specified threshold, adding another electrode helps improve the overall grounding system's effectiveness by lowering the resistance and enhancing safety. Proper grounding is essential for the safety and reliability of electrical installations, which is why the code mandates this additional measure when a single electrode is insufficient.

Two additional electrodes are required.

A transformer must be installed.