What is the maximum resistance allowed for a ground rod, according to standard practices?

The maximum resistance allowed for a ground rod is commonly recognized as 25 ohms or less in standard electrical practices. This standard is crucial because a lower resistance ensures that ground faults can effectively dissipate excess electrical current into the earth, minimizing the risk of electric shock or fire.

The objective of having a ground rod is to establish a reliable path for electricity to ground, especially during fault conditions. If the resistance exceeds 25 ohms, it may not provide a sufficient safety margin to protect both personnel and equipment from electrical surges or malfunctions. Thus, maintaining this standard is essential for ensuring electrical safety and operational integrity in various systems, particularly in installations that involve heavy electrical loads or sensitive electronic equipment.

Other options, such as 30 ohms, 40 ohms, or 50 ohms, exceed this maximum value, which could potentially compromise safety during electrical fault conditions. Therefore, the standard practice of maintaining the ground resistance at 25 ohms or less is fundamental in electrical installations.