What is the maximum allowable grounding resistance for power sources?

The correct choice of 25 OHMS or less for the maximum allowable grounding resistance for power sources is based on the established standards and practices in electrical safety. Grounding is essential for providing a safe path for fault currents to flow, which helps prevent electrical shock and equipment damage.

According to the standards, a grounding resistance value of 25 OHMS or less is typically deemed safe for ensuring that fault currents can effectively dissipate into the earth, minimizing the risk of electrocution to personnel and reducing equipment failure. Values above this recommendation could lead to higher risk of electric shock and may not adequately protect sensitive electrical equipment from damage during fault conditions.

The other values provided are either below or above the acceptable level, with those that are lower, such as 10 OHMS, representing stricter requirements that may not be universally applicable, depending on the specific system and environment. Higher values, such as 30 OHMS, are less safe and can be insufficient to effectively mitigate electrical hazards. Therefore, maintaining a grounding resistance of 25 OHMS or less is a widely accepted practice among electrical safety guidelines.