The grounding for lightning arrestors should be what in relation to 25 ohms?

The grounding for lightning arrestors should be less than 25 ohms to ensure effective protection against lightning strikes. A lower resistance grounding system allows lightning current to dissipate more readily into the earth, reducing the potential for damage to equipment and enhancing safety. The ideal grounding system minimizes the impedance that the lightning current encounters, which is crucial because high resistance can result in increased voltage during a lightning event, potentially causing electrical failures and hazards. Grounding systems with resistance greater than 25 ohms may not provide adequate protective measures, allowing for dangerous levels of voltage to affect equipment and personnel. Thus, maintaining a grounding resistance significantly below this limit is essential for maximizing the effectiveness of lightning arrestors.