A supplemental electrode is needed when the resistance to earth is what value or greater?

A supplemental electrode becomes necessary when the resistance to earth is 25 ohms or greater. This requirement exists to ensure safety and effectiveness in grounding systems, especially in electrical installations.

When the resistance to ground exceeds this threshold, the grounding system may not adequately dissipate fault currents, potentially leading to hazardous conditions. Using a supplemental electrode helps to lower the overall resistance to earth, reducing the risk of electrical shock and improving the performance of protective devices. Additionally, grounding systems play a crucial role in preventing equipment damage from surges and reducing the likelihood of electrical fires.

It’s important for professionals in the field to understand these grounding requirements to comply with safety regulations and ensure reliable operation of electrical systems.