The resistance of a grounding electrode decreases under which condition?

The resistance of a grounding electrode is closely related to the moisture content of the surrounding soil. In rainy conditions, the soil becomes saturated with water, which significantly enhances its conductivity. Wet soil provides a better conduction path for electrical currents, thereby reducing the overall resistance of the grounding electrode.

The other conditions, such as dry conditions, colder temperatures, and extremely hot temperatures, can increase soil resistivity. In dry conditions, for example, the lack of moisture can lead to higher resistance, making the grounding system less effective. Extremely hot temperatures can also reduce the moisture content of the soil, further increasing resistance. Cold temperatures may not directly decrease resistance but can lead to changes in the soil structure that may increase resistivity as well. Therefore, rainy conditions are ideal for achieving lower resistance in grounding systems.