What method can be used effectively when testing a large ground system like a substation?

The slope method is particularly effective for testing large ground systems, such as those found in substations, because it is designed to provide accurate measurements of ground resistance across various dynamic conditions. When employing the slope method, multiple readings are taken at different distances from the grounding system's electrodes. This approach allows for a comprehensive assessment of the ground's resistance, as it accounts for the varying soil characteristics and the potential impact of nearby ground connections.

By analyzing the slope created by these readings, technicians can determine the equivalent resistance of the grounding system without interference from lateral paths. This method is especially beneficial in complex grounding systems, like those in substations, where traditional single-point resistance testing may not capture the entire grounding behavior effectively.

The other methods, such as the flat, curve, and resistance methods, might not provide the same level of accuracy or detail, particularly in the context of large and intricate ground systems, where soil conductivity and distance play critical roles in overall performance.