Surge breakdown properties of soil

The impulse grounding impedances of a grounding system are directly related to the surge breakdown properties of soil. Surge tests were performed on horizontal grounding electrodes buried in a huge sandpond with a diameter of 5 m. Sensitive papers were buried around the electrodes to obtain the breakdown region. The influential factors in surge breakdown of soil were analyzed, such as soil resistivity, burial depth of the electrodes and surface density of the surge current. The relationship between the average thickness and the surface density of the surge current around the electrodes was observed, and can be classified into two regions. The relationship between the average thickness and the soil resistivity can be divided into three regions which were related to the conductivities of the soil. The shallower the burial depth of the electrodes, the more serious the effect of ground to the discharging region and the larger the deformation of the breakdown region.