LIGHTNING RODS IN SAND SERIES

Due to the conductive benefits of the material, fewer grounding electrodes may be required to achieve the targeted ground resistance saving both time and money on the total installation. Low ground resistance can also be achieved with other techniques, such as:ĭepending on the application, conductive ground enhancement material is often preferred over the aforementioned options. These products can be referred to as “grounding” or “earthing” enhancement materials. These materials are ideal for use in areas with high resistivity soils, including rocky earth, mountaintops and sandy soil. Conductive enhancement materials are some of the most cost-effective ways to overcome high soil resistivity. To finalize the dissipation of a lightning current safely into the earth, high conductivity ground must be present. The Most Cost-Effective Grounding Solution for High Resistivity Soil

This has implications in certain application such as higher touch or step potentials, or in more extreme cases failure of reliable operation of over-current or over voltage devices. If the soil has high resistivity, and the ground electrode not sufficiently arranged to offset this, the dissipation of the electrical current running through the system will result in a higher voltage on the grounding system. At some point distant from the earth conductor, the current dissipation becomes large enough and the current density small enough that the resistance is negligible. Each successive shell has a greater area for current flow and consequently, lower resistance.

LIGHTNING RODS IN SAND SERIES

When currents flow from a ground electrode into the surrounding soil, they’re often described as flowing through a series of concentric shells of increasing diameter. *Typical resistivity for various soil types Why Soil Resistivity Matters for Grounding The chart below shows some of the ranges in resistance for typical soil types: Could be metals, salts or other substances, like oil. Igneous rocks, for example, are more resistive than ore minerals.

Temperature. Cold or frozen ground will be more resistive than warm ground.

Dry ground, like sand in a desert, is highly resistive. Rocky soil or gravel has especially high resistivity. Since testing soil resistivity is not always possible, be aware of the factors affecting soil resistivity: For example, soil with low resistivity during humid, warmer seasons may have a higher resistivity during cold (freezing as an extreme) or dry seasons. Because of this, change in season or weather patterns can have an impact on soil resistivity, and therefore grounding system performance. In addition to the type of soil, other factors that can influence soil resistivity are temperature and moisture level. Understanding how the soil resistivity varies with depth is important for the designer, as it can determine if a deep or shallow ground electrode design is desired. A common method to achieve this is the Wenner 4-Point Test, which involves four probes spaced at equal distances to determine the profile of the soil resistivity at various depths. Preferably, a measurement of the soil resistivity is conducted before the grounding system is designed. However, despite this, a high soil resistivity still represents challenges to these designs and can exasperate shortcomings or under design. In a number of applications, the ground resistance itself is not as critical as the grounding layout (i.e. In the majority of applications, a low ground resistance is preferred or even require, therefore more often than not a low resistivity is preferred. Quite simply, soil resistivity is how resistive the soil is to the flow of electricity. However, designers and installers of grounding systems should not overlook another important factor-soil conditions.īelow, we explore what soil resistivity is, how it is determined and the ways in which grounding systems are affected by various soil resistivity. Grounding is a very complex subject. The proper installation of grounding systems requires knowledge of national and international standards, grounding conductor materials and compositions, and grounding connections and terminations. Proper grounding proves to be an important issue when designing and installing power and lightning protection systems. The goal of any grounding system is to provide a low-impedance path for fault and lightning-induced currents to enter the earth, ensuring maximum safety from electrical system faults and lightning.Ī properly installed grounding system not only helps protect buildings and equipment from damage caused by unintentional fault currents or lightning surges, but more importantly, it also protects people.

Lightning rods in sand