Soil Resistivity Measurements

Soil resistivity tests measure the electrical conductivity of the soil to allow the creation of an electrical equivalent soil model that can be used in earthing design software such as CDEGS.

One of our Principal Engineers completed a PhD in soil resistivity testing and analysis before joining ERM, including the development of the recommended range of Wenner spacings that are used in the British Standard and throughout the industry today. They subsequently contributed to the testing section in BS EN 50522. No company in the UK has more experience in this field than ERM.

Soundings are conducted using the Wenner method with spacings of up to 100m or more where necessary; that’s end-to-end test lead lengths of 300m or more. Whilst smaller spacing measurements may be adequate for the assessment of 11kV distribution earths or isolated lightning protection such as protection electrodes, these larger-spacing measurements are vital for the analysis of large-area sites such as:

• Substations
• Power Stations
• Railways
• Solar Parks
• Wind Farms

The use of only small-spacing measurements for large sites invites error and uncertainty in the calculation of earth potential rise, touch and step voltages or third party interference.

ERM is also able to conduct long-distance soil resistivity surveys geared for the pipeline industry to facilitate pipeline corrosion studies or for new or refurbished overhead lines (OHL). These studies are designed to evaluate the change in soil resistivity along a pipeline or OHL route, with the surveyed area sometimes exceeding 100km.

ERM has a strict environmental policy with regard to field testing. All land access is pedestrian only so that land is left in the way it is found.