Aarding: Soil characteristics, measurements and potentials

Do you want to be an earthing expert? This online course consists of five modules: A01 to A05. A description is listed below.

Module A01; Module about soil characteristics.

This course module provides information about geo-electrical soil types and how layers are built up. It is a great start to get familiar with soil characteristics, before looking into the other modules.

Tools: In this module no tools are provided.

Module A02; Module about electrical soil measurements.

This course module provides detailed descriptions of the different methods to measure the resistivity of soil and helps you understand the benefits of the different options that are available. Also tools will be provided to perform some basic analysis on example measurement results. With these tools you will be able to understand the theory and determine soil models that can be applied in detailed studies. On the other hand, you will understand how to perform measurements and acquire sufficient data for further analysis. The three methods for which the tools are provided will also be compared, using data from an existing situation.

Tools: three excel tools are made available; Wenner-method analysis tool; VES (Schlumberger) method analysis tool; Driven rod method analysis tool. The tools for the Wenner-method and Driven rod method are limited to two-layer models, the tool for the VES-method has the option to analyse up to 8 layers.

Module A03; Module about electrical soil potential calculations (generic).

This module explains the theory for the calculation of soil potentials. First the basics are described, then more complex situations are explained. Tools will be provided to perform some basic calculations and explain the theory. With these tools you will be able to perform some simple calculations. For more complex calculations it is recommended to use dedicated (commercial) software.

Tools: five excel tools are made available; The first tool calculates soil potentials that occur due to a current point injection in a uniform soil structure. The second tool does the same, but then for a conductor, using segmentation. The third tool let’s you calculate soil potentials for a conductor in the earth, taking a double layer soil structure into account. At the moment the functionality is limited to a conductor in either the top layer or the bottom layer. The fourth tool lets you calculate the Earth Potential Rise (EPR) for a vertical conductor using analytical expressions. The fifth tool combines the previous tools, so that you are able to calculate touch potentials for a vertical conductor in a uniform soil.

Module A04; Module about electrical soil potential calculations for overhead line towers.

This module repeats the steps from module A03, but then zooms in on the application for overhead line towers and shows you some detailed aspects to take into account.

Tools: five excel tools are made available; The first tool calculates soil potentials that occur due to a current injection in a vertical conductor in a uniform soil structure. This is actually the same tool as in the previous module (2nd tool). The second tool lets you do the same, but then for a tower with four legs (four vertical conductors).  The third tool lets you calculate the Earth Potential Rise (EPR) of a four legged tower, using the ‘geometric and contact resistance’-method. The fourth tool combines the previous tools for the four-legged configuration, so that you are able to calculate touch potentials. At the moment this is limited to uniform soil structures. The fifth tool that is provided will let you determined the reduction factor of an overhead line.

Module A05; Module about electrical soil potential calculations for substations.

This course module repeats the steps from module A03 and A04, but then applicable to substations.

Tools: one excel tool is made available; This tool lets you calculate the Earth Potential Rise (EPR) using the ‘geometric and contact resistance’-method. Other tools are currently being developed, but this is for the long term. For more detailed calculations we advise you to explore the application of commercial software.

At the end of each module your knowledge will be tested. What you should know is that only the questions in final chapter (“Test your knowledge”) are used for grading your final score. All other questions are for feedback and learning purpose only.

Important:

• In order to proceed with the next module the questions at the end of the module need a grading of 70% or higher. If you fail to pass the in one attempt, you will be given a resit. If the second attempt also fails you will need to contact the instructor for a manual reset and give it another try.
• In order to finish the course successfully, all modules shall be graded 70% or higher. Then, at the end of the course you will receive a certificate.

Prerequisites for the use of the tools: Microsoft Office Excel shall be installed with the option to run VBA macro’s. If the user wants to extend or change the tool experience with Excel and VBA will be necessary.

Other

References: this module refers to the EPRI Guide for transmission line grounding (Grounding guide), IEEE std.80, IEEE std.81, Cenelec standard EN 50522, and other documents.

Key words: soil resistivity; soil layers; soil models; Wenner method; Schlumberger method; driven rod; soil potentials; earth potential rise; grounding; earthing; touch potential; earthing resistance; low frequency

Trefwoorden: bodemweerstand; bodemlagen; bodemmodellen; Wenner methode; Schlumberger methode; verticale aardelectrode; spanning ten opzichte van verre aarde; aarding; aanraakspanning; aardverspreidingsweerstand; laagfrequent