Earthing System Design & Installation
Design
The earthing system design is carried out using Earthing Design Software called CDEGS and some minor calculations are performed using MathCAD. The RESAP and MALZ programmes contained within the CDEGS software enable analysis of earth resistivity measurements and 3-D modelling of large complex earth electrode systems.
All systems are designed to comply with the relevant up to date BS, IEC and EA standards.
RESAP – Analysis of Earth Resistivity Measurements
This particular program caters for the determination and modelling of multi-layer soil structures. The purpose of Earth Resistivity tests related to power system design is to assist in the determination of an appropriate soil model which can be used to predict the effect of the underlying soil characteristics on the performance of a grounding system during ground faults.
MALZ – Frequency Domain Analysis of Buried Conductor Networks
This particular program caters for the 3-Dimensional modelling of large complex Earth Electrode Systems, allowing full consideration of the Series and Mutual Impedance’s of the actual Earth Electrodes, within a multi layer Soil Structure. Thereby allowing for a detailed analysis of both the Current Distribution and Voltage Profile, during any simulated Earth Fault condition, throughout the 3-Dimensional model.
Installation
The earthing installation is carried out to local and national standards to ensure that all metalwork is bonded to the same potential to minimise the risk of electric shock under fault conditions.
Bare copper conductor is installed in the ground at approx 600mm depth to minimise the earth potentials in the ground under fault conditions. Earth rods are installed to reach lower values of soil resistivity to ensure the integrity of the earthing system.
Earth electrode resistance tests are performed at the site on completion of the earthing installation to ensure that the design value is met and to provide a benchmark for future tests to check the integrity of the installation.
The ‘Slope Method’ of testing is adopted to provide the earth electrode resistance of the installation. The Slope Method is the industry standard for earth electrode testing.