Earth Testing and Design
A proper earthing design and earth testing regime is essential to ensuring the safety of personnel, plant and the public in the event of a power system fault. There are many conditions under which a power system fault can impress a voltage upon an earthing system with the two most common being through lightning strikes (causing flashover or diverted to earth through surge arrestors) and live conductors inadvertently contacting earth.
When this occurs, the resultant current gives rise to an increase in the earth potential in the immediate area around the fault. Having an earthing system that is adequately designed and properly maintained will offer protection to personnel, plant and the public by limiting the voltage rise and directing the current flow into the general mass of earth. An earthing system that directs current flow into the general mass of earth with little resistance or impedance also allows for correct operation of protection devices ensuring any faults are cleared in the minimum time possible offering maximum safety and ensuring power system stability.
Megavar offers services in both earthing design and earth testing with these covered in more detail below:
Earthing Design:
To ensure an earthing system will be adequate for the protection of personnel, plant and the public it must be well designed from the beginning, to ensure all possible scenarios are considered and allowed for. Megavar uses the powerful earthing and grounding system software CDEGS™ to allow new earthing systems to be fully designed and modelled for performance.
Design of an earthing system is with strict adherence to relevant Australian Standards – such as AS2067-2008, AS3835.1, AS3835.2 and AS3000 – as well as International Standard IEEE80 and Energy Network Association Document ENA – EG1 2006. By following the requirements and guidelines of these documents it is possible to create an earthing system offering the highest degree of safety, by reducing earthing system impedance to the general mass of earth, limiting Earth Potential Rise (also know as Earth Grid Voltage Rise) and minimising Step and Touch Potentials in the area.
Earthing System Compliance:
Following the installation of a new earthing system and periodically throughout the life of the earthing system, it should undergo earth testing to determine its electrical condition and ongoing level of performance. There are many factors that can cause degradation of an earthing system, with some of the contributory factors even occurring below the ground. Megavar engineers are earth testing experts and use state of the art testing equipment to perform the following earth system testing in accordance with IEEE81:
- Soil Resistivity
- Earthing System Impedance using Fall of Potential Method
- Voltage Contour measurements
- Step and Touch Potential
- Continuity Checks
Megavar engineers also perform inspections of the complete installation in accordance with AS2067-2008, AS3000 and ENA-EG1 2006.
