Thank you for your question regarding 0.5-ohm earth resistance grounding systems. It is our pleasure to help.
A 0.5-ohm ground system is a very difficult to achieve standard. Typically, a 1.0-ohm is considered difficult. The reason for this is that the closer you get to zero (0) ohms (an impossible number), the more exponentially difficult it becomes. In this regards, a 0.5 ohm grounding system is by at least an order of magnitude more difficult to achieve than a 1.0-ohm grounding system.
Generally speaking, systems with extremely low resistance-to-ground (earth resistance) readings, have additional design requirements beyond simple earth resistance. Often they are massive grids designed for Human Safety by reducing Step & Touch Voltage Hazards. Would this be your case?
Here is some information regarding the design of grounding system:
Here is some information regarding the testing of grounding systems:
Here is some information regarding Step & Touch Voltage Hazards:
We are of course more than happy to visit your site and help you with your project. We have extensive international experience, and are based out of California in the United States. The process would start by collecting excellent Soil Resistivity data, which is based on the size and shape of the proposed grid, and as such we would need to see site plans.
Please feel free to contact us at anytime. We do have translation services available by appointment, if that would be of assistance.
The Engineering Team at E&S Grounding Soltuions