50 Shades Freed – Unleashing CDEGS!

50 Shades Freed – Unleashing CDEGS!

CDEGS earthing plot

During my previous blog, where we explored the analogy of the car when comparing to Earthing Studies using CDEGS – if your project is a high value, critical asset, and/or infrastructure effecting large populations – then this is likely to require a more demanding level of performance in the foundational design data.

Right-sizing your CDEGS Studies!

A critical asset is going to call for critical design – Something that is robust, technically secure design/safety data with extremely low percentage of error.  So make sure your provider has matched an appropriate CDEGS module to the task you want studied – Not all CDEGS are the same!

Entry-level CDEGS modules are Circuit Theory Based and have some features to try and remove the user (who might be the weak link).  These modules are restricted to simple scenarios, below ground only and do not account for mutual inductance effects or self impedance of conductors – so this might be OK for simple generator earths, tower earths, etc. but anything with a little more complexity, then the error factor will grow (as much as 50%).

There is nothing wrong with the entry-level CDEGS packages when matched to a simple scenario, where Power Systems knowledge is not so important either.  However, as a general rule of thumb, the higher the Voltage levels on the Power Systems concerned, the more factors come into play which demand better performance/knowledge levels from your CDEGS provider.

If in any doubt, a useful score card is the price on the table … Nissan Micra investment may be appropriate for a less critical or less risky project like a generator base at the lower end of the Voltage spectrum where a 15-50% error could be an acceptable business risk.

However, as the Voltage level increases and/or other risk factors come into play, such as 3rd party foot traffic, Hot Zone, transient issues, poor soil structure or EMI (electromagnetic interference) a much more technically robust approach is needed to ensure designed-in safety from the system.

The similarities with Cars does not end here – Single CDEGS license packages start from Nissan Micra money… going right up to Ferrari 488 money (£200,000).  Both can claim to be ‘Cars’ – but which would you choose to post the fastest lap, and which would be a better to go the furthest on a gallon of fuel?


Make sure the appropriate version of CDEGS is being used on your project, the error percentages can be significant – start asking the question … “what CDEGS module(s) are you using??”

There’s a bewildering quantity of CDEGS modules – so if you’re not sure whether what is being used on your project is fit for purpose – drop us a line on the chat line below for a quick response.


Regular readers of this blog will know GreyMatters have championed CDEGS for many years. But now there is a viable and attractive alternative to CDEGS. I explain “Why I chose this alternative” in this article. And compare several past projects, done with CDEGS and the alternative – in this article.

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  • Earthing Design Services & Lightning Protection Design – If high voltage power systems and lightning are causing you concern why not see how we can help with a quick ‘live chat’ below as a start.
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  • Get Certified – Start your journey to become certified in Power Systems Earthing & Design.

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BS EN 50522:2022 Updates: Ensuring Safety and Reliability

Get Grounded: Introducing ‘How-To’ Sessions in Earthing Design

Soil Resistivity Testing – Common Mistakes

Soil Resistivity Testing Method – The Wenner 4 Probe Test

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