Clients often ask us why we use CDEGS HIFREQ instead of any of the other packages available in the market. And our usual response is simply. "It’s the market leading product (Top 1%)". So, I thought it might be useful to quantify exactly why it is the leading product and also why it commands a leading price. In addition, to demonstrate how some of the less capable products leave you and your staff exposed to unquantified risks.
If Only Mother-Nature Was So Accommodating
Almost all, of the other products in the market are limited in the number of soil models they can consider. While, CDEGS HIFREQ is able to consider a soil model of as many layers as REALITY requires. As a result, we're better able to represent what the Wenner test measures. It may be more ‘convenient’ for developers to avoid having to invest time both in:
- a) developing the complex computations algorithms and
- b) having to wait for computations to complete - simplification = speed.
However, mother-nature isn’t so accommodating or obliging. By assuming that a geology will be made up of a two-layer structure. This is evidenced in a recent geological / resistivity study. Which covered over 1,500 sites in Northern Europe, where less than 20% fell into the simplistic 2-layer model.
So, this begs the question “what about the remaining 80% of geologies?”
By attempting to shoehorn an oversimplified 2-layer soil model into a safety critical an Electrical Earthing Design introduces massive risk (error) into your subsequent Electrical Earthing System.
It Has To Be CDEGS HIFREQ Above The Ground
While all products consider below-ground resistive effects. And some consider complex conduction through the soil. Only CDEGS HIFREQ allows for above ground inductive effects. (For example where a fence runs parallel to a high voltage overhead line, it might have a dangerous voltage imposed on it.)
Another limitation of a lot of the less capable packages is what is called (in computational electromagnetic circles) the equipotential assumption. I.E. however long the conductor segment is, the whole of it is at the same voltage. While this is perfectly applicable in some applications. For electrical earthing in real world situations, it can lead to a massive underestimation in touch voltages. For computational purposes it is a very useful tool. Because, it significantly reduces compute time and effort. But at GreyMatters, safety of life is always our priority, which means we never assume equipotentiality exists.
Some packages assume all conductive parts are made out of copper. Which means (through rose tinted glasses) that they are able to conduct electricity better than they might in the real world. When we approach an electrical earthing model. We take advantage of all the conductive paths we have available to us. Of course, assuming it is safe to do so. Part of this safety assessment is checking the voltage rise that might occur during a fault. Which will, of course, vary due to the composition of the materials being studied.
When it Gets Larger and More Complex
With larger and more complex sites. Only CDEGS HIFREQ is able to model the complete power system supplying the fault. So that all the return paths can be accounted for accurately. As a result, it is also possible to see if induced voltages (due to the unbalanced load during the fault) cause a hazard on fence lines etc.
As a Top 1% specialist Electrical Earthing Consultancy having access to the Top 1% tools makes perfect sense. So, whilst we may not be the cheapest, if safety is important to you ... if having a technically secure design is important to you ... and you want to avoid any nasty surprises or embarrassment further down the line, then drop us a line or contact us.
If you want to learn what differences there are within CDEGS versions, then access a PDF comparison paper HERE.
Hugh is a Research Engineer at GreyMatters, joining in 2014. He graduated from the University of Bath, sponsored by the IET's Power Academy scheme. Hugh has a strong technical background with National Grid working on T&D schemes at voltages from 132 kV to 400 kV. Outside of work, you can find him cycling and fly fishing, or backstage at various local amateur dramatic companies.