In our previous post, 7 Deadly Sins of Electrical Earthing… Part 2, we continued the 7 deadly sins of earthing/grounding, up to and including Sin # 5. We now conclude with sins 6 – 7.
Sin #6 – Instrument of Envy
Recently, a well meaning electrical contractor measured an electrically large earth system using a general tester, which claimed to measure earth resistance as well. The instrument stated to use a very low signal current in order not to disrupt the protection, e.g. 2 mA max with test leads 15 m long.
So, what’s wrong with this picture?
2 mA at 9 V from a £ 200 instrument (c. US$ 300) and the site’s earth electrode covers an area 760,000 m2 on high resistivity soil using 15 m long leads. Ummm.
Unlike the above scenario, it’s no accident that Electrical Earthing Specialists develop and invest large sums of money in instrument packages to deliver accurate/reliable results which can deal with the most demanding geologies in the world – and this doesn’t come cheap. But thankfully, there is no need to suffer instrument envy in silence when an Electrical Earthing Specialist has done all the work – so you don’t have to!
From solid granite cliffs found in the Nordics, to the dolomite mountains of the Cape … to the slate fields in Wales. Using the very best measuring equipment with high signal voltage/current such as CDEGs Finite Element Analysis Software and latest techniques will ensure confidence in accurate measurements in any geology – there isn’t a geology in the UK and Europe that cannot be measured with confidence – so there’s no need to suffer equipment envy … this is available to you now.
Sin #7 – Misplaced Pride
Don’t take things on face value. Having a misplaced confidence or pride in safety calculations or solutions without taking the time to critically analyse the findings can be a mistake.
Critical thinking is the ability to think clearly and rationally. It includes the ability to engage in reflective and independent thinking.
Since 2010, current accepted wisdom within the IEC has shifted its position on how to deliver an effective Electrical Earthing System, and just because a designer is using CDEGS – not all versions of CDEGS are the same. Stay critical and find out what version is being used. Some versions are suited to small simple systems (circuit theory based); other versions have been specially developed for the larger more complicated designs to take account of inductive, capacity and resistive couplings (based in Electromagnetic Field theory).
Using an underpowered version of Finite Element Analysis (FEA) software CDEGS can lead to huge errors in the final design, errors of 400% plus can be found if an inappropriate version is used, which when dealing with a human safety critical component is not ideal.
If in doubt what version has or is being used – ask! There are some simple guidelines from the developers (SES Inc.) about which version of CDEGS software is appropriate for what application or take 2 minutes to read https://greymattersglobal.com/50-shades-darker-cdegs-myths-busted.
FEATURED IMAGE: leadnet.org
Inspired by the THE SEVEN DEADLY SINS OF ELECTRICAL Earthing DESIGN whitepaper published by E&S Grounding Solutions
Ian is a Principal Consultant at GreyMatters, with 26 years experience solving HV earthing, EMC, and lightning problems for clients worldwide. When he’s not busy studying problems and designing solutions, you can find him mountain biking, sailing and racing motorbikes in the summer. In the winter he tends to head off to the mountains chasing the snow with friends and family. Ian holds a Master’s Degree, and Degrees in both Mechanical and Electrical disciplines, and is one of the top 1% accredited CDEGS consultants and advisor to international utility companies, data-centre and infrastructure developers globally.
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