Case Studies

CS3 finds fence posts not bonded as required

When it comes to Earthing and Lightning protection, not everything is as it seems from the outskirts. This is why taking the appropriate precautions and testing is imperative for each project.

In a ground grid integrity test in Wisconsin, USA, the CS3 identified a number of substation security fence posts which were missing the bonds specified in the construction drawing. The station had been built within the last 3 years however cost-effective test methods weren’t available at the time of commissioning to validate the fence bonds to the level required.
The posts were bonded to a grading ring as is customary, however the bonds were specified to be made below grade to mitigate copper theft issues. This made visual inspection of the installation by the asset owner difficult as the substation was built as a turn-key project and handed over at completion.

During testing of the entire substation, it quickly emerged that there was a noticeable difference in the measured resistance between the properly bonded posts and those which were not properly bonded below grade. Whilst no visible difference existed between the properly and poorly bonded posts, the effectiveness of the bond could not be concealed from the highly accurate and noise-resistant CS3’s measurement algorithms.

Also, all the fence posts (as shown in the drawing) were verified within 40 minutes while the substation was live. The entire station was tested within 3 hours, including every metallic structure within the fence and a number of items outside, such as transmission towers, padmount transformers, distribution assets, water pipes. Never assume that all requirements are being upheld without confirmation from the appropriate equipment. Make sure you utilize the right tools and get the task done right the first time.

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