Case Studies

Ground Grid Testing Case Study

CS3 finds missing bond with 1A test current

Safearth puts safety and precision first, which is why we are trusted globally when it comes to earthing and lightning protection. When you get an outside expert to assist with a project, the results can often be alarming and unexpected.

For example, in a ground grid integrity test in Wisconsin, USA, Safearth’s CS3 identified a set of 3 PT’s which had their main grid bond deteriorated or severely damaged below grade. The result was that the three PT’s exhibited 80-85mΩ to the main ground grid, whereas the other structures in the yard were measured at between 1-3mΩ from the reference point. Upon detailed inspection, it was determined that the PT’s were connected to the main grid only by the ground shield/core of the control wiring from the control house.

It’s important to consider the impact of other test methods on this situation; were a high current test to be used, it’s possible that the control wiring conductor(s) could have been damaged by 10-100A and this may have led to an outage when the control system lost communication from the PT’s.

Also it should be considered that all the measurements shown were taken within a 2-minute interval. With each measurement taking only 2-4 seconds, the speed of identification and resultant confidence could not be higher, especially in the short time taken. The entire station was tested within 3 hours without any outages, including every metallic structure within the fence and a number of items outside, such as transmission towers, padmount transformers, distribution assets, water pipes.

If Safearth had not come in a discovered this with our custom made equipment, the future consequences could have been catastrophic long term.

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