We’ve written previously about why we use CDEGS HIFREQ and (X)GSA_FD for earthing studies. Also, the reasons to invest in the top 1% of tools, knowledge and consultants. But once you’ve invested in building the model to understand what earthing is required, what are the other things you can do with this model. Additionally, answer other questions you might have?
Electromagnetic Interference Studies (EMI)
Knowing you have HV infrastructure on-site, in an EMI study, you can look at the above-ground effects. Such as induced and impressed voltages on metallic structures. For example, fences due to the proximity of the HV conductors. So, CDEGS is not for buried electrodes and pipes, it can provide insights into anything above ground also. For example;
On a large tier 4 data centre site, there is a site security fence routed between a 380 kV Overhead Line(OHL) and a 220 kV OHL. For an EMI study, we extended the model we used for a rise of earth potential study to include the OHLs and fence to discover the standing voltage on the fence, as well as the impressed voltage during a fault on the OHL. The insight provided informed the client what he should do. In this case, it was necessary to break up the fence with insulating panels to prevent the build-up in charge.
Using the model, you could also optimise the number of gaps introduced, to reduce costs and maintain site security.
High-Frequency Studies – lightning
What happens when your earth system gets struck by lightning? If you have lots of sensitive electronic equipment, simple compliance with IEC 62305 may not be sufficient. Also, the standard is a wide-ranging guide that tries to advise on anything from your home, right up to large hazardous environments like oil refineries.
So, while the basic compliance is usually sufficient to meet the requirements of your insurance company. There are times, you need a greater level of insight to determine how a lightning event might ruin your day. A High-Frequency study may help you to answer questions on whether additional measures are necessary.
When Network Rail was electrifying the Great Western Mainline, they used a totally new electrification system. They commissioned numerous transient (time-domain) studies to determine the impact of a lightning attachment on the Overhead Catenary System(OCS). Using this study, we were able to determine whether:
- A) the signalling equipment, which shares the earth with the OCS, would be able to handle a lightning strike, and
- B) to understand the hazard posed to maintenance staff working trackside during a lightning storm.
These are just a handful of the possibilities to extend on the earthing models we’ve already built, to give you MORE answers on your plant and equipment – above ground. After all, we’ve already built the model, why not ask some more questions? With that in mind, we’d love to hear from you if there are any other questions YOU want answers for.