What's the Difference between Earthing and Bonding?

What's the difference between earthing and bonding? That's a question our readers and clients ask often. Also, we're asked quite a bit about earthing and bonding in general. So, there’s an unusually large amount of confusion around the term Earthing and Bonding. Or, for our friends in the states; you might come across the term grounding and bonding.

Therefore,  in this piece, I aim to clarify the difference between - what is Earthing and what is bonding and whether there is a difference.

Breaking things down into simple terms; Earthing - grounding can mean all things to all people. Hence, it is more realistic to think of Earthing as the ‘electrode’ itself. Also, known as the Earth Termination. This reference refers to the physical hardware, such as the copper conductors, rods, etc., that sits buried directly in the geology itself.

Alternatively, Bonding on the other hand usually refers to the above ground interconnections between the equipment or structures to be bonded.

Difference between Earthing and Bonding - Summary

So, to summarise Earthing and Bonding difference can be categorised as follows:

Earthing is the stuff ‘in’ the ground, and;

Bonding is the stuff ‘above’ ground.

Thus, knowing that some earthing system “stuff” is going to sit above ground level. And some will be below ground is a useful way of thinking about E&B (earthing and bonding). It’s also imperative to understand as part of an E&B design strategy that each item has a subtly different purpose. - You can learn more about earthing in our Acadamy portal where there’s a free trial to dip your toe in (excuse the blatant pitch!).

going the extra mile

Going the extra mile on Rail networks

One thing is for sure, E&B is a safety-critical aspect on all HV networks, including Rail Network electrification schemes. And as part of GreyMatters mission to help save lives while making life as easy as possible to deal with us, you’d expect us to jump through some crazy-hard hoops in the process, right?


As a result, one such ‘hoop' Sentinel. I have to confess, and it's quite a significant commitment to making initially (November 2017) to become the only Earthing Consultancy on the planet to my knowledge to offer full Sentinel sponsor status for Network Rail E&B projects. This status means PTS certified engineers get trackside in the UK easily without any faff or hassle and full RISQS compliance comes built-in to keep the regulators happy on the governance side.

Not only that but we also made some eye-watering (for us) investment in high-energy testing equipment. Furthermore, the readings we take do not suffer from the common, yet not fully recognised rail-related external influences. Often these sources of error usually cause no-end of uncertainty in a rail environment, i.e. lots of lovely conductive structures that run in parallel for miles.  Incidentally, these are quite a headache as a source of interference, when testing using the conventional equipment. Again, this attention to detail is something that makes GreyMatters entirely different. As a result, it’s also something that other sectors can benefit from - not just rail.

Anyway, hopefully, this piece clears up the confusion regarding E&B (Earthing and Bonding) you might have held previously and given a small insight into E&B testing headaches on rail projects too.

Ian Griffiths SelfieIan Griffiths CEng, MBA, BEng, MIET

Ian Griffiths, writes this post. Principal Engineer at GreyMatters, an Earthing & Lightning Consultant of 27 years, one of the top 1% UKAS accredited CDEGS consultants and professional advisor to international utility companies, data centre and infrastructure developers.

"Working with GreyMatters has totally changed my expectations of a professional engineering consultancy firm … for the better! Technically, they were on the money! More importantly however ... they kept me updated throughout the entire project, which was so refreshing, and therefore quickly put my mind at ease that things were being taken care of." (C. Turgis)
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