Electrical Earthing Testing in Urban Environments

Electrical earthing testing.  We are asked frequently – How do you test an Earth arrangement in London?

Here’s the scenario.  You are faced with Electrical earthing testing a substation. And that is located right in the middle of a densely built-up area. Also, with hard surfaces everywhere together with congested buried infrastructure in every direction.

So, any lead deployment invariably obstructed by something, e.g. roads, cars, walls, buildings, etc.  And, assuming the leads can be accommodated. An electrical earth test is likely to suffer in-ground noise and interference from the city’s / town’s infrastructure.  Also, not to mention the curious passers-by. Whom would like nothing more than to see you struggle for a laugh by stealing your test leads. When you turn your back.

Electrical Earth Test to EN 50522 2010, pg 30, states:

8 Measurements

Measurements shall be carried out after construction, where necessary, to verify the adequacy of the design.

9.2 Measurements

Design and installation of the earthing system shall allow measurements to be carried out periodically. Or following major changes affecting fundamental requirements, or even for continuity tests.

We’ve posted many blogs on the importance of following best practice. When doing Electrical earth Fall of Potential testing. And also, some of the pitfalls with the technique. But, sometimes it’s simply not possible to deploy leads to the distance required. And, escape the area of influence of the Earth system while avoiding physical obstructions. This problem is quite common in densely-populated cities like London.

The Method

In situations like this, and for an accurate electrical earth test it’s imperative to have an accurate soil model. Also, by using the Wenner method. And to use a bit of ingenuity. Perhaps you can’t deploy leads to escape the area of influence of the Earth system entirely. But, you can avoid the sphere of influence of 1 rod. Or maybe you can use a clamp meter. The principal aim of these tests is to validate the soil model against what you encounter on site.

If you can get good agreement between the resistances, you CAN measure on-site and in the model. Then use the modelled Earth resistance as your “real world” earth resistance. Therefore, you have expertly calibrated your model against the real world.

CDEGS HIFREQ

This electrical earth test situation is another of these situations where the CDEGS version becomes essential. But, only HIFREQ can accurately model the interactions between the test leads and the earth system. Also, to give you full confidence that the model indeed agrees with the measured results.

So, these earth testing techniques, in combination with CDEGS, trained and accredited engineer. Allow us to deliver right-sized electrical earthing designs in the most complicated of environments.

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