What are the Different Types of Earthing Systems?

March 20, 2019

Let's get a little more technical. For earthing systems, let's really delve deeper into their inner workings. As electrical experts, trenching companies already know about the 5 primary earthing circuit types. They use the armoured sheaths of underground power cables. Heck, they even use the Earth itself as a zero-ohm impedance line. In this way, a grounding spike can replace a steel-wire-armoured sheath.

Defining the Different Earthing Systems

The following labels have already been touched upon in a few articles. A TN-S system was perhaps compared to a TT solution or an IT circuit. Meanings were assigned to the letters, but they were vague. To fix this omission, here's a list of those letters and their meanings:
T - Denotes an Earthing connection is connected to Earth
N - A Neutral line that's connected to the Earth at or near the power source
S - Combined at the transformer, the neutral and Earth conductors are kept separate as they enter a powered structure
I - An isolated or impedance-connected Earthing system
C - The Earth and Neutral conductors are combined to form what's known as a P.E.N system

Having determined the different codes, let's put them together to create a number of contemporary and outdated Earthing systems.

IT and TN-C Wiring

These two lesser-known solutions are not generally in use on consumer properties. The IT system isn't used in homes or smaller properties. With the Earth connection missing or replaced by a predetermined impedance value, equipment running on this layout will not deliver a high fault current. Due to its unique fault-delivering properties, this system is used today in chemical plants, fuel depots, and oil refineries. It's an explosion and combustion safeguarding configuration. Meanwhile, most TN-C circuitry is obsolete. Known also as concentric wiring, circuit neutrals and earth lines are "Combined." Once upon a time, mineral-insulated cables required only a single current-carrying wire, for the other two conductors used the cable sheath.

TN And TT System Dominance

Every trenching worker can recognize a TT layout. They're the circuits that don't use return Earth lines. Instead, the Earthing system is built outside a property, usually in a pit full of grounding spikes. Finally, there are a few variations on a theme when it comes to TN systems. There's the aforementioned TN-C configuration, the TN-C-S earthing system, with its Earth terminal block and combined neutral. Then there's the ever-prevalent TN-S layout, a system that uses an underground cable's sheath to bypass certain issues, including the soil resistivity problems that trouble some regions.

Be aware, different types of circuit breakers and residual current devices will be required, depending on the type of Earthing System employed. Also, those Earthing configurations react differently to fault currents, so some systems work better as life-protecting solutions while others perform better as equipment protectors.

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