Earthing and Electrical Grounding Installation Explained

October 11, 2016

The principles that target earthing and grounding installation work inform our finest electrical engineers of the essential nature of these safety-oriented wiring systems. In fact, grounding work is at least as important as the workmanship used to busily hook live conductors to their corresponding connectors, for this practice ensures a low impedance pathway is in place when or if a dangerous electrical fault develops. Here's a closer look at the principles and mechanisms that guide the installation of an earthing system.

Don't Blow a Fuse

In olden days, and this wasn't so long ago, special thin wires or "fuses" were plugged into fuse boards. Located in the electrical distribution cupboard, these linkages would heat and melt when dangerously high electrical currents flowed in a circuit. The same principle is in place today, except circuit breakers have replaced the thin wire of the fuse. They operate in the same manner, though, by creating an open circuit when a high current is detected.

Earthing and Grounding Fundamentals

Fuses are covered first because this is the mechanism that protects us from a severe electrical shock when an electrical circuit goes wrong. But it's the earthing network that plays the biggest role in this process. Every housing, every exposed metal casing on an electrically powered piece of equipment must be grounded. The ground wire in a cable, for example, is carefully connected to a ground post inside its corresponding electrical device. It then connects at the other end of the cable (after passing several other connecting junctions) to some form of grounding electrode, perhaps one that's sunken into a pit outside the structure where the equipment is installed. Now, if the live conductor short-circuits to the exterior housing, a potentially fatal electrical shock is promptly avoided, but how?

Following the Shock Path

Instead of entering a user's body and using that body as a conduit to the ground, the shorted current uses the easiest possible path to ground. It follows the low-impedance earthing path, generates a high current, and trips the circuit breaker. And this entire process takes place in milliseconds, so it's hopefully too fast to endanger others. This path of least resistance principle is the primary reason for a grounding network, but there are others. Grounding techniques work with bonded metal to provide a super-fast route for electric energy when lightning strikes, so fires are eliminated. The terminating end of the earthing system traditionally enters a ground pit as one or more electrodes, so soil resistivity and other contributing factors can affect the integrity of the low impedance value.

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