What is the Purpose of Installation of Earthing Systems?

February 27, 2019

To be brief, different types of earthing systems have been developed to provide life and equipment protecting mechanisms. In even briefer terms, they feature different fault-channelling capabilities. As a key principle, think of the planet Earth as the ultimate low-impedance pathway. By embedding a grounding electrode in the soil, a damaged electrical circuit instantly "shorts" a dangerous line current straight to the ground via a low resistance channel, which is connected to every exposed piece of metal.

Earthing Configuration Pros and Cons

On a TT earthing system, a special pit is excavated near an electrically powered structure. There are copper plates and electrodes sinking into that ground trench. Back at the local substation transformer, a second ground connection is installed. If a fault develops, the low-impedance earth line forms through the soil. Of importance here, the soil conditions can raise the connection's impedance. Next, with the earth conductor supplied this time, as used on a TN-S system, the ground wire connects to the cable sheathing back at the distribution board. Unfortunately, because of the continuity differences and voltage drops encountered on TN systems, higher voltage faults may migrate onto low voltage line segments.

Earthing Systems Save Lives And Protect Equipment

Due to their different line architectures, various fault types are handled more efficiently by alternative earthing systems. For TT systems, lives and equipment housings are protected by Residual Current Devices (RCDs), which makes the system a perfect solution for a domestically graded power supply. Many homes and large apartment complexes incorporate trenches and pits, which host electrode spikes and plates. For TN systems, the lower fault voltages, produced as a result of the PEN (Protective Earthed Neutral) conductor's low impedance, make this design a better fit for industrial complexes. Basically, the different ground configurations and line continuities provide markedly unique responses when the earth and neutral lines are connected in their assorted, system-dependent configurations. Even an IT earthing system, which hasn't been mentioned thus far, has its own singular application zone, which is usually found inside usage-critical sites, such as a petrochemical installation.

For IT earthing systems, there's either no earth connection at all or a high-impedance linkage between the earth electrode and all active system parts. That's something of a unique configuration. On earthed systems, large currents flow instantly to ground. Circuit protecting devices trip or blow, and a life/equipment saving safety factor is established. For IT shielded equipment, including larger chemical processing factories, those system feature superior fire protection capacities and lower fault currents, so the installation can keep right on operating and processing its chemical loads.

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