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Why is Good Grounding Important?

The transient nature of lightning with its associated fast rise times and large magnitude currents mean that special consideration needs to be given to grounding, for lightning protection to be effective.

Grounding and Bonding For Electrical Systems
Grounding and Bonding For Electrical Systems (on photo: Grounding rod; credit:

Many factors such as soil resistivity variations, installation accessibility, layout and existing physical features are all site specific and tend to affect decisions on earthing methods employed.

The primary aim of a direct strike grounding system is to efficiently dissipate lightning energy into the ground and to help protect equipment and personnel.

A typical grounding system
A typical grounding system

Earthing Principles

Low impedance is the key to lightning protection. All earthing connections should be as short and direct as possible to minimize inductance and reduce peak voltages induced in the connections. The ground electrode system must efficiently couple lightning surges into the ground by maximizing capacitive coupling to the soil.

The resistance of the ground itself to lightning currents must also be minimized. Only when all these factors are taken into account will maximum lightning protection be achieved.

Ground Impedance

Soil resistivity is an important design consideration. It varies markedly for different soil types, moisture content and temperatures and gives rise to variations in ground impedances.

The voltage generated by a lightning discharge depends primarily on the risetime of the current and the impedance (primarily inductance) of the path to ground. Extremely fast rise times result in significant voltage rises due to any series inductance resulting from long, indirect paths, or sharp bends in the routing of ground conductors.

This is why short, direct ground connections are important.

Title:Guide to Grounding and Bonding For Electrical Systems – ERICO International Corporation
Size:18.5 MB
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Guide to Grounding and Bonding For Electrical Systems – ERICO International Corporation
Guide to Grounding and Bonding For Electrical Systems – ERICO International Corporation

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  1. Shahriar Alam Rana
    May 07, 2019

    This is great site for Electrical Engineering.
    Thank you very much for so many very useful guides and engineering books.

  2. Mário Sotomaior
    Feb 08, 2017

    I found several times the ground connection cable throw a galvanized pipe. My point of view is this is incorrect as a ferromagnetic path around the cabe increases the indutance. Could you please share your opinion regardind this matter. Thanks

    Jan 18, 2016

    Dear David
    This is very considerable that you noticed to inductance of lightning path and transient phenomenons as well. Rise time is very important factor that appears in di/dt term. Many people only consider about DC resistance in lightening grounding system.
    R. A.

  4. Slavisa Jovanovic
    Jan 17, 2016

    This is a great portal!
    Thank you very much for a great number of very useful guides and engineering books!

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