This article was posted 02/13/2006 and is most likely outdated.

How to Protect Your House and It’s Contents from Lightning
 

 
Topic - Grounding and Bonding
Subject - How to Protect Your House and It’s Contents from Lightning

February 13, 2006 

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How to Protect Your House and

It’s Contents from Lightning

 

This guide is intended to provide useful information about the proper specification and application of surge protectors, to protect houses and their contents from lightning and other electrical surges. The guide is written for electricians, electronics technicians and engineers, electrical inspectors, building designers, and others with some technical background, and the need to understand lightning protection.

 

Click here to download: This IEEE Guide for Surge Protection of Equipment Connected to AC Power and Communication Circuits

 

Mike Holt Comment: This document is an excellent, but I have a problem with the statement

“High surge currents impinging on a power distribution system having a relatively high grounding resistance can create enormous ground potential rises, resulting in damage. Therefore, an evaluation of the service entrance grounding system at the time of the SPD installation is very important [2.3.1]”.

 

Grounding. The contact resistance of the electrical system to the earth (ground resistance) plays an insignificant role in reducing ground potential rise (GPR) of surge protection devices at a residence. It’s unfortunate that all surge protection writings make the same statement, because this gives the impression that ground resistance of the grounding electrode system serves a purpose in surge protection, that it doesn’t.

 

If you feel that the contact resistance of the electrical system to the earth does reduce ground potential rise, please send me a copy of a study that supports your position.

 

Bonding. Now I do agree that a low-impedance path from the surge protectors to the source, such as the equipment grounding conductor, or the neutral conductor at service equipment is critical in reducing ground potential rise. But this really has to do with bonding, not grounding!
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Comments

  • The paper's Article 2.3.1 refers to Section 4 to support its position that "...high grounding resistance can create enormous ground potential rises." Section 4 doesn't address the issue of high grounding resistance; it's more focused on high rate-of-rise surge currents getting into the grounding system from other sources and causing potential gradients on the grounding conductors. I agree that the grounding electrode-to-earth resistance has little effect on the voltage "seen" by the SPD. However,with a high grounding impedance, a surge will result in the voltage on the electrical conductors being higher than if the impedance was lower, even after the SPD has operated. This won't effect the protection level of the equipment in the building as long as it's isolated from "remote" earth.

    James Wilson

    • Reply from: Bruce Rockwell   
    What is "Remote Earth"?

    What are you indicating isolated from "Remote Earth"

    Earthing, as long as it is done correctly, is a good thing. This does not necessarilly mean we are direct connected into the soil, just that there is proper connection to an electrode (via throundinmg electrode conductor). All electrodes present in a facility need to be bonded together. Remember the ground system is made up of a few unique components:

    Equipment Grounding Conductor

    Grounded Conductor

    Electrode (Sometimes referred to as "Earth")

    Grounding Electrode Conductor

    Isolated Ground - Just an equipment grounding conductor isolated from its utilization point back to the source. The source being a separately dervived system (ups/transformer/generator) or the building service if there is no transformer in between..

    Lets not forget the MBJ - Main Bonding Jumper which is the neutral to ground connection at the service and the BJ - Bonding Jumper needed at separately dervied systems to connect neutral and ground and sometimes allowed elsewhere.

    When considering grounding issues, always be clear about what part of the system you are investigating. Missing a component or having one where it should not be is never good.

    Reply from: Mike Holt   
    Remote Earth is a term indicating a point in the earth that is at least 50 ft away from any metal parts that you are attempting to measure voltage-to-earth from.
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